Experimental evaluation of Musca domestica (Diptera:Muscidae) as a vector of newcastle disease virus

House sies, Musca domestica L. (Diptera: Muscidae), were examined for their ability to harbor and transmit Newcastle disease virus (family Paramyxoviridae, genus Avulavirus, NDV) by using a mesogenic NDV strain. Laboratory-reared sies were experimentally exposed to NDV (Roakin strain) by allowing sies to imbibe an inoculum consisting of chicken embryo-propagated virus. NDV was detected in dissected crops and intestinal tissues from exposed sies for up to 96 and 24 h postexposure, respectively; no virus was detected in crops and intestines of sham-exposed sies. The potential of the house sy to directly transmit NDV to live chickens was examined by placing 14-d-old chickens in contact with NDV-exposed house sies 2 h after sies consumed NDV inoculum. NDV- exposed house sies contained 10 4 50% infectious doses (ID50) per sy, but no transmission of NDV was observed in chickens placed in contact with exposed sies at densities as high as 25 sies per bird. Subsequent doseÐresponse studies demonstrated that oral exposure, the most likely route for sy-to- chicken transmission, required an NDV (Roakin) dose 10 6 ID50. These results indicate that house sies are capable of harboring NDV (Roakin) but that they are poor vectors of the virus because they carry an insufÞcient virus titer to cause infection.