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Оглавление
Cryptosporidium
BASICS
DEFINITION/OVERVIEW
Cryptosporidia are apicomplexan parasites typified by possessing an apical complex, and with four naked sporozites within each oocyte. Cryptosporidia can be distinguished from other coccidian parasites by the location that they occupy within the host cell membrane, their capacity for autoinfection, and their resistance to anti‐parasitic medication. Possessing a durable oocyst wall consisting of a double layer of a protein–lipid–carbohydrate matrix, cryptosporidia are highly resistant to environmental degradation and chemical disinfection. Historically, oocyst morphology has been used for species identification, but this is considered unreliable and species assignment is now determined by molecular characteristics. Cryptosporidia are ubiquitous in the environment and are globally distributed.
ETIOLOGY/PATHOPHYSIOLOGY
Cryptosporidium pestis has been recovered from captive tortoises, with an additional species in chelonians, C. ducismarci, yet to be ratified.
C. ducismarci has been isolated from intestinal lesions in tortoises and additionally from asymptomatic ball pythons and chameleons.
Cryptosporidium oocysts from chelonians can cause severe infections in snakes when experimentally transferred.
Transmission is direct, with reptiles becoming infected after ingesting oocysts that have been shed in feces.
Autoinfection may also occur with some oocysts releasing their sporozoites within the host’s body.
No pre‐patent period has been determined.
SIGNALMENT/HISTORY
Infected animals usually have a history of chronic wasting accompanied by diarrhea and inappetence.
CLINICAL PRESENTATION
Subclinical (carrier state): animals may appear healthy and are able to shed oocysts intermittently for years.
Enteritis: a chronic debilitating enteritis without gastric involvement that may be accompanied by concurrent disease.
RISK FACTORS
The greatest risk factor for developing infection is poor quarantine of new animals entering a collection.
Husbandry
N/A
Others
N/A
DIAGNOSIS
DIFFERENTIAL DIAGNOSIS
Enteritis—bacterial or other protozoal disease.
DIAGNOSTICS
Examination of feces: unstained smears are useful but sensitivity of detection increases with an acid‐fast stain and is greatest with an IFA stain.
Sensitivity may be increased if performed postprandially.
An important limitation of these tests is their lack of specificity to differentiate Cryptosporidium spp.
False positive results can occur in animals that have ingested food items (i.e., mice) infected with other Cryptosporidium spp. that are not pathogenic to reptiles.
Serum antibody titers: can be assessed using an ELISA but antibodies take 6 weeks to develop. Best if combined with fecal or gastric lavage.ELISA positive, fecal positive—animal infected and shedding.ELISA negative, fecal negative—not infected.ELISA negative, fecal positive—recent infection (<6 weeks) or passing non‐reptilian Cryptosporidium spp.ELISA positive, fecal negative—has been infected at some point but not shedding or shedding at undetectable levels.
PCR: a highly sensitive test that can be used for either fecal or lavage samples. Can also differentiate between Cryptosporidium spp.
PATHOLOGICAL FINDINGS
Gross: intestinal lesions may include mucosal thickening with mucus accumulation.
Histopathology: intestinal lesions consist of a mixed inflammatory response with up to 80% of epithelial cells containing parasites.
TREATMENT
APPROPRIATE HEALTH CARE
Elimination of cryptosporidia from reptiles is difficult and rarely rewarding.
NUTRITIONAL SUPPORT
Force‐feeding with easily digestible proteins.
Direct feeding by stomach tubing can be performed in some species; placement of an esophagostomy tube should be considered for chronic management.
Supportive fluid therapy should be provided.
CLIENT EDUCATION/HUSBANDRY RECOMMENDATIONS
Clients should be made aware of the insidious nature of infection, the unlikelihood of successful treatment, the risks that affected animals pose to the remaining collection, and the known zoonotic potential of some species of Cryptosporidium.
Cryptosporidium oocysts are hardy and can persist in the environment for long periods, so thorough cleaning and disinfection is important.
Methods for disinfection include:ammonia (5%) or formal saline (10%) solution contact for 18 hoursexposure to moist heat (45–60 degrees C) for 5–9 minutesfreezingthorough desiccation alone, or after any chemical application
MEDICATIONS
DRUG(S) OF CHOICE
Trimethoprim sulfonamide 30 mg/kg PO SID for 14 days, then 1–3 times weekly for 3 months may reduce oocyst shedding but does not eliminate cryptosporidium organisms from the gastrointestinal mucosa.
