Crocodilians Flashcards
1
Q
What order are crocodilians in?
What are the three families?
What are the smallest and largest species?
A
Taxonomy
- Clade Archosauria: also includes bird and extinct dinosaurs.
- Order Crocodylia
- Three families: Alligatoridae, Crocodylidae, and Gavialidae
- 23 recognized species
-
Tomistoma schlegelii, formerly “false gharial”, was included in the family Gavialidae
- Now recognized under Crocodylidae, and the common name Tomistoma is more widely accepted.
- Crocodiles/caretakers contribute to habitat and species conservation, poverty reduction and education → commercial operations that breed millions of crocodiles, 1.4 million crocodile skins traded between 2004-2013 (F9)
Taxonomy from Path Book:
- 3 families, 8 genera, 23 species: Crocodylidae (crocodiles), Alligatoridae (alligators, caiman), and Gavialidae (gharial and false gharial) - small 2m dwarf caiman to 6-7 m estuarine (SW) crocodile
- Tropical to subtropical, found on all continents except Antarctica and Europe
- Free-ranging, zoo, and extensive commercial crocodilian production (meat, skin)
- Commercial mainly American alligator, Nile croc, freshwater croc, estuarine (SW) croc
- Captive-bred, farmed stock, or reared from eggs/juveniles from wild (ranching)
- Commercial mainly American alligator, Nile croc, freshwater croc, estuarine (SW) croc
- Unique anatomy – integumentary sensory organs, adaptations for amphibious nature, unique cardiovascular and respiratory anatomy (see E-contents)
2
Q
Describe the arrangement of crocodilian scales.
Do crocodilians shed?
What glands do crocodilians have?
What are the intradermal sensory organs?
Do crocodilians have external ears?
A
Integument
- Skin is comprised of ß- (outer scales) and α- (hinge regions) keratin.
- Layers arranged in alternating lateral distribution (vertical in squamates and tuataras)
- Lateral arrangement = shedding in a gradual exfoliation pattern
- Crocodiles DO shed skin, but not as easily appreciate as in other reptiles
- No sweat glands.
- Dorsal scutes over head and back contain bony plates (osteoderms).
- Glandular secretions may occur from paired gular glands on ventral mandible, lips, cloaca depending on spp.
- The skin of all crocodilians possesses intradermal sensory organs (ISO)
- Highly sensitive nerve endings similar to the lateral line in fish
- In Alligatoridae, ISO are found strictly on the head
- Crocodylidae and Gavilaidae found throughout the body, prominently on ventral skin
- Paired gular and paracloacal glands
- True function is not fully elucidated, compounds secreted varies
- Ears – Covered by flap that closes during diving. Inner ear infections uncommon but may result in neuro signs.
3
Q
How many chambers does the crocodilian heart have?
What vascular connections allow for shunting?
Describe the flow of blood during diving.
A
Cardiovascular System
- Key anatomic features allow right to left shunting
- True 4 chambered heart. Prominent pericardial sac that contains a large amount of fluid
-
Foramen of Panizza – septal connection between R and L aortas
- Perfusion of the coronary vessels and brain during blood shunting
- Anastomosis between L and R aortas
- L aorta originates from the right ventricle
- Past the anastomosis, the L aorta becomes the celiac artery and R aortoa becomes the dorsal aorta.
- Cog-teeth-like valves in the pulmonary outflow of the right ventricle help control shunting.
- Shunting cannot be predicted or controlled
- Gas anesthesia alone is not recommended b/c, if shunting occurs it can lead to unpredictable levels of anesthesia.
- Shunting allows prolonged submergence
- During diving, increased pulmonary pressure leads to an increase in central pressure
- Leads to blood flow through the foramen of Panizza to the L aorta and systemic circulation allowing conservation of oxygen and perfusion of organs.
- ONLY reptiles with 4 chambered heart!
- Adaptations for aquatic lifestyle:
- Right aorta (supplies lungs) and left aorta (bypasses lungs).
- Connective tissue extensions into pulmonary outflow tract of RV, restricts blood flow to lungs during diving, allows for L->R shunt.
- Foramen of Panizza – Opening between left and right aortic arches allowing pressure equalization during diastole.
- Acts as pressure valve.
- Results in some venous admixture.
- When submerged, air in lungs restricts blood flow through pulmonary capillary beds, results in pulmonary hypertension which increases RV and pulmonary arterial pressures.
- Blood flows R to L through FP.
- Deox blood diverted away from lungs through left aortic arch to organs not sensitive to hypoxia.
- Can stay submerged 5-6 hours.
- Shunting of blood away from lungs will delay inhalant ax uptake and removal, assisted vent required during ax.
- Blood volume LESS than mammals (3.5-5.5%). Max blood removal 0.03-0.05%.
- Renal portal system is present, complications not reported.
4
Q
Crocodilians have several mechanisms to protect their respiratory system while in the water.
How do they prevent water from getting into their nares?
