Waterborne parasite may soon be treatable

Because the parasite C. parvum is resistant to chlorine and difficult to filter, cryptosporidiosis epidemics are hard to prevent. (Credit: Ben Schumin/Flickr, font by Vernon Adams)

By blocking a protective enzyme in the microscopic parasite C. parvum, scientists have made it vulnerable to its host’s immune system.

In the developing world, Cryptosporidium parvum has long been the scourge of freshwater. A decade ago, it announced its presence in the United States, infecting over 400,000 people—the largest waterborne-disease outbreak in the county’s history.

Its rapid ability to spread, combined with an incredible resilience to water decontamination techniques, such as chlorination, led the National Institutes of Health (NIH) to add C. parvum to its list of public bioterrorism agents.


Currently, there are no reliable treatments for cryptosporidiosis, the disease caused by C. parvum, but that may be about to change with the identification of a target molecule. The findings of the study have been recently published in the journal Antimicrobial Agents and Chemotherapy.

“In the young, the elderly and immunocompromised people such as people infected with HIV/AIDS, C. parvum is a very dangerous pathogen. Cryptosporidiosis is potentially life-threatening and can result in diarrhea, malnutrition, dehydration, and weight loss,” says first author Momar Ndao, director of the National Reference Centre of Parasitology at the McGill University Health Centre, who is also an assistant professor in the departments of medicine, immunology and parasitology.

C. parvum is a microscopic parasite that lives in the intestinal tract of humans and many other mammals. It is transmitted through the fecal-oral contact with an infected person or animal, or from the ingestion of contaminated water or food. Since the parasite is resistant to chlorine and difficult to filter, cryptosporidiosis epidemics are hard to prevent.

A thick wall protects the oocysts of C. parvum, which are shed during the infectious stage, and allows them to survive for long periods outside the body until they spread to a new host.

“Most protozoan (single-celled) parasites like C. parvum use enzymes called proteases to escape the body’s immune defenses,” explains Ndao. “In this study, we were able to identify a protease inhibitor that can block the parasite’s ability to circumvent the immune system, and hide in intestinal cells called enterocytes, in order to multiply and destroy the intestinal flora.”

The discovery is the first time a molecular target has been found for the control of C. parvum.

“The next step will be to conduct human clinical trials to develop an effective treatment for this parasite, which affects millions of people around the world,” concludes Ndao.

Source: McGill University