Amphibians

Question 1

What are the three orders of amphibians?

What are the families of toads, poison frogs, tree frogs, and true frogs?

What are the families of true salamanders?

Answer 1

• Taxonomy:
  
  • Class Amphibia
    
    • Order Anura – Frogs and toads
      
      • Bombinatoridae – Eu and Asian fire-bellied toads
      • Bufonidae – True toads
      • Ceratophyridae – SA horned frogs
      • Dendrobatidae – Neotropical poison frogs
      • Hylidae – Tree frogs
      • Hyperoliidae – Af reed frogs
      • Megophryidae – Asian toads
      • Microhylidae – Narrow-mouthed frogs
      • Pipidae – African and neotropical tongueless frogs
      • Rhacophoridae – Afro-Asian tree frogs
      • Ranidae – True frogs
    • Order Caudata (Urodela) – Salamanders and newts
      
      • Plethodontidae – Lungless salamanders
      • Sirenidae – Sirens
      • Salamandridae – True salamanders
      • Ambystomatidae – Mole salamanders (Axolotl)
      • Hynobiidae – Asian salamanders
    • Order Gymnophiona – Caecilians
      
      • Aquatic spp – Typhlonectidae
      • Terrestrial neotropical and west African spp – Herpelidae, Dermophiidae

Question 2

What is unique about amphibian skin compared to reptilian skin?

What is its function?

What happens if it is damaged?

Answer 2

• Integument
  
  • Not covered by keratinized structures.
  • Thin stratum corneum shed and eaten periodically.
    
    • Dysecdysis one of the hallmarks of chytrid.
  • Lymphatic spaces under the dorsal skin.
  • Skin vital for respiration and fluid balance.
    
    • Disruption -> loss of homeostasis, death.
    • Susceptible to desiccation, toxins, metabolites including nitrogen metabolites (ammonia, nitrite).

Question 3

Describe the amphibian circulatory system.

How does the heart change between larval and adult amphibians?

What portal systems do they have?

What is the funciton of lymph hearts?

What is the function of endolymphatic sacs?

Answer 3

• Cardiovascular System
  
  • Larval amphibians – 2 chambered heart
  • Adults – 1 ventricle, 2 atria
  • Hepatic and renal portal vein systems.
    
    • Veins of the hind limb and tail combine to form the paired Jacobson’s veins.
  • Lymph circulated through lymph hearts.
    
    • Anterior lymph hearts dorsal to transverse processes of third vertebrae.
    • Posterior lymph hearts lateral to urostyle.
    • Direction of lymph flow is toward posterior LH with return of lymph to systemic circulation via renal portal veins.
  • Endolymphatic sacs in anurans are large, extend from inner ear down length of spinal column.
    
    • Crystals of calcium carbonate function as physiologic calcium storage.
    • White material surrounding brain or white nodules lateral to vertebral bodies may be seen grossly on necropsy.

Question 4

What are the main modes of amphibian respiration?

Give some examples of each type.

Answer 4

• Respiratory System
  
  • Respiration via skin, MM, gills, and/or lungs.
    
    • Skin – Gas exchange through highly vascularized dermis.
      
      • Especially important in aquatic spp and lungless salamanders.
      • Adaptations for cutaneous respiration:
        
        • Intraepidermal blood vessels in cryptobranchid salamanders (hellbendsrs, giant sal).
        • Development of elaborate skin folds to increase SA for gas exchange in some spp.
    • Gills – Covered in most anuran tadpoles, some paedomorphic salamanders, or externally exposed (early anuran tadpoles, all aquatic salamander larvae, some paedomorphic salamanders.
    • Lungs – After metamorphosis.
      
      • Thin-walled, saclike with foldind to increase surface for gas exchange.
      • Air forced in lungs via force-pump mechanism of floor of buccal cavity.

Question 5

Describe the digestive system of amphibians.

Why is the liver a greyish color?

What is the epithelial type of the epithelium of the oral and esophageal mucosa?

What makes the tongue sticky? What frogs don’t have tongues?

Answer 5

• Digestive System
  
  • Melano-macrophages in liver increase in size and/or freq with age, chronic inflammation, environmental stress, emaciation.
  • Unlike stratified squamous epithelium of mammals and birds, oral and esophageal mucosa is lined by ciliated pseudostratified columnar epithelium.
  • Tongue is covered by mucus producing epithelium that helps with prehension of prey.
    
    • Pipidae (Af clawed frogs) lack a tongue.
  • SI lacks distinct crypts present in mammals and birds.
  • Physiologic glycogen storage resulting in hepatocellular vacuolation is common in liver of many amphibians.

Question 6

Describe amphibian reproduction.

What is the process from ovulation to oviposition?

What group of amphibians has an intromittent organ?

What are drivers for reproduction?

What is the primary mode of reproduction for frogs?

What about salamanders and caecilians?

What are nuptial pads? What is the Bidder’s organ?

Answer 6

• Reproductive System
  
  • Paired testes – Lobed in urodeles, not lobed in anurans.
    
    • Attach to kidneys by mesorchium.
  • Paired ovaries suspended by mesovarium from kidneys.
  • Ovulation results in rupture of the ovisac connective tissue and release of the ova into the coelom.
    
    • Ciliated epithelium within the coelom moves the ova to the opening of the oviduct.
  • Copulatory organs only present in male caecilians and a small number of Anura and Caudata.
  • Repro driven by environmental determinants (temp/humidity).
    
    • Only males are able to attract females by calls.
    • Many spp sexually dimorphic.
    • Males often smaller in anurans.
    • Secondary sexual characteristics during breeding system – Nuptial pads in anurans, marked swollen cloaca in salamanders and newts.
  • Mating via physical contact i.e. amplexus or actual copulation in caecilians.
  • Most anurans and some salamanders and newts have external fertilization.
    
    • Majority of anurans are oviparous, external egg development.
  • Most salamanders and newts and all caecilians have internal fertilization.
    
    • Both oviparous and viviparous spp.
  • Male toads (Bufonidae) have a Bidder’s organ – Discrete aggregate of inactive ovarian tissue at the cranial pole of the testes.
  • Parental care common in salamanders, rare in anurans.

Question 7

Describe the urinary system of amphibians.

Can amphibians concentrate urine? Why is that?

Do amphibians have a bladder?

What is their primary nitrogenous waste?

Answer 7

• Urinary System
  
  • Adult amphibians have paired, mesonephric kidneys.
    
    • Metanephric kidney seen in reptiles, birds, and mammals, does not develop in amphibians.
    • Collecting ducts and a loop of Henle are absent and therefore amphibians cannot concentrate urine.
    • Ciliated renal tubules open into the coelomic cavity.
      
      • Collect and filter coelomic fluid.
    • Amphibians have a relatively high GFR vs other vertebrates, reduced with dehydration or water availability.
  • Bladder – Important site of water storage, plays role in osmoregulation.
  • Aquatic amphibians excrete nitrogen as ammonia through urine and gills.
  • Terrestrial and arboreal spp excrete mainly urea.
    
    • Many spp can tolerate high circulating urea levels.
  • Only a few spp in the genera Phylomedusa (waxy monkey tree frog) and Chiromantis (foam nest tree frogs) excrete uric acid.
    
    • Gout is an unusual diagnosis.

Question 8

Describe the musculoskeletal system of amphibians.

What is unique about their bones?

What is unique about the spinal anatomy of frogs?

What group is capable of regeneration?

Answer 8

• Musculoskeletal System
  
  • Bones are hollow, lightweight but fully ossified.
    
    • Amphibians lack significant medullary trabecular bone.
  • Epiphyseal cartilage is a mushroom shaped cap with 3 distinct regions:
    
    • Articular cartilage, lateral articular cartilage, inner growth cartilage centered over the tubular long bone.
    • Longitudinal bone growth occurs by intramembeanous ossification within the periosteum.
    • Inner growth cartilage contributes primarily to radial bone growth.
  • Anurans – Ilium attached to the spine by pair of sacral ribs.
    
    • Caudal vertebrae are fused and constitute a single bony structure (urostyle).
  • Salamanders have the ability to regenerate normal limbs, tails, and jaws following traumatic amputation.

Question 9

Describe the nervous and sensory systems of amphibians.

How many cranial nerves do they have?

Who has a lateral line system?

What triggers a feeding response?

Answer 9

• Nervous System
  
  • Cerebrum, midbrain, cerebellum.
    
    • Cerebrum – Process sensory input – olfaction and sight, learning.
    • Cerebellum – Coordination, medulla oblongata controls heartbeat and respiration.
    • Pineal body involved in hibernation and estivation.
    • 10 cranial nerves – Lack XI and XII.
• Special Senses
  
  • Lateral line in larvae and aquatic amphibians.
  • Caecilians – Tentacle below the eye.
  • Feeding mainly evoked by moving prey.

Question 10

Describe the amphibian endocrine system.

What is the primary driver of metamorphosis?

How does metamorphosis take place in anurans versus salamanders or caecilians?

Metamorphosing amphibians are more susceptible to what diseases?

What organ produces calcitonin

Answer 10

• Endocrine System
  
  • Metamorphosis controlled by the thyroid gland.
    
    • Production of T3 and T4 play crucial roles.
    • Anuran tadpoles first develop hind legs, then front.
      
      • Tail is resorbed, lungs replace the gills.
      • Spiral-shaped GIT of tadpoles is modified for prey items.
      • Jaw and tongue and mature immune systems develop.
    • Tailed amphibians grow front legs first, then hind limbs.
      
      • External gills disappear, develop eyelids.
    • Caecilians lose the lateral line as adults.
    • Metamorphosis results in increased susceptibility to drowning or infectious disease.
    • Chytrid – Mass mortalities shortly after metamorphosis.
  • Metamorphosis (Path book):
    
    • Complex remodeling of body systems initiated by transcriptional effects of thyroid hormone.
    • Experimentally inhibited thyroid hormone or developmental lack of thyroid hormone -> grow out to giant size but never metamorphose.
    • Important changes:
      
      • Limb development, apoptosis-mediated resorption of the tail musculature.
      • Long and coiled GIT in herbivorous anuran tadpoles becomes short to reflect carnivore diet.
      • Immune system undergoes extensive reorganization to avoid undesirable recognition of emerging adult tissue antigens.
  • Calcitonin is secreted by ultimobranchial bodies.

Question 11

Describe the defining anatomical characteristics of anuran amphibians.

What skin glands do they have?

What subatances do they produce?

What is the function of the pelvic patch?

What are their mechanisms of respiration?

Answer 11

• Anurans:
  
  • Adults have no tail.
  • Vision important for feeding, triggered by movement.
  • Single row of small teeth, upper jaw.
    
    • Absent altogether in toads (Bufonidae).
  • Cloaca located slightly dorsal.
  • Skin – Roles in thermoregulation, fluid balance, respiration, transport of essential ions, respiration, and sex recognition.
    
    • Cutaneous uptake of sodium is active in keratinocytes with Na/K ATPase to produce osmotic gradients and facilitate water absorption.
    • Update of Cl- mediated by mitochondria-rich flask cells in epidermis.
    • Water absorption primarily across the pelvic patch.
    • Epidermis has 1-2 layers of keratinized cells in the stratum corneum.
    • Granular glands (dermis) – Contain eosinophilic granules composed of biogenic amines and polypeptides that function as defensive toxins against predators or part of the innate cutaneous immunity.
      
      • Antimicrobial peptides, under sympathetic nerve control.
    • Mucus glands (dermis) – Protective and reduce evaporative water loss.
    • Holocrine serous glands secrete bioactive molecules, antimicrobial peptides, steroids, alkaloids, hormonelike pepeitdes.
    • Toxins – i.e. Tetrodotoxin in family Dendrobatidae. Largely derived from prey items, loss of toxicity in captivity.
    • Anurans have a Eberth-Kastschenko layer in dermis – deposition of Ca phosphate, proteoglycans, glycosaminoglycans subjacent to epidermis, function unknown. Mistaken for dystrophic mineralization on histo.
    • Misc – Mental glands, nuptial pads, melanophores, xanthophores and erythrophores, iridophores.
  • All anurans may absorb water through the ventral pelvic skin (pelvic patch) and also resorb water in kidney and from urinary bladder.
  • Lymph contains all components of blood besides RBC, pulsatile lymph hearts move lymph in one direction.
    
    • Lymph heart failure should be ddx for SQ or coelomic cavitary accumulation of fluid.
  • Larval stages maintain gills for respiration; adults respire via lungs, buccopharyngeal cavity, cutaneous respiration.
  • Heart – 3 chambers: 2 atria, 1 ventricle. Complete interatrial septum.
  • Renal portal system.
  • Amphibians cannot synthesize carotenoids (vit A).
  • Reproduction:
    
    • Thumbs present hypertrophies in males (nuptial) pads, help hold female during amplexus.
    • Fertilization is external in anurans except genus Ascaphus.

Question 12

What are the defining anatomical characteristics of caudatan amphibians?

What family of caudates has tail autonomy? Which has no limbs?

What does it mean if they are neotenic?

What are secondary male sexual characteristics?

Compare caudate versus anuran immune function.

Where is the major site of erythropoiesis in salamanders?

Describe salamander reproduction.

