Figure 2: Description of transmission modes of Cryptosporidium. Following ingestion (and possibly inhalation) by a suitable host (e.g., human host), excystation occurs (infective stage, (1)). The released sporozoites invade epithelial cells of the gastrointestinal tract or other tissues, complete their cycle producing oocysts which exit host (diagnostic stage, (2)) and are released in the environment (3). Transmission of Cryptosporidium mainly occurs by ingestion of contaminated water (e.g., surface, drinking or recreational water), food sources (e.g., chicken salad, fruits, vegetables) or by person-to-person contact (community and hospital infections) (4). Zoonotic transmission of C. parvum occurs through exposure to infected animals (person-to-animal contact) or exposure to water (reservoir) contaminated by feces of infected animals (4). Putignani and Menchella, 2010.