Picture of Picture of pathogens on a cutting board

© Dennis Kunkel Microscopy

What is Cryptosporidium parvum?

Picture of Picture of pathogens on a cutting board

© Dennis Kunkel Microscopy

Cryptosporidium parvum is a protozoan and an obligate intracellular parasite (a parasite that cannot survive without a host) that commonly causes an opportunistic infection in immunocompromised hosts.

What diseases are caused by Cryptosporidium parvum?

Cryptosporidiasis, a diarrheal disease is characterized by watery diarrhea, nausea and vomiting, dehydration, abdominal cramps and fever. Symptoms usually resolve in 2-4 weeks in immunocompetent hosts. Cryptosporidiosis can also manifest as pulmonary or tracheal disease, causing cough and fever. However, these patients also manifest with the intestinal component of the disease.

Who is more susceptible to infection from Cryptosporidium parvum?

Immunocompromised hosts, such as people infected with HIV/AIDS are unable to clear the parasite and could manifest with a serious illness. Young children and pregnant women are also at an increased susceptibility. Outbreaks are common in day care centers.

Epidemiology of Cryptosporidium parvum

Fecal-oral route is the most common mode of transmission of the disease. The parasite can survive in food, water, soil or in vertebrate hosts.

Incubation Period

Not precisely known; 1-12 days is the likely range with a mean of 7 days.


Identification of cysts in fecal smears or by intestinal biopsy.


Symptomatic treatment of the diarrhea by administering plenty of fluids to prevent dehydration is the primary management. A new drug, Nitazoxanide has been approved for the treatment of cryptosporidiosis.