Answer 12

• Caudata:
  
  • Presence of a tail.
  • Plethodontid salamanders exhibit tail autonomy.
  • All have four limbs except for Sirenidae (small forelimbs, no hind).
  • Larval salamanders distinguished from anuran tadpoles by presence of external gills.
  • Some spp are neotenic or pedomorphic – retain juvenile gills throughout adulthood.
  • Male secondary sexual characteristics in Plethodontidae – Mental glands, tail glands, cirri, hypertrophied jaw muscles, swollen vents from enlargement of seasonally responsive cloacal glands.
  • Hyobranchial apparatus is dramatically adapted – Essential feeding structures should be considered during any invasive procedure, can be extensive.
  • Mechanisms of respiratory exchange in amphibia via four routes:
    
    • Branchial, buccopharyngeal, cutaneous, pulmonary.
    • Branchial – All amphib larvae. Some neotenic salamanders as primary route.
    • Cutaneous – Used to greater extent in caudates vs anurans.
      
      • Anurans – Cutaneous respiration occurs primarily as a means of carbon dioxide exchange with majority of O2 exchange in the lungs.
      • Caudates – Take up most O2 through cutaneous respiration, even in spp with lungs.
        
        • Respiratory capillaries concentrated in skin of taxa that rely on cutaneous gas exchange i.e. Plethodontidae and Cryptobrachidae.
          
          • Cryptobrachidae also use modified skinfolds to increase surface area.
  • Caudates have weak immune systems vs anurans.
    
    • Lack of red and white pulp compartmentalization in spleen, production of only two Ig types, lack of detectable humeral responses to soluble antigens, chronic rejection of skin allografts.
  • Spleen is a major site of erythropoiesis, especially in salamanders.
  • Reproduction:
    
    • Triggered by temperature changes, photoperiod, rainfall.
    • Individual females may skip one or more years between repro events to replenish energy stores.
    • Salamanders primarily use chemical and olfactory cues for communication during reproduction.
    • Eggs often retained.
      
      • May be due to improper environmental cycling, improper mating opportunities or suitable oviposition sites, nutritional deficiencies, stress.
    • Eggs adhered to substrate should not be detached.
    • Water level in container should never contact the eggs, can result in rapid swelling and premature rupture of egg capsule.

Question 13

Describe the defining anatomical traits of caecilians.

Discuss housing Typhlonects spp with fish - what concerns might there be?

What is unique about their dermis?

What about their lungs?

Do they have a bladder?

What is the function of the tentacle?

Describe caecilian reproduction.

Answer 13

• Caecilians
  
  • Order Gymnophonia
  • Most nocturnal.
  • Most common spp in captive animals – Dermophis mexicanus, Geotrypetes seraphini, Ichthyophis kohtaoensis, Shistometopum thomense, Typhlonectes natans.
  • Longevity in captivity ~11 years.
  • Mucus from Typhlonectes spp may be toxic to fish, although some have been kept with fish spp.
  • Only amphibians with scales within the dermis.
  • Most have functioning right lung, vestigial left lung; 2 lungless spp described.
    
    • The left lung is absent in some caecilians and lungs are absent altogether in the plethodontid salamanders.
  • Resp cycle – Single, long exhalation with series of short inhalations through buccopharyngeal pumping.
    
    • Prevents mix of inspiratory and exp airflow, unlike majority of amphibs.
    • Pulmonic, buccopharyngeal, and cutaneous respiratory methods.
  • Metabolic rate lower vs other amphibian orders.
  • Bilobate bladder.
  • Concertina movement – Hydrostatic pressure generated between skin and muscle layer important for burrowing.
  • Lateral lines with ampullary organs.
  • Tentacle – Chemosensory and tactile organ, protrudes from opening between each eye and nostril, attaches to tear duct and vomeronasal organ.
    
    • Innervated by trigeminal nerve.
    • Major means of environmental perception.
  • No cone photoreceptors.
  • Prey detected via olfaction and grasped in jaws; bicuspid teeth.
  • Reproduction:
    
    • Male has a complex erectile phallodeum.
    • Internal fertilization reported to occur in all spp.
    • Oviductal (not cloacal) sperm storage for up to a few weeks has been reported.
    • Most spp viviparous.
    • Post-hatch or newly born animals resemble adults.

Question 14

Describe teh appropriate husbandry of anurans.

What is their main source of energy?

Describe the feeding strategies of tadpoles versus adults.

What are their temperature requirements?

Answer 14

• Anurans:
  
  • Compensate daily thermal fluctuation by modifying behavior and metabolic changes.
  • Keep within POTZ; some hibernate or estivate.
    
    • Generally 70-75 F or 21-24 C (note this is cooler vs reptiles).
  • Fats preferred substrates of aerobic metabolism, main source of energy during hibernation.
  • Heat lamps may desiccate amphibians, avoid.
  • Most sick amphibians do better in cooler vs warmer environment (unlike reptiles).
  • Tadpoles and aquatic spp need dechlorinated water.
  • Dilute chlorine disinfection of choice, rinse thoroughly.
  • Tadpoles – Herbivorous or omnivorous.
  • Adults – Carnivorous. Terrestrial anurans only target moving prey.
  • Energetic spp. i.e. Dendrobates should have insects available ad lib; insect farm essential.
  • Feeding anurans in captivity – Provide few inverts of different spp and sizes.
    
    • Hazardous to supplement the diet directly, better to prevent single-item prey sources and provide balanced diets to the prey.

Question 15

Describe the husbandry of caudate amphibians.

What temps are generally preferred?

What enclosure concerns are there?

What is important in their prey drive?

What foods have been recommended? Should any be avoided?

Answer 15

• Caudates:
  
  • Preferred temps are in general lower than most frogs.
    
    • 10-20C.
  • Air conditioning and water chillers required in most cases.
  • Humidity critical component of refugia selection by terrestrial salamanders.
  • Prevent escaptes – Foam weather stripping, silicone sealant, duct tape to seal gaps around lids, screening to prevent entering the plumbing.
  • Substrates should regularly be rinsed and allowed to cycle until stagnant or foul odors dissipate.
    
    • Addition of springtails (order Collembola) to substrate may facilitate decomposition of waste, supplemental food source for salamanders.
  • Most nocturnal or crepuscular.
  • Anorexia likely due to compromised health or inadequant environment.
  • Olfactory cues in conjunction with movement important for prey.
    
    • Will feed on nonliving prey.
    • Lateral line system.
  • May consume smaller conspecifics, consider for exhibits.
  • Broad diversity of inverts recommended for diet.
    
    • Red wiggler Eisenia foetida may be refused because it produces defensive secretions.
    • Insects provide the staple diet of most terrestrial salamanders.
    • Large aquatic taxa – crustaceans, fish, other vertebrates.
      
      • Exclusively fish = deficiencies.
      • Frequent feeding of rodents = obesity.
    • Crayfish have been shown to be a vector for chytrid, significant infection risk to captive salamanders.

Question 16

Describe the husbandry of caecilians.

What substrate is recommended? Should any be avoided?

What do they eat?

Answer 16

• Caecilians
  
  • Prefer much higher temperatures vs caudates ~25C.
  • Humidity 70-80% recommended.
  • Some animals require moisture gradients within soil.
  • Soil and leaf litter should be sterilized.
  • Vermiculite should be avoided – Potential FB.
  • Peat moss, manure are acidic, can cause skin irritation – avoid.
  • Scolecomorphus spp do not burrow, need flat surfaces with hiding spots.
  • Aquatic caecilians depend on breathing air.
    
    • Aquariums should provide ready access to air-water interface.
    • DO should be > 80%.
  • All caecilians are carnivorous.
    
    • One African spp (Boulengerula) eats only termites.

Question 17

Describe ideal amphibian water quality needs.

What water sources can be used?

What disinfection and decontamination protocols can be used for enclosures?

Answer 17

• Water Quality
• Tap water usually good- low chlorine, pH 6-8, hardness is mod to high.
  • pH <4 or >11 are lethal
  • Hardness- dissolved ca & mg & carbonates and bicarb
    
    • Lower hardness, lower capacity to be buffered with crazy pH flux
    • Chlorinated water…leave out for 24 hrs, avoid chloramine treated water
  • More crucial – monitoring nitrogen metabolites, i.e. ammonia, nitrate, & nitrite
    
    • Max levels: ammonia (0.02 mg/L), nitrite (0.1), nitrate (50mg/L)
    • New tank syndrome no bacteria there to break down the above
  • Dissolved Oygen, 5mg/L
    
    • Oversaturation can cause gas bubble disease
  • Heating to 80C (176F) for 30 mins will kill most pathogens (Ranaviruses, Batrachochytrium, and trombiculid mites
  • Humidity- at least 80C
  • Quarantine for at least 6 wks
  • Decontamination- sodium hypochlorite or Virkon S or by heat treatment, rinse after disinfection (phenols & chloroxylenol have residuals).
  • Toxins- Zinc and copper from copper tubes

Question 18

Describe an ideal amphibian preventative medicine protocol?

What diseases should be screened for?

Answer 18

• Quarantine minimum 30 days.
  
  • Preliminary reports indicate caecilians may carry Bd, testing may be appropriate.
  • Routine water quality evaluation.
  • Routine evaluation for early identification of abnormalities.
  • Prevent escape of enclosures.
• Ranavirus
  
  • Ranavirus can live in aquatic environments for several weeks without a host.
    
    • Bleach 3% and chlorhexidine 0.75% for 1 minute contact time are effective disinfectants.
• Protocol for screening live foods and decorative plants suggested to minimize accidental intro of pathogens into collections.
  
  • Dipping food items and live plants in hypertonic salt baths < 5 min and following with chlorinated tap water < 30 min or acriflavin bath 1-2 hours helps reduce unwanted organisms.

Question 19

Describe amphibian restraint generally.

Describe the proper physical restraint for each amphibian group.

Answer 19

• In general:
  
  • Caution potential toxic effects of latex, vinyl, and nitrile gloves when working with amphib larvae. Reactions appear spp specific.
  • Thoroughly rinsing gloves in FW before use with adults or larvae to remove talcum and reduce potential toxins recommended.
  • Many amphibians bite!
  • Some salamanders have tail autotomy, avoid placing pressure on tails.
• Anurans:
  
  • Grasp large anurans behind the forelegs – May give off a release call, alarming.
• Caudates:
  
  • Salamanders will attempt to spin or roll when in hand.
  • Avoid restraint by tail, may induce autotomy.
• Caecilians
  
  • Iatrogenic jaw fractures anecdotally reported during gavage feeding.

Question 20

Anesthesia of amphibian is typically performed with baths.

What are some common side effects, describe the process of preparing a bath.

What are the agents used in baths? How do doses compare to fish?

What injectables have been used? Have any been documented with mortalities?

What about inhalants? What is a potential side effect of gas anesthesia in amphibians?

Answer 20

• Chemical restraint:
  
  • MS222, isoeugenol, benzocaine are ax of choice for amphibs in general.
  • Apnea and cardiac depression common side effects of ax.
  • Baths – Care must be taken to prevent drowning, keep solution below the humeroscapular joint and carefully monitor. Line induction tubs with plastic bags.
  • MS222:
    
    • Range from 1-2 g/L needed for surgical ax in most frogs and salamanders, but 3 g/L needed for many toads (Bufo spp).
    • Can administer intracoelomically.
    • Sx plane of anesthesia – Resp effort may slow or stop, cardiac rate often unaffected.
    • Renal circulation may become reduced a high concs of MS222.
    • Erythema of ventral skin or other light-colored skin is first sign of ax induction with MS222.
    • Light plane of ax – Loss of righting and corneal reflex, persistent withdrawal reflex, spont movement, gular resp, and cardiac impulse (visible heartbeat).
    • Overdose – Cardiac impulse slows or becomes difficult to detect.
  • Clove oil (eugenol active ingredient):
    
    • Immersion, generally short term, few spp studied
  • Propofol
    
    • Intracoelomic or IV in frogs, deep anesthesia, lethal in some.
    • Topical and intracoclomic generally inconsistent induction time, depth, and time to recovery, no advantages over MS222.
  • Ketamine less satisfactory vs MS222 and isoeugenol, large volumes may be needed, induction time is extremely variable, level of anesthesia varies greatly between spp.
    
    • Spontaneous movement even if withdrawal reflex is lost.
    • Recovery time is variable.
    • Some spp extremely sensitive or resistant, dosages are all over the place. Wait 30 min before changing the dose.
    • Ketamine-diazepam induction and recovery significantly prolonged.
  • Alfaxalone
    
    • Neuroactive steroid and general anesthetic.
    • One study using 5 mg/L bath in axolotl for surgery.
    • Sedation and light anesthesia with IM injection Australian green tree frogs.
    • In general, doses insufficient for painful procedures, more studies needed.
  • Sevoflurane/isoflurane
    
    • Use topically as water-soluble gels.
      
      • Sevo may be preferred.
      • Downside – Induction needs to be performed under a fume hood or other scavenging system.
    • Induction chamber use
      
      • Some spp do not tolerate volatile anesthetics.
      • Epidermal damage may occur if in contact with halothane or iso for prolonged periods of time.
      • Can intubate and maintain on gas, but alt resp patterns i.e. cutaneous and buccopharyngeal makes maintenance at a steady plane of ax challenging.
      • Uncuffed endotracheal tuubes recommended.

Question 21

What analgesics have been used in frogs?

Injection into what anatomical site may enhance analgesia duration?

Answer 21

• Analgesia
  
  • Opioids (i.e. buprenorphine) injected into lymph sacs may provide significant analgesia for up to 4 hours.
  • Dexmedetomidine in dorsal lymph sac may provide analgesia up to 8 hours (high doses i.e. 40-120 mg/kg).
  • Meloxicam significant decrease in serum PGE2, suggests anti-inflammatory effects/analgesia.

