Crocodilian Medicine

Jim Wellehan, DVM, PhD, DACZM, DACVM (Virology, Bacteriology/Mycology)

how are crocodilian hearts different from other vertebrate hearts

they can preferentially shunt oxygenated vs. unoxygenated blood into the left aortic arch

what does the left aortic arch supply, primarily

the stomach and GI

what is the foramen of panizza

aperture between r and l aortic arches

what shrinks the foramen of panizza

adrenaline

what is the subpulmonary conus

cog-tooth valve that blocks pulmonary outflow

what opens the subpulmonary conus

adrenaline

the left aorta shunting blood control ____ of the stomach

acidity

crocodilians have _____ airflow, despite NOT having air sacs

circular

what is the nitrogenous waste product of crocodilians

uric acid

how is uric acid eliminated

tubular secretion

what is added to uric acid to make it a colloidal suspension

protein

why is it important to make uric acid into a colloid suspension

the uric acid will get stuck in the tubule and block it

what does Wellehan hypothesize alligators were before ectothermic

endothermic

what ruled the earth during the Permian period

mammalian ancestors

what caused the end-permian extinction

increased heat, increasing CO2, increasing acidification

% species killed at end-permian extinction

90%

archosaurs are great in a ____ environment

hot

what do you do first when examining an alligator

examine from a distance

what do you examine from a distance

• attitude

• activity

• position

abnormal position can be caused by?

• asymettrical air

• dysequilibrium

• asymmetrical ballast?

what are examples of assymmetrical air

• pneumonia

• pneumocoelom

• GI gas

• SQ emphysema

what are examples of dysequilibrium

• Otitis media / interna

• CNS disease

what is seen in low body condition

• muscle wasting

• sunken supertemporal fossae

• tail lying flat on the side

you should _____ let your guard down around crocodilians

NEVER

what is most important in handling / restraining alligators

1. experienced handlers

2. always strap down to a board

anesthetic SOP

• safely contained to adminster premed

• premed

• induction

what is the premed for an alligator (do not remember dose probably)

• midazolam 0.1 mg/kg

• hydromorphone 0.05 mg/kg

• medetomidine 0.02 mg/kg

what class of drugs are crocodilians more sensitive in

opiods (hydromorphone)

what shouuld you place in the mouth of an alligator

bite block (never hands

how do you intubate a crocodilian

• push down gular ridge

• intubate through glottis

what class of opioids are effective in crocodiles

μ

options for analgesia

• opioids

• NSAIDs

• local analgesics

which of the options for analgesia are the most effective

opioids

local analgesics

cloacal exam

• sex determination

• cloacal wash

pulmonary endoscopy

• flexible endoscope through endotracheal tube

• can observe pathology

• can collect samples

GI endoscopy

• flexible endoscope

• can observe pathology

• can collect samples

• can remove foreign bodies

best imaging modality: rads or CT

CT

examples of imaging modalities

• rads

• CT

• U/S

• MRI

why are rads not great in crocodilians

osteoderms get in the way

how to place catheter

• flex tail laterally

• advance into vein as for blood collection

what stops you from advancing the catheter fully in an alligator caudal tail vein

the vein courses dorsoventally, and the catheter will not advance fully

what is the best route for enrofloxacin: PO or IV

IV (cannot reach tx concentrations PO)

dosages for for enrofloxacin

5 mg/kg IV q36h

what can enrofloxacin cause adversely

local tissue damage

oxytetracycline dosage

10 mg/kg IV or IM q5d

should you give enrofloxacin IV to a great horned owl

no, it will arrest

inhumane euthanasia options

• freezing

• decapitation without destruction of the brain

human euthanasia options

• rapid destruction of brain

  • gunshot

  • captive bolt

• chemical euthanasia

  • telazol followed by pentobarbitol (or KCl if you want a good pathology report)

what can hypothermia cause

• immunosuppression

• decrease GI function

alligators vs. crocodiles more adapted to cold weather

alligators

nutrional diseases of crocodilians

• obesity

• nutritional secondary hyperparathyroidism

• starvation

• hypovitaminosis A

• thiamine deficiency

• hypovitaminosis E

clinical signs of hypovitaminosis A in crocodilians

loss of teeth bc not normal development

where can thiamine and hypovitaminosis E come from

thawing frozen fish

what can result from hypovitaminosis E

white muscle disease and fibrosis

what are alligators more tolerant of than mammals

Pb (lead)

