What is coccidiosis?
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. The species isospora canis causes most clinical infections in dogs. Cryptosporidium parvum is another coccidian parasite that may cause diarrhoea in some puppies.
How did my dog become infected with coccidia?
An infected dog passes oocysts (immature coccidia) in the feces. These oocysts are very 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 “sporulate” or become infective. If a susceptible dog ingests the sporulated oocysts, the oocysts will release “sporozoites” that invade the intestinal lining cells and set up a cycle of infection in neighbouring 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 diarrhoea or other clinical signs. When the coccidial oocysts are found in the stool of a dog without diarrhoea, they are generally considered a transient, insignificant finding.
However, in puppies and debilitated adult dogs, coccidiosis may cause severe, watery diarrhoea, 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. Re-infection of susceptible 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. 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 faeces are important in minimizing risk of transmission of all canine parasites to humans, or to other animals.