[Experimental swine influenza. Comparison of the pathogenicity of swine-type wild influenza viruses and strains of human type H3 N2 whose reservoir is swine].

Intra-nasal inoculation of 10-day-old piglets, free of specific pathogenic flora, with swine influenza virus A/H1 N1 and A/H3 N2 produces lesions of viral pneumonia without detectable clinical signs. Following indirect contamination all the strains studied were able to multiply in the respiratory tract; in those cases where no macroscopic lesion was seen, microscopic examination revealed variable modification of the pulmonary tissue depending on the virus causing infection. Influenza virus type H3 N2 are naturally found in many groups of pigs and can therefore play an important role in the respiratory pathology of the hog. Experimental results when compared to findings in the field indicate that the severity of the disease is linked to associated etiological factors as well as to the virulence of the viral strains themselves.