Cryptosporidium Infection, Cryptosporidiosis

Cryptosproidium are coccidia-like parasites that develop in the epithelial cells in the digestive, respiratory, and urinary tracts of animals. Cryptosporidia causes reduced uptake of fluids, electrolytes, and nutrients from the gut. Clinical signs of cryptosporidiosis in cats and dogs vary from none to chronic or intermittent diarrhea. Fluids and other supportive measures should be used in animals with diarrhea, but there is no proven safe and effective treatment of cryptosporidiosis. Cryptosporidia oocysts are very resistant to environmental damage, chlorination, and standard cleansers. This makes Cryptosporidium spp an important food- and waterborne pathogen. Extreme temperatures and prolonged contact with ammonia destroy the oocysts.

Diagnosis of Cryptosporidium Infection

The small size of Cryptosporidium oocysts makes them difficult to detect. Oocysts are often overlooked unless an examiner is specifically looking for them. Fecal flotation techniques used routinely in veterinary laboratories are adequate to demonstrate Cryptosporidium oocysts if large numbers are present.

Cryptosproidium was recognized as an important zoonosis in the early 1980s. Early studies assumed that all infections in mammals, including humans, were caused by the parasite Cryptosporidium parrum. Recent studies using molecular biologic tools and host-specificity studies indicate that cats and dogs have their own unique species of Cryptosporidium (C. felis and C. canis, respectively). Surveys indicate that up to 38.5% of cats and up to 44.8% of dogs are infected with Cryptosporidium spp. Cryptosporidium felis is primarily found in cats and Cryptosporidium canis in dogs; Cryptosporidium hominis is the newly recognized parasite in humans. Molecular studies indicate that C. hominis and C. parrum have been responsible for drinking water associated outbreaks of human cryptosporidiosis.

Prevention of Cryptosporidium Infection

Initial studies indicate that owning a cat or dog does not increase the risk of humans acquiring cryptosporidiosis, although human infections with C. felis and C. canis have been found in patients with AIDS, immunosuppressed patients, and children from impoverished areas. Current guidelines from the US Public Heath Service and Infectious Diseases Society of America recommend that HIV-infected humans should not take into their homes stray dogs or cats, animals with diarrhea, or dogs and cats younger than 6 months of age. They further recommend that if a dog or cat younger than 6 months of age is acquired by an HIV infected person, the animal should be tested for Cryptosporidium spp. C. canis is a Cryptosporidium sp. of public health significance, and under favorable conditions, the transmission of C. canis from dogs to humans may occur.

Adapted from
1. Lindsay, D.S. and A.M. Zajac, compend Cont Educ Pract Vet, pp 864-874, 2004, as reported in VetMed, Volume 11, issue 2, January, 2005, Iowa State University, Ames, Iowa
2. Possible Transmission of Cryptosporidium canis among Children and a Dog in a Household Lihua Xiao, Vitaliano A. Cama, Lilia Cabrera, Ynes Ortega, Julie Pearson, and Robert H. Gilman