Coccidiosis

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Coccidia oocysts

Coccidiosis is a parasitic disease, usually of the intestinal tract, caused by microscopic organisms called coccidia, which are a type of protozoa. They are obligate intracellular parasites, which means that they must live and reproduce within an animal cell. The disease spreads from one animal to another by contact with infected feces or ingestion of infected tissue. It is most severe in young or weak animals in which it causes bloody diarrhea. Most animals infected with coccidia are asymptomatic. One wellknown type of coccidiosis is toxoplasmosis, caused by Toxoplasma gondii.

Genus and species that cause coccidiosis

• Genus Cystoisospora is the most common cause of intestinal coccidiosis in dogs and cats and is usually what is meant by coccidiosis. Species of Cystoisospora are species specific, meaning they only infects one type of species. Species that infect dogs include C. canis, C. ohioensis, C. burrowsi, and C. neorivolta. Species that infect cats include C. felis and C. rivolta. The most common symptom is diarrhea. Sulfonamides are the most common treatment.
• Genus Cryptosporidium contains two species known to cause cryptosporidiosis, Cryptosporidium parvum and Cryptosporidium muris. Cattle are most commonly affected by Cryptosporidium and their feces are a common source of infection for other mammals, including humans. Infection occurs most commonly in individuals that are immunocompromised, e.g. dogs with canine distemper, cats with feline leukemia virus infection, and humans with AIDS. Very young puppies and kittens can also become infected with Cryptosporidium, but the infection is usually eliminated without treatment.
• Genus Hammondia is transmitted by ingestion of cysts found in the tissue of grazing animals and rodents. Dogs and cats are the definitive hosts, with the species H. heydorni infecting dogs and the species H. hammondi and H. pardalis infecting cats. Hammondia usually does not cause disease.
• Genus Besnotia infect cats that ingest cysts found in the tissue of rodents and opossum, but usually does not cause disease.
• Genus Sarcocystis infect carnivores that ingest cysts from various intermediate hosts. It is possible for Sarcocystis to cause disease in dogs and cats.
• Genus Giardia contains one important species, Giardia lamblia, which causes giardiasis. It is a common parasite in dogs, cats, and humans in North America. It can cause diarrhea and is found in water contaminated with feces. Treatment in animals is usually with metronidazole or albendazole.
• Genus Toxoplasma has one important species, Toxoplasma gondii. Cats are the definitive host, but all mammals and some fish, reptiles, and amphibians can be intermediate hosts. Therefore, only cat feces will hold infective oocysts, but infection through ingestion of cysts can occur with the tissue of any intermediate host. Toxoplasmosis occurs in humans in mainly immunocompromised individuals, but the fetus is at risk in pregnant women who ingest either contaminated meat or cat feces. Symptoms in cats include fever, weight loss, diarrhea, vomiting, uveitis, and central nervous system signs. Disease in dogs includes a rapidly progressive form seen in dogs also infected with distemper, and a neurological form causing paralysis, tremors, and seizures. Dogs and cats are usually treated with clindamycin.
• Genus Neospora has one important species, Neospora caninum, that affects dogs in a manner similar to toxoplasmosis. Neosporosis is difficult to treat.
• Genus Hepatozoon contains one species that causes hepatozoonosis in dogs and cats, Hepatozoon canis. Animals become infected by ingesting an infected Rhipicephalus sanguineus, also known as the brown dog tick. Symptoms include fever, weight loss, and pain of the spine and limbs. Treatment is difficult.

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