Describe the function of the gular valve.
What is the tracheal and lung anatomy of crocodilians?
How does respiration occur without a diaphragm?
A
Respiratory System
- Nostrils located dorsally and can be closed with muscular flaps
- Closing nares controlled by skeletal muscle, can be obtunded by immobilizing agents allowing water into resp tract.
- There is a complete hard palate creating a true division between the oral and pharyngeal cavities
- There is a gular valve composed of the velum palati dorsally and the gular fold ventrally
- The velum palati is a soft tissue extension of the dorsal palate.
- The gular fold is a cartilaginous extension of the basihyoid cartilage
- Together they create a tight seal separating the oral and pharyngeal cavity
- Elongated soft palate (palatine flap) presses against gular fold or valve, allows opening of mouth under water without aspiration.
- Has to be displaced to visualize glottis for intubation.
- Elongated soft palate (palatine flap) presses against gular fold or valve, allows opening of mouth under water without aspiration.
- Complete tracheal rings and multicameral lungs with a single left and right lung lobe
- Despite the absence of air sacs, there is a unidirectional flow of air similar to birds
- Respiration is an active process: intercostal muscles and the diaphragmaticus muscle (aka post-hepatic septum)
- Diaphragmaticus originates from the ischia and last gastralia and inserts on the caudal aspect of the liver
- Incomplete separation. Respiration and buoyancy.
- Primary resp muscle groups:
- Intercostal muscles.
- Postpulmonary and posthepatic membranes act as diaphragm.
- If thoracic cavity is compressed, can’t breathe.
- Primary resp muscle groups:
5
Q
Describe the dentition of crocodilians.
Describe the anatomy of the crocodilian stomach.
Describe the metabolic changes associated with food ingestion.
How many liver lobes do crocodilians have?
What biliary product do crocodilians produce?
A
Digestive System
- Polyphyodonts (teeth continually replaced) with thecodont dentition (teeth in sockets)
- Teeth are conical, hollow, and without roots. Dental disease is low clinical significance.
- The tongue is attached to the floor of the mouth along the entire ventral surface
- Stomach has two distinct regions, the corpus and the pars pylorica
- The corpus or cardiac region is the first compartment and glandular portion
- Past the corpus there is a sphincter that opens into the pars pylorica
- Function of pars pylorica is unknown
- Profound plasma alkalemia is associated with food ingestion.
- High production of hydrochloric acid in the stomach lead to shift of chloride ions from plasma and leaves a large amount of sodium to react with plasma carbonic acid
- This results in large amounts of sodium bicarbonate causing an alkaline tide
- Shifts in plasma pH occurs frequently
- GALT throughout the intestines. Can be observed grossly, esp in cases of enteritis.
- There are prominent ileocolic and colon sphincters.
- Small and large intestines have extensive mesentery that creates a true separation between the lungs, liver, stomach, and the rest of the organs (intestines, spleen, kidneys, and gonads)
- Two liver lobes, with the right being larger. A gallbladder is present within the right lobe.
- Unlike most reptiles and birds, crocodilians produce bilirubin.
- Icterus and elevated bilirubin levels have been observed with liver fibrosis
6
Q
What is the reproductive strategy of crocodilians?
What changes occur in females during vitellogenesis?
How do you sex a crocodilian?
Describe the temperature dependent sex determination of crocodilians.
A
Reproductive System
- Oviviporous. During vitellogenesis, higher lipid, phosphorus, Ca, and vit E in the blood.
- Plasma may appear white (lipemia)
- Most species undergo a refractory period after ovulation,
- Exception: mugger crocodiles produces two clutches per year under
- Animals can be sexed via cloacal exams.
- Male phallus is on ventral cloaca near opening of the vent it can easily everted
- Female clitoris is similar to the phallus but smaller and will not evert
- Palpating the cloaca is not accurate enough. It is important to attempt to evert the phallus to confirm it is a male. Developed clitoris is easily confused with a phallus.
- Temperature dependent sex determination
- Low incubation temperatures (84°F–86°F) result in females
- Temps above 34°C (93°F) result in malformations or embryonic deaths
- Data on mid-range and high-range temps vary.
7
Q
Do crocodilians have a bladder?
What is their primary nitrogenous waste?
A
Urinary System
- Both ammoniotelic and uricotelic, with ammonia excretion being predominant.
- No urinary bladder, urine is often stored in the urodeum and coprodeum
- Kidney and cloaca are primary for the excretion of nitrogenous waste but not salt excretion.
8
Q
A deceased crocodilian with its mouth open may still close its mouth - describe what is occuring and when it can occur.
Describe the vertebral anatomy of crocodilians.
How many digits do crocodilians have? How many have claws?
A
Musculoskeletal
- If the mouth of an adult that has recently died is opened, a point comes where the muscles are stimulated to close with tremendous force. The effect may occur up to 24 hours after death.
