The Effect of Hemophilus Influenzae Suis Vaccines on Swine Influenza Bi

Early experiments indicated that the bacterium, Hemophilus influemae suis, (1) administered intranasally to swine, conferred no immunity to swine influenza (2). These had not been intended to test the possible value of the organism for use as a prophylactic agent in controlling swine influenza, and no experiments in which the bacterium was administered in other ways than intranasally were conducted. More recent experiments (3), however, have indicated that, when accompanied by human influenza virus, H. influenzae suis does play a r61e in immunizing swine to swine influenza. It has been found that while swine recovered from infection with a mixture of human influenza virus and tt. influenzae suis were usually immune to swine influenza, those recovered from infection with human influenza virus alone were usually not immune. These experiments were believed to indicate that H. influenzae suis, in the presence of a con-comitant human influenza virus infection, immunized swine to the bacterial component of the swine influenza etiological complex (4). The apparent discrepancy between the earlier and the more recent experiments could be explained by assuming that when the bacterium alone was administered intranasally to swine it was applied super-tidally to an intact mucosa that was impermeable to its deep penetration. The inability of the bacterium to penetrate the respiratory tract mucous membranes could account for its failure to induce an immunity response. However, when H. influenzae suls was given intranasally to swine in mixture with human influenza virus it was not only afforded a portal of entry into deeper tissues through lesions produced by the virus, but the influence of the virus may have en