coccidiosis: a common cause of diarrhea

What is it?

Coccidiosis is a parasitic disease that affects cattle, sheep, goats, swine, and poultry. The disease is caused by microscopic protozoan organisms known as coccidia that inhabit the cells of the intestinal lining.

Each class of livestock has a species-specific coccidia; there is no cross-infection between species. In ruminants, coccidia are of the genus Eimera. Not all coccidia species are pathogenic.

Coccidia are everywhere in the environment. It is nearly impossible to find a sheep or goat without coccidia. They are a normal inhabitant of the gut. Most sheep and goats tolerate a low level of coccidia with no adverse effects. However, a high level of coccidia can result in clinical disease.

How do they get it?

Lambs and kids are most susceptible to coccidiosis at 1 to 4 months age, though younger animals may become infected. Stress plays an important role in the development of coccidiosis. Clinical signs of coccidiosis are most commonly observed shortly following stress such as weather changes, weaning, overcrowding, long truck rides, and unsanitary conditions.

Signs of clinical coccidiosis develop 17 days after infection with pathogenic levels of coccidia oocysts. Pneumonia outbreaks sometimes occur at the same time or following an outbreak of coccidiosis.

The disease spreads from one animal to another by contact with infected feces. Fecal contamination of hay, grain, bedding, pasture, teats, water troughs, creep feeders, etc. are all sources of infection. Initial transmission of coccidiosis to the lamb and kid occurs via the ewe and doe. Lambs and kids, once infected, then contaminate each other. Animals which survive a coccidia outbreak usually develop a good immunity to clinical disease. Clinical coccidiosis can occasionally occur in adult animals, usually in response to stresses.

Clinical coccidiosis occurs more often in intensive management systems than in extensive ones because of the concentrating effects on both host and parasite. Feed lot conditions provide ideal circumstances for an outbreak of coccidiosis.

Coccidia Life Cycle

Coccidia Diagram.jpg


The primary sign of animals suffering from coccidiosis is diarrhea. The diarrhea may be mild to severe, depending upon the level of infection. The diarrhea is usually not bloody, but it can contain blood or mucous and be very watery. Anoroexia (off feed), dehydration, weakness, rough hair coat, and death may all occur as a result of coccidiosis.

Scouring usually occurs 17 days after infection; however, coccidia oocysts may not be evident in the fecal sample for another 5 days. Fecal flotation may or may not be a useful diagnostic tool, because while the presence of coccidia oocysts in the manure provides a link to coccidiosis, the absence of coccidia oocysts in a manure sample doesn’t mean coccidia are absent.

Sub-clinical coccidiosis (no symptoms) probably accounts for a significant portion of production loss.

Reference: Coccidiosis in Lambs by J.S. Rook, DVM, Michigan State University.