Coccidiosis

Coccidiosis in Dogs

What is coccidiosis?

Coccidiosis is an intestinal tract infection caused by one-celled organisms (protozoa) called coccidia. Coccidia are sub-classified into a number of genera, and each genus has a number of species. At least six different genera of coccidia can infect dogs. These microscopic parasites spend part of their life cycle in the lining cells of the intestine. Most infections are not associated with any detectable clinical signs. These infections are called sub-clinical infections. Most clinical infections in dogs are caused by the species Isospora canis. Cryptosporidium parvum is another coccidian parasite that may cause diarrhea in some puppies.

How did my dog become infected with coccidia?

Oocysts (immature coccidia) are passed in the feces of an infected dog. These oocysts are very resistant to environmental conditions and can survive for some time on the ground. Under the right conditions of temperature and humidity these oocysts “sporulate”. If the sporulated oocysts are ingested by a susceptible dog they will release “sporozoites” that invade the intestinal lining cells and set up a cycle of infection in neighboring cells. Dogs may also be indirectly infected by eating a mouse that is infected with coccidia.

What kinds of problems are caused by coccidiosis?

Most dogs that are infected with coccidia do not have diarrhea or other clinical signs. When the 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. Since the oocysts are much smaller than the eggs of intestinal worms, a careful fecal evaluation must be made. Infection with some of the less common coccidial parasites is diagnosed with a blood test.

How is the coccidial infection treated?

The most common drug used to eliminate coccidia is a sulfa-type antibiotic. It is usually given for ten to fourteen days. In severe infections, it may be necessary to repeat the treatment. Other drugs are also used if diarrhea and dehydration occur. If the sulfa-type drug is not effective, other treatments are available. Re-infection of dogs is common so environmental disinfection is important. The use of diluted chlorine bleach [one cup (250 ml) of bleach mixed in one gallon (3.8 L) of water] is effective if the surfaces and premises can be safely treated with it.

Are the coccidial parasites of my dog infectious to humans?

The most common coccidia found in dogs do not have any affect on humans. However, less common types of coccidia are potentially infectious to humans. One parasite, called Cryptosporidium, may be carried by dogs or cats and may be transmitted to people. This parasite has also been found in the public water supply of some major cites. It poses a health risk for immuno-suppressed humans such as AIDS patients, those taking immune suppressing drugs, cancer patients, or the elderly.

Good hygiene and proper disposal of dog feces are important in minimizing risk of transmission of all canine parasites to humans, or to other animals.


Coccidiosis in Cats

What is coccidiosis?

Coccidiosis is an intestinal tract infection caused by a one-celled organism or protozoa called coccidia. Coccidia are not parasitic worms. They are microscopic parasites that live within cells of the intestinal lining. Because they live in the intestinal tract and commonly cause diarrhea, they are often confused with worms.

How did my cat become infected with coccidia?

Oocysts or immature coccidia are passed in the stool of the cat. They lie in the environment and eventually sporulate and mature into a more developed oocyst that can infect the cat again. Other cats, dogs, or mice may also become infected. This process can occur in as little as six hours, but it usually takes seven to ten days. If the sporulated oocysts are swallowed, they mature in the cat's intestine to complete the life cycle. If a mouse should swallow the oocysts, the cat may also become infected if it eats an infected mouse.

What are the clinical signs of coccidiosis?

Most cats that are infected with coccidia do not have diarrhea or any other clinical signs. When the eggs or oocysts are found in the stool of a cat without diarrhea, they are generally considered a transient, insignificant finding. However, in kittens and debilitated adult cats, they 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. Since the oocysts are much smaller than the eggs of the intestinal worms, a very careful study must be made. Infection with some of the less common coccidial parasites may be diagnosed with a blood test.

How is coccidiosis treated?

The most common drug used to eliminate coccidia is a sulfa-type antibiotic. It is typically administered for ten to fourteen days. The medication is sweet tasting and most cats will take it with little difficulty. If the sulfa-type drug is not effective, other treatments are available. Additional medication may be needed if diarrhea and dehydration occur. Reinfection of cats is common so environmental disinfection is important. The use of diluted chlorine bleach [one cup (250 ml) of bleach mixed in one gallon (3.8 L) of water] is effective if the surfaces and premises can be safely treated with it.

Are the coccidial parasites of my cat infectious to humans?

The most common coccidia found in cats do not have any affect on humans. However, less common types of coccidia are potentially infectious to humans. One parasite, called Cryptosporidium, may be carried by cats or dogs and transmitted to people. This parasite has also been found in public water supplies in some major cities. Another coccidial organism, Toxoplasma, is of particular concern to pregnant women because of the potential to cause birth defects in newborns. These two coccidial parasites pose an increased health risk for immunosuppressed humans (i.e., AIDS patients, those taking immune suppressant drugs, cancer patients, etc.). Good hygiene and proper disposal of cat feces are important in minimizing risk of transmission of all feline parasites to humans. Although there is risk of the cat transmitting these two particular parasites to humans, it does not warrant removing the cat from the household except in very rare instances.



This client information sheet is based on material written by Ernest Ward, DVM.

© Copyright 2005 Lifelearn Inc. Used with permission under license. January 13, 2017

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