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Cryptosporidiosis

By Arnold Plotnick, MS, DVM, ACVIM

Overview

Cryptosporidiosis is a disease caused by the protozoan parasite Cryptosporidium. The species of the organism that affects mammals most commonly is Cryptosporidium parvum. A number of mammalian species including rodents, cattle, dogs, cats, and people can develop gastrointestinal tract disease due to infection with the organism. The fact that serum antibodies are detected in many species of animals, including cats, suggests that exposure to the organism is fairly common. The infective form of the organism is the oocyst. These oocysts are spread via fecal contamination of food or drinking water. The organism is very infective. It only takes a few oocysts to cause disease in people.

Cryptosporidiosis may be a primary disease, or it may be a secondary disease in people or animals with weakened immune systems. The risk of exposure increases in crowded or unsanitary conditions. For example, cryptosporidial diarrhea is common among children in daycare centers. In cats and dogs, it is more commonly seen in young animals (less than 6 months old).Typically, cryptosporidiosis is a self-limiting disease in animals with competent immune systems; many animals (cats in particular) will be infected but show no clinical signs at all. Others will have mild diarrhea, but recover uneventfully. Even though young animals are more susceptible to becoming infected, some young animal may show no clinical signs when infected. People of all ages can get cryptosporidiosis, and it is commonly seen in people who work with cattle. It is frequently diagnosed in veterinary students after contact with infected calves. The signs in people are similar to those of animals: acute onset of lethargy, abdominal cramps, and profuse watery diarrhea. The illness generally subsides without treatment, although persistent diarrhea and dehydration occasionally develops. The severity of the disease depends on the immune competence of the person, although people with healthy immune systems can certainly contract the illness, as demonstrated in 1993 when 400,000 people in Milwaukee developed diarrhea as a result of contracting the organism via the public water supply. Immunocompromised people, such as those with HIV/AIDS , may suffer severe diarrhea that never resolves, and may even prove fatal.

Diagnosis

fecal examination – animals suspected of having cryptosporidiosis should have a fecal sample carefully sent to a laboratory for special staining and examination techniques.
serology – detection of antibodies against the organism identifies animals that have been exposed to the organism, but it does not necessarily diagnose active infection.
intestinal biopsy – intestinal biopsy often reveals the organism as well as the damage that the organism may have caused to the intestinal tract.

Treatment

Although more than 100 drugs have been screened, there are very few drugs available to successfully treat cryptosporidiosis. There are several treatment options:
no treatment – infections in immunocompetent animals or persons are usually self-limiting, and full recovery often occurs.
antibiotics – many antibiotics have been used in an attempt to treat cryptosporidiosis. Paromomycin, tylosin, and azithromycin have all been shown to have reasonable efficacy when treating the disorder.
high fiber diet – feeding a high fiber diet in conjunction with antibiotic therapy and supportive care may be beneficial in helping resolve the diarrhea more quickly.
supportive therapy – severe dehydration may require hospitalization and intravenous fluid therapy for several days.
Optimal treatment for your pet requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your pet does not rapidly improve.
Administer all prescribed medications as directed. Alert your veterinarian if you are experiencing problems treating your pet.
Owners of infected animals need to be aware that their cat should be isolated from people who are immunocompromised.