Question 22

Describe the effects of the following environmental issues with amphibians:

Dehydration

Poor water quality

Deep water with dendrobatid frogs

Frogs of varying size in same enclosure

Hyperthermia

Hypothermia

Answer 22

• Dehydration quickly progresses to desiccation.
  
  • Rehydration accomplished by placing in shallow layer of well-oxygenated, chlorine-free water that is spp specific temp.
  • Intracoelomic fluids may be needed.
  • ARS, or salin 0.9% one part to two parts 5% dextrose.
  • Do not exceed 25 ml/kg for initial fluid doses.
  • Avoid fluids containing potassium initially unless hypokalemia is confirmed.
• Water quality.
  
  • Ammonia and Cl tox can be treated with sodium thiosulfate baths followed by well-oxygenated fresh water.
  • Nitrite/nitrate tox may respond to tx with methylene blue.
• Dendrobatid frogs may drown if maneuvered into deep water by cagemates.
• Amphibians may try to ingest one another.
• Clear-sided enclosures often a source of traumatic rostral injuries.
• Hyperthermia – Especially aquatic amphibians.
  
  • Do not exceed 80-85F, 27-29C.
  • CS – Frenzied swimming, uncoordinated jumping or walking, lethargy, death.
  • Autolysis rapid.
  • Therapy aimed at returning to normal body temp, bathe in FW ice baths or administer cool ICe fluids.
  • Corticosteroids may be helpful.
• Hypothermia – Rarely life threatening.
  
  • CS – Lethargy.
  • Return to preferred body temp over 12-24 hours.

Question 23

What solution should be used for surgical prep in amphibians? What should be avoided?

Describe the closure technique for amphibian skin.

What is unique about salamander amputations?

What is the approach like for amphibian coeliotomy?

What is a significant complication with caecilian surgery?

Answer 23

• Surgery:
  
  • Prep – May include hydration, prophylactic antimicrobials.
    
    • Povidone iodine diluted with sterile saline 1:10.
    • Avoid use of alcohol on skin.
  • For extensive skin surgery, can perform chemical cauterization with metacresolsulfonic acid and formaldehyde 36%. Lotagen has astringent action and promotes granulation and epithelialization.
  • Everting suture patterns, simple interrupted, use nonabsorbable materials for skin closure.
  • Amputated limbs may regenerate in salamanders in newts – Leave amputation sites OPEN.
    
    • Closure may cause abnormal regeneration or prevent it completely.
  • Paramedian approach to the coelom recommended – avoids ventral abdominal vein on midline.
  • Aquatic caecilian spp – Dermatitis and subsequent osmotic imbalance appears to be a major complicating factor that increases morbidity.
    
    • Persistent cloacal prolapse in T. natans noted to cause morbidity and mortality in one caecilian review.

Question 24

What suture is recommended for amphibian surgery? What two should be avoided?

What toes should not be used for toe clips?

What are some potential issues with amphibian ocular surgery?

Answer 24

• MARMS – 107. Amphibian Soft Tissue Sx
  
  • Monofilament nylon showed the least histo reaction and recommended as the suture of choice in amphibian skin closure
  • Chromic gut and silk elicited the greatest reaction & high rate of dehiscence and not recommended.
  • Polydioxanone, poliglecaprone 25, and polyglactin should be used internally and for muscle closure, although polyglactin is likely to cause greater inflam­mation
  • Tapered needed with wedge-on suture least traumatic
• Cyanoacrylate tissue glue good- watertight and antimicrobial
• Sterile saline or 2% providone iodine in sterile saline soln to prep
• No fasting necessary
• Powder free gloves
• Buprenorphine is good for pain or dexmedetomidine in dorsal lymph sac
• Toe Clip- remember the nuptial pads and first 3 toes important for grasping female
• Ocular Surgery
• Amphibians have a membranous orbit and poorly defined lacrimal bone
  
  • Do not to damage the membrane that separates the globe from the buccal cavity
• Control bleeding
• Celioscopy: Helpful in sexing and visualization
  
  • Insuflation pressures of 0.5 to 2mm Hg with flow rate < 0.5L/min
  • Paramedian incision best to access liver, be careful of ventral midling vein

Question 25

What are some benefits and uses of minimally invasive surgery in amphibians?

What are some potential risks?

Descrie the approach for laparoscopic exam and biopsy.

Describe endoscopic orchiectomy.

Answer 25

F9 Ch 54 Minimally invasive surgery of amphibians

• Laparoscopy in amphibians may permit the visualization of almost all the coelomic organs from a single point of entry
• Indications: Gender ID, retrieval of FB from upper GI, assessment of intracoelomic lesions, diagnostic tool for nonspecific presentations, biopsies of tissues and organs, reproductive endosurgery.
• Size may be a contraindication, as are compromised individuals with greater anesthetic risk
• General anesthesia & analgesia is requisite for MIS
• Risks from damaging the ventral abdominal
• Laparoscopic Examination and Endoscopic Biopsy
  
  • Dorsal recumbence is recommended, unless sp. is laterally compressed
  • Insufflation can be used at a lower rate that sm. Mammals
    
    • CO2 insufflation w/ pressures of 0.5–2 mm Hg with a flow rate not exceeding 0.5 L/min
  • Surgical prep:
    
    • Cleansing the surgical site with sterile gauze soaked in 0.75% chlorhexidine solution and left on the surgical site at least 10 minutes prior to surgery
  • Coelom permits the visualization of liver, gallbladder, heart, lungs, digestive tract, gonads, kidneys, bladder, and fat body from a single entry point
  • Monofilament nylon is the best choice of suture in amphibian skin
  • On recovery, the animal is transferred to a warm, anesthetic-free bath and is rinsed copiously with fresh, well-oxygenated water
• Endoscopic Orchiectomy
  
  • Incision with an 11 blade to insert atraumatic 5mm forceps
  • Cauterize surrounding vessels and epididymis with diode laser
  • Deflate animal post procedure
  • Close with 1-2 interrupted sutures

Question 26

Describe nutritional secondary hyperparathyroidism in amphibians.

What period of development is calcium intake critical?

How can calcium be supplemented to tadpoles?

What are typical clinical signs?

What are the first bones to show signs of radiolucency?

How can this be treated?

Answer 26

• MBD aka Nutritional Secondary Hyperparathyroidism
  
  • Most common form of MBD in amphibians.
  • Usually results from dietary Ca deficiency, vitamin D3 deficiency, or combinations.
  • Most of the commonly fed prey items have an inverse Ca:P ratio and low total calcum.
  • Intake of Ca during larval stage critical for normal skeletal development and calcium homeostasis of adults.
    
    • Consider environmental water composition when evaluating altered intake ratios of Ca:P.
    • Fluorosis may contribute, but the animals from that report also lacked adequate UVB exposure.
  • Ca absorption depend son available UVB, dietary vit D3, Ca, healthy GIT, kidneys, integument, MSK system.
  • Cuttlebone or other Ca source should be provided for tadpoles of many spp.
  • CS – Typically starts with spastic tetany after stenuous movement i.e. leaping, improves during rest. Coelomic distension from GI stasis, gas buildup may be seen.
    
    • Spinal deformities, angulation of long bones, bowed mandibles (osteomalacia).
  • Lateral processes of the vertebrae and urostyle become radiolucent early in the course.
    
    • Long bones become radiolucent after the ghosting of the lateral processes of the vertebrae and urostyle.
  • Tetany, spastic movement, muscle fasciculation, bloat, limb paralysis, ridigity considered a medical emergency.
    
    • Tx: 100 mg/kg Ca gluconate ICe, IM, IV, SQ SID-BID or more until signs resolve.
      
      • Then continue weekly injections until eating, then switch to heavy oral supplementation with Ca carbonate.
      • Oral or injectable vit D3 may facilitate Ca utilization.
      • Baths of 2-5% Ca gluconate and 2-3 IU/mL vit D3 may be helpful in some spp but should not be the single course of correction.
      • Tx requires several months for resolution of rad changes.
      • Supportive nutritional care with critical care diets, etc PRN.
      • Calcitonin therapy reported in reptiles NOT effective in amphibians – major structural differences between amphibian calcitonin and salmon calcitonin used for tx osteoporosis in humans.

Question 27

Describe hypovitaminosis A in amphibians.

Why is it called short tongue syndrome?

Why are amphibians especially sensitive?

What are some sequelae to this disorder?

Answer 27

• Hypovitaminosis A (Anurans; not reported in caudates)
  
  • Short tongue syndrome.
    
    • Squamous metaplasia of the mucous glands of the tongue, does not stick to prey.
    • Submit entire tongue on necropsy for examination of a longitudinal section (not cross section).
    • Bladder, kidneys, eyelids should also be assessed histologically.
      
      • Lesions commonly found in oral mucosa, esophagus, cloaca, and urinary bladder.
    • Frozen liver submitted for vit A analysis – Confirmatory diagnosis requires determination of hepatic retinol.
  • Unable to synthesize carotenoids, leads to vision loss, epithelial hyperplasia, squamous metaplasia, keratinization of mucosal epithelium.
  • Captive-reared insects lack significant amounts of pre-formed vit A and the plant-based carotenoids found in wild sinecs that are converted to active vit A.
  • Squamous metaplasia within the kidney or urinary bladder may result in hydrocoelom. Conjunctival swelling has been reported.
  • Impaired immune system, secondary infection by Bd and other pathogens.
  • Insects generally low in vitamin A.
  • Supplements lose potency if stored in areas with high humidity, warm temps, or both.
  • Multivitamins should be used within 6 months of opening.
  • Human-grade vit A supplements can be diluted with propylene glycol to appropriate concentrations, may be irritating to some amphibians.

Question 28

Obesity is a common issue for amphibians. What are the most common sites of adipose deposition?

Answer 28

• Obesity
  
  • Amphibians regularly offered rodents.
  • Most stored fat is in coelomic fat pads -> grossly distended abdomen and normal limbs and tail.
    
    • Gonadal fat bodies located cranial to gonads and kidneys, numerous finger-like structures in anurans.
    • Other common sites of adipose deposition:
      
      • Epicardium, tail (plethodontid salamanders).
      • Inguinal region (toads, Bufonidae).
      • Bone marrow.

Question 29

Amphibians are voracious eaters.

What can occur if an amphibian eats too large or too many prey items in a short time?

What are the sequelae to this?

How can this be managed?

Answer 29

• Gastric overload or impaction
  
  • Result of eaving a single overly large prey or consuming too many prey items in a short period of time.
  • Amphbians stimulated to eat when seeing movement, can ingest smaller cage mates.
  • Swallowing overly large meals may affect respiratory ability.
  • Bacterial decay can outpace enzymatic digestion, leads to bloat and endotoxemia, can lead to perforation.
  • Undigested hair and bones can cause impactions.
  • Gastric washes with hypotonic saline may remove ingesta if acute.
  • Endoscopic retrieval.
  • Gastroenterotomy.
  • Consider pre and post op abx.

Question 30

Describe corneal lipidosis in amphibians.

What are the clinical signs? How common is it?

Are there any known risk factors?

How can it be managed?

Answer 30

• Corneal lipid deposision aka lipid keratopathy aka corneal lipidosis.
  
  • Most commonly reported ocular disease in amphibians.
  • Presence of cholesterol clefts.
  • Associated with captive diets that differ in cholesterol content or other lipid composition compared to diets of free-ranging animals.
  • Hazy white discoloration at limbus with extension over time to completely cover the cornea with thick white nodules and plaques.
    
    • May present as a vertical line across the cornea.
    • Most also have hypercholesterolemia.
  • Females may be at increased risk.
  • Associated with pinkie mice and cultured crickets, which have different FA profiles vs wild prey.
  • Tx unrewarding, can debulk lesions and manipulate the diet.
  • Use of wild-caught insects vs monoculture crickets, feeding small amphibians or reptiles instead of mice.
  • Basking spots should be offered to any amphibian with corneal lipidosis, inappropriate thermoregulation in some spp may play a role in development.

Question 31

Describe the effects and causes of the following renal disorders in amphibians:

Renal oxalosis

Gout

Ammonium urate urolithiasis

Metastatic mineralization

Answer 31

• Renal oxalosis
  
  • Waxy monkey frogs that consumed crickets fed an oxalate-containning plant.
  • Tadpoles of wild anurans feeding on oxalate containing plants.
  • Leads to renal dysfunction and calculi, hycrodoclom or SQ edema, white foci within kidneys.
• Gout
  
  • Unkonwn etiology, probably results from combo of dehydration, renal failure, inappropriate diets, toxicities.
  • Most likely to occur in those amphibians that excrete uric acid.
    
    • Waxy tree frogs (Phyllomedusa sauvagii).
• Ammonium urate urolithiasis
  
  • Formation of large urinary bladder stones reported in waxy monkey frogs.
  • Contributing factors – Unique uricotelic metabolism of this spp, high-protein captive diets, dehydration.
• Metastatic mineralization reported for captive frogs with dietary hypervitaminosis D.

Question 32

What are some common causes of gastric or cloacal prolapse in amphibians?

Answer 32

• Gastric and cloacal prolapse.
  
  • Usually indicates a serious disorder when noted in salamanders.
  • Cloacal prolapse is commonly seen.
    
    • Predisposing factors – Dehydration, hypocalcemia, hypoglycemia, malnutrition, GI GB, cystic calculi, gastroenteritis, hyperthermia, trauma, parasitism.
    • Keep tissue moist and protected, genetly try to replace, abx if indicated. Tx underlying cause.

Question 33

Describe the effects and management of the following amphibian toxicities:

Chlorine & chlaramines - what levels are concerning?

