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Pathogen & Environment

Causal Agent:

Many species of Cryptosporidium exist that infect humans and a wide range of animals. Although Cryptosporidium parvum and Cryptosporidium hominis (formerly known as C. parvum anthroponotic genotype or genotype 1) are the most prevalent species causing disease in humans, infections by C. felis, C. meleagridis, C. canis, and C. muris have also been reported.

Life Cycle

Life cycle of Cryptosporidium parvum and C. hominis

Sporulated oocysts, containing 4 sporozoites, are excreted by the infected host through feces and possibly other routes such as respiratory secretions The number 1. Transmission of Cryptosporidium parvum and C. hominis occurs mainly through contact with contaminated water (e.g., drinking or recreational water). Occasionally food sources, such as chicken salad, may serve as vehicles for transmission. Many outbreaks in the United States have occurred in waterparks, community swimming pools, and day care centers. Zoonotic and anthroponotic transmission of C. parvum and anthroponotic transmission of C. hominis occur through exposure to infected animals or exposure to water contaminated by feces of infected animals The number 2. Following ingestion (and possibly inhalation) by a suitable host The number 3, excystation The letter A occurs. The sporozoites are released and parasitize epithelial cells (The letter B, The letter C) of the gastrointestinal tract or other tissues such as the respiratory tract. In these cells, the parasites undergo asexual multiplication (schizogony or merogony) (The letter D, The letter E, The letter F) and then sexual multiplication (gametogony) producing microgamonts (male) The letter G and macrogamonts (female) The letter H. Upon fertilization of the macrogamonts by the microgametes (The letter I), oocysts (The letter j, The letter K) develop that sporulate in the infected host. Two different types of oocysts are produced, the thick-walled, which is commonly excreted from the host The letter j, and the thin-walled oocyst The letter K, which is primarily involved in autoinfection. Oocysts are infective upon excretion, thus permitting direct and immediate fecal-oral transmission.