This disease is caused by a species of coccidia commonly found in the feces of puppies and, occasionally, adult dogs.

The main sign of coccidiosis is diarrhea.

Because infection is mild, symptoms usually do not occur unless the pup’s resistance has been lowered by a concurrent disease, malnutrition, or immunosuppression. Coccidiosis is a particular problem in neonatal puppies who are overstressed by filth, crowding, chilling, and poor sanitation. Puppies acquire the infection from contaminated premises or from their mother, if she is a carrier. When kennel sanitation is poor, puppies reinfect themselves from their own feces. An outbreak of coccidial diarrhea can also occur in association with roundworm infestation or the trauma of shipping.

Coccidiosis is an opportunist disease and depends on other factors (e.g. stress) and infections.

Always look for another precipitating cause. Five to seven days after ingesting oocytes, infective cysts appear in the feces. The first sign is mild diarrhea that progresses until the feces become mucuslike and tinged with blood. The diarrhea is accompanied by loss of appetite, weakness, and dehydration. Dogs who recover become carriers. Infected dogs and carriers can be identified by finding oocysts in a microscopic slide of fresh stool.


Treatment in adult dogs usually is not necessary, due to the mild nature of the diarrhea. Puppies with severe diarrhea may need to be hospitalized for fluid therapy. Antibiotics that have good efficacy against coccidiosis include sulfadimethoxine, trimethoprin-sulfa, furazolidone, and amprolium.


Known carriers should be isolated and treated. Wash down infected quarters daily with boiling water and/or dilute bleach or chlorhexidine solution to destroy oocysts. Coccidiosis can be prevented by maintaining clean quarters and providing an appropriate whelping environment, as described in Caring for the Newborn, page 490.