- Approx. 55 to 67 vertebrae: 8-9 cervical, 15-16 thoracolumbar, 2 sacral, and 30 to 40 caudal
- Procoelous vertebrae (concave anteriorly and convex posteriorly. Mammals have acoelous vertebrae (flattened on both ends).
- Except the atlas, axis, the two sacral, and the first caudal vertebrae, which are all acoelous.
- Eight pairs of ribs and eight pairs of gastralia or floating ribs
- Sacral ribs are heavy bones that articulate with the transverse processes of the sacral vertebrae
- Limbs have five digits with claws on the medial three digits
9
Q
Describe the differences in the central nervous of crocodilians compared to other reptiles.
What cranial nerve is enlarged in crocodilians? Why might this be?
Where does the spinal cord terminate?
A
Nervous System
- Diff from other reptiles: They have a cerebral cortex, lack a pineal body, and have a larger cerebellum
- Enlarged trigeminal nerves: possibly serves the increased sensory function of skin on the face and head, along with the ISO
- The spinal cord extends almost to the tip of the tail, no cauda equina
10
Q
Describe the ocular anatomy of crocodilians.
Describe the aural anatomy of crocodilians.
A
Special Senses
- Vision
- The upper lid may contain a bony structure, tarsus, which is absent from the lower lid
- The third eyelid arises ventral and cranial and moves in a dorso-caudal direction.
- The nictitans is transparent to translucent in most species.
- Harderian gland on the inner aspect of the nictitans. Lachrymal gland is present on the medial aspect of the orbit
- Tapetum lucidum is well developed and located on the dorsal aspect of the retina.
- Anterior binocular vision is not well developed.
- An approach directly from the front or from behind is advisable and safer
- Hearing
- The external auditory meatus are slit like openings, protected by a dorsal shelf of bone.
- Tympanic membrane is present. Hearing is well developed.
11
Q
Describe appropriate enclosure desing for crocodilians.
What is their general temperature preferences? Can all species handle cold weather?
How does UVB supplementation affect growth?
Describe appropriate flooring and substrate.
Describe the overstimulation of the intradermal sensory organs.
A
F8 Crocs
- Husbandry
- POTZ 25C-35C.
- Seasonal temp fluctuations may result in anorexia during winter months. 4-5 mos.
- Anorexia with normal temps warrants dx workup.
- Temps outside the POTZ will influence digestion and immune function.
- Enclosure design
- Mechanical, biologic, chemical filtration.
- Dry basking area critical.
- Dominance and intraspecies aggression must be considered.
- Pica and consumption of rocks, etc common.
- Larger rocks less than 20 cm, pieces of PVC, support system components, coins, metal FB may warrant removal. Gastric lavage or endoscopy.
Mader Ch 25 Husbandry and Management of Crocs
- Specific Housing Requirements:
- Priorities – water quality, appropriate diet, enough space for growth and number of animals.
- May be territorial depending on species, may grow larger than others.
- Males and females can both become aggressive during breeding season.
- Keep separate if not enough space in primary enclosure.
- Not all crocodilians can tolerate cold weather.
- Some species can burrow and create tunnels/escape exhibits.
- Adept climbers, avoid chain-link and horizontal fencing.
- Temp and humidity varies with spp: 25-32 deg C.
- Higher temps may be more susceptible to certain dz i.e. WNV.
- Water temps should also be controlled, maintained during wash and refilling periods to avoid drastic temperature shock.
- UVB requirements unknown.
- May be expected to thrive with minimal UVB as long as offered whole prey or commercial diet supplemented with vit D3.
- Studies with 5 month old broad-snoted caimans ID immune activity alterations and genotoxic effects after exposure to 30% UVA 5% UVB Sylvannia Reptistar lights.
- Photoperiods of natural sunlight associated with greater growth than artificial lighting regimes and darkness.
- Most captive crocodilians not offered artificial UVR within large enclosures.
- Provide a gradient for young animals exposed to artificial UVR.
- May be expected to thrive with minimal UVB as long as offered whole prey or commercial diet supplemented with vit D3.
- Land – soil, grass, sand, concrete surfaces can be used.
- All-concrete flooring least idea, pressure sores and irritation.
- Concrete ramps in and out of water should slope over 1-2 m to minimize haul-out efforts and reduce risk of skin abrasions.
- Intradermal sensory organs (ISO) – highly sensitive free nerve endings similar to the lateral line of fish.
- Mechanical sensitivity exceed primate fingertips.
- Waterfalls and other features creating surface water movement could cause overstimulation and stress.
- Monitor behavior of animals in these enclosures.
- Intradermal sensory organs (ISO) – highly sensitive free nerve endings similar to the lateral line of fish.
12
Q
Describe the appropriate diet composition for crocodilians.
How does it vary with age?
How frequently should crocodilians be fed?
Are any toxicity or deficiencies reported?
A
- Feeding and nutrition (Mader):
- True carnivores – require high-protein, high-fat, low fiber.
- Juveniles – inverts, amphibians, reptiles.
