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Last updated January 1, 2014

Cryptosporidium: Health Threat to Humans and Reptiles

Compiled by Melissa Kaplan


Cryptosporidium affects humans as well as wild and captive animals. Humans and captive animals can become infected when drinking contaminated water (and the majority of municipal water supplies do not eradicate or kill Cryptosporidium, nor do most water purification devices people attached to their faucets or main water lines). When herp keepers feed their captive herps wild-caught prey, they are also exposing their herps to the risk of Cryptosporidium. Cryptosporidium can be relatively benign in healthy humans and animals, but can be deadly in those who are immunocompromised and otherwise considered to be at high risk for bacterial, viral and parasitic infections. Since captive herps, especially wild-caught ones, are always stressed to some degree, feeding wild-caught prey increases their risk of contracting parasites.

Genetic diversity of Cryptosporidium spp. in captive reptiles.
Xiao L, Ryan UM, Graczyk TK, Limor J, Li L, Kombert M, Junge R, Sulaiman IM, Zhou L, Arrowood MJ, Koudela B, Modry D, Lal AA. Appl Environ Microbiol. 2004 Feb;70(2):891-9.
The genetic diversity of Cryptosporidium in reptiles was analyzed by PCR-restriction fragment length polymorphism and sequence analysis of the small subunit rRNA gene. A total of 123 samples were analyzed, of which 48 snake samples, 24 lizard samples, and 3 tortoise samples were positive for Cryptosporidium: Nine different types of Cryptosporidium were found, including Cryptosporidium serpentis, Cryptosporidium desert monitor genotype, Cryptosporidium muris, Cryptosporidium parvum bovine and mouse genotypes, one C. serpentis-like parasite in a lizard, two new Cryptosporidium spp. in snakes, and one new Cryptosporidium sp. in tortoises. C. serpentis and the desert monitor genotype were the most common parasites and were found in both snakes and lizards, whereas the C. muris and C. parvum parasites detected were probably the result of ingestion of infected rodents. Sequence and biologic characterizations indicated that the desert monitor genotype was Cryptosporidium saurophilum. Two host-adapted C. serpentis genotypes were found in snakes and lizards. [Full text]


Proliferative enteritis in leopard geckos (Eublepharis macularius) associated with Cryptosporidium sp. infection. Terrell SP, Uhl EW, Funk RS. J Zoo Wildl Med. 2003 Mar;34(1):69-75.
Twenty-three leopard geckos (Eublepharis macularius) with various clinical histories of weight loss, anorexia, lethargy, and diarrhea were submitted either intact or as biopsy specimens to the University of Florida Anatomic Pathology Service. Gross necropsy findings in the intact geckos included marked reduction of subcutaneous adipose tissue stores at the tail base and mild thickening and reddening of the small intestine. Histologic examination revealed Cryptosporidium sp. infection associated with hyperplasia and mononuclear inflammation of the small intestine in all geckos. Parasites and lesions were only rarely observed in the stomach and large intestine of geckos. The histologic and ultrastructural lesions in the small intestine of leopard geckos infected with Cryptosporidium sp. have not been well characterized previously. This report implicates Cryptosporidium sp. as the cause of disease in the geckos and describes the range of histologic lesions observed.


Aural-pharyngeal polyps associated with Cryptosporidium infection in three iguanas (Iguana iguana). Uhl EW, Jacobson E, Bartick TE, Micinilio J, Schimdt R. Vet Pathol 2001 Mar;38(2):239-42
Cryptosporidium spp. infection was associated with aural-pharyngeal polyps in three iguanas (Iguana iguana). All iguanas were presented for masses protruding from the ear canal, and the disease was characterized by a chronic clinical course. The masses consisted of nests of cystic glands surrounded by abundant fibrous connective tissue and lined by hyperplastic cuboidal to pseudostratified columnar epithelium that was moderately to heavily colonized by cryptosporidial organisms. Electron microscopy revealed that the majority of organisms were trophozoites.


Successful hyperimmune bovine colostrum treatment of Savanna monitors (Varanus exanthematicus) infected with Cryptosporidium sp. Graczyk TK, Cranfield MR, Bostwick EF.J Parasitol 2000 Jun;86(3):631-2
Therapy based on the protective passive immunity of hyperimmune bovine colostrum (HBC) (raised against Cryptosporidium parvum in cows) was applied to 4 Savanna monitors (Varanus exanthematicus) with gastric Cryptosporidium sp. infections. All lizards were moderately emaciated, and their fecal and gastric lavage samples contained moderate numbers of Cryptosporidium sp. oocysts. The first 3 of 7 gastric HBC treatments at 1-wk interval each decreased the numbers of oocysts in the fecal and gastric samples to undetectable levels. Neither feces nor lavages of the HBC-treated lizards contained Cryptosporidium sp. oocysts after the HBC therapy, whereas such samples of a single control lizard remained positive for oocysts. Two of the HBC-treated lizards died spontaneously due to metastasized carcinoma and septicemia of unknown etiology, respectively, and 2 lizards treated and killed during the experiment were histologically negative for developmental stages of Cryptosporidium sp. The control lizard died spontaneously of septicemia of unknown etiology and contained developmental stages of Cryptosporidium sp. in the gastric region. The HBC therapy was efficacious in V. exanthematicus and is recommended for lizards with gastric cryptosporidiosis.