Disinfectants

Ammonia - what levels are you concerned about?

Answer 33

• Toxicities (Mader Ch 89 Amphib Medicine):
  
  • Keeping spring water that is aerated is an inexpensive solution for clinics seeing occasional amphibians.
  • Chlorine (Cl2) is easily removed.
    
    • Sodium thiosulfate, sodium hydroxymethanesulfonate (AmQuel), and/or carbon filters.
    • Chloramine (NH2Cl) – Combo of chlorine and ammonia.
      
      • Difficult to remove.
      • Sodium thiosulfate can be used to break apart the chlorine and ammonia and remove the chlorine, but ammonia remains.
      • Zeolite or biological filter needed to remove the ammonia.
      • Sodium hydroxymethanesulfonate effectively splits the chlorine ammonia bone and also neutralizes the resulting ammonia.
  • Avoid use of plastic containers that have held anything other than water.
  • Many common disinfectants are toxic to amphibians:
    
    • Povidone iodine, chlorhexidine, quaternary ammonium compounds, chlorine, ammonia.
    • Stoskopf reported an incident of iodine intoxication of poison dart frogs, resulted in agitation and abnormal posture before death.
      
      • Suspected to have diffused out of a plastic enclosure despite rinsing prior.
  • Ammonia > 0.2 ppm suspicious for toxicosis.
    
    • Levels > 1 ppm verification of toxicity.
    • Complete water change recommended.
    • Sodium hydroxymethanesulfonate may be used to temporarily bind ammonia if water change is not practical.
  • Chlorine intoxication is likely if a major water change has occurred within the past 24h.
    
    • Dangerous levels > 0.5 ppm.
    • Bath of 100 mg/mL sodium thiosulfate can be used to treat confirmed chlorine toxicosis.
  • Heavy metals i.e. lead, copper, Zn may be in plumbing.
  • Salt toxicosis may occur with marine aquariums kept near an amphibian enclosure.
    
    • Keep amphib enclosures away from marine tanks and label containers distinctly to avoid confusion.
  • Presticides.
    
    • If needed for treatment around amphibians, insect growth regulators are preferred over toxicants.
  • Nicotine.
    
    • Secondhand tobacco smoke is irritating.
    • Keep in smoke-free rooms.

Question 34

What parasite is associated with polymelia or amelia (supernumerary or missing limbs) in amphibians?

What is spindly leg syndrome?

Answer 34

• Miscellaneous (Path book):
  
  • Limb malformations
    
    • Trematode parasite Ribeiroia ondatrae
      
      • Polymelia or amelia n free-ranging anurans.
        
        • Supernumerary limbs or missing limbs.
      • Enhanced by environmental eutrophication.
      • Disruption of the embryonic limb bud by encysting metacercaria.
    • Spindly leg syndrome
      
      • Thin underdeveloped forelimbs from time of metamorphosis.
      • Cause is unknown – Genetic vs malnutrition, water quality, enclosure temps, etc.
      • Animal generally dies, euthanasia is recommended

Question 35

What are some potential causes of coelomic effusion and lymphedema in amphibians?

Answer 35

• Coelomic effusion and lymphedema are common nonspecific clinical presentations.
  
  • Commonly caused by chronic renal disease.
  • Polycystic nephropathy occurs in captive anurans from Panama.
  • Hypocalcemia with secondary lymph heart failure.
  • Hypoproteinemia.
  • GIT disease.
  • Heart failure.
  • Renal toxicity.
  • Congenital anomalies of lymph hearts.
  • African clawed frogs – Ovarian hyperstimulation syndrome following lab tx with human chorionic gonadotropin.
  • Infectious causes of edema – Ranavirus infection, sepsis, mycobacteriosis, metacercariae of echinostome trematodes.

Question 36

What is the most common tumor of northern leopoard frogs? What virus is it caused by?

What other neoplasms are commonly reported?

Answer 36

• Neoplasia:
  
  • Lucke’s renal adenocarcinoma.
    
    • Free-ranging and captive northern leopard frogs.
    • Ranid herpesvirus 1.
  • Chromatophoromas, melanophoromas, iridophoromas.

Question 37

Ranavirus is what type of virus?

What are the most common ranaviruses around the world?

Which is the only one reported in chelonians in North America?

How does life stage affect susceptibility in amphibians?

Answer 37

• Iridoviridae.
  
  • Large, icosahedral, DNA viruses, enveloped or nonenveloped.
  • Worldwide, significant morbidity and mortality.
• Geographic and Host Distribution.
  
  • Frov Virus 3 (FV3).
    
    • First reported in leopard frogs.
    • Outbreaks now throughout the world.
  • Various ranaviruses account for epizootics:
    
    • FV3, ambystomma tigrinum virus (ATV), soft-shelled turtle iridovirus (STIV), Bohle iridovirus (BIV).
    • FV3 is the only iridovirus in turtles in NA and most commonly reported for anurans.
    • ATV – salamanders, W US.
    • BIV – main ranavirus in Australia.
  • ALl ranaviruses
    
    • Frog Virus 3 – FV3 (anurans)
    • Tadpole edema virus - TEV
    • Ambystoma tigrinum virus – ATV (salamanders)
    • Bohle iridovirus – BIV (anurans)
    • Midwife toad virus (anurans)
  • All ranaviruses have a wide species distribution, significant differences in species susceptibility even within same isolate.
    
    • All anurans, caudates, chelonians considered susceptible.
      
      • Some uniquely sensitive i.e. tiger salamanders to ATV, wood frogs to FV3, eastern box turtles to FV3.
    • NA – larval amphibians considered more susceptible.
    • EU – adult mortality more commonly reported.
    • Adult chelonians more commonly develop FV3-like lesions.
    • All age classes should be considered susceptible to the disease.
      
      • Juvenile/larval age classes may be at increased risk in some species.

Question 38

Describe the pathogenesis of ranavirus.

How is it transmitted?

Are their any proposed reservoirs?

What are typical clinical signs in salamanders? Frogs? Tadpoles? Chelonians?

What are the common lesions?

What are the inclusion bodies like? Where can they be found

Answer 38

• Pathogenesis.
  
  • Transmission – contact with infected individuals, water, fomites.
    
    • Chelonians cohoused with infected amphibians or exposed to shared water with infected fish induced disease in 20-30%.
    • FV3-like DNA detected in mosquitoes during an eastern box turtle mortality event, may be another route of transmission.
    • Proposed amphibian reservoir spp include those that develop over 1 year (bullfrog), have neotenic development (tiger salamanders), or have aquatic adult life stages (red-spotted newt).
    • Caudate salamanders likely both the reservoir and hosts of FV3 infection in Canada.
  • EBT that recovered from a ranavirus infection experimentally reinoculated a year later demonstrated less than 20% mortality.
    
    • Surviving animals continued to shed, potential reservoir.
• Clinical Signs and Pathology.
  
  • Systemic disease, epithelial necrosis.
  • Skin ulcerations or systemic hemorrhaged in absence of skin lesions.
    
    • Salamanders – abnormal swimming patterns, subcutaneous edema.
    • Frogs – loss of pigmentation, lordosis, epithelial sloughing, petechiation.
    • Larval amphibians – erythema at tail base, ventrum, legs, swelling of multiple areas of body.
    • Multisystemic infections – Hematopoietic tissues, endothelial cells, epithleial cells.
    • Erythema, petechial and ecchymotic hemorrhages.
    • Tiger salamanders and Chinese giant salamanders – Raised cutaneous plaques or polyps.

Tadpole edema virus, adults asymptomatic.

    * Ecchymosis and petechiation of the skin are common.
    * Chelonians – nasal, ocular, oral discharge, oral plaques.
        * Epithelial lesions less consistent than fish and amphibians.
* Pathologic findings similar between adults and juveniles of both amphibians and reptiles.
    * Systemic organ failure due to cellular necrosis in the spleen, liver, kidney, and intestine.
    * Hemorrhagic syndromes common in anurans in the UK and in salamanders in western NA.
    * Tiger salamanders – polypoid lesions over most of body.
    * Nonspecific changes – lymphocytosis, lymphoid depletion, vacuolation of hepatocytes and renal tubular cells.
        * Basophilic viral inclusions inconsistently observed.
            * Erythrocytes, leukocytes, epithelial cells, meninges, gills, neuroepithelium, nasal tissues, adipose, trachea, muscle, osteoclasts.
    * Histologic lesions can include:
        * Necrosis of hematopoietic tissues.
        * Multicentric hemorrhage with vasculitis and endothelial necrosis.
        * Necrosis of epithelial cells – Kidney, liver, skin, etc.
        * Characteristic basophilic intracytoplasmic inclusion bodies frequently observed.
            * May be present within glandular cells of the stomach.

Question 39

Describe the diagnosis of ranavirus.

What test is commonly used?

What samples should be submitted?

What treatments have been used?

How does temperature affect the course of disease?

What disinfectants are useful in preventing spread?

Answer 39

• Diagnosis.
  
  • PCR commonly used, but limited and does not confirm active infection.
  • Dx most successful on fresh or frozen tissues. Recovery from fixed tissues is possible.
    
    • Evaluation of antemoretem toe clip and postmortem liver samples both effective methods for detection.
  • Specificity and sensitivity of PCR – tail clips underestimate prevalence, agreement increases as time after exposure increases.
  • Reptiles – necropsy tissues commonly tested.
    
    • Whole blood and oral swabs sensitive and specific in agreement with tissue sampling.
    • It is recommended that a dual testing strategy of both whole blood and oral swabs is needed for greatest testing success.
    • qPCR detects fewer viral copies than conventional PCR.
  • Immunohistochemistry – useful for quick confirmation of pathogen in formalin-fixed tissue.
  • Serologic assays.
    
    • May result in false positives.
• Treatment and Prevention.
  
  • Therapeutic intervention in wild settings often impractical.
  • Acyclovir – guanine analog antiviral drug, active against herpesvirus due to presence of the thymidine kinase TK enzyme, which rapidly activates acyclovir to the monophosphate form.
    
    • Several isolates of iridoviruses have been shown to have TK genes or functional TK enzymes.
    • No significant differences in survival based on dose in one study.
  • Other mechanisms – temp alteration, disinfection.
    
    • Viral loads highest at 10 deg C vs 26 deg C.
    • Chlorhexidine 0.75%, sodium hypochlorite 3%, potassium peroxymonosulfate 1% effective at inactivating ranavirus after 1 minute exposure.
    • Potassium permanganate (100%) after 60 minutes, chlorhexidine 0.25% and sodium hypochlorite less than 3% ineffective.

Question 40

Describe the affects of ranavirus outbreaks in wild amphibians and turtles.

How high is mortality?

How do demographics affect mortalities?

Are there any documented outbreaks in captivity?

Were any copathogens observed and how did that affect cases?

What is the conservation impact of ranavirus?

Answer 40

• Mortality Events.
  
  • Significant impact on local populations.
    
    • Up to 90% mortality.
    • Animals in higher-density population shad higher mortality rates and died more quickly.
    • Extinction events were unlikely because as mortality reduced density below a critical threshold, remaining animals were able to recovery.
    • Turtles – less well described.
      
      • An outbreak in a zoo demonstrated 40% mortality, detection of copathogens (herpes, mycoplasma). Turtles with copathogens had a nonsignificantly lower mortality than individuals only detected with ranavirus.
  • In captive animals, clinical course of disease may be short with minimal signs.
    
    • Several reports in which surveys of reptiles and amphibian populations failed to demonstrate molecular evidence or exposure to ranavirus.
• Conservation.
  
  • Global trade in amphibians significant factor in disease epidemiology and threatens conservation.
    
    • Bait salamander used by fishermen – significant threat to releasing ranavirus into native populations.
    • Infect fish without killing them, potentially leading to viral persistence and spread of infections.
    • Humans have both directly and indirectly increased ranaviral dz in amphibians, reasonable to consider similar case for reptiles.

Question 41

What are the two amphibian herpesviruses?

Describe their effects.

What are the inclusion bodies?

Answer 41

• Ranid herpesvirus 1 (RaHV-1)
  
  • Cause of Lucke’s renal adenocarcinoma.
  • Cooler winter temps <7C permissive for replication.
  • Proliferation of neoplastic cells minimal during that time.
  • In contrast, when temps are warmer the calid phase begins with increased proliferation of neoplastic cells and great reduction in viral replication.
    
    • Mets during calid phase may go to the liver.
    • Viral shedding occurs in spring, during spawning, offspring become infected.
    • CS – Emaciation, hydrocoelom, hydrops related to renal failure.
      
      • Coeliocentesis may yield neoplastic cells.
  • Cowdry type A intranuclear inclusion bodies typical of herpesvirus may be seen during the algid phase (winter months).
• Ranid herpesvirus 3 – Europe, gray to white coalescing skin lesions/vesicular.

Question 42

What is the usual etiologic agent of red leg syndrome?

Are any other bacterial involved?

What is an important viral differential?

Answer 42

• Red leg syndrome aka bacterial dermatosepticemia
  
  • Historically Aeromonas hydrophila
  • Other gram-negatives i.e. Pseudomonas aeruginosa, Elizabethkingia meningoseptica (Flavobacterium meiningosepticum), Klebsiella pneumonia, Crhyseabacterium indologenes.
  • Gram-positives i.e. Streptococcus inae.
  • CS – Cutaneous hyperemia, hemorrhage distributed on limbs, digits, ventral abdomen.
    