- Older – includes fish, birds, mammals.
- Commercial feeds available for captive alligators.
- Lead toxicosis has been reported in alligators fed nutria killed with lead shot.
- Lead suspected to also affect reproduction.
- Has not been observed in C. porosus.
- May be species-specific sensitivity to lead.
- Thiamine supplementation if offering frozen fish.
- Obesity is common.
- Young crocs – feed three to four times weekly, adults once weekly.
- GI foreign bodies common from people throwing coins and trash into exhibits.
- Keep hoses, buckets, tools out of exhibit areas.
- Lead toxicosis has been reported in alligators fed nutria killed with lead shot.
- Nutrition (F8):
- Frozen prey items should not be stored > 3 mos.
- Thiaminase in frozen stored fish -> hypovitaminosis B.
- Supplements i.e. Ca and mineral powders should be frozen, discarded after 6 mos.
- Prepared food items – Whole prey recommended.
- Commercial pelleted diets available, may result in obesity.
- Whole prey items contain about one third caloric density vs pelleted diet.
- Juveniles have higher feeding rates, diets include smaller items.
13
Q
Describe your ideal preventative medicine protocol for crocodilians.
How frequently would you perform exams?
What tests would you perform?
How does training play a role?
A
- Preventive Medicine (F8):
- Juveniles – Annual first 3-4 yrs, PE, transponder, weight, blood collection for CBC/chem +/- serum trace minerals, FA profile, EEE, WNV titers, rads.
- Adults – Exams q2-3 yrs, established training programs.
- PE, transponder, weight, CBC, chem, trace minerals, FA profile, EEE, WNV titers, whole blood lead and Zn, rads.
- Crocs can be trained to enter crates.
14
Q
Describe the appropriate physical restraint of a crocodilian.
What species are more aggressive?
How should you approach the animal?
How many people are needed for restraint?
Is there a size limit for safe physical restraint?
What tools are useful in the restraint?
What physiologic concerns do you have for the animal?
A
Mader
- Crocodiles are more aggressive vs. caimans and alligators that are more defensive.
- Fast, will lunge forward and move heads side to side and turn quickly.
- Approaching best performed from behind, never front or sides.
- Minimum of one person for every meter of body length (tip of snout to tip of tail) for animals up to 2m.
- Beyond 2m, two persons for every additional meter.
- Manual restraint for crocs up to 3.5 m length. Larger than this, chemical immobilization only safe option.
- Manual restraint.
- First goal is control head, then tail and limbs.
- Mouth can be easily held closed.
- Teeth exposed even when jaws are closed can cause injury.
- Tail must always be controlled to prevent lashing.
- Limbs must be controlled to prevent rolling and escape.
- Saying close as possible to animal minimizes risk of injury.
- When collecting samples, work in line with long axis of the animal, avoid being beside them.
- Applying pressure over eyes helps decrease visual stimulation and induces vagal tone.
- Hatchlings, juveniles up to 1 m can be restrained with one hand to hold mouth closed and other to control lower body and tail.
- Once mouth is taped, control by grasping cervical area and tail.
- Support neck, hold rear limb facing away from person’s body at base of tail.
- Animals between 1-3 m can be caught by hand or with catchpole or snare.
- Prepare to rotate snare to prevent injury or strangulation, will start to roll.
- Grab tail ASAP until mouth can be securely closed, be aware that they can still turn around.
- Animals > 3.5 m, form a single line to approach animal form behind, quickly land on top of animal in synchrony.
- Larger animals, use special nets and ropes to secure before taping the mouth.
- Roping the jaw and then taping is advisable.
- Multiple ropes can be used to restrain head, tail, limbs before hands-on contact.
- Can tie/tape limbs to body for transport or tie/tape to wooden board.
- Ensure limbs are not too tight for long periods of time.
- Roping the jaw and then taping is advisable.
- Overheating is possible, especially if thrashing with mouth closed.
- Place tie or rope around the tape on ventral side of jaws between mandibles, pull from distance after other restraints have been removed.
- Operant conditioning is recommended.
- Electrical stunning.
- Commercial crocodile farms in Australia and South Africa.
- Has been used for immobilization and transport of Crocodylus porosus, C. niloticus.
- No increase in corticosterone or glucose in C. porosus.
- In C. niloticus, blood lactate levels significantly higher in animals captured in a noose vs stunning.
- Electrical stunning could be a useful technique to reduce stress of restraint and improve safety for both animals and personnel.
- Has been used for immobilization and transport of Crocodylus porosus, C. niloticus.
- Commercial crocodile farms in Australia and South Africa.