Cryptosporidium serpentis oocysts and microsporidian spores in feces of captive snakes. Graczyk TK, Cranfield MR. J Parasitol 2000 Apr;86(2):413-4
Fecal smears of 90 snakes, 29 lizards, and 8 turtles and tortoises were tested for Cryptosporidium spp. oocysts and microsporidian spores. Microsporidian spores measured mean = 3.7 microm in length and mean = 2.3 microm in width and were present in feces of 19 snakes and 1 lizard (16%); 13 of these snakes also shed Cryptosporidium serpentis oocysts. The oocysts were numerous in all positive samples, whereas microsporidian spores were always sparse, irrespective if whether fecal samples contained the oocysts. Retrospective examination of reptile clinical records revealed that all animals shedding microsporidian spores died naturally due to diseases, pathologic conditions, and clinical problems or were killed due to severe cryptosporidiosis. The present study indicates that microsporidian infections in reptiles have the features of an opportunistic infection.


Clinical and pathological observations on natural infections of cryptosporidiosis and flagellate protozoa in leopard geckos (Eublepharis macularius). Taylor MA, Geach MR, Cooley WA. Vet Rec 1999 Dec 11;145(24):695-9
A group of adult leopard geckos (Eublepharis macularius) which had been losing weight for several months were found to be infected with Cryptosporidium species. Histological and electron microscopical investigations on the intestines of five of the lizards revealed the presence of large numbers of the developmental stages of Cryptosporidium species attached to the mucosal surface of the lower intestine, and large numbers of flagellate protozoa, suspected to be predominantly Trichomonas species, in the gut lumen. The clinical signs were attributed to the presence of one or both types of parasites.


Intestinal Cryptosporidium sp. infection in the Egyptian tortoise, Testudo kleinmanni. Graczyk TK, Cranfield MR, Mann J, Strandberg JD. Int J Parasitol 1998 Dec;28(12):1885-8
An adult Egyptian tortoise (Testudo kleinmanni) presented with clinical signs of enteritis and died 5 weeks after initiation of antibiotic therapy. Histological examination of the small intestine revealed heavy infection with Cryptosporidium sp.; over 80% of epithelial cells harboured the pathogen. No Cryptosporidium developmental stages were present in the stomach or the lungs. The intestinal lamina propria and mucosa were infiltrated by heterophils, lymphocytes and macrophages. The present study constitutes the first report of Cryptosporidium sp. infection in T. kleinmanni, and the first histological documentation of intestinal cryptosporidiosis in Chelonia.


Cryptosporidium Found In Woodland Creatures.
American Society for Microbiology
Watch out. Those innocent woodland creatures could be harboring the Cryptosporidium parasite, say researchers from Columbia University. They report their findings in the March 2001 issue of the journal Applied and Environmental Microbiology.

"We performed a wildlife survey, focusing on white-tailed deer and small mammals, to assess whether they may serve as environmental sources of Cryptosporidium," say the researchers. They collected fecal samples from several locations in lower New York State over a two year period and tested them for the parasite. They found evidence of the parasite in samples from white-tailed deer, chipmunks, skunks, racoons and muskrats.

"These data provide evidence that there is sylvatic transmission of Cryptosporidium parvum involving deer and other small mammals. This study affirmed the importance of wildlife as potential sources of Cryptosporidium in the catchments of public water supplies," say the researchers.


Cryptosporidium parvum infection involving novel genotypes in wildlife from lower New York State. J. Perz and S. Le Blancq. 2001. Applied and Environmental Microbiology, 67: 1154-1162.
Cryptosporidium, an enteric parasite of humans and a wide range of other mammals, presents numerous challenges to the supply of safe drinking water. We performed a wildlife survey, focusing on white-tailed deer and small mammals, to assess whether they may serve as environmental sources of Cryptosporidium. A PCR-based approach that permitted genetic characterization via sequence analysis was applied to wildlife fecal samples (n = 111) collected from September 1996 to July 1998 from three areas in lower New York State. Southern analysis revealed 22 fecal samples containing Cryptosporidium small-subunit (SSU) ribosomal DNA; these included 10 of 91 white-tailed deer (Odocoileus virginianus) samples, 3 of 5 chipmunk (Tamias striatus) samples, 1 of 2 white-footed mouse (Peromyscus leucopus) samples, 1 of 2 striped skunk (Mephitis mephitis) samples, 1 of 5 racoon (Procyon lotor) samples, and 6 of 6 muskrat (Ondatra zibethicus) samples. All of the 15 SSU PCR products sequenced were characterized as Cryptosporidium parvum; two were identical to genotype 2 (bovine), whereas the remainder belonged to two novel SSU sequence groups, designated genotypes 3 and 4. Genotype 3 comprised four deer-derived sequences, whereas genotype 4 included nine sequences from deer, mouse, chipmunk, and muskrat samples. PCR analysis was performed on the SSU-positive fecal samples for three other Cryptosporidium loci (dihydrofolate reductase, polythreonine-rich protein, and beta-tubulin), and 8 of 10 cloned PCR products were consistent with C. parvum genotype 2. These data provide evidence that there is sylvatic transmission of C. parvum involving deer and other small mammals. This study affirmed the importance of wildlife as potential sources of Cryptosporidium in the catchments of public water supplies.


