Risk Indicators for the Seroprevalence of Mycoplasma hyopneumoniae,Porcine Influenza Viruses and Aujeszky's Disease Virus in Slaughter Pigs from Fattening Pig Herds

Epidemiological aspects of Mycoplasma hyopneumoniae (Mh), influenza H_***2N₁ and H₃N₂ viruses, and Aujeszky's disease virus (ADV) were investigated in slaughter pigs from 50 fattening pig herds. Herd factors as potential risk indicators for respiratory disease were obtained by means of a questionnaire. At slaughter, blood samples were collected from each herd, and the proportion of seropositive pigs per herd was assessed for each of these pathogens. The median herd-level seroprevalence of the agents were: Mh 88%, H_***3N₁ 100%, H₃N₂ 60% and ADV 90%. The percentage of herds in which all investigated fattening pigs were seronegative for these agents was: Mh 0%, H_***N₁ 0%, H₃N₂ 12% and ADV 18%. The percentage of herds in which all investigated fattening pigs were seropositive for these agents was: Mh 8%, H₁N₁ 71%, H₃N₂ 22% and ADV 40%. A positive association was found between influenza H₁N₁ and H₃N₂ viruses, and a negative association between influenza H₃N₂ virus and ADV. There were no risk indicators for the seroprevalence of Mh. Three risk indicators were associated with the seroprevalence of influenza H₁N₁ virus: a fully slatted floor, an increasing number of pigs in the municipality and dry feeding. Three risk indicators were found for the seroprevalence of influenza H₃N₂ virus: purchase of pigs from ≥two herds, an increasing number of pigs in the municipality and natural ventilation. The seroprevalence of ADV was influenced by two risk indicators: an increasing number of pig herds in the municipality and an increasing number of pigs per pen.