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United States Department of Agriculture

Agricultural Research Service

Title: Cryptosporidium and Other Opportunistic Protozoans Potentially Transmitted from Animals to Humans

Author
item Fayer, Ronald

Submitted to: Colegio Brasileiro De Parasitologia Veterinaria
Publication Type: Proceedings
Publication Acceptance Date: June 24, 2002
Publication Date: September 5, 2002
Citation: FAYER, R. CRYPTOSPORIDIUM AND OTHER OPPORTUNISTIC PROTOZOANS POTENTIALLY TRANSMITTED FROM ANIMALS TO HUMANS. Colegio Brasileiro de Parasitologia Veterinaria. 2002.

Interpretive Summary: AIDS has assumed a major, almost overwhelming, public health importance in many parts of the world. Persons with AIDS become susceptible to a variety of opportunistic pathogens that cause high morbidity and mortality. Many viruses, bacteria, fungi, and parasites can become opportunistic pathogens. Protozoan parasites such as Cryptosporidium, Toxoplasma, Microsporidia, and Isospora are important opportunistic pathogens that can be spread from animals to humans. The role of farm animals in the epidemiology of these diseases is not always clear but molecular tools are helping to more precisely identify the parasites and their sources.

Technical Abstract: The pandemic of the Human Immunodeficiecy Virus and the resultant acquired immunodeficiency disease HIV/AIDS has assumed a major, almost overwhelming, public health importance in many parts of the world. HIV steadily weakens the body's immune system, increasing susceptibility to a variety of opportunistic pathogens responsible for high morbidity and mortality. Many viruses, bacteria, and fungi can become opportunistic pathogens. Protozoa such as Cryptosporidium, Toxoplasma, Microsporidia, and Isospora also are important opportunistic pathogens. Organisms that normally cause little or no disease in immune competent persons can be an opportunistic pathogen in HIV/AIDS persons. Cryptosporidiosis, found in humans and ruminants, presents primarily as diarrheal disease. Highly virulent isolates cause mortality in cattle while less virulent isolates cause morbidity and mortality in immunosuppressed humans and animals. Toxoplasma gondii is a protozoan parasite with a life cycle in the intestine of felids. Fecal stages from cats infect 350 species of vertebrates and develop into cysts in immune competent hosts. When persons that harbor cysts become immune compromised, parasites within cysts begin to multiply rapidly, often in the central nervous system, causing lesions, illness, and mortality. Of over 1000 species in the phylum Microspora, 13 species in 7 genera infect humans, mostly AIDS patients. The most common symptom is diarrhea. Food animals may serve as sources of some of these species. Giardia, the most common flagellate of mammals and birds and the most common intestinal parasite of humans, has been reported in lambs and calves with prevalence up to 100%, suggesting farm animals as possible sources of human infection.

Last Modified: 4/19/2014
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