    • Ddx ranavirus!
    • May also see bloating from GI gas, hydrocoelom, hydrops, sudden death.
    • Typically multiple animals affected.
    • Culture of blood and internal organs of dead amphibians recommended.

Question 43

What are the most common mycobacteria to affect amphibians?

What are the typical signs?

How does infection occur?

How are these diseases best diagnosed?

What is the recommended management?

Answer 43

• Mycobacteriosis
  
  • Mycobacterium marinum.
  • M. chenolae, M. fortuitum, M. xenopi, M. ranae, M. ulcerans, M. liflandii.
  • Chronic subclinical infections become lethal with immunosuppression.
  • Adult animals.
  • Nodules, abscesses, effusion, coelomitis.
  • Demonstration of acid-fast bacteria with inflammatory lesions.
    
    • Fite’s stain more reliable for aquatic mycobacteria on histo.
    • If Acid-fast bacteria detected, samples should be submitted for culture or PCR and identification.
      
      • Speciation important since some spp have more zoonotic potential.
  • Infection occurs through direct contact with infected cohorts, consumption of infected organisms, exposure to infected water.
  • Can remain subclinical for long periods of time.
  • CS typically includes weight loss despite a good appetite.
  • Immediate euthanasia is recommended because tx is ineffective, and the diseases are likely to be zoonotic.
    
    • Removal and euthanasia of infected individuals is required to control the spread throughout the colony and prevent infection of human handlers.

Question 44

What brucella organism is commonly isolated in amphibians?

What are the lesions found with this infection?

Answer 44

• Brucellaceae
  
  • Gram-negative facultatively intracellular bacteria
  • Abscesses, spinal arthropathy with enlarged intervertebral joints, pyogranulomatous inflammation.
  • B. inopinata-like organisms readily isolated.

Question 45

What chlamydial organism commonly affects amphibians?

Is there a species that is especially susceptible?

What are the typical clinical signs?

How is this diagnosed?

What might you see on histology?

What is the treatment of choice?

Answer 45

• Chlamydia (Chlamydophila) pneumoniae
  
  • African clawed frogs
  • Chlamydia psittacii
  • C. pneumoniae.
  • Amphibians may be reservoir hosts.
  • CS – cutaneous hyperemia, excessive shedding of skin, SQ edema, hepatosplenomegaly.
  • Dx PCR.
  • Large intracytoplasmic granular basophilic inclusions – Common in spleen or liver.
  • TEM – Characteristic elementary and reticulate bodies.
  • Tx – Doxycycline drug of choice, although tetracycline may be effective.

Question 46

An aquatic caecilian presents with white-fuzzy growths over its skin. What is your primary differential?

How does temperature affect the incidence of this organism?

How is it diagnosed?

How can it be treated?

Answer 46

• Saprolegnia
  
  • Primarily aquatic amphibians, caused by 20+ spp of fungi.
  • Opportunistic, following skin trauma or low environmental temps, high environmental organic loads, or poor water quality i.e. high ammonia.
  • Cottonlike, covers underlying cutaneous ulcers.
  • Acute infections characterized by light-colored fungal mats, more chronic infections may turn green with algae or brown as debris is trapped in the fungal strands.
    
    • Secondary bacterial infections may occur.
  • Incidence markedly decreases at water temps over 68F (19C).
  • Wet mounts of cotton mat reveals fungal hyphae.
    
    • Thin-walled, nonseptate, usually nonbranching hyphae.
    • Stain poorly with PAS and well with GMS.
    • Postmortem overgrowth should be considred.
  • Tx – Salt, itraconazole, or benzalkonium baths.
  • Topical miconazole, dilute benzalkonium chloride, malachite green for isolated lesions.

Question 47

Describe the effects of amphibian chromomycosis.

What are the lesions typically seen?

How does this disease differ from saprolegniasis?

What is the recommended management?

Answer 47

• Chromomycosis
  
  • Light-tan or gray to dark raised nodules.
  • Signs of debilitation, weight loss.
  • Presumptive dx based on finding pigmented fungi in wet mounts.
  • Tendency to become systemic, unlike saprolegniasis.
  • Chromomycotic granulomatous lesions throughout viscera.
  • Tx unrewarding.
  • Euthanasia is recommended for infected amphibians due to zoonotic potential.

Question 48

How do the fungal diseases caused by fusarium, mucro, and rhizopus appear in amphibians?

What differentials should be considered?

Answer 48

• Fusarium spp, zygomycetes (Basidiobolus ranarum, Mucor spp, Rhizopus spp).
  
  • Similar gross findings to chytrid and chromoblastomycosis, ranaviriosis, red leg.
  • Fusarium hyphae typically slender with parallel walls, frequent separation.
  • Mucor hyphae are wide and infrequently septate.
    
    • Mucor amphibiorum, disseminated mycosis in Australian anurans.

Question 49

What microsporidian commonly affects amphibians?

What species is especially susceptible?

What is the recommended treatment?

Answer 49

• Microsporidiosis.
  
  • Pleistophora myotrophica – Myositis, high mortality in Eu common toads.
    
    • White discoloration and streaking of pectoral, abdominal, femoral musculature.
    • Tx with chloramphenicol sodium succinate ICe in combo with topical oxytet and polymyxin B appeared effective.

Question 50

What are the two etiologic agents causing chytridiomycosis in amphibians?

Compare host range, clinical signs, and gross lesions.

What are some possible environmental sources of chytrid.

How does it affect tadpoles?

Answer 50

• Etiological agents – Batrachochytrium dendrobatidis (Bd), Batrachochytridium salamandrivorans (Bs).
  
  • Both are intracellular pathogens of keratinocytes.
  • Life cycle is simple:
    
    • Intracellular fungal bodies (thalli) mature to form zoosporangia containing infective flagellated zoospores.
• Bd – OIE reportable
  
  • Broad host range, infects 520+ spp.
    
    • Anurans, caudates, and caecilians.
      
      • Panamanian golden frogs highly susceptible.
    • Global distribution linked to international movement of amphibs for research and pet trade. Asia proposed origin.
  • Grows on sterile bird feathers and arthropod exoskeletons, keratinous paw scales of waterfowl, GIT of crayfish.
    
    • Crayfish = Potential nonamphibian vector for Bd.
  • Motile zoospores can swim and infect cohorts.
  • Bd feeds on keratin, anurans with keratinized skin usually affected more than tadpole, which only have keratinized mouthparts.
  • CS – Sudden death with no obvious signs to progressive lethargy, excessive shedding, ventral erythrma and petechiation, deformities of keratin beaks in tadpoles, cutaneous lesions on tips of toes.
    
    • Shedding numerous small discolored skin fragments rather than large translucent to white sheets that are normally shed.
  • Gross lesions – Skin in postmetamorphic amphibs and keratinized mouthparts in larval anurans.
    
    • Hyperplasia, excessive shedding, necrosis of digits/feet, dehydration, lethargy, abnormal behavior. Depigmentation of tadpole mouthparts.
• Bs (first described 2013)
  
  • Restricted to salamanders and newts.
    
    • Near-extinction of the fire salamander, Salamandra salamandra in the Netherlands.
  • Found in Europe, Asia. NOT North America.
  • CS – Skin erosions all over the body, ataxia, anorexia, death within 7 days of infection.
  • Gross lesions – Multifocal superficial erosions and extensive epidermal ulcerations, excessive shedding of skin, anorexia, apathy, ataxia, death.

Question 51

Describe the diagnosis of chytridiomycosis.

What is the most sensitive test?

What is the recommended sampling protocol?

What lesions are found on histopathology?

Answer 51

• Dx confirmation
  
  • Cytology – Detection of zoosporangia provides rapid diagnosis.
    
    • Biopsies of drink patch or toe tips often productive.
  • PCR or qPCR can be done on skin swabs from mouthparts of live anuran larvae and from the ventral pelvic patch, hind legs, and feet of live postmetamorphic, fresh dead, frozen, or ethanol-preserved postmetamorphic amphibs.
    
    • PCR even more sensitive than histo or wet mount exams.
    • Newly developed PCR for Bs.
  • Histo
    
    • Bd = Multifocal hyperplastic and hyperkeratotic dermatitis, sloughing of keratin, numerous fungal zoosporangia.
      
      • Epidermal hyperplasia and orthokeratotic hyperkeratosis with intracellular chytrid thalli within the straum corneum.
    • Bs = Erosive skin lesions associated with presence of numerous intracellular colonial thalli that spreads over the epidermis with marked necrosis of the adjacent keratinocytes.
      
      • Hyperplasia and hyperkeratosis ABSENT.
      • Multifocal necrosis of keratinocytes associated with numerous chytrid-type fungal thalli.
      • Prominent necrosis with development of erosions and ulcers as well as frequent thalli with multiple internal septa should raise suspicion for Bsal.
    • Zoosporangia can be found intracellular within keratinocytes.
  • EM, IHC.

Question 52

Describe the treatment of chytridiomycosis.

What drugs have been used?

How can temperature be used as treatment?

What disinfectants are effective?

What quarantine precautions should be taken?

Answer 52

• Tx/prevention
  
  • Itraconazole baths
    
    • 0.01% in 0.6% saline 5 minutes daily for 11 consecutive days.
    • Safe and effective tx in most situations, different concentrations and durations reported.
  • Voriconazole baths/sprays
    
    • 125 mg/L for 7 days.
    • Used in a few species, effectively treated a salamander.
  • Chloramphenicol bath
    
    • Effectively treated green tree frogs.
  • Terbinafine dissolved in ethanol and diluted for bath
    
    • Popular treatment, commercially available as athlete’s foot spray.
  • Increased temps
    
    • Effective for some spp, gradual increase in environmental temp over a period of two days, then maintained at that temp, up to 10 consecutive days reported.
    • Elevating temp to 25C for 10 days has been effective for Bs.
• Disinfectants that effective kill Bd:
  
  • Virkon – Ozone (potassium peroxymonosulfate), sodium dodecylbenzenesulfonate, sulfamic acid, and inorganic buffers at 2 g/L.
  • Dilute bleach (4%).
• Quarantine recommendations: at LEAST 2 months (60 days).
  
  • PCR on arrival and 7 weeks later.

Question 53

What is the amphibian lungworm?

Describe its life cycle.

What are teh gross and histological findings?

How should affected amphibians be treated?

Answer 53

• Rhabdias spp (fam Rhabdiasidae) – Amphibian lungworm (40+ spp).
  
  • Free-ranging and captive anurans and caudates.
  • Direct LC.
    
    • Hermaphroditic adults in lung produce eggs or larvae that are swallowed and pass through the GIT, shed in feces.
    • In environment, larvae develop into male and female adults, mate to produce infective larvae that penetrate the skin of the host and migrate internally to the lung.
  • Gross – Mottled white-black worms within the airway lumen of lungs.
  • Histo – Scant platymyarian musculature, vacuolated lateral chords, uterus with developing larvae, intestinal tract containing abundant dark pigmented material.
  • Embryonated eggs or larvae can be seen in fecals or tracheal wash specimens. Fecal parasite or oropharyngeal mucus exams.
  • Ddx – digenetic trematodes genus Haematoloechus, monogenean trematodes genus Pseudodiplorchis.
  • Infected amphibians should be isolated and strict hygiene practiced, preventing spread to other amphibians or superinfection of the original animal.
  • Baths with ivermectin or levamisole weekly for 12+ weeks may be needed to reduce or eliminate Rhabdias spp.

Question 54

How do strongyloides species affect amphibians?

What makes this parasite so difficult to control?

How can this be treated?

Answer 54

• Strongyloides spp – Proliferative enteritis in free-ranging and captive anurans.
  
  • Direct LC.
  • Larvated eggs or adults observed in fresh fecals.
  • May cause severe intestinal lesions, PLE and generalized malnutrition.
    
    • Oral fenbendazole and levamisole applied o the pelvic patch has been used to decrease both Strongyloides and Rhabdias.

Question 55

What is the capillarid nematode that affects amphibians?

What species is particularly susceptible?

What are the lesions?

How is this diagnosed?

How should these frogs be treated?

Answer 55

• Capillarid nematode – Pseudocapillaroides xenopi.
  
  • Infects epidermis of free-ranging and captive African clawed frogs.
  • Excessive skin shedding and roughening, discoloration of the skin surface and multifocal cutaneous erosions or ulcers.
  • Heavy infections cause a wasting syndrome.
  • Bioperculate eggs.
  • Larvated eggs within the uterus of the female is a feature unique to this species.
  • Dx – Eggs or adults on histo or wet mount of shed skin fragments or skin scrape, PCR.
  • Cutaneous hemorrhage and exfoliation, nematodes and ova can be found in mucus and skin scrapings.
  • Tx with thiabendazole PO and levamisole SQ or ivermectin and levamisole baths effective.

Question 56

What digenean flatworms affect amphibians?

How do these affect them?

Answer 56

• Digenetic trematodes
  
  • Clinostomum marginatum – Head of red spotted newts, interferes with feeding.
  • Encystment of metacercariae of Ribeiroia ondatrae within limb buds of anurans assoc with limb malformations.
  • Digeneans in genus Haemotoloechus common in lungs of anurans.
  • Gorgoderid digenetic trematodes of genera Gorgoderina and Phyllodistomum inhabit Wolffian ducts and UB of anurans and caudates, subclinical infections.
  • Praziquantel has been used in many amphibian spp without ill effects, may eliminate adult and larval trematodes and cestodes.

Question 57

What myxozoans affect amphibians?

What lesions occur as a result?