Paromomycin 100 mg/kg PO SID for 7 days; then twice weekly for 6 weeks; and 360 mg/kg q48h for 10 days resulted in complete resolution in experimentally infected bearded dragons (Pogona vitticeps).
Hyperimmune bovine colostrum 1% body weight by volume PO once weekly for 6 weeks. Currently not available commercially.
PRECAUTIONS/INTERACTIONS
Euthanasia should be strongly considered for affected animals to limit spread.
If euthanasia is not an option, diseased reptiles should be separated from the remaining collection and strict barrier nursing protocols enacted to prevent spread.
FOLLOW‐UP
Regular fecal examination and ELISA assays for suspected at risk animals.
PATIENT MONITORING
Monitor for signs of disease, i.e., wasting, diarrhea, persistent regurgitation.
EXPECTED COURSE AND PROGNOSIS
Grave prognosis, likely chronic wasting and death.
MISCELLANEOUS
COMMENTS
N/A
ZOONOTIC POTENTIAL
C. pestis is a known zoonotic risk; C. ducismarci shows genetic similarities to other zoonotic Cryptosporidium spp.
Caution should be used when working with suspected cases.
SYNONYMS
N/A
ABBREVIATIONS
ELISA = enzyme‐linked immunosorbent assay
IFA = immunofluorescent antibody
IM = intramuscular
IV = intravenous
PCR = polymerase chain reaction
PO = per os
SC = subcutaneous
Suggested Reading
1 Cranfield MR, Graczyk TK. Cryptosporidiosis. In: Mader DR, ed. Reptile Medicine and Surgery. 2nd ed. St. Louis, MO: Elsevier Saunders; 2006:756–762.
2 Fayer R. Taxonomy and species delimitation in Cryptosporidium. Exp Parasitol Jan 2010; 124(1): 90–‐97.
3 Fayer R, Graczyk TK, Cranfield MR. Multiple heterogenous isolates of Cryptosporidium serpentis from captive snakes are not transmissible to neonatal BALB/c mice (Mus musculus). J Parasitol 1995;81(3):482–484.
4 Graczyk TK, Owens R, Cranfield MR. Diagnosis of subclinical cryptosporidiosis in captive snakes based on stomach lavage and cloacal sampling. Vet Parasitol 1996;67:143–151.
5 Grosset C, Villeneuve A, Brieger A, Lair S. Cryptosporidiosis in juvenile bearded dragons (Pogona vitticeps) effects of treatment with paromomycin. J Herp Med Surg 2011;21:10–15.
6 Pedraza‐Diaz S, Ortega‐Mora LM, Carrion BA, et al. Molecular characterisation of Cryptosporidium isolates from pet reptiles. Vet Parasitol 2009;160(3–4):204–210.
7 Plutzer J, Karanis P. Genetic polymorphism in Cryptosporidium species: An update. Vet Parasitol 2009;165(3–4):187–199.
8 Richter B, Rasim R, Vrhovec MG, et al. Cryptosporidiosis outbreak in captive chelonians (Testudo hermanni) with identification of two Cryptosporidium genotypes. J Vet Diagn Invest 2012;24(3):591–595.
9 Scullion FT, Scullion MG. Gastrointestinal protozoal diseases in reptiles. J Exot Pet Med 2009;18(4):266–278.
10 Shahiduzzaman M, Daugschies A. Therapy and prevention of cryptosporidiosis in animals. Vet Parasitol 2012;188(3–4):203–214.
11 Traversa D. Evidence for a new species of Cryptosporidium infecting tortoises: Cryptosporidium ducismarci. Parasit Vectors 2010;3(21):1–4.
12 Traversa D, Iorio R, Otranto D, et al. Cryptosporidium from tortoises: Genetic characterisation, phylogeny and zoonotic implications. Mol Cell Probes 2008;22(2):122–128.
13 Uhl EW, Jacobson E, Bartick TE, et al. Aural‐pharyngeal polyps associated with Cryptosporidium infection in three iguanas (Iguana iguana). Vet Path 2001;38:239–242.
Author T. Franciscus Scheelings, BVSc, MVSc, PhD, MANCVSc (Wildlife Health) DECZM (Herpetology)