West
Capture Equipment
- Ropes
- Too small – cinch too tightly on animal, burn handler’s hands
- Too big – won’t close tight enough on jaws
- Nylon ropes are generally the strongest
- Cotton & sisal work well but rot if not dried
- Woven or braided ropes are less likely to kink or fail than twisted ropes
- Catch Poles
- Designed so noose & rope attachment separates from rod (breaks away with twisting)
- Tape – silver duct tape is best, but over time they can work it off their jaws
Capture & Handling Basics
- Strike Zones – the arc of the head swinging from side to side
- Safer to approach an animal, secured by rope around its neck, from the front than from the side
- Roping
- Neck noosing – placing rope over the head and cinching it around the neck – adult alligator, caiman, and heavily bodied crocodiles have large jowls for the rope to take hold
- Top jaw noosing – for slimmer body profiled animals, greater control of the head but all the force of the animal’s head movement is transferred to the restrainer
- Securing the jaws
- Duct tape preferred – good adhesion, animals can work it off their jaws in long procedures, doesn’t get too tight
- Electrical tape has a lot of stretch and can be applied too tightly causing ischemia
- Cable straps – slender-snouted species – they can damage the jaws too so be careful
- Cover the eyes
- Juveniles (<1 m) – grab by hand behind the head, secure the jaws
- Subadults (<2 m) – catchpoles recommended for these animals
- Adults – multiple people using ropes (2 good for 2 m animals, 4 for 3-4 m animals)
- In water – drain the pool till it just covers the eyes, watch for damage to the animal as pools are mostly hard sided
- On land – identify sites where the ropes can be tied off – large crocodilians can uproot small trees
- Rope or catchpole secure the head, pull the animal into the work area and tie it to a tree or post
- Re-evaluate if rolling occurs
- Mounting – safe with experience and proper technique, less secure than tying them somewhere or shifting them
- Very large crocodiles can build up dangerously high levels of lactic acid
- Releasing the animal is just as dangerous
- Jaw rope remains secure while other bindings are removed THEN it is removed
15
Q
Why is darting not ideal for drug delivery for anesthetizing crocodilians?
What is the better way to administer the initial drug dose?
What analgesics have been used?
What muscle relaxants have been used for immobilization? What are the effects of overdose? Are any species more susceptible?
What injectable anesthetics have been used?
What is the preferred induction agent?
Injection of propofol in what sites has resulted in mortalities?
A
Drug Delivery
- Darts – not so great
- Accurate shots in water are heard, osteoderms may deflect the dart, can drown if in water
- Hand or pole syringe – need restraint
- Injection sites
- Base of the tail caudal to hindlegs – large amount of fat if obese
- IM injections in front legs
- IV – lateral or ventral tail veins
Analgesia
- Opioids – morphine and meperiedine in juvenile saltwater crocs showed evidence of analgesia with thermal antinocieption
- Meloxicam has also been used
Tranquilizers/Sedatives
- Diazepam 20 minutes prior to succinylcholine resulted in smoother induction in American alligators then without it
Immobilizing Drugs
- Muscle relaxants
- Gallamine triethiodid – flaccid muscle paralysis
- Auditory, visual and tactile responsive
- Overdose results in bradycardia, GI hypermotility, increased salivation, mydriasis, respiratory muscle paralysis and death
- Commonly used in Nile crocodiles; low therapeutic index in American alligators and false gharials
- Reverse with neostigmine – well away from water
- Succinylcholine
- Produced depolarization before muscle relaxation, leading to hyperkalemia, lactic acidosis, and muscle damage – not recommended
- Administration of diazepam first, helped somewhat in alligators
- No reversal
- Atracurium – not recommended
- Gallamine triethiodid – flaccid muscle paralysis
- Opioids
- Etorphine has variable effects – worked in some alligators, did nothing in nile crocodiles but dilate pupils
- Ketamine – narrow window between little effect and death in Nile crocodiles
- Alpha 2, ketamine, midazolam combos produce sedation but higher doses than in mammals are needed
- MS-222 can be given IM as well
- Propofol
- 15-25 minutes of surgical anesthesia with righting reflexes returning in 25-40 minutes
- Preferred induction
- Alfaxalone also useful
- Inhalants anesthesia
- Complete tracheal rings – don’t overinflate cuffed tubes
- Anesthesia and restraint (F8):
- Struggling -> marked lactic acidemia, may become unconscious, drown, die.
- Cover eyes with damp towel, tape jaw shut or open with speculum.
- Avoid taping nostrils shut, avoid pulling legs.
- Slings, ladders, etc.
- Disadvantages to darting – Difficult to shoot animals in water, may drown, hard to tell if dart has fully discharged, osteoderms over dorsum.
- Hand injection with behavioral restraint more popular.
- Ax protocols recommended by author:
- Adults – Medetomidine, ketamine, iso.
- Juveniles or adults that are restrained – IV propofol, isoflurane.
- IV injection sites – Int jugular/occ sinus (NOT propofol -> mort), ventral or lateral coccygeal veins.
- Depth monitored via withdrawal reflex of limbs, increasing or decreasing HR, righting response, bite and corneal reflexes.
- Analgesia – Morphine, meperidine, meloxicam, tramadol, ketoprofen. Torb may sedate.
