Amphibian Medicine & Diagnostics Flashcards
What are the 6 general steps of metamorphosis in frogs? In what 3 general ways does the lifestyle change?
tadpole —> tadpole with rear legs —> tadpole with front and rear legs —> froglet with small tail —> adult frog
- gills to lungs (aquatic to terrestrial)
- herbivorous to carnivorous
- immune system develops
What are 2 important reportable diseases that commonly affect frogs?
- Chytridiomycosis (Bd)
- Ranavirus
What is the most important factor of amphibian health?
environment —> poor husbandry causes disease, can use wild frogs to monitor changes in the environment
What environmental information is important to ask about when getting a history on amphibian patients?
- water quality - oxygen, ammonia, temperature
- soil/substrate - humidity
- cleaning equipment - chemicals used, proper rinse following
- cagemates - quarantine
What 3 reflexes are tested on amphibians?
- blinking reflex
- righting reflex - should turn upright when places upsidedown
- withdrawal reflex - back legs should tuck in when pulled out
How should an examiner maintain hygiene and health of the amphibian when handling them? Why?
- ensure hands are moist
- avoid leaving soap, lotion, or latex gloves on
amphibian skin is responsible for absorption, excretion, and respiration
What is a drinking patch?
patch on the ventrum where frogs absorb water directly through their skin
Other than reflexes, what other tests are useful for amphibian patients?
- fecal exam
- CBC/chem
- skin swabs (Chytrid!)
- biopsy
- necrospy
+/- urine tests
What is a common difference in amphibian RBCs?
elliptical and nucleated
Where does hematopoiesis occur in Caecilians and aquatic newts?
LIVER, kidney, spleen, thymus —> NOT in bone marrow
(hematopoietic tissue in liver can look like hepatitis!)
Where does hematopoiesis occur in frogs, toads, and terrestrial salamanders?
- ANURANS (frogs and toads) = bone marrow and kidney
- CAUDATA (salamanders) = liver*, kidney, thymus
- BOTH = spleen produces RBCs in adults
How does the thymus develop in amphibians?
present for life and produces CD3+ T lymphocytes (most IHC stains work!)
What 3 bleeding techniques are less commonly used for collecting blood from amphibians? What is an alternative method?
- toe clipping - doesn’t bleed much
- ligual plexus
- cardiocentesis - commonly terminal collection, can cause tamponade
facial venipuncture - vein runs over maxillary bone
On what amphibians can facial venipuncture be performed on?
- true frogs (Ranidae)
- tree frogs
- toads (Bufonidae)
What equipment is required to perform blood collections on amphibians?
- needle for pricking vein
- capillary for collection
What is the most important diagnostic ran on amphibian blood samples first? What information is gained?
blood smear
differential counts
Label the following amphibian WBCs.
- heterophil
- eosinophil
- basophil
- lymphocyte
- monocyte
- thrombocyte - can look like clumps of lymphocytes, do not count as WBCs!
Why must a hemocytometer be used for amphibian RBCs? What is it used to do?
their RBCs are nucleated and won’t be properly counted by normal counters used on other species
total cell count - no published data —> check cagemates or data based on another similar genus
How is blood prepared for total blood counts with amphibian blood?
- collected in a heparinized capillary tube
- known volume placed into an unopette
- diluted in Natt-Herrick solution, which differentially stains WBCs, RBCs, and thrombocytes
- charged into a hemocytometer, which is used to count the cells and calculate the concentration per liter (10^12 or 10^9 /L)
What is the major downfall of hemocytometry? What are 2 alternatives?
needs time and skills
- back-calculation from smear
- automated cell counters - impedance cell (particle) count works well, flow cytometry is untrustworthy
How is the centrifuge used for amphibian hematology?
- PCV
- plasma - manual TP, chemistry profiles
What biochemical metabolite can be manually counted? What are the most important analytes automatically colored?
TS —> refractometer
- TP*
- cholesterol and triglycerides*
- albumin
- globulins
- enzymes (LDH, etc.)
(plasma of amphibians is commonly varying colors)
What nitrogen waste products are excreted by different species of amphibians?
- AMMONIA - metabolized in the skin and gills of tadpoles and aquatic species
- UREA - metabolized in the liver and kidney of terrestrial species
- URIC ACID - metabolized in the liver and kidney of tree frogs
How does the specific gravity of plasma compare to urine in amphibians?
should be the same —> kidney does not concentrate urine
How do erythrocyte size, TP, thyroid hormones, glucocorticoids, and calcium differ as amphibians go through metamorphosis?
decreases - adults have slightly smaller RBCs compared to tadpoles
increases - higher osmotic pressure needed in the blood of terrestrial amphibians
increases - metamorphosis controlled by T3 and T4
increases - results in lymphopenia and neutrophilia
increases
In what 3 ways do amphibians prepare for extreme climates?
- lower freezing point by producing proteins that force ice crystals to form parallel to cell walls
- PCV increases as temperature drops (especially in bullfrogs)
- glucose, fibrinogen, heat shock protein, and plasma osmolality increase prior to overwintering
need time to adapt, cannot handle quick changes in temperatures
How does ammonia typically affect amphibians?
causes sudden death of tadpoles (irreversible once ammonia spikes!)
- need to monitor water quality!
What amphibian is most commonly affected by gas bubble disease? What causes it?
aquatic African clawed frogs
drastic changes in temperature changes the solubility of nitrogen (+/- O2), making it difficult to eliminate, which causes gas supersaturation —> bubbles form under skin and in the blood
(over 100% total gas pressure)
What are the 2 most common signs of gas bubble disease?
