Dog - Coccidiosis

What is coccidiosis?

Infection with Protozoan (one-celled) organisms known as coccidia. These are microscopic parasites living within cells of the intestinal lining. Since they live in the intestinal tract they can be associated with diarrhoea problems especially in puppies up to three months of age but coccidia are usually associated with other causal organisms.

How did my dog become infected?

Oocysts (immature coccidia) are passed in the faeces. They remain in the environment and eventually mature into infective oocysts. Dogs, cats and mice may become infected. This process can occur in as little as 6 hours, but it usually takes 7-10 days. If the sporulated (infective) oocysts are swallowed, they mature in the dog's intestine to complete the life cycle. If the infective (sporulated) oocysts should be swallowed by a mouse, the dog may also become infected by eating the mouse.

What kinds of problems are caused by coccidial infection?

Many infected dogs do not have diarrhoea or any other clinical signs. When the eggs (oocysts) are found in the faeces of a dog without any signs they are generally considered a transient, insignificant finding. However, in puppies and debilitated adult dogs, they may cause severe, watery diarrhoea, dehydration, abdominal distress and vomiting. In severe cases, death may occur although this is not common in the UK.

How is coccidial infection diagnosed?

Coccidiosis is diagnosed by performing a microscopic examination of a faeces sample. Since the oocysts are much smaller than the eggs of intestinal worms, a very careful study must be made. Infection with some of the less common coccidial parasites is diagnosed with a blood test.

In the UK diarrhoea due to coccidial organisms (Isospora species) can occur but this is often associated with other causes, e.g. poor husbandry etc.

What is the treatment?

There are several remedies. The most common drug used to eliminate coccidia is a sulphonamide antimicrobial drug.

It is given for 10-14 days. Supportive medication is used if diarrhoea and dehydration occur. If the sulpha drug is not effective, other drugs are available. Reinfection of dogs is common so environmental disinfection is important. The use of chlorine bleach is effective if the surfaces and premises can be safely treated with bleach.

Are the coccidial parasites of my dog infectious to humans?

The most common coccidia found in dogs do not have any effect on humans. Less common types are potentially infectious to humans. Coccidial parasites pose a health risk for immuno-suppressed humans (i.e. AIDS patients, those taking immuno suppressive drugs, cancer patients, the elderly, etc). Good hygiene and proper disposal of dog faeces are important in minimising risk of transmission of all canine parasites to humans. Although there is risk of the dog transmitting parasites to humans it does not warrant removing the dog from the household except in very exceptional circumstances.