Cryptosporidium / Coccidia

Coccidia are a group of protozoan parasites that are extremely common. Coccidia infection is especially common in young animals housed in groups (in breeding facilities, pet stores, shelters, rescue areas, kennels, etc.) This is a common parasite and is not necessarily a sign of poor husbandry.

Coccidia live in the intestinal tract and if they proliferate, or at times of stress, will also cause chronic bloody stools.

After an outbreak of a specific species of coccidia, the flock will develop a resistance to the exposed coccidia species but remain resistant to other infective species. An infection may be mild enough to go unnoticed while a large infective dose of coccidia may produce severe lesions that can cause death. Coccidia survive for long periods outside the bird’s body, so infection can occur simply by placing a bird in a contaminated cage or aviary.

Avian hosts harbor multiple species of Cryptosporidium. In chickens, C. baileyi infects the bursa, cloaca, and respiratory system and can lead to severe clinical illness and death. Unnamed species of Cryptosporidium occur in quail and ostriches. In quail, the parasite infects the small intestine and mortality in hatchlings can reach 90-100%. The species in ostriches infects the cloaca and can cause cloacal prolapse and death in chicks. Enteric coccidia have both internal and, sometimes, external antigens that interact non-specifically but strongly with mucins in feces.

Coccidia infection causes a watery diarrhea which is sometimes bloody and can even be a life-threatening problem to an especially young or small pet.


It is difficult, if not impossible, to prevent coccidiosis by sanitation alone. It is best prevented by addition of a drug (coccidiostat) to the feed that controls the growth of coccidia in the digestive tract. Many coccidiostats are available commercially. Coccidiostats should not be indiscriminately used and recommendations must be followed precisely. A coccidiosis vaccine is also available commercially. The product is useful only in certain types of poultry operations and must be used as recommended. Seek expert advice before using the vaccine.

References / Related Resources: – a great German site which provides great image and descriptions on this topic …. Cryptosporidium Research at Kansas State UniversityTopics in Cryptosporidium ResearchThe Coccidia of the World
Supported by NSF-PEET DEB 9521687 – Donald W. Duszynski1, Lee Coucspan, and Steve J. Upton2, 1Department of Biology, University of New Mexico, 2Division of Biology, Kansas State University.

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