The microscopic organism called coccidia lives in the intestines of a dog or cat and causes a disease referred to as coccidiosis. Signs include diarrhea, vomiting, loss of appetite, and lethargy. Puppies and kittens can become dehydrated and even die from an infection, though some pets never show any signs at all. A pet can pick up the infection from the soil, an infected animal’s feces or by eating an infected rodent. Fortunately, there are medications to treat coccidiosis in both dogs and cats.


Coccidiosis is a common parasitic intestinal condition caused by a microscopic, single-celled organism known commonly as coccidia. Though there are several types of coccidia, dogs with this condition are usually infected with Isospora canis, while cats are infected with Isospora felis.

Infected dogs and cats shed cysts containing the parasite in their stool. These cysts can survive in the environment for as long as a year. Other pets can become infected by swallowing the cysts from a contaminated environment, usually during grooming. Dogs and cats can also contract the parasite by eating an infected rodent.

Once inside the pet’s digestive tract, the cysts break open and the parasite enters an intestinal cell, where it reproduces. The cell eventually ruptures, releasing the parasites and damaging the intestinal lining.

The coccidia species that infect dogs don’t infect cats, and vice versa. However, the cysts in the feces from one dog can infect another dog, and the cysts in the feces from one cat may be infective to another cat. It’s very unlikely that a human will become infected with the species of coccidia that affect dogs and cats.

A high incidence of coccidiosis is seen in kenneled dogs, especially when they are housed under intensive conditions for a long time. Puppy mills and other busy breeding kennels are most often plagued by coccidiosis, so buyers are cautioned to investigate these facilities for signs of diarrhea.

Symptoms and Identification

Signs of coccidiosis include watery diarrhea that will often be tinged with blood or mucus. Pets with this condition may also experience vomiting, a loss of appetite and lethargy. Puppies and kittens can be severely affected, exhibiting dehydration, weight loss, and, in some cases, even death.

Older pets usually have milder signs. Some pets can show no signs at all while still shedding the parasite cysts in their feces.

A diagnosis of coccidiosis is made by identifying parasite cysts on a fecal exam. Any new pet being introduced into the home should have a fecal sample tested as soon as possible to diagnose coccidiosis or other intestinal parasite infections. Because some pets never show any signs, fecal tests during annual physical examinations are considered standard practice for all pets.

Affected Breeds

All breeds of dogs and cats are considered equally susceptible.


Several oral medications may be used to treat coccidiosis. Most pets will require daily treatment for 5 to 10 days, but some pets will have to be retreated if the infection isn’t resolved after the first or even second go-round. In multi-dog or multi-cat households, it’s a good idea to treat the other dogs and cats, respectively, to prevent reinfection from other pets that may carry the parasite but show no signs.

Pets (particularly puppies and kittens) with severe dehydration may need fluid therapy and hospitalization.

Since the cysts are often difficult to find on a fecal exam, veterinarians will sometimes treat pets if there’s a high suspicion of coccidiosis, even if no cysts are found in their stool.


Preventing pets from being infected by coccidia cysts in the environment, washing his or her bedding and cleaning any kennel/heavily populated areas with an ammonia product should be a basic practice, especially if multiple dogs/cats share the area. Picking up and disposing of feces as soon as possible, and keeping pets from hunting rodents, if possible, are also considered fundamental preventive measures.

This article was reviewed by a Veterinarian.