Transmission of swine influenza virus by lungworm migration.

Experimental evidence is presented which confirms the reports by Shope (1, 2) that swine lungworms can serve as an intermediate host in transmitting swine influenza virus to pigs. The virus is present in a masked non-infective form as he showed and a provocative stimulus is necessary to initiate infection. Multiple injections of Ascaris extract or the migration of Ascaris larvae furnished the needed provocation. The virus could be elicited in the spring and summer as well as fall and winter, from the pathogen-free, colostrum-deprived pigs.