16
Q
Describe the approach to a coeliotomy in a crocodilian.
What is the preferred approach?
What are some unique sturctures within the crocodilian coelom that may be encountered?
What are some difficulties encountered post-operatively?
A
Mader Ch 101 Crocodilian Coeliotomy
- Coelomic surgery in crocodilians far more challenging due to anatomy
- limited window for accessing coelomic cavity
- Ventral skin thicker than on flanks and can be quite challenging to suture together, especially in older animals and those with ventral osteoderms (caiman)
- Good apposition of ventral skin often not possible à delayed healing
- Stainless steel sutures may be required
- Low skin elasticity in this area
-
Lateral flank approach may be preferred, midline and paramedian possible
- Skin on lateral aspect of body thinner and more pliable, hold sutures better
- Less pressure from body weight and viscera
- Suture line can be maintained dry if animal is kept in shallow water
- Ribs have to be incised to access stomach and liver
- Incision made caudal to last rib and cranial to pelvis, then incise muscle layers
- Upon entering coelom, mesenteric sac can be visualized and must be incised before intestines can be accessed
- Most of small intestines can be exteriorized, access to cranial colon and caudal aspect of stomach, duodenum fixed inside coelom, limited access other organs
-
Unique to crocodilians
-
Gastralia - free-floating ribs
- Found immediately caudal to sternum, originates from ischia and last gastralia and inserts on connective tissue on caudal aspect of liver
- Right and left gastralia joined by cartilage at midline
- Incision into ventral coelom requires cutting through gastralia
- May become more fibrotic or calcified as animal ages
- Cutting through gastralia generally has no detrimental impact on animal
-
Diaphragmaticus muscle
- Plays role in buoyancy – don’t transect during surgery
-
Distinct mesentery surrounding the intestines
- Duodenum lies in close association with stomach, right liver lobe, and gallbladder
- Incision has to be made through this to access the spleen, gonads, adrenals, and small and large intestines
- Also makes celioscopy challenging
- Suturing this mesentery challenging, herniation of intestines through incision is possible complication
- Do not have a centrally located ventral abdominal vein but rather two lateral abdominal veins
- Prominent pubic bones that extend ventrocranially from pelvis and articulate with ischium
- Obscure visualization of mesenteric “sac”
- Must be transected to access the small and large intestines
- Incision over this area not recommended
-
Gastralia - free-floating ribs
- Post -op care difficult
- When maintained outside of water, the weight of their bodies and viscera will place additional strain on the ventral skin incision, affecting its integrity and cleanliness
17
Q
Describe the effects of the following nutritional deficiencies in crocodilians:
Hypovitaminosis E - what are the causes? What are the lesions? Is this seen in the wild?
Hypovitaminosis A - what are the causes? What are the lesions?
Thiamine Deficienciy - What are the causes? What are the lesions?
A
-
Hypovitaminosis E (assoc w/ steatitis/fat necrosis)
- Caused by diets w/ fish high in polyunsaturated FAs, feed rancidity, or both
- Gross - discrete nodular/diffuse, firm yellow/brown adipose, fluoresce yellow/orange under UV
- Lesions often most severe in the tail – can result in immobility
- Can impinge on GI tract and cause decreased GI motility
- Histo – saponification, pigment consistent w/ ceroid in phagocytic cells (resp. for fluorescence)
- Pansteatitis in wild Nile crocs also been diagnosed; may be d/t similarly affected prey fish or Se deficiencies (Se deficiency not well studied in reptiles)
-
Hypovitaminosis A (retinol)
- Essential fat-soluble vitamin; storage primarily in liver
- Meat-only diets can be deficient if not adequately supplemented
- Hypovit-A assoc w/ development of squamous metaplasia
- Abundant sloughed keratin w/in glandular ostia can occur in lingual glands à grossly nodules on dorsal surface of tongue
- Can also affect large collecting ducts in kidneys à renal/visceral gout, 2nd tubulonephritis
- Squamous metaplasia of conjunctival and corneal epithelia possible
-
Thiamine (vit B1) deficiency
- Water-soluble vitamin, present in meat, fish, and plant sources
- Thiamine deficiency à neurologic disease
- Can present as abnormal buoyancy, head tilt, limb paresis, anisocoria, lethargy, lack of vocalization, stargazing
- Results from 1 of 2 mechanisms of thiamine destruction, or both
- Degradation of Vit B1 d/t repeated freezing/thawing
- Enzymatic destruction by thiaminases present in fish (esp if not maintained frozen)
- Gizzard shad and smelt have high thiaminases
- No gross lesions
- Histo – multifocal gray matter necrosis; denervation atrophy w/ in skeletal muscles of hindlimb
18
Q
Describe the following metabolic diseases in crocodilians:
Gout: What is the primary nitrogenous waste? How does gout form in crocodilians? Are there any predisposing factors? What are teh lesions?
Metabolic Bone Disease - What are teh lesions?
