Mechanical transmission of Cryptosporidium parvum oocysts by flies.

Long term field studies and laboratory experiments demonstrated that synanthropic filth flies can mechanically transmit infectious oocysts of Cryptosporidium parvum, an anthropozoonotic protozoan parasite which significantly contributes to the mortality of immunocompromised or immunosuppressed people. C. parvum oocysts are acquired from unhygienic sources, and can pass trough fly gastrointestinal track without alteration of their infectivity and can be subsequently deposited on visited surfaces. Transmission of the oocysts by adult flies occurs via: (1) mechanical dislodgement from the exoskeleton; (2) fecal deposition; and (3) regurgitation, i.e., vomits. Filth flies can cause human or animal cryptosporidiosis via deposition of infectious oocysts on the visited foodstuf, and the biology and ecology of synanthropic filth flies indicate that their potential for mechanical transmission of C. parvum is high.