Answer 57

• Myxozoans
  
  • Genus Cystodiscus develop spore-forming plasmodia in gallbladder of anurans, caudates, caecilians. Incidental.
  • Most renal myxozoa are also incidental but fatalities have been reported.
    
    • Frog kidney enlargement disease caused by Hoferellus anurae occurred in wild-caught African hyperoliid frogs.

Question 58

Describe the effects of the following protozoal infections in amphibians:

Tetrahymena

Trypanosoma ranarum

Cryptosporidiosis

Coccidiosis

Answer 58

• Protozoa
  
  • Opalinids, flagellates, ciliates normal commensals in GIT of amphibians.
  • Trichodina incidental on wet mounts, skin, gills.
  • Tetrahymena invasive to skin and muscle, disseminate to visceral organs of tadpoles.
    
    • Frequent water changes and improved sanitation and filtration may help eliminate ciliated protozoa in aquatic amphibians.
  • Trypanosoma ranarum flagellates incidental on blood smears.
    
    • Quinidine therapy may be used with signs of anemia.
    • Sudden death may occur, splenomegaly common post mortem, trypanosomes can be seen on impression smears of spleen.
  • Cryptosporidiosis – apicomplexan.
    
    • Cryptosporidium fragile colonizes superficial gastric epithelium of black-spined toads.
    • Wt loss, mild gastric epithelial hyperplasia without assoc inflammation.
    • Oral tetracyclines and paromomycin sulfate may be warranted with high densities of ciliated protozoa in feces or gastric washes.
  • Variety of apicomplexans – Hematozoon spp, Lankesterella spp.
  • Intestinal coccidiosis – Eimeria, Isospora, Goussia spp. Not significant.

Question 59

What entamoeba species affects amphibians?

What are teh clinical signs?

How is this diagnosed and treated?

Answer 59

• Entamoeba ranarum – GIT commensal, dz rare.
  
  • Transmission via ingestion of cysts.
  • Direct LC, rapid spread within collection.
  • Cysts durable in environment, are ingested, then trophozoite stage excysts to mature in the colon.
  • Directly attack colonic mucosa, liver and kidneys can be infected.
  • CS – Anorexia, dehydration, wasting.
  • Stools change in consistency – liquid, tinged with blood.
  • Dx – Accurate ID of cyst or trophozoite from fecal sample or colonic wash.
  • Direct for active trophozoites, cysts found on direct smears or with floats.
  • Detection of cyst may be enhanced with Lugol’s iodine.
  • 4-16 nuclei.
  • Tx – Metronidazole 50 mg/kg PO q14 days or daily for 3-5 days with fluid therapy. Decrease dose if animal starts showing neuro dz.

Question 60

What venipuncture sites can be used in amphibians? Describe for anurans, caudatans, and ceacilians.

What is the preferred anticoagulant?

Do amphibians have neutrophils or heterophils?

Answer 60

• Clinical techniques:
  
  • Fluid samples with low TP and low cell counts lacking cytologic evidence of infection more likely to be associated with organ dysfunction or physiologic and environmental factors.
  • Frog blood volume considered 10%; 10% withdrawn safety from healthy frogs and 5% from ill frogs. 0.5 mL can be taken from a 10 gram frog.
  • Venipuncture (Anuran):
    
    • Lingual venous plexus.
      
      • Avoid breaking mandible.
      • CTA used to draw the tongue forward.
      • Vessels on underside of tongue and buccal floor.
      • Puncture with needle and use a HCT tube to draw blood up.
      • Samples can be contaminated with saliva and mucus.
    • Ventral (midline) abdominal vein
      
      • Insert needle cranio-dorsal, midway between sternum and pelvis.
    • Femoral vein, cardiocentesis (visualize, penetrate apex of ventricle).
  • Venipuncture (Caudate) – Ventral tail vein, ventral abdominal vein (if sedated, otherwise concern with autotomy), cardiocentesis.
  • Venipuncture (Caecilians) – Cardiocentesis.
  • Lithium heparin preferred anticoagulant.
    
    • Does not affect the values of plasma calcium, dosium, or ammonia.
    • EDTA lyses RBCS.
    • Ammonium heparin gives falsely elevated NH3 levels.
    • Sodium heparin should be avoided for evaluation of electrolytes.
  • Blood smears should be made immediately.
    
    • Preheparinize syringes may lead to lower and inconsistent values.
    • CBC performed same as avian and reptile spp.
    • Amphibians have neutrophils (peroxidase-positive).
    • Natt & Herrick’s solution or “eosinophil indirect method” i.e. Avian Leukopette to count granulocytes (only recommended in spp it has been verified for).
    • N:L ratio positively correlates with corticosterone.
    • Because of presence of injured epithelial cells after handling, amphibian monocyte counts may show a relative and absolute increase on subsequent leukocyte profiles.
    • Slender salamanders (genus Batrachoceps) – Majority of erythrocytes are anucleate in normal individuals.
    • Rickettsiae, parasites, and viral inclusions may be detected on smears.
      
      • Trypanosomes, microfilariae are extraerythrocytic.
      • Hemogregarines are intraerythrocytic.
      • Low levels probably not clinically significant.
    • Normal blood values may be influenced by environmental conditions, life cycle stage, nutrition, other variables.
  • Lymph can be used for biochemistry analysis.

Question 61

List some differentials for acute mortalities in amphibians.

Answer 61

• Acute mortalities
  
  • Most commonly due to infectious dz, sudden environmental change, or toxins.
    
    • Chytrid, ranavirus, lungworm, bacterial septicemia.
    • Tank flooding or drying, temp changes.
    • Chloramine, chlorine, ammonia, bleach, insecticides.
  • Bd often causes death without clinical signs.
  • Ranaviruses implicated in mass mortality events – hemorrhages, edema.
  • Septicemia usually gram-negatives, gram-positives also.
    
    • Atypical myco and chlamydophila result in chronic granulomatous dz.

Question 62

List some differentials for coelomic distension in amphibians.

Answer 62

• Coelomic distension
  
  • Fluid or soft tissue (ova, fat), or rarely gas.
  • Hydrocoelom/lymphedema
    
    • Coelomic cavity effusion – hydrocoelom.
    • Generalized lymphatic system swelling – lymphedema.
      
      • Rounded appearance over pelvis, loss of linea alba, exophthalmos, limb swelling.
    • Major causes include cutaneous lesions, infectious dz, renal or hepatic disease, environmental problems.
      
      • Chytrid, ranavirus, bacterial septicemia.
        
        • Cytology or histo and PCR can differentiate.
        • Cytology, culture and susceptibility of fluid.
    • Renal disease common.
      
      • Infectious dz capable of direct renal damage include local or systemic bacterial, viral, fungal agents i.e. mucormyosis, chromomycosis, zygomycosis, myxozoan and microsporidial parasites.
      • Noninfectious causes of renal dz – Dehydration, neoplasia, nutrition (oxalates, high protein, hypovit A), and toxins (aminoglycosides, heavy metals, polyvinyl chloride glue).
    • Hepatic disease via hepatocyte necrosis, impaired intrahepatic circulation, low plasma protein levels.
    • Inappropriate husbandry – exposure to cool temps has been associated with transient hydrocoelom, resolves without intervention.
  • Obesity – Coelomic cavity often firm on palpation.
  • Repro activity – egg masses, may be retained until suitable environmental cues are received.
    
    • May have focal edema around the upper thighs.
  • Impaction, FBs – Gas accumulation can be severe, bacterial overgrowth can lead to sepsis.
    
    • Ocular dz may predispose consumption of foreign material.
  • Organomegaly – Neoplasia and granulomatous disease.
    
    • Lymphoma, GI carcinomas, nephroblastomas, sertolic cell tumors, pancreatic carcinomas.
    • Focal granulomatous lesions.
    • Atypical myco, chlamydiosis, fungal infections most commonly reported cause of granulomas.

Question 63

List some differentials for the following gastrointestinal signs:

Tissue prolapse

Diarrhea

Answer 63

• GI signs.
  
  • Tissue prolapse.
    
    • Intestinal, urinary, or repro.
    • Cloacal tissue generally small, smooth, pink.
    • Colon smooth to ridged with tubular appearance.
      
      • Central lumen or feces may be visible on impression smear.
    • UB rounded with thin wall and fluid contents.
    • Oviduct includes narrow, coiled tubules, may have longitudinal lines and eggs.
    • Cloacal and colon prolapses most common followed by UB.
    • Common causes of prolapse – Parasitism, intussusception, GI FB, neoplasia, septicemia, toxemia, dehydration, extraluminal GI blockage i.e. renal neoplasia, toxins, hypoglycemia, hypocalcemia, malnutrition.
    • Tissue impression smears and FNA of tissue may help ID.
    • Iatrogenic gastric prolapse has been reported in leopard frogs ax with clove oil, resolves during recovery.
  • Diarrhea – Differentiate from polyuria.
    
    • Inappropriate temp, humidity, diets high in carbs.
    • Amoebiasis, coccidiosis, some metazoans i.e. Strongyloides, Acanthocephalus ranae.
    • Ciliates typically nonpathogenic.
    • Mucor amphibiorum can be primary cause of gastroenteritis.
    • Ranaviruses can cause intestinal distension and hemorrhage, diarrhea.

Question 64

Describe differences in bone mineralization observed in European common spadefoots in regards to UVB exposure and Vit D supplementation - Adults vs juveniles?

Answer 64

EVALUATION OF BONE MINERALIZATION BY COMPUTED TOMOGRAPHY IN WILD AND CAPTIVE EUROPEAN COMMON SPADEFOOTS (PELOBATES FUSCUS), IN RELATION TO EXPOSURE TO ULTRAVIOLET B RADIATION AND DIETARY SUPPLEMENTS

van Zijll Langhout M, Struijk RP, Könning T, van Zuilen D, Horvath K, van Bolhuis H, Maarschalkerweerd R, Verstappen F.

Journal of Zoo and Wildlife Medicine. 2017 Sep;48(3):748-56.

Highest Hounsfield units (HU) in:

Adults with dietary supplementation (no UVB) than those with only UVB

Juveniles with only UVB (no dietary supplementation) compared to only dietary supplementation (no UVB)

Adults (nocturnal) can get sufficient vitamin D from diet, while juveniles rely on UVB radiation

Conclusion: CT is a practical tool for assessing bone mineralization in European common toads, and European common toad adults are not dependent on UVB for vitamin D3 and juveniles are more dependent on access to UVB radiation.

Question 65

What was observed in bullfrogs administered alfaxalone vs propofol?

Answer 65

Cardiovascular effects of alfaxalone and propofol in the bullfrog, Lithobates catesbeianus.

Williams CJ, Alstrup AK, Bertelsen MF, Jensen HM, Leite CA, Wang T.

Journal of Zoo and Wildlife Medicine. 2018 Mar;49(1):92-8.

Alfaxalone at 10 mg/kg caused:

Sedation and loss of righting reflex

Decreased respiratory rate

Increased heart rate (> 60 min when IV)

Increased MAP (decreased after 10 min IV)

Did not provide analgesia (no loss of noxious stimulus response)

Propofol IV caused increased MAP only for first 5 minutes

No change to heart rate

Alfaxalone 10mg/kg IM pilot - loss of RR within 5min, loss of muscle tone 10min, recovery at 60min, no loss of nociception (toe pinch), RR declined , HR stable

Conclusions: Alfaxalone at 10 mg/kg IV or IM in bullfrogs caused an increase in heart rate and a transient increase in MAP, while propofol only transiently increased MAP.

Question 66

Describe what was observed in dart frogs administered ketamine midaz dexmed vs alfaxalone midaz dexmed SC.

Answer 66

Comparison of subcutaneous administration of alfaxalone–midazolam–dexmedetomidine with ketamine–midazolam–dexmedetomidine for chemical restraint in juvenile blue poison dart frogs (Dendrobates tinctorius azureus)

Yaw TJ, Mans C, Martinelli L, Sladky KK. .

Journal of Zoo and Wildlife Medicine. 2020 Jan;50(4):868-73.

Ketamine-midazolam-dexmedetomidine caused:

Sawhorse stance/more limb rigidity (more pronounced after antagonists delivered)

Decreased heart rate (min 20 -50)

Increased respiratory rate

Alfaxalone-midazolam-dexmedetomidine caused decreased respiratory rate and heart rate (min 15-50)

Both protocols caused loss of righting reflex, similar recovery times, and some gastric prolapse

Gastric prolapse more prevalent in AMD group

Conclusions: Ket-midaz-dexmed decreased HR, increased RR, and caused limb rigidity. Alfax-midaz-dexmed decreased HR and RR; some gastric prolapse (AMD > KMD)

Question 67

What was observed in white’s tree frogs anesthetized with MS-222 at 0.5 g/L or 2 g/L?

Answer 67

Anesthetic Efficacy of MS-222 in White’s Tree Frogs (Litoria caerulea)

Krisp AR, Hausmann JC, Sladky KK, Mans C.

Journal of Herpetological Medicine and Surgery. 2020 Jan;30(1):38-41.

MS-222 at 0.5 g/L produced light sedation and loss of palpebral reflex in most frogs

Corneal and righting reflexes were present in all frogs

MS-222 at 2.0 g/L produced surgical anesthesia within 20 min with all reflexes lost except corneal reflex

Time dependent decreased in heart rate

Dose and time dependent respiratory depression.

Concentration for MS-222 to produce general anesthesia much lower in leopard frogs (0.4 g/L)

Conclusions: In White’s tree frogs, MS-222 at 0.5 g/L produces sedation but 2 g/L produces general anesthesia with time dependent decrease in heart rate and dose and time dependent respiratory depression.

