HOST FOR SWINE INFLUENZA VIRUS I. THE Pm~SENC~. OF SWINE I_t~LU~.lqZA VIRUS IN I-IsALTH'g AND SUSCEPTIBLE PIGS

In this series of papers data will be presented which demonstrate the fact that the swine lungworm serves under natural conditions as a reservoir and intermediate host for the swine influenza virus. The virus can persist in a masked form within its worm host for long periods of time, and months or even years may elapse between its transmission from one swine to the next. The period during which the virus survives in the lungworm is more than adequate to account for its persistence between epizootics of swine influenza. In this first paper facts will be presented which show that healthy susceptible pigs sometimes contain the swine influenza virus and may undergo attacks of influenza if the virus is provoked to activity by multiple intramuscular injections of the bacterium Hemophilus influenza* suis (1). Of the two agents which act in concert to cause swine influenza (1), it has been shown that the bacterial component, H. influenza, suis, is capable of eliciting an immune response that affords only partial protection against the disease (2). Swine influenza virus vaccines, on the other hand, confer a complete immunity to swine influenza (3). The observations now to be recorded were made as a result of further study of the use of H. influenza, suis vaccines in the prophylaxis of swine influenza.