A
-
Gout
-
Ammono-uricotelic (produce 1° liquid nitrogenous waste as ammonia w/ increased uric acid during times of fasting)
- Uric acid levels surpassing renal threshold for clearance à gout precipitates
- Precipitates form w/in kidneys, serosal surfaces, and w/in and around joints
- Form of gout does not correlate w/ underlying cause
- Predisposing factors – low enviro. temps, dehydration, bacterial nephritis, sepsis, squamous metaplasia of collecting ducts, nephrotoxicosis; protein overload (no fast) may contribute
- Grossly – deposits of white, chalky to gritty material – most common on serosal surfaces (esp. pericardium) and in/around joints
- Renal parenchyma – pinpoint to slightly larger white foci
- Cytology – wet mounts à Dz-assoc. UA crystals acicular (needle-like), often radiating arrays
-
Ammono-uricotelic (produce 1° liquid nitrogenous waste as ammonia w/ increased uric acid during times of fasting)
-
Metabolic bone disease, similar to other carnivorous reptiles
- Presumably due to Ca:P imbalance (like other reptiles)
- Importance of UV relative to MBD in crocs not clear; lack of vit D may exacerbate the condition
- Gross – bone softening/elasticity; dental changes including diaphanous appearance, loss/malposition of teeth, skeletal changes (kyphoscoliosis, spinal fracture, long bone malformations, axial skeleton shortening)
- In juv. Farmed SW crocodiles – bones were pliable but otherwise morphologically normal
- Other changes include cystic degeneration/hyperplasia of parathyroid gland
19
Q
Toxicity is not common in crocodilians, but what is the most common toxin that affects them?
A
Toxic
- Toxic disease is uncommon
-
Lead toxicity not commonly reported as a clinical condition
- May be variable lead tolerance b/w spp. and age groups
- Relatively high tissue/blood levels reported in wild/captive, but clinical conditions & lesions rare
- In farmed Am. Alligators reduced reproduction d/t embryonic death may be only indication
20
Q
Describe the lesions associated with poxviral infection in crocodilians.
How does it vary between caiman and crocodiles?
What are the inclusion bodies?
A
-
Poxvirus
- Caiman poxvirus occurs largely in young (<1 yr) animals
- Gray-white circular papules, flat or depressed
- Commonly on dorsal head & body, oral mucosa, palpebrae, limbs
- May regress uneventfully or progress to large coalescent areas
- Histo – markedly hypertrophied epidermis (acanthosis) and intracellular edema, hyperkeratosis, necrosis
-
Intracytoplasmic inclusion bodies in ballooning keratinocytes
- Variably sized: small intensely eosinophilic to large hyaline forms
- Crocodile poxvirus in young (<1yr) farmed Nile crocs
- Circular brown raised ulcerated lesions, esp. on head/ventrum
- Brown, plaque-like lesion in oral mucosa
- Typical intracytoplasmic inclusion bodies – lesions in oral cavity may lack incl. bodies
- Morbidity typically very high, mortality typically low
- 2ndry presentation - “Pit holes” can occur in Nile crocs
- Deep holes in the scales of the ventral coelom
- Intracytoplasmic inclusions restricted to hyperplastic epithelium lining cysts
- Debris-filled cysts in hatchlingsàcollapsed cysts 2-3 yrs
- SW and FW crocodiles present w/ gross lesions similar to caiman (relatively mild, focal, flat)
- Caiman poxvirus occurs largely in young (<1 yr) animals
21
Q
Describes herpesviral disease in crocodilians.
What viruses are at play?
What are the three syndromes in estuarine (SW) crocodiles?
What is the disease in freshwater crocodiles?
A
-
Herpesvirus
-
Crocodyline herpesvirus-1,2, and 3 (CrHV-1,2,3) have been identified in farmed estuarine and freshwater crocs
- Initially one report in SW crocs – dermatitis, amphophilic intranuclear inclusion bodies
-
CrHV-1 and CrHV-2 assoc. w/ 3 dz syndromes in estuarine crocs
- Systemic lymphoproliferative syndrome w/ encephalitis (SLPE)
- Strongly linked w/ the herpesvirus (vs. other 2)
- Affects juv. in pens experiencing ↑ mortalities, poor growth, ill thrift
- Minimal gross lesions beyond poor BCS; if present may be conjunctival hyperemia, splenomegaly, pulmonary edema
- Conjunctivitis/pharyngitis (CP) (see below)
- Lymphonodular skin lesions (LNS) (see below)
- Systemic lymphoproliferative syndrome w/ encephalitis (SLPE)
- CrHV-3 is assoc. w/ lymphoproliferative syndrome in freshwater crocs
-
Crocodyline herpesvirus-1,2, and 3 (CrHV-1,2,3) have been identified in farmed estuarine and freshwater crocs
31
Q
What are teh clinical signs associated with Paratrichosomiasis in crocodilians?
What species are affected?
Why is this of economic importance?
