Abstract
An outbreak of pneumonia affecting pigs (10–14 weeks old) was investigated; the mortality rate was low and recovery was slow. Hæmophilus influenzæ was recovered from half the pigs examined and the presence of a virus was demonstrated by the intranasal instillation of a filtrate of pneumonic lung. The virus was subsequently established in ferrets and neutralizing antibodies were demonstrated in the blood of convalescent pigs to the ferret-adapted virus.
Four further outbreaks of pneumonia in pigs revealed the presence of a virus and in two of these the agent was adapted to the ferret. Hæmophilus influenzæ was obtained from only a few of the pigs.
The lungs of pigs at a public slaughterhouse were examined for pneumonia and lesions were found in some cases. Hæmophilus influenzæ was recovered from three of forty affected lungs and transmission experiments with material from two lungs were made. The disease was reproduced in pigs and one of the strains was later adapted to the ferret.