Cryptosporidium species are protozoan parasites that cause diarrheal disease with a global distribution. They mainly affect children, causing a self-limited diarrhea in healthy individuals; nevertheless, in people with acquired immunodeficiency disorder or AIDS, the disease can be quite severe and result in weight loss or malnutrition.
Intestinal cryptosporidiosis continues to be an important public health concern worldwide, most notably through outbreaks caused by contaminated food or water, and sometimes also from the infected host. Therefore adhering to proper sanitation and hygiene measures is important for preventing this illness.
Water Treatment and Water Avoidance
Water purification is a public health measure of paramount interest. In this respect, it must be noted that chlorination has little effect on the Cryptosporidium oocysts. For this reason, purification should ideally involve filtration and flocculation. Ultraviolet radiation or ozonation can also disinfect contaminated water, although these methods are seldom used.
Recreational water bodies (such as lakes) may pose a danger for immunocompromised hosts who should completely avoid untreated water. Swimming pools currently represent an important source of infection, thus anyone with diarrhea should not swim in public facilities. Fecal deposition and other types of recreational water contamination should instigate aggressive measures, including temporary closure of the pool.
Strict adherence to such improved water treatment, along with enhanced screening, has dramatically decreased the number of outbreaks linked to drinking water in the United Kingdom and the US. The technology is indeed available to remove the threat of Cryptosporidium outbreaks, though at the cost of additional operating costs and infrastructure.
But despite these advancements in the inactivation of oocysts for the production of potable water, outbreaks may still occur. These may be either due to treatment barrier failures, or due to an insufficient risk characterization of catchments, resulting in inadequate treatment barriers that prevent the entry of infectious oocysts into drinking water systems.
Infected or potentially infected water can be decontaminated by using personal measures such as boiling or filtration using filters with a pore size of 1 µm or smaller. This is especially recommended when traveling to developing countries where public water supply is likely to be contaminated, or as a routine procedure in the case of immunocompromised hosts.
Even though intestinal cryptosporidiosis can be transmitted within health-care facilities and daycare centers, the risk is negligible if there is an adequate adherence to standard precautions. Gloves should be worn and hands washed after handling material that is contaminated with fecal matter, while instruments (such as endoscopes) need to be meticulously disinfected between uses.
Chemoprophylaxis may also be considered, but is generally not recommended. For this purpose, antimicrobial agents such as rifabutin and clarithromycin are most often used, based on the results of retrospective studies and controlled trials that noted a lower incidence of the disease in treated groups when compared to placebo groups.
Research on Vaccines
To date, no effective vaccine is at our disposal to prevent intestinal cryptosporidiosis. A proof of concept that a vaccine might represent an effective preventive approach stems from observing age-related declines of infection rates among children from developing countries, as well as human challenge research studies demonstrating protection linked to previous exposure.
Nevertheless, efforts to develop an efficacious vaccine are hampered by incomplete understanding of the immune responses correlating with protection. Immunodominant antigens found on the surface of the invasive stage of the parasite, as well as antigens associated with sexual and intracellular stages are potential targets of interest. In addition, passive and other new immunotherapies are also being investigated.
Reviewed by Liji Thomas, MD
- Monis P, King B, Keegan A. Removal and Inactivation of Cryptosporidium from Water. In: Cacciò SM, Widmer G, editors. Cryptosporidium: parasite and disease. Springer Science & Business Media, 2013; pp. 515-552.
- Clinton White Jr. A. Cryptosporidiosis (Cryptosporidium Species). In: Bennett JE, Dolin R, Blaser MJ, editors. Principles and Practice of Infectious Diseases, Eighth Edition. Elsevier Health Sciences, 2015; pp. 3173-3183.