Seroepidemiology of Mycoplasma hyopneumoniae in pigs from farrow-to-finishfarms

A prospective study was carried out on three intensive farrow-to-finish far ms. The aims were to estimate the incidence of Mycoplasma hyopneumoniae inf ection, to determine when pigs become infected and the pattern of transmiss ion of infection and to verify the relationship between seroconversion and clinical signs. One batch of pigs per farm was followed from farrowing-to-s laughter. Blood samples were taken at 10, 27, 70, 94, 125 and 147 days of a ge, from 44, 48 and 44 pigs per farm. Colostrum and blood samples were also taken from the sows. Animals were checked clinically once a week and cough ing rates were recorded. Antibodies against M. hyopneumoniae were detected by a blocking ELISA. At 27, 70 and 94 days of age most pigs on the three fa rms were seronegative, suggesting that no circulation of M. hyopneumoniae o ccurred during the growing period. Thereafter, a high proportion of pigs se roconverted, indicating that infection occurred soon after the transfer of the animals to the finishing houses. Differences were detected between farm s in the incidence of seroconversion. Seropositive pigs were widely distrib uted among the finishing pens, suggesting that in addition to direct contac t, other methods of transmission, such as indirect or airborne transmission , may have been important. Coughing started at around the same time as sero conversion. The results showed that the critical period for the transmissio n of M. hyopneumoniae is around the beginning of the finishing period, when pi,as have low concentrations of antibodies against the agent. (C) 2001 El sevier Science B.V. All rights reserved.