Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 2003
Publication Date: December 9, 2004
Citation: Fayer, R. 2004. Cryptosporidium - a waterborne zoonotic parasite. Veterinary Parasitology. 182:37-56.
Interpretive Summary: Cryptosporidium parvum is a protozoan parasite responsible for the largest outbreak of waterborne disease ever recorded. Cryptosporidium parvum, found worldwide, has been reported to infect 155 species of mammals. It is highly prevalent in preweaned dairy calves and is also found in older cattle. A cycle of transmission exists among feral rodents living in areas of animal agriculture and the domesticated animals. An environmentally resistant fecal-borne stage is transmitted among susceptible animals in contaminated feed and water. Other wild animals likely participate. Following rainfall events feces from these animals are carried by runoff into surface waters such as rivers and lakes that are used for drinking and recreational waters. Humans and animals that ingest such water can acquire cryptosporidiosis. This disease is characterized primarily by diarrhea lasting approximately a week in otherwise healthy persons. Persons suffering from conditions or receiving medications that reduce their immune competency can suffer severe, chronic, even life-threatening cryptosporidiosis resulting in dehydration and possibly dissemination to other organs of the body. Taxonomy, biology, pathology, and treatment are reviewed and future trends are discussed.
The genus Cryptosporidium is composed of 13 valid species. Speciation, once based on morphology of the oocyst stage and host specificity, now requires molecular data to confirm identity. Isolates of C. parvum, reported in 155 species of mammals and found to be composed of several genotypes, will require molecular data to verify future identification. Two former genotypes are now recognized as separate species- C. canis and C. hominis. Waterborne oocysts have been found in surface water (including rivers, lakes, estuaries, and marine waters) used for drinking water and/or recreation, as well as swimming pools. Primary potential sources of contamination of all surface waters include runoff from urban streets, agricultural land (especially cattle farms) and wildlife habitats, leaky septic tanks, and sewage outfalls. Oocysts of C. hominis (formerly C. parvum genotype 1) are responsible for the largest waterborne disease outbreak ever recorded. Future trends are discussed.