Question 68

What is an important anatomical feature of mountain chicken frogs to keep in mind for anesthesia?

Answer 68

Inhalatory isoflurane anesthesia in mountain chicken frogs (Leptodactylus fallax).

Barbon AR, Routh A, Lopez J.

Journal of Zoo and Wildlife Medicine. 2019 Jun;50(2):453-6.

Bag with frog filled with 5% iso and O2.

Intubated with 2.5-3.5mm cuffed tubes that were shortened and maintained on gas anesthesia for surgery.

ETT was inflated PRIOR to placement in the trachea so that it sealed off the larynx. Ventilated manually

Heart rate decreased over time

Mtn Ckn frogs do not have a trachea or bronchi. Larynx is directly connected to lung

Conclusions: You can provide inhalant anesthesia via a modified endotracheal tube in a mountain chicken frog.

Question 69

How did Bd exposure of American toads, N Leopard Frogs, and Cricket Frogs affect survival and growth, and how did food availability influence survival and growth in those species?

Answer 69

Lethal and sublethal amphibian host responses to batrachochytrium dendrobatidis exposure are determined by the additive influence of host resource availability.

Rumschlag SL, Boone MD.

The Journal of Wildlife Diseases. 2020 Apr;56(2):338-49.

Mortalities from Bd were typically within 24 hours, sooner if low food

BD exposure and low food availability combined led to:

Lowest survival rates in American toads

Lowest growth rates in northern leopard frogs

BD exposure did not influence survival of northern leopard frogs and cricket frogs

Cricket frogs were unaffected by BD exposure

Conclusions: Bd and low food availability influence survival of the American toad and growth of the northern leopard frog. Bd did not influence either in the cricket frog.

Question 70

Which group of salamanders died acutely following infection with Bd? Aneides spp vs Eurycea spp

Answer 70

BATRACHOCHYTRIUM DENDROBATIDIS IN A CAPTIVE COLLECTION OF GREEN SALAMANDERS (ANEIDES AENEUS), LONG-TAILED SALAMANDERS (EURYCEA LONGICAUDA), AND TWO-LINED SALAMANDERS (EURYCEA BISLINEATA)

Bauer KL, Steeil JC, Walsh TF, Evans MJ, Klocke B, Gratwicke B, Siegal-Willott JL, Neiffer DL.

Journal of Zoo and Wildlife Medicine. 2018 Jun;49(2):454-9.

First salamander found dead acutely without clinical signs, three others died during treatment

Diagnosed via cytology and histopathology (dermatitis and hyperkeratosis with visible chytrid)

Treated other Eurycea spp. salamanders with 0.01% itraconazole baths and had no mortalities

Chytrid swabbing protocol = ventral surface 10x + each foot 5 times

Conclusions: Difference in mortality and fungal load suggests Aneides sp. may be more susceptible to Bd than Eurycea sp.

Question 71

Describe the seasonality in Bd detection in amphibians in central OK, USA

Answer 71

SEASONALITY IN BATRACHOCHYTRIUM DENDROBATIDIS DETECTION IN AMPHIBIANS IN CENTRAL OKLAHOMA, USA

Watters JL, McMillin SL, Marhanka EC, Davis DR, Farkas JK, Kerby JL, Siler CD.

Journal of Zoo and Wildlife Medicine. 2019 Jun;50(2):492-7.

Key Points:

42% were positive, none had clinical signs

Most common positives: Blanchard’s cricket frog, American bullfrog, southern leopard frog

Highest loads found on Anaxyrus woodhousii, Gastrophryne olivacea, Pseudacris fouquettei

Prevalence highest in FALL > spring > summer

Conclusions: Highest prevalence of Bd was in the FALL then spring. Positive PCR were negative for lesions. More rainfall = higher prevalence. Blanchard’s cricket frog was the most common positive (of the species that had >10 animals caught)

Question 72

Describe Bd prevalence at human-made sites vs natural sites? Did this influence community composition of frogs?

Answer 72

Higher Infection Prevalence in Amphibians Inhabiting Human-made Compared to Natural Wetlands

Spencer R. Siddons, Marin C. Bray, and Catherine L. Searle

Journal of Wildlife Diseases, 56(4), 2020, pp. 823–836

Anthropogenic practices can decrease Bd growth and transmission of Bd:

Increased salinity

pH <4 or >8

Pesticides

Increased or decreased water temp (optimal range for Bd is 17-25*C)

Habitat loss in tropics (due to increased temps from less canopy cover?)

Key Points:

Bd prevalence higher at human-made sites than natural

No difference in frog dentistry community composition

Conclusions: Human-made wetlands may play a role in sustaining frog communities, but may also pose a higher risk for Bd infection than natural wetlands.

Question 73

How did ranavirus detection prabability differ in tail samples vs livers?

Answer 73

Estimating occurrence, prevalence, and detection of amphibian pathogens: Insights from occupancy models.

Mosher BA, Brand AB, Wiewel AN, Miller DA, Gray MJ, Miller DL, Grant EH.

Journal of wildlife diseases. 2019 Jul;55(3):563-75.

Background:

Ranavirus (an iridovirus) = generalist pathogen linked to die-offs of amphibians in US

Larval amphibians especially susceptible

Affinity for vascular endothelial cells

Key Points:

pH does not affect ranavirus prevalence

Ranavirus detection probability was higher (6.7x higher odds of detection) in tail samples than livers

Ranavirus prevalence high for wood frogs than for spotted salamanders in Maryland

Conclusions: Can monitor non-lethally for ranavirus with PCR on tail clips.

Question 74

What pathology has been associated with brucella spp infections in amphibians?

Answer 74

Clinicopathologic features of infection with novel Brucella organisms in captive waxy tree frogs (Phyllomedusa sauvagii) and Colorado River Toads (Incilius Alvarius)

Helmick KE, Garner MM, Rhyan J, Bradway D.

Journal of Zoo and Wildlife Medicine. 2018 Mar;49(1):153-61.

Key Points

Novel Brucella infection in amphibians, caused femoral osteomyelitis, SQ and renal abscesses, sepsis.

No single organ system involved in all cases, no repro pathology

SQ abscessation more specific sign, otherwise vague (color changes, lethargy, anorexia, wt. loss)

Treatment with systemic enro, surgical removal of localized lesions, chloramphenicol baths effective in some cases

Need PCR to differentiate from Ochrobactrum anthropi

Potential zoonotic risk, host species, geographic range, etc. not known for Brucella isolates from amphibians

Take home message: Brucella species have been identified in amphibians, cause osteomyelitis, SQ and renal abscesses, sepsis.

Question 75

What pathogen was associated with internal granulomas and gallbladder empyema in a population of Chinese gliding frogs?

Answer 75

Mycobacteriosis in a Zoo Population of Chinese Gliding Frogs (Rhacophorus dennysi) Due to Mycobacterium marinum

Milnes EL, Delnatte P, Lentini A, May K, Ma J, Jamieson FB, Slavic D, Smith DA.

Journal of Herpetological Medicine and Surgery. 2020 Jan;30(1):14-20.

Cases: Symptomatic and asymptomatic Chinese gliding frogs with internal granulomas diagnosed with M. marinum

Clinical signs: gallbladder empyema (n=2), found dead (n=2), dermal lesions (ulcerative or proliferative)

Pneumonia (n=4) and internal granulomas (all)

GenoType Mycobacterium CM assay incorrectly assigned isolate as MtbC due to cross reaction

Sequencing correctly identified it as M. marinum

Most common Mycobacterium spp in amphibians: M. marinum, M. fortuitum, M. ulcerans, M. xenopi

No reports of Mycobacterium tuberculosis complex

Conclusions: M. marinum caused death, dermal lesions, gallbladder empyema, or no clinical signs in Chinese gliding tree frogs.

Question 76

Name two dz of anurans that are reportable to the OIE. What diagnostics are recommended by the OIE?

Answer 76

DETECTION AND REPORTING OF RANAVIRUS IN AMPHIBIANS: EVALUATION OF THE ROLES OF THE WORLD ORGANISATION FOR ANIMAL HEALTH AND THE PUBLISHED LITERATURE

Black Y, Meredith A, Price SJ.

Journal of wildlife diseases. 2017 Jul;53(3):509-20.

Ranavirus and chytridiomycosis are reportable to the OIE

Ranavirus = iridovirus with patchy global distribution and broad host ranges (amphibians, reptiles, fish)

OIE recommends sequencing all PCR positive results

Does not recommend qPCR

Conclusions: Ranavirus is an OIE-reportable disease and PCR positives should be sampled.

Question 77

What pathogen has been associated with toe lesions in hellbenders? Which pathogen was most prevalent during a survey in TN?

Answer 77

GEOGRAPHIC AND INDIVIDUAL DETERMINANTS OF IMPORTANT AMPHIBIAN PATHOGENS IN HELLBENDERS (CRYPTOBRANCHUS ALLEGANIENSIS) IN TENNESSEE AND ARKANSAS, USA.

Hardman RH, Sutton WB, Irwin KJ, McGinnity D, Reinsch SD, Freake M, Colclough P, Miller BT, Da Silva Neto JG, Souza M, Fitzpatrick B.

Journal of Wildlife Diseases. 2020 Oct;56(4):803-14.

Background:

Batrachochytrium dendrobatidis is associated with amphibian mass mortality and extinctions

Batrachochytrium salamandrivorans is highly lethal to salamanders

Hellbender = fully aquatic salamander with declining populations

Reported Bd mortalities in captive individuals (50% mortality in a head start program)

Ranavirus causes vascular and epithelial damage

Chinese giant salamander with ranavirus often have swollen digits and necrosis

Key Points:

Bd and ranavirus were found in all regions (Bd > ranavirus)

No Bsal

No correlation with lesions and Bd zoospore load

Some recaptured individuals had cleared Bd

Toe lesions were seen in many hellbenders

Some associated with increased ranavirus prevalence

Ranavirus correlated with lower BCS

Highest ranavirus load in middle TN

Conclusions: Bd and ranavirus are found in hellbender habitats. Wild hellbenders commonly have toe lesions.

Question 78

What were the most common causes of mortality in captive panamanian golden frogs at the MD zoo?

Answer 78

CAUSES OF MORTALITY IN CAPTIVE PANAMANIAN GOLDEN FROGS (ATELOPUS ZETEKI) AT THE MARYLAND ZOO IN BALTIMORE, 2001–2013

Eustace R, Wack A, Mangus L, Bronson E.

Journal of Zoo and Wildlife Medicine. 2018 Jun;49(2):324-34.

Greatest number of deaths in younger frogs (201)

Most frogs found dead (rather than euthanized)

Most deaths during breeding season (Nov-May)

Energetically demanding; frogs focus solely on breeding and often do not feed during this period

Dermatitis was the most common cause of death: hyperkeratosis > ulcers > acanthosis > necrosis

Frequently associated with invasion by filamentous fungi (83.9%) like Zgomycetes and wartermolds

Kidney disease caused 8% deaths and present in 41% frogs

Clinical signs: hydrocooelom, lymphedema

One clutch has polycystic kidney disease

Lymphedema associated with renal disease, dermatitis, multifactorial, GI disease

GI disease deaths were caused by mycotic enteritis, rarely parasites

Tetany syndrome caused deaths in females

Hind limbs are rigid and fix in extension or held dorsally over the height of the back

Lacks a righting reflex

Conclusions: Panamanian golden frogs died most commonly from dermatitis. Tetany syndrome is seen only in females. Deaths are most common in the breeding season.

Question 79

What neoplastic lesion was common in a retrospective of mountain chicken frogs from Eu zoo collections?

Answer 79

A RETROSPECTIVE REVIEW OF POST-METAMORPHIC MOUNTAIN CHICKEN FROG (LEPTODACTYLUS FALLAX) NECROPSY FINDINGS FROM EUROPEAN ZOOLOGICAL COLLECTIONS, 1998 TO 2018

Ashpole IP, Steinmetz HW, Cunningham AA, Barbon A, Stidworthy MF, Garcia G, Sangster CR, López

Journal of Zoo and Wildlife Medicine. 2021;52(1):133-44.

Common findings in adult mountain chicken frogs in European zoos:

Low body condition score (most common in adult and captive-bred frogs0

Most common organ system = gastrointestinal tract

Most common process = intestinal inflammatory disease

Most common neoplasia = intestinal/colonic adenocarcinoma (27.2%!)

Associated with adhesions or fistula between colon and bladder

More common in older frogs

Enteric nematodiasis

Juvenile mountain chicken frogs had inflammatory disease or musculoskeletal trauma

Wild-born lived longer than captive-bred

Lucke’s renal carcinoma in leopard frogs associated with ranid herpesvirus 1

Conclusions: Mountain chicken frogs are susceptible to gastrointestinal inflammatory disease and intestinal/colonic adenocarcinoma.

Question 80

What was the most common site and type of neoplasia in an analysis of amphibian neoplasia case reports? What common treatment improved prognosis?

Answer 80

Analysis of Published Amphibian Neoplasia Case Reports.

Hopewell E, Harrison SH, Posey R, Duke EG, Troan B, Harrison T.

Journal of Herpetological Medicine and Surgery. 2020 Sep;30(3):148-55

Herpesvirus-induced, Luckes´ renal adenocarcinoma in wild northern leopard frogs

Most common tumors:

Chromatophoroma > lymphoma/leukemia > papilloma

50:50 benign:malignant, but chromatophoromas were malignant

Most common species: Xenopus and axolotls

Most common site: skin

Most common treatment: surgical excision

Improved prognosis

Conclusions: Most common tumor in frogs is a benign chromatophoroma.

