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Numerous protozoans are found on reptiles; many are harmless commensals. The most serious protozoal pathogen of reptiles is
Entamoeba
invadens
. Clinical signs are anorexia, weight loss, vomiting, mucoidal or hemorrhagic diarrhea, and death. Entamebiasis may be epidemic in large snake collections. Herbivores appear less susceptible than carnivores; a number of reptiles that seldom become affected or die can serve as carriers, including garter snakes, northern black racers, and box turtles. While most turtles are resistant, the giant tortoises are
susceptible. Other resistant groups include eastern king snakes, crocodiles, and cobras (possibly as an adaptation that allows them to eat snakes). Most boas, colubrids, elapids, vipers, and crotalids are highly susceptible. Transmission is by direct contact with the cyst form. Hepatic abscesses containing numerous
E
invadens
trophozoites are common in chronic cases. At necropsy, gross lesions may extend from the stomach to the cloaca. The intestine shows areas of ulceration that tend to coalesce, caseous necrosis, edema, and hemorrhage. Multifocal abscesses in a swollen, friable liver are seen in the hepatic form. Identification of trophozoites or cysts in a wet preparation of fresh feces or tissue impressions, or in histologic sections, is diagnostic. Turtles and snakes should not be housed together. |
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E
invadens
is best treated with metronidazole (20 mg/kg, PO, every 48 hr). Iodoquinol (50 mg/kg, PO, sid) has been advocated for a 3-wk course in chelonians. Dimetridazole may be given PO for 10 days at 40 mg/kg. Emetine hydrochloride may be given at 2.5-5 mg/kg, IM or SC, sid for 10 days. Tetracycline and paromomycin have been used but are considered ineffective against the hepatic form. The zoonotic potential for this disease should not be taken
lightly, and strict sanitation and hygiene measures should be observed. |
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Flagellates, especially
Hexamita
spp
, have been reported to cause urinary tract disease in chelonians and intestinal disease in snakes. The “giardia” seen in some cases of enteritis in snakes may actually be
Hexamita
or one of the relatively nonpathogenic flagellates that inhabit the intestinal tract of snakes. Differentiation between the species requires expertise, and special preservatives and stains are required to identify most of these organisms. Metronidazole at 25-50 mg/kg, PO, repeated in 3-5 days has been used to treat flagellates. Indigo snakes, king snakes, and uracoan rattlers should be treated at the low end of this dosage range. Fenbendazole at 50 mg/kg, PO for 5 days is
more effective at eliminating
Giardia
in mammals than is metronidazole. Early studies with fenbendazole are very encouraging and it would appear to be the drug of choice for treating flagellates. |
| Several coccidial organisms have been reported:
Klossiella
from the kidney,
Isospora
from the gallbladder and intestine, and
Eimeria
from the gallbladder. The severity of disease varies with the coccidia and affected species. Due to their direct life cycle, these parasites can increase to tremendous numbers, especially in immunosuppressed reptiles. Oocysts are not fragile and can survive for weeks in a dessicated condition. Fastidious, daily cleanings are necessary to remove all feces and feces-contaminated food and water. Insects and other food items must be removed on a daily basis as they are another
source of contamination (eg, crickets may eat the oocysts while gathering fluid from the feces). Treatment is sulfadimethoxine at 50 mg/kg, PO, for 3 days and then every 48 hr until infection is resolved. Treatment often takes 2-3 wk and success should be measured by serial fecal samples. |
| Trimethoprim/sulfa at 30 mg/kg every 48 hr as needed is another drug useful in the treatment of coccidia. Care should be taken when using sulfa in reptiles with dehydration or renal compromise. If in doubt, a balanced electrolyte solution should be administered PO at appropriate dosages. Even under the best conditions, treatment will eliminate coccidia in only 50% of cases. Treatment resulting in a reduction of coccidia is still important and coccidial numbers should be
periodically monitored. |
| Plasmodial (malarial) organisms, as well as other intracellular blood protozoans, have been reported in reptiles. Their significance is unknown, and treatment is not considered necessary. |
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Cryptosporidiosis is frequently reported in association with postprandial regurgitation, marked weight loss, and chronic debilitation. The organism affects the GI mucosa (in snakes), resulting in marked thickening of the rugae and loss of segmented motility. A mass in the gastric region is often, but not always, palpable, and contrast radiographs or endoscopic examination reveals rugal thickening. Many lizards, including
old world chameleons and savannah monitors, are affected primarily in the intestine. Mucosal thickening develops as a result of invasion by numerous cryptosporidial organisms. Diagnosis can be made using acid-fast stains on fresh feces or on the coating from regurgitated items or endoscopic gastric biopsies, which will identify the tiny oocysts. While several treatments have been suggested, none have been consistently effective. Intensive supportive care will often stabilize and help
prolong the life of the affected reptile. Euthanasia is a valid option for the infected reptile. Cryptosporidiosis was previously considered a zoonotic disease; however, it now appears that the strains commonly found in reptiles do not affect mammals.
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