Cryptosporidiosis: Infection and transmission

Cryptosporidiosis is a disease caused by Cryptosporidium spp, an obligate intracellular protozoan parasite. Cryptosporidium muris was first described by Tyzzer in 1910 and Cryptosporidium parvum was described two years later. However, it was not until the 1970s that Cryptosporidium was determined to be a significant cause of gastrointestinal disease in humans.

It is a frequent cause of diarrheal disease in humans, and several groups of humans are particularly susceptible to cryptosporidiosis. In developing countries, Cryptosporidium infections occur mostly in children younger than 5 years.

In immunocompromised persons such as human immunodeficiency virus-positive (HIV) patients, the incidence and severity of cryptosporidiosis increases as the CD4 lymphocyte cell count falls.

The persistent diarrhea and malabsorption can become life-threatening, particularly in acquired immunodeficiency syndrome (AIDS) patients.

Cryptosporidium is a small protozoan parasite that infects the microvillous region of epithelial cells in the digestive and respiratory tract of vertebrates. It is an obligate intracellular parasite of man and other mammals, birds, reptiles and fish. It requires its host to multiply.

When the oocysts enter the gastrointestinal tract, the invasive Cryptosporidium causes damage to the small intestinal epithelium. It disrupts the barrier function and absorption capability that leads to mild-to-severe diarrhea and other abdominal symptoms.

Cryptosporidiosis is an opportunistic parasitosis. It is characterized by self-limiting gastroenteritis in otherwise healthy people, while it is more severe in immunocompromised subjects in HIV-infected patients and constitutes a serious threat leading to chronic or fulminant disease, wasting and death.

The infection is spread in a number of ways: from person to person, from animals, via food, and by water. Cryptosporidiosis is now the most common cause of waterborne disease in the world.

Cryptosporidium oocysts transmission can occur following direct or indirect contact with an infected host usually via the fecal–oral route. Person to-person contact, zoonosis, and the consumption of contaminated food or water are well known mechanisms for fecal–oral transmission.

The largest cryptosporidiosis outbreak reported to date in the USA occurred in Milwaukee, Wisconsin in 1993 when over 403,000 individuals were sickened out of a potentially exposed population of 1.6 million.
Cryptosporidiosis: Infection and transmission