Coccidiosis in Dogs and Cats


Coccidiosis is common in dogs and cats, and is a not infrequent cause of diarrhea and even death in puppies and kittens. Crowding and lack of sanitation promote its spread. Coccidia sometimes seed a breeding kennel, boarding kennel or veterinarian's wards so heavily that most of the puppies born or brought there become infected.


Coccidiosis can be diagnosed at necropsy by finding coccidia in the intestinal lesions. It can be diagnosed in affected animals by finding oocysts in association with diarrhea or dysentery. However, care must be taken to differentiate coccidiosis from coccidiasis, since many animals may be shedding oocysts without suffering from disease. Other disease agents should be searched for and found absent. The presence of a wave of oocysts during and shortly after an attack of enteritis and their marked diminution or disappearance soon thereafter would suggest that coccidia caused the attack.

Sporulated oocysts of coccidia of dog and cat

The oocysts of Isospora bigemina are usually sporulated when they are passed in the feces. They are often ruptured, releasing the sporocysts. These are very small, and will often be overlooked unless the high dry power of the microscope is used in making a fecal examination. In addition, they resemble Cryptosporidium oocysts and might be mistaken for them.


There is no good treatment for coccidiosis in dogs and cats once the signs of disease have appeared. All the coccidiostatic agents on the market are preventive rather than curative in action. The fact that coccidiosis is a self-limiting disease has often led to the belief that some ineffective drug, administered at the time natural recovery was due to begin, was responsible for the cure. Uncontrolled studies on coccidiosis therapy, such as that of Duberman (1960) with nitrofurazone, are worse than useless, since they may lead to false conclusions regarding a drug's value.

Craige (1949), a clinician with considerable experience in handling canine coccidiosis, considered treatment in an unsatisfactory state. Sometimes the animals would respond to sulfonamides, but he had better success by combining a sulfonamide with quinacrine, sulfocarbolates, tannin-yeast, iodine preparations, etc. McGee (1950) used sulfamethazine. Altman (1951) used chlortetracycline. Supportive treatments such as these, and particularly the use of antibiotics such as chlortetracycline and oxytetracycline to control secondary infections, may be helpful even tho they do not act on the coccidia themselves.


Sanitation and isolation are effective in preventing coccidiosis. Animal quarters should be cleaned daily. Runways should be concrete. Ordinary disinfectants are ineffective against coccidian oocysts, but boiling water, if it is still boiling when it reaches the oocysts, will kill them.