Infection status of Mycoplasma hyopneumoniae in experimental pigs at a commercial farm

Abstract

The objective of this study was to investigate the profiles of Mycoplasma hyopneumoniae (MH) infection at different ages of pig in a sow – finishing herd using serological and molecular methods. A total of 30 study piglets were born from non-vaccinated sows with MH. They were injected one-dose of inactivated MH vaccine at the 10th week. MH infection status was evaluated by using ELISA to detect MH antibodies from blood samples, and PCR to detect MH DNA in nasal swabs or oral fluid samples every other week from newborn to slaughter time. The results of this study showed that PCR positive proportions were low at 1st-2nd week (7-13%), then increased significantly during 5th -7th week (73-79%) and reduced at 8th week (33%); finally became negative after 13th week of age. This pattern corresponds to the one of antibody level. In particular, the level of maternal antibodies against MH was very high due to maternal immunity, then decreased gradually to negative at 7-8 weeks of age, and finally increased gradually from 13 weeks of age to all positive at 25 weeks of age. In conclusion, the result showed that in this herd, MH might invade pigs by the time of 5-7 weeks of age after maternal immunity disappears, and humoral response can overcome the infection at week 13. This should be noted to have appropriate strategies to control MH at the farm.