WATER QUALITY: Sequential disinfection process provides safer drinking water
James E. Kloeppel, Physical Sciences Editor, News Bureau, UIUC

CHAMPAIGN, Ill. -- Fresh from the faucet, a killer may be lurking in your glass. Cryptosporidium parvum is a parasitic protozoan that can infiltrate a city’s water supply -- as happened in Milwaukee in March 1993, when more than 400,000 people were infected. With symptoms similar to food poisoning, outbreaks of cryptosporidiosis can prove deadly for individuals with immune system deficiency problems.

Researchers at the University of Illinois are developing a cost-effective treatment strategy for providing drinking water free of this harmful contaminant.

"Most surface-water disinfection systems in the U.S. were originally designed, or subsequently modified, to control contamination by another dangerous microbe, Giardia lamblia," said Benito Marinas, a UI professor of civil and environmental engineering. "Unfortunately, the disinfectant concentration and contact time in these systems are generally inadequate for killing C. parvum."

Destroying the parasite is also complicated by the fact that, outside its host, C. parvum enters a spore-like dormant stage, Marinas said. "Encased in a dense wall of proteins and lipids, this ‘oocyst’ is extremely resistant to chlorine -- the disinfectant most commonly used in water treatment plants."

Marinas and graduate students Amy Driedger and Jason Rennecker have found that sequentially applying two disinfectants -- such as ozone and chlorine -- is much more effective in killing C. parvum than either treatment alone. The primary disinfection step can result in secondary disinfection rate increases of up to 2,200 percent, compared to the rates for a single disinfectant.

While some water treatment plants already use ozone to kill G. lamblia, they are not designed to kill C. parvum, which requires 25 to 40 times greater ozone exposure. But, by first using ozone -- at levels to kill G. lamblia -- and then following with chlorine, the researchers can easily destroy C. parvum.

"Ozone not only attacks the oocyst wall – thereby opening the door for the next disinfectant – it also oxygenates the wall and changes the very nature of the material, making it more susceptible to chlorine," Marinas said. He and his students are currently characterizing the synergistic effects that take place, and optimizing the sequential disinfection process.

Using chlorine as the secondary disinfectant also carries an additional benefit, Marinas said.

"Unlike ozone, which decomposes rapidly, chlorine will remain in the distribution system for a long time, offering protection against any subsequent contamination."

Because the sequential disinfection process works most effectively at low temperatures, it offers a potential solution to killing C. parvum oocysts during the wintertime in regions where the water temperature approaches the freezing point, Marinas said.

The researchers published their latest findings in the January issue of Water Research, a journal of the International Water Association. The U.S. Environmental Protection Agency and the Illinois Water Resources Center provided funding for the work.


More on Cryptosporidium...

Cryptosporidium sp. in a free ranging house gecko (Hemidactylus turcicus) in Israel, Parassitologia 2001 Sep;43(3):91-3

Occurrence of Cryptosporidium sp. oocysts in fecal and water samples in Austria, Acta Trop 2001 Oct 22;80(2):145-9

Six new species of coccidia (Apicomplexa: Eimeriidae) from East African chameleons (Sauria: Chamaeleonidae),J Parasitol 2000 Apr;86(2):373-9

Hyperimmune bovine colostrum treatment of moribund Leopard geckos (Eublepharis macularius) infected with Cryptosporidium sp.,Vet Res. 1999 Jul-Aug;30(4):377-82.

More from PubMed (keywords: Cryptosporidium AND reptile)

Working Group on Waterborne Cryptosporidium Handbook (1.1 mb PDF)
(See Access Adobe to convert this .pdf file to .html)

CDC's FOODNET publications on Cryptosporidium

Morbidity & Mortality Weekly (MMWR): Cryptosporidium reports

CDC's Division of Parasitic Diseases Cryptosporidium Fact Sheets

CDC: Preventing Cryptosporidosis: A Guide to Bottled Water and Water Filters

Cryptosporidium (AvianBiotech)

Novel Cryptosporidium genotypes in cryptic cryptosporidosis cases: First report of human infection with a cervine genotype, EID 8(3), Mar 2002

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