Cryptosporidium

Abstract

Seven species of the intracellular, protozoan parasite, Cryptosporidium, cause diarrhea in humans. Cryptosporidium completes its life cycle in individual hosts, and its infectious dose is small (ID50 = 9-1042 oocysts). Its virulence and pathogenicity are poorly understood. The drug of choice for immunocompetent individuals is nitazoxanide and modifications of treatment regimens may also increase its usefulness for immunocompromised individuals. Immune reconstitution using highly active antiretroviral therapy and secondary prophylaxis should be considered in HIV-infected individuals. Transmission to humans can occur via any mechanism by which material contaminated with feces containing infectious oocysts from infected human beings or non-human hosts can be swallowed by a susceptible host. Biotic reservoirs include all potential hosts of human-infectious Cryptosporidium species, while abiotic reservoirs include all vehicles that contain sufficient infectious oocysts to cause human infection, the most commonly recognized being food and water. Both foodborne and waterborne outbreaks have been documented. In three out of the six foodborne outbreaks documented, contaminated foodstuffs were implicated as the vehicles of transmission, but in another two, foodhandlers, rather than indigenous contamination of foodstuff, were implicated in disease transmission. Increased global sourcing and rapid transport of soft fruit, salad vegetables, and seafood can enhance both the likelihood of oocyst contamination and oocyst survival. Standardized methods for detecting oocysts on foods must be maximized as there is no method to augment parasite numbers prior to detection. Oocyst contamination of food can be on the surface of, or in, the food matrix and products at greatest risk of transmitting infection include those that receive no, or minimal, heat treatment after they become contaminated. Heating at ≥64.2 for 2 min and exposure to UV light ablates Cryptosporidium parvum infectivity for neonatal mice, while drying/desiccation for 4 h or exposure to 0.03% H2O2 for ≥2 h ablates oocyst viability. Disinfectants and other treatment processes used in the food industry may be detrimental to oocyst survival or lethal, but further research in this important area is required. Both foodborne and waterborne outbreaks have been documented. In three out of the six foodborne outbreaks documented, contaminated foodstuffs were implicated as the vehicles of transmission, but in another two, foodhandlers, rather than indigenous contamination of foodstuff, were implicated in disease transmission. Increased global sourcing and rapid transport of soft fruit, salad vegetables, and seafood can enhance both the likelihood of oocyst contamination and oocyst survival. Standardized methods for detecting oocysts on foods must be maximized as there is no method to augment parasite numbers prior to detection. Oocyst contamination of food can be on the surface of, or in, the food matrix and products at greatest risk of transmitting infection include those that receive no, or minimal, heat treatment after they become contaminated. Heating at ≥64.2 for 2 min and exposure to UV light ablates Cryptosporidium parvum infectivity for neonatal mice, while drying/desiccation for 4 h or exposure to 0.03% H2O2 for ≥2 h ablates oocyst viability. Disinfectants and other treatment processes used in the food industry may be detrimental to oocyst survival or lethal, but further research in this important area is required.