A
-
Paratrichosomiasis (cutaneous)
- Paratrichosoma crocodylus (N. Guinea, estuarine, FW crocs)
- P. recurvum (American and Morelet’s crocs)
- Infections not clinically significant, but lesions affect appearance of hide (commercial value)
- Serpentine, tightly curved/hairpin “zigzag trails” on lateral or ventral skin
- Acute lesions – subtle, less distinct slightly erythematous tracts
- Presumably eggs elevate toward surface w/ maturation of epidermis and shed w/ keratin layers
34
Q
Conjunctivitis and pharyngitis of unknown etiology has been described in crocodilians.
What species are affected?
That lesions are present?
What organisms are suspected to play a role? Why is their involvement questioned?
A
-
Conjunctivitis w/ or w/o pharyngitis (CP)
- Nile, Siamese, estuarine crocodiles
- Classically described as assoc. w/ Chlamydia, but herpesviruses may play a role (both PCR pos.)
- Gross – bilateral thickening and edema of nictitating membrane w/ mucopurulent to fibrinocaseous exudate and gray discoloration and opacification of the cornea
- Corneal changes - edema, erosion, ulceration, and keratitis; rupture occurs in some cases
- Multifocal erosion or ulceration of the pharynx w/ adherent fibrinocaseous debris in the caudal oral cavity, based of tongue, and gular flap; lesions may extend into larynx
- No organisms (or inclusion bodies) found in any lesions thus far
39
Q
Describe the positioning for radiography of crocodilians.
Is lateral recumbency acceptable?
A
Positioning/restraint:
- Tape mouth shut
- For larger crocodilians - in the field, keep radiation safety in mind
- Vasovagal response - tape over eyes
- Keep sandbags out of view
Whole body rads
- Lateral recumbency is acceptable bc organs are compartmentalized and do not shift in coelom compared to other reptile sp; All except skull, tail, distal limbs
40
Q
Describe the appropriate positioning and imaging of the cranial and caudal coelom of crocodilians.
A
- Cranial coelom
- Right lateral (potentially left as well) and DV views; Front limbs extended cranially
- Multiple views may be necessary on larger patients - include all pulmonary boundaries
- Peak inspiration ideal
- Caudal coelom
- Right lateral and DV standard; Hind-limbs neutral or taped causally along tail base
- Multiple views
41
Q
Describe the appropriate positioning and views needed to assess the crocodilian skull radiographically.
A
Skull
- Lateral and VD or DV views minimum (vertical lateral is acceptable)
- Front legs against body/away from head
- Head extended at 90 degree angle perpendicular to table top if in lateral
- Thin foam wedge or paper towels to elevate nose
- Mandibles superimposed; Open mouth images with mouth gag
42
Q
List a few differentials for the following presentations in crocodilians:
Anorexia, Lethargy, Acute mortalities
A
- Stress and Immunosuppression
- Major factors in disease in captive crocodilians
- Stress response includes catecholamines, glucocorticoids, glucose, and lactate
- Anorexia, Lethargy, and Acute Mortalities
- Bacterial disease
- Poxvirus, herpesvirus, West Nile virus
- Thermostat malfunction
- Foreign bodies
- Physiological anorexia (part of reproductive cycle)
- Dystocia
- Hyperparathyroidism (juveniles)
43
Q
Describe the lesions produced by the following diseases in crocodilians:
Dermatophilosis (what is another name)
Poxvirus
West Nile Virus
A
- Dermatologic Signs
- Dermatophilosis (Brown Spot Disease) → ulcers between scales on ventrum
- Pox Virus → macular skin lesions
-
West Nile Virus → lymphohistiocytic proliferative syndrome of alligators (LPSA)
- Seen in survivors of WNV
- Affects hide quality
44
Q
List a few differentials for the following systemic signs in crocodilians:
Neurological signs
Respiratory signs
Musculoskeletal signs
GI signs
Ocular signs
A
- Neurological Signs
- West Nile virus → pearcute mortality (yearlings), circling, head tilt, tremors, death in alligators
- Mitigate with mosquito control and vaccination
- West Nile virus → pearcute mortality (yearlings), circling, head tilt, tremors, death in alligators
- Respiratory Signs
-
Mycoplasma alligatoris → lethargy, white ocular discharge, paresis, edema, pneumonia, pericarditis, polyarthritis
- M. crocodyli affects Nile crocodiles
- Mycobacteriosis → pneumonia with acid-fast bacteria
-
Mycoplasma alligatoris → lethargy, white ocular discharge, paresis, edema, pneumonia, pericarditis, polyarthritis
- Musculoskeletal Signs
- Nutritional secondary hyperparathryoiism
- Gout → limb paresis, joint swelling
- Vitamin A,B,C,E deficiency
- Gastrointestinal Signs
- Infectious enteritis → obstructions from fibrous material
- Ocular Signs
- Chlamydia → hepatitis and conjunctivitis and keratitis
