My puppy has coccidiosis. What is it?

Canine coccidiosis is an infection of the intestines caused by a one-celled parasite named lsospora canis. Infected puppies usually have watery, pasty, foul-smelling, tan-colored diarrhea that is sometimes tinged with blood.

Puppies kept in an unclean environment or those who are particularly stressed are especially susceptible to coccidiosis. They become infected when they ingest feces from other dogs or puppies who have the parasite. The diarrhea can cause weight loss, dehydration, and lethargy. Left untreated, the infection can be fatal.

Some infected puppies, however, show few or no symptoms of illness. Veterinarians diagnose coccidiosis by microscopic examination of a stool sample for the presence of the cyst form of the parasite. It is sometimes difficult to find the cysts, and treatment may be initiated based on symptoms alone.

Medications do not kill coccidia, but they do inhibit their reproduction and give a puppy’s immune system time to overcome the infection. Administer treatment as directed by your veterinarian, usually once daily for two to four weeks; he or she will recommend a follow-up examination of your dog’s feces.

Adult dogs exposed to infected puppies are unlikely to become infected because they have mature immune systems. However, any adult dog with an immunosuppressive condition (pregnancy, cancer, infection) is more susceptible. Humans can become infected with other species of coccidia (cryptosporidium and toxoplasma) but not with Isospora canis.