toxins for crocodilians

• lead

• zinc

• mercury

• organochlorines

adenovirus

• hepatitis and poor growth

• not characterized well

poxvirus

• skin lesions

two types of pox virus

• caiman pox

• crocodile pox

  • been sequenced

herpesvirus lesions

• pharyngitis / conjunctiviits

• lymphoid proliferation / nonsupparative encephalitis

• lymphohistiocytic infiltration of the dermis

how many herpes viruses are there

3 (1 FW, 2 SW)

iridovirus / ranavirus

• DNA virus that is good at humping hosts

• lots of quick deaths

west nile virus (flavivirus)

• high titers in american alligators

• deaths

• pix skin lesion

• diphtheric lesions in retropharynx

• potential zoonotic

• insect vector

  • possible fecal-oral transmission

what histo do you find in west nile skin lesion

lymphoplasmacytic inflammation

when does fecal-oral transmission occur in west nile virus

high temp (causes higher viral load)

bacterial diseases of crocodilians

• rhodococcus equi

• mycobacterium sp.

• Dermatophilus crocodyli

• chlamydia sp.

• mycoplasma alligatoris

• mycoplasma crocodyli

• proteobacteria

what does rhodococcus equi cause in crocodilians

sepsis

what to worry about for granulomatous mycobacterial infections

zoonosis

what is the most common skin disease found in an australian study on crocodiles

dermatophilus crocodyli

what does chlamydia cause in crocodilians

• hepatitis

• high mortality

• granulomas

what should you watch out for with chlamydia

zoonosis

mycoplasma alligatoris lesions

• polyserositis

• polyarthritis

• hepatitis

• pneumonia

• pericardiits

• likely all lies because there is likely another pathology going on (faulty study?)

what happens when crocodilians get mycoplasma alligatoris

explodse and die

what species is not pathogenic for mycoplasma alligatoris

siames crocodiles

families of proteobacteria (except enterobacteriales)

• aeromonadales

• pseudomonadales

• xanthomonadales

what do you think when you culture proteobacteria from crocodilians

all opportunists, look for underlying reason

proteobacteria usually have ______ resistance profiles

extensive

enterobacteriales (from Proteobacteria)

• salmonella

• citrobacter

• serratia

• klebsiella

• morganella

• proteus

• providencia

what are likely NOT oppportunisitc enterobacteriales spp.

• salmonella

• providencia

nannizziopsis crocodili

• fungus

• invasive cutaneously

• often fatal

opportunistic fungi

• purpureocillium lilacinus

• fusarium moniliforme

  • drug resistant!

• beuveria bassiana

• metarhizium anisopliae

what is shared among beauveria bassiana and ametarhizium anisopliae

insect pathogens

coccidiosis

• goussia

• eimeria

• isospora

what does goussia cause

visceral coccidosis

nematodes

• ascarids

• enoplea

ascarids

• large worms (more pathogenic)

• larvarl migration

• indirect life cycle

most common ascarid

Dijardinascaris sp.

intermediate host of dujardinascaris sp.

fish, shrimp

enoplea

• trichinella zimbabwensis

• paratrichosoma

trichinella zimbabwensis

• infects pigs

• crocodile sushi = bad idea

paratrichosoma sp.

• skin parasites

• leaves zig zag lesion

  • typically an alligator farmer problem due to quality of hide

nematode diagnosis

fecal float

nematode treatment

benzimidazoles 25(-50) mg/kg PO

pyrantel 5 mg/kg PO

what do you need to worry about with ivermectin and benzimidazoles in crocodilians

toxic (higher doses of benzimidazoles causes myelosuppression)

pentastomids

• indirect life cycle

• may be fatal to host

• sebekia sp. most common in N america

humans can be _____ hosts to pentastomids

secondary (ZOONOTIC)

whta is the only effective treatment of pentatomids

removal

leeches

• placobdella spp.

• vectors of hepatozoon / hemogregarina

what is the treatment of leeches

salt, manual removal

what are hepatozoon and hemogregarina spp.

blood parasites