Interaction between Ascaris suum and Pasteurella multocida in the lungs of mice.

In an experiment including 8 groups of 15 mice, the effect of migrating Ascaris suum larvae in the lungs on the establishment and pathogenicity of aerosol exposure to Pasteurella multocida was investigated. Following aerosol exposure to P. multocida, mice with migrating A. suum in their lungs developed more severe pneumonia and septicaemia than did parasite-free mice. The parasite-induced effect on bacterial pathogenicity was more marked for a non-toxin-producing P. multocida as compared with a toxin-producing strain of P. multocida, possibly due to the higher spontaneous pathogenicity of the non-toxigenic strain of P. multocida. The present results should encourage controlled experiments on possible interactions between A. suum and various airborne microbial infections in pigs.