EFFECT OF PASTEURIZATION ON INFECTIVITY OF CRYPTOSPORIDIUM-PARVUM OOCYSTS IN WATER AND MILK

Cryptosporidium parvum is a major cause of diarrheal disease in humans and has been identified in 78 other species of mammals, The oocyst st age, excreted in feces of infected humans and animals, has been respon sible for recent waterborne outbreaks of human cryptosporidiosis. High temperature and long exposure time have been shown to render oocysts (suspended in water) noninfectious, but for practical purposes, it is important to know if high-temperature-short-time conditions (71.7 degr ees C for 15 s) used in commercial pasteurization are sufficient to de stroy infectivity of oocysts, In this study, oocysts were suspended in either water or whole milk and heated to 71.7 degrees C for 15, 10, o r 5 s in a laboratory-scale pasteurizer. Pasteurized and nonpasteurize d (control) oocysts were then tested for the ability to infect infant mice, No mice (0 of 177) given 10(5) oocysts pasteurized for 15, 10, o r 5 s in either water or milk were found to be infected with C. parvum on the basis of histologic examination of the terminal ileum. In cont rast, all (80 of 80) control mice given nonpasteurized oocysts were he avily infected. These data indicate that high-temperature-short-time p asteurization is sufficient to destroy the infectivity of C. parvum oo cysts in water and milk.