Coccidiosis is an intestinal tract infection caused by a single-celled organism (a protozoa) called coccidia. There are four different species that can infect dogs.
These microscopic parasites spend part of their life cycle in the lining cells of the intestine. Despite damaging these cells, most infections in dogs are not associated with any detectable clinical signs. Infections without clinical signs are called sub-clinical infections. The species that most commonly causes clinical infections in dogs is I. canis, but Cryptosporidium parvum (another coccidian parasite) can as well, especially in puppies.
Coccidiosis lurks in dirty yards
Your dog most likely became infected with coccidia from swallowing oocysts (immature coccidia) that are found in dog faeces and soil contaminated with faeces. Infected dogs pass oocysts in the faeces. 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 become infective. If a susceptible dog ingests them, the oocysts will release ‘sporozoites’ that invade the intestinal lining cells and set up a cycle of infection in neighbouring cells. Dogs may also become infected indirectly by eating a mouse that is infected with coccidia.
What will coccidiosis do to my dog?
The most common clinical sign of coccidiosis is diarrhoea, but most dogs that are infected with coccidia do not have any clinical signs. 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 it diagnosed?
Coccidiosis is usually diagnosed by performing a faecal flotation test to look for oocysts under the microscope. Since the oocysts are much smaller than the eggs of intestinal worms, a careful evaluation must be made. Infection with some of the less common coccidial parasites may be diagnosed with a blood test.
How is it treated?
Your veterinarian may prescribe an antibiotic, which is usually given for 5-25 days. In severe infections, it may be necessary to repeat the treatment. If the diarrhoea is severe and your dog is dehydrated, other medications and treatments, such as IV fluids, may be required. If the antibiotic is not effective at clearing the infection, other treatments are available which your veterinarian will discuss with you. Some dogs may not require much in terms of medical treatment, depending on the severity of the condition.
Reinfection of susceptible dogs is common so environmental disinfection is important. The oocysts are very resistant to environmental conditions and disinfectants. 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. Be sure to test clean a small area of any affected materials since bleach can damage many surfaces. Steam cleaning may also be used to destroy oocysts. Be sure to remove any faeces as quickly as possible from the environment to prevent reinfection.
Is my family at risk?
The most common species of coccidia in dogs do not have any effect on humans. However, less common species of coccidia can potentially infect humans. One species in particular, called Cryptosporidium, may be transmitted to people. It poses a health risk for those who are immunosuppressed, such as people with HIV, people taking immune suppressing drugs, cancer patients, and the elderly.
Good hygiene and proper disposal of dog faeces are important in minimising the risk of transmission of all canine parasites to humans or other animals.