What is coccidiosis?

Coccidiosis is an intestinal tract infection caused by a single-celled organism (protozoa) called coccidia. Coccidiosis typically refers to gastrointestinal infections with Cystoisospora species of coccidia, though other species can be found.

These microscopic parasites spend part of their life cycle in the lining cells of the intestine. Despite damaging these cells, most infections in dogs are not associated with any detectable clinical signs. Infections without clinical signs are called subclinical infections. Puppies are commonly infected.

How did my dog become infected with coccidia?

Your dog likely became infected with coccidia from swallowing oocysts (immature coccidia) that are found in dog feces and any environment contaminated with feces. Infected dogs pass oocysts in the feces. These oocysts are resistant to a wide variety of environmental conditions and can survive for some time on the ground.

Under the right conditions of temperature and humidity, these oocysts become infective. If a susceptible dog ingests these, the next stage will invade the intestinal lining cells and set up a cycle of infection in neighboring cells. Dogs may also become infected indirectly by eating a mouse that is infected with coccidia.

Puppies are commonly diagnosed with coccidiosis. After birth, puppies can be infected by exposure to their mother’s feces, especially with puppies’ tendency to explore. Coccidiosis is of particular danger for puppies since their immune system is underdeveloped.

What are the clinical signs of coccidiosis?

The most common clinical sign of coccidiosis is diarrhea, but most dogs infected with coccidia do not have any clinical signs. When coccidial oocysts are found in the stool of a dog without diarrhea, they are generally considered a transient, insignificant finding. However, in puppies and debilitated adult dogs, coccidiosis may cause severe, watery diarrhea, dehydration, abdominal distress, and vomiting. In severe cases, death may occur.

How is coccidiosis diagnosed?

Coccidiosis is diagnosed by performing a microscopic examination of a stool sample. Infection with some of the less common coccidial parasites may be diagnosed with a blood test.

How is coccidiosis treated?

Your veterinarian may prescribe a sulfa-type antibiotic called sulfadimethoxine (Albon®), which may require prolonged treatment. In severe infections, it may be necessary to repeat the treatment. If the sulfa-type antibiotic does not clear the infection, other treatments are available, including sulfa antibiotics combined with another drug, amprolium, or off-label use of ponazuril {Marquis®} or toltrazuril {Baycox®). Your veterinarian will discuss these treatments with you. Additional supportive treatments may be needed if diarrhea and dehydration occur.

Dogs are frequently reinfected from the environment, so disinfection is important. The oocysts are resistant to environmental conditions and disinfectants. Diluted chlorine bleach is effective as a disinfectant (one cup or 250 mL of bleach mixed with one gallon or 3.8 L of water). Be sure to test clean a small area of affected materials since bleach can damage many surfaces. Steam cleaning may also be used to destroy oocysts. Be sure to remove your pet’s feces from the environment as quickly as possible to prevent reinfection.

Can I get coccidiosis from my dog?

The most common species of coccidia in dogs does not infect humans. However, less common species of coccidia can potentially infect humans. One species, called Cryptosporidium, may be transmitted to people, especially those with compromised immune systems. Cryptosporidium has also been found in public water supplies in some major cities. Good hygiene and proper disposal of dog feces are important in minimizing the risk of transmission of all canine parasites to humans.