Question 81

What was the most common cause of death in captive caecilians over a 10 yr retrospective?

Answer 81

POSTMORTEM FINDINGS IN EIGHT SPECIES OF CAPTIVE CAECILIAN (AMPHIBIA: GYMNOPHIONA) OVER A TEN-YEAR PERIOD

Flach EJ, Feltrer Y, Gower DJ, Jayson S, Michaels CJ, Pocknell A, Rivers S, Perkins M, Rendle ME, Stidworthy MF, Tapley B.

Journal of Zoo and Wildlife Medicine. 2020 Jan;50(4):879-90.

Question 82

What was observed in a study of MS-222 for euthanasia of smokey jungle frogs?

Answer 82

Immersion in tricaine methanesulfonate (MS-222) is not sufficient for euthanasia of smokey jungle frogs (Leptodactylus pentadactylus).

Balko JA, Posner LP, Chinnadurai SK.

Journal of Zoo and Wildlife Medicine. 2019 Apr;50(1):89-95.

Key Points:

Initial excitement phase

Death in 17/18 frogs in the study but is NOT sufficient for euthanasia

Took too long

Multiple episodes of regaining consciousness

Take home: MS-222 at the doses used did result in death of most of the frogs but took too long to be humane. Return of spontaneous movement occurred following submersion.

Question 83

How did TonoLab vs TonoVet compare for IOP measurement in white’s tree frogs measured in AM and PM?

Answer 83

MEASURING INTRAOCULAR PRESSURE IN WHITE’S TREE FROGS (LITORIA CAERULEA) BY REBOUND TONOMETRY: COMPARING DEVICE, TIME OF DAY, AND MANUAL VERSUS CHEMICAL RESTRAINT METHODS

Hausmann JC, Krisp A, Sladky K, Miller PE, Mans C.

J Zoo Wildl Med. 2017 Jun;48(2):413-419.

In amphibians, aqueous humor flows out of the iridocorneal angle into two ciliary venous sinuses instead of an episcleral venous plexus.

TonoLab = a rebound tonometer designed for the smaller cornea of rats

TonoLab higher than TonoVet in morning and midday

Diurnal variation in IOP has been reported (lower in the AM in bearded dragons)

Lower IOPs in manually restrained animals compared to unrestrained (with TonoVet)

Type II error or part of a “death feigning” response

Anesthesia with MS-222 was not a significant change

Anesthesia tends to decrease IOP in mammals due to reduced extraocular/adnexal muscle tone

Conclusions: In White’s tree frogs, diurnal variation in IOP, manual restraint decreases IOP, and anesthesia with MS-222 does not significantly affect IOP.

Question 84

What was the most common ocular abnormality in six spp of anura?

Answer 84

Common abnormalities = corneal lipid keratopathy, corneal fibrosis, cataracts, lenticular sclerosis

Lipid keratopathy common in mossy tree frogs, Mexican giant tree frogs, cuban tree frogs

May be related to diet , vitellogenesis, environmental

Cataracts were most common abnormality

Lower IOP in eyes with cataracts in giant waxy monkey tree frogs

Lenticular sclerosis was second most common finding; unrelated to IOP

Canine “d” setting significantly higher than “p” setting for most animals - when measuring IOP in anurans

Conclusions: Cataracts were most common abnormality and associated with lower IOP in giant waxy monkey tree frogs.

Question 85

What was observed in evaluation of plasma concentrations of ketoprofen and meloxicam after SC and topical administration in smoy jungle frogs?

Answer 85

Plasma concentrations of ketoprofen and meloxicam after subcutaneous and topical administration in the smoky jungle frog (Leptodactylus pentadactylus).

Balko JA, Watson MK, Papich MG, Posner LP, Chinnadurai SK.

Journal of Herpetological Medicine and Surgery. 2018;28(3-4):89-92.

Meloxicam only detected at the 3h time point with SQ injection and not detected at all after topical administration

Ketoprofen detected at 3h, 8h, 24h

Decline in ketoprofen over time was more variable in cutaneous route than SQ

Conclusions: Topical and SQ ketoprofen could be systemically detected, but topical and SQ meloxicam were not.

Question 86

What is the mechanism of itraconazole?

What was observed in panamanian golden frogs after topical itraconazole baths?

Answer 86

THE PHARMACOKINETICS OF TOPICAL ITRACONAZOLE IN PANAMANIAN GOLDEN FROGS (ATELOPUS ZETEKI)

Rifkin A, Visser M, Barrett K, Boothe D, Bronson E.

Journal of Zoo and Wildlife Medicine. 2017 Jun;48(2):344-51.

Key Points:

No adverse effects documented

0. 001% bath kept >MIC for 1 hour: likely too low a dose and frequent treatments would be required.
1. 01% bath did not ever leave the skin enough to calculate AUC

Repeated dosing lead to toxic accumulation

Take Home Message: Systemic absorption and distribution of itraconazole (0.01% and 0.001%) in Panamanian golden frogs after topical bath. 0.01% bath found to exceed MIC for at least 36 hours, suggesting that it shouldn’t be dosed daily.

Question 87

What treatment was effective in eliminating clinical signs and deaths caused by chytridiomycosis in captive hellbenders?

Answer 87

EFFICACY AND SAFETY OF CHLORAMPHENICOL TREATMENT FOR BATRACHOCHYTRIUM DENDROBATIDIS IN HELLBENDERS (CRYPTOBRANCHUS ALLEGANIENSIS)

Anthony L. Ashley

J. of Zoo and Wildlife Medicine, 52(1):373-378 (2021)

Clinical signs of Bd in hellbenders: ventral erythema, excessive mucus, and rocking from side to side

Chloramphenicol bath at 200 mg/L continuously x 2 weeks in clinically affected Bd hellbenders:

Stopped deaths

Positive at 1 month after treatment

Negative at 2-3 years after treatment

Treatments that did not prevent deaths in Bd-infected hellbenders:

Chloramphenicol at 20 mg/L daily x 2 wks

Itraconazole baths

Conclusions: Chloramphenicol baths at 200 mg/L appeared to eliminate clinical signs and deaths caused by chytridiomycosis in captive hellbenders by decreasing the burden of Bd

Question 88

What was observed in a study evaluating terbinafine implants in juvenile hellbenders?

Answer 88

Efficacy of subcutaneous implants to provide continuous plasma terbinafine in hellbenders (cryptobranchus alleganiensi) for future prophylactic use against chytridiomycosis.

Hardman RH, Cox S, Reinsch SD, Schwartz HC, Skeba S, McGinnity D, Souza MJ, Miller DL.

Journal of Zoo and Wildlife Medicine. 2021 Apr;52(1):300-5.

Background:

Batrachochytrium dendrobatidis (Bd) motile zoospores infect keratinized epithelium

Disrupt skin osmoregulation

Highly susceptible species: Panamanian golden frog

Resistant species: many salamanders

Bd-positive and healthy CA slender salamanders brought into captivity 100% die from Bd

100% mortality in head-started hellbenders despite high prevalence in wild

Terbinafine: lipophilic antifungal that concentrates in skin even when given orally

Terbinafine implants provided therapeutic levels in cottonmouths

Key Points:

Terbinafine implant in juvenile hellbenders → levels above Bd zoospores MIC for at least two time points

Not above MIC for Bd zoosporangia

Conclusions: Terbinafine implants may be effective as a prophylactic for hellbenders at risk of Bd.

Question 89

A recent study described vascular tumors in two argentine horned frogs.

What are the most common neoplasms of amphibians?

What were the two neoplasms in this study?

Both were positive for what marker?

Answer 89

Vascular Tumors in Two Argentine Horned Frogs (Ceratophrys ornata)
Mitsuhiro Ikeda1, Hirotaka Kondo1, Yuki Iwata1, Iori Koizumi2, Naoto Tsunesumi3, Hisashi Shibuya1
Journal of Herpetological Medicine and Surgery, 32(2) : 119- 122

Key Points:
- Most common tumors in amphibians are chromatophoroma, lymphoma/leukemia and papilloma
- Case 1: splenic hemangiosarcoma
- Case 2: lymphangioma
- Described two vascular tumors of Argentine horned frogs and the usefulness of anti-CD31 antibody.

Question 90

A recent study characterized the tissue enzyme activities of the marine toad.

What is the scientific name of the marine toad?

What enzymes are consistent with skeletal muscle damage?

What enzymes are consistent with cardiac disease?

What enzymes are liver specific?

Answer 90

JHMS 2022 32(3):219-24
Characterizing Tissue Enzyme Activities in the Marine Toad (Rhinella marina)
Cabot ML, Heugten KA, Smith D, Ridgley F, Minter LJ

Key Points:
- Elevated CK, LDH, & AST may suggest skeletal muscle damage
- Elevated CK, LDH, ALP, & AST may suggest cardiac disease
- None of the enzymes evaluated seem to be specific to the liver

Question 91

A recent study described hepatocellular toxicity from common buckthorn in Green frog tadpoles.

What is common buckthorn?
- WHat is its secondary metabolite? What does it cause?
- What are the clinical signs of affected animals?

How prevalent was mortality in tadpoles exposed to buckthorn metabolites?
- What lesions were found on gross & histopathology?
-

Answer 91

Hepatocellular toxicity of the metabolie emodin produced by the common buckthorn (Rhamnus cathartica) in green frog (lithobates clamitans) tadpoles.
Brenes R, Nguyen LM, Miller DL, Rohde ML.
The Journal of Wildlife Diseases. 2022;58(2):341-347

Background
- Common buckthorn – invasive plant spp, family Rhamnaceae, produces allelopathic substances and secondary compounds in leaves, bark, and fruits
– Secondary metabolite emodin – anthaquinone, deformities and mortality in inverts, fish, amphibian larvae; high concentrations – oxidative stress in liver, inflammation, congestion, necrosis, damage to lipids, DNA, proteins
– Clinical signs: dull skin color, mouth gaping/dyspnea, red skin, excess mucus, disorientation, seizures
– Metabolized in the liver
- Tadpoles – liver function changes from hematopoietic in early developmental stages to metabolic; young tadpoles potentially more susceptible to toxicosis

Key Points
- Emodin concentration based on field sample ranges
- 85% mortality of tadpoles at advanced developmental stage when exposed to 2.5 ppm emodin
– All displayed clinical signs: dyspnea, erythema, lethargy, spasms
- Gross necropsy: enlarged nodular livers, accumulation of yellow/gold material (emodin powder) in gallbladder and biliary system
- Histo: bridging portal fibrosis, marked bile duct proliferation

Conclusions
- Green frog tadpoles at advanced developmental stages had high levels of mortality and liver damage when exposed to emodin 2.5 ppm
– Liver damage: oxidative stress, hepatocyte death, fibrous replacement
- The wide distribution of this invasive plant (in the Midwest) could be a threat to amphibian populations, especially early breeding-species.

Question 92

Describe the updates on Chytrid fungus as outlined in the new F10 chapter:

What are the two organisms - how does their pathology differ?

What are some nonamphibian hosts?

What bacterium has antifungal properties - what is the metabolite that does that?

How do red-backed salamanders and NA bullfrogs fight infection?

How is this diagnosed?

How is it treated?

What conditions does chytrid grow best in?

Answer 92

Fowler 10 Chapter 61 Update on Amphibian Chytrid Fungus
- Batrachochytrium dendrobatidis (Bd) (1998)
– Ubiquitous organisms
– Bd was the first chytrid to affect a vertebrate
– Morbidity and mortality are not simply based on the species of amphibian infected
- Infects epidermal cells of amphibians, leading to impaired skin function
- Second chytrid fungus → (2013) Batrachochytrium salmandrivorans (Bsal)
– Similar to Bd, main difference is that Bsal is more pathogenic to salamanders and Bd is more of a concern in anurans
– Bsal → skin ulcerations
– Bd → epidermal hyperplasia and hyperkeratosis
- Most info here for Bd (specific Bsal info will be noted)
- Tadpoles play a major role in maintenance in the environment → in their mouthparts and transitions to the hind limbs during metamorphosis
- Nonamphibian hosts: dose-dependent mortality in zebrafish juvenies; gill recession in crayfish; attracted to and will adhere to/proliferate on keratinous toe scales of aquatic birds
- Peptides and microbes in amphibian skin can be protective against Bd and Bsal to inhibit chytrid growth
- Janthinobacterium lividum (bacterium isolated from skin of red-backed salamander) produces a metabolite (violacein) that has antifungal properties against Bd
– Can be protective when applied to other species
- Some animals have physiological changes that help to fight infection
– Red-backed salamander increases food intake to keep weight up
– North American bullfrog tadpoles increase cardiac output by elevating stroke volume (rather than HR) to preserve energy to fight infection
– Tadpoles infected develop faster
- Bd grows best b/w 17 and 25C
- Bd susceptible to desiccation in drought environment
- Wide range of chemicals w/ varying degrees of effect on Bd morbidity and mortality
- Diagnosis relies heavily of PCR, secondarily histology
– Just because it is found, does not mean it is the cause of illness
– Need negative results several times over several weeks to confirm truly negative
- Mainstay tx for years has been itraconazole 0.01% solution for 5 min x 11 days
– Sometimes kills pts over the infection
– Not as effective in tadpoles and can cause depigmentation
- Good biosecurity is important in prevention and management
– Nitrile gloves have a cidal effect against Bd (latex and polyethylene do not)
- Major threat to amphibian pops all over the world
– No single “magic bullet” for tx