- bubbles in skin (footweb)
- possible skin hemorrhage
What are 3 common findings on histopathology caused by gas bubble disease?
- bubbles
- single cell necrosis in epidermis
- dermal inflammation (subacute)
How is gas bubble disease treated/prevented?
aeration of tanks with air stones or cascades and maintenance of stable temperatures
(tends to be irreversible)
What is the most common cause of fungal dermatitis in amphibians? 3 others?
Saprolegnia
- Achyla
- Leptolegnia
- Epistylis
(secondary invaders due to poor environment or skin ulcers)
What is the most common finding in amphibians with fungal dermatitis? How is it treated?
velvety, fuzzy growth on tadpoles
- salt
- use formaldehyde CAREFULLY
What are the 2 major options of feeding amphibians? What should be avoided?
- dust insects with vitamins and calcium (must be eaten right away to ensure they get the provided nutrients)
- gut load insects with laying hen food rich in vitamins and calcium
spinach - high in oxalates, which causes the production of calculi in tadpoles kidneys resulting in death within a few days of metamorphosis
Do amphibians require UV light?
not proven, but better safe than sorry
What abnormal finding is seen in this necropsy of an African clawed frog?
- normal ovaries and heart
- splenomegaly —> HSA vs lymphoma
What cells are infiltrating this section of amphibian liver?
lymphocytes —> CD3+ stain confirms T cell lymphoma
What normal finding on necropsies can be confused for parasites?
body fat organs
What samples are most important for taking samples of during necropsies? What must be fixed before removal? When can bacteriology be done?
- all organs
- skin, muscle, and bone marrow of digits, pelvic patch, and thighs
- open lumen of stomach and lungs
brain, can freeze liver and everything else (70% ethanol)
within 2-4 hours
What 3 findings on biochemistry and blood smears are indicative of ranavirosis?
- lymphopenia
- degenerate cells
- inclusion bodies
What lungworm commonly affected frogs? Where else can it be found? How is it diagnosed?
Rhabdias spp
body cavity
fecal exam, Baerman technique for larvae
What frogs are most commonly affected by lungworms? How do they become infected?
wild frogs caught and transitioned into captivity
- frog starts infected subclinically
- hermaphroditic adults (Rhadbias) are shed into substrate
- adults proliferate in the soil and can infect all frogs in the tank —> autoinfection
How is Rhabdias infection treated?
topical ivermectin
(lungworm)
What epidermal worm affects frogs? What frogs are most commonly infected? How are they affected?
Pseudocapillaroides xenopi
Xenopus —> clawed frogs
hyperplastic skin (epidermis) causes respiratory distress and alters hydration and acid-bas balances
How is capillariasis treated?
ivermectin 0.002 mg/g —> extremely well-tolerated by frogs
What frogs are most commonly affected by Ichthyiophonus? What signs are seen?
wild caught wood frog (Rana sylvatica) tadpoles
multiple white spots on skin
Ichthyiophonus:
white spots on skin, can infect muscle
- most commonly self-limiting
What is the infection cycle of Trypanosoma like? Why?
daily cycle with highest counts at mid-day
hides in kidney vessels (glomeruli) at night because they are transmitted by mosquitoes active during the day
What frogs are most commonly infected by Trypanosoma?
wild green frogs
How does Hepatozoon infection compare to Trypanosoma?
no daily cycle —> infects immature RBCs and causes mild anemia
What frogs are most commonly affected by Hepatozoon? How do they become infected?
most common in green frogs (unlikely to cause death)
must eat infected mosquito
What is red leg syndrome?
hyperemia of the legs indicative of a secondary bacterial infection (dermatosepticemia)
ALWAYS look for underlying causes —> virus, fungus, habitat (humidity, ammonia, temperature)
Dermatosepticemia:
red leg syndrome
How does Salmonellosis affect frogs?
frogs are most commonly carriers and transmit it to humans (usually younger children)
How can total proteins turn out normal if a refractometer reading is high?
total proteins measure albumin and globulin, but the refractometer measures total solids, which include cholesterol and triglycerides
What frogs are most commonly affected by corneal lipidosis? What are the 2 most common causes?
Cuban and White’s tree frogs
- high cholesterol in diet (crickets!)
- lack of basking in heat (needs basking area around 90 degrees F)
Corneal lipidosis:
increased opacity
- tree frogs!
Corneal lipidosis:
opacity taking over entire globe, possibly painful
What are 2 important aspects of amphibian anesthesia?
- MS-222 mixed in water
- topical Benzocaine (20% OTC)
Edema disease in amphibians:
What is a common cause of renal adenocarcinoma in frogs? How does this affect the frog?
herpesvirus
causes increased concentrations or urea, uric acid, or ammonia due to altered filtration
What is indicative of bacterial or fungal disease as causes of edema disease in frogs?
aspiration of fluid high in protein and cells with possible presence of microorganisms = coelomitis
What causes Mycobacteriosis in frogs? How are they infected? What is a common sign?
Mycobacterium marinum
commonly found in water (pools, fish tanks) and act as opportunistic pathogens, waiting for a bout of immunosuppression to cause systemic infection
digital granulomas
Mycobacteriosis, Wright Giemsa:
- negatively-stained rods in fluid
- macrophages
(would stain positive with acid-fast stains)
Mycobacteriosis, acid-fast stain:
acid-fast positive rods in fluid with macrophages
Mycobacteriosis, Gram stain:
G+ rods in macrophages
