What is cryptosporidiosis?
Cryptosporidiosis is a gastro-intestinal infection in humans and animals caused by a microscopic organism called Cryptosporidium (plural Cryptosporidia).
Cryptosporidium is a simple, one-celled parasitic species, not a worm, bacteria, or virus. The parasite occurs worldwide and can be found in water, food, soil, or any other contaminated surface. Cryptosporidium is a very small form of coccidia (see handout “Coccidiosis in Dogs”).
Cryptosporidium can be a cause of illness, especially watery diarrhea, in animals and people. However, most dogs and people infected with Cryptosporidium do not have diarrhea, vomiting, or any other signs of illness.
How do dogs get cryptosporidiosis?
Cryptosporidium lives in the intestines and sometimes the stomach of infected animals and people (host). As part of its reproduction, it produces two different kinds of “oocysts” – little packages of the parasite. One is thin-walled and further infects the host intestine; the other is much thicker-walled and is released into the environment in feces.
When an animal ingests an oocyst, the package “opens” and the parasites infect the intestinal cells, starting the process again, in a new host. Thick-walled cysts are extremely resistant and may survive despite steaming, freezing, thawing, drying, or use of chemical disinfectants, and can be difficult to filter out of water due to their tiny size.
As few as 10 oocysts can cause illness in people or pets. Dogs become infected by eating something contaminated by these oocysts, including feces, prey animals, water, and food.
What are the clinical signs of cryptosporidiosis?
When Cryptosporidium is found in the stool of a healthy, adult dog without diarrhea, it is generally considered a temporary, insignificant finding. However, in puppies and immunosuppressed adult dogs, they may cause diarrhea and weight loss, and could be life-threatening. Some dogs may stop eating. Diarrhea is typically watery and may be chronic or random.
How is cryptosporidiosis diagnosed?
A routine fecal flotation test may fail to detect these tiny oocysts. Special stains may reveal the presence of Cryptosporidium; however, more specific tests, looking for small amounts of protein or DNA, may be most accurate. Unfortunately, DNA testing can be so sensitive that it can detect parasites that may be unrelated to your pet’s clinical signs. Your veterinarian will make that determination and recommend appropriate treatment when needed.
How is cryptosporidiosis treated?
Most infections in healthy animals do not require specific treatment. If dehydration or severe diarrhea is present, supportive treatment with medications and intravenous fluids may be needed. In severe cases or if a patient is immunocompromised, antibiotics may be prescribed to try to control the infection, though no medication has been found to eliminate Cryptosporidia.
A highly digestible diet, probiotics, and added dietary fiber may help resolve diarrhea more quickly. Your veterinarian may recommend follow-up fecal testing and other testing, depending on your dog’s health status.
Cryptosporidia oocysts can infect an animal immediately after they are passed into the environment, so feces should be quickly removed and disposed of.
What is the prognosis for cryptosporidiosis?
The prognosis for cryptosporidiosis is good in most cases. Debilitated or geriatric animals, and those with incompetent immune systems, are at increased risk of complications.
Can my dog transmit cryptosporidiosis to me or my family?
The species of Cryptosporidium normally seen in dogs (Cryptosporidium canis) is very unlikely to cause disease in humans unless they are immunocompromised. The species more likely to cause disease in humans (Cryptosporidium parvum) comes from cattle and can also be spread between people and from people to pets. There is a possibility that dogs could spread this species from cattle to humans; however, this has not been proven. There is a species that infects people only (Cryptosporidium hominis).
If your dog is diagnosed with cryptosporidiosis, it is essential that you disinfect the environment and maintain good personal hygiene to prevent accidental spread to humans. Handwashing with soap and water is important as hand sanitizers are not generally effective against Cryptosporidium. People undergoing chemotherapy or with immunodeficiencies such as AIDS or cancer should use extreme care, especially when handling feces or administering medications.
"Handwashing with soap and water is important as hand sanitizers are not generally effective against Cryptosporidium."
Environmental decontamination can be difficult, as no disinfectant has been found completely effective. A 3% hydrogen peroxide solution may be most effective if left on surfaces for 20 minutes before rinsing. Bleach may also be recommended prior to applying hydrogen peroxide. Never mix bleach and hydrogen peroxide. If bleach has been recommended, make sure it is thoroughly rinsed off before you apply the hydrogen peroxide solution.
