Profiling natural antibodies to Mycoplasma hyosynoviae in commercial pigs.

Mycoplasma hyosynoviae (M. hyosynoviae) is a commensal bacterium that can induce lameness in growing and finishing pigs, contributing to welfare concerns in swine production. The objective of this study was to characterize the natural humoral immune response to M. hyosynoviae in various ages of pigs commercially raised in the United States. Three > 2500 sow farms and their downstream sites were enrolled in the study. One herd presented a history of M. hyosynoviae-associated lameness in growing/finishing age pigs (affected), while two farms and their downstream flows were apparently healthy (non-affected). Blood samples (n = 3395) were collected cross-sectionally at various ages and stages of production in sows, piglets, and replacement gilts. An indirect ELISA assay was employed for the detection of M. hyosynoviae IgG antibodies in serum. A Kruskal-Wallis test was utilized to investigate the differences in M. hyosynoviae S/P ratios among sows, piglets, and gilts in each herd. A logistic regression analysis was performed to assess the proportion of pigs positive for M. hyosynoviae antibodies within each herd. Sows showed the highest detection of M. hyosynoviae antibodies when compared to piglets and replacement gilts, regardless of production stage. Mycoplasma hyosynoviae antibodies tended to wane at approximately eight weeks of age in the piglets in all herds. Replacement gilt seroconversion to M. hyosynoviae in the two non-affected herds increased later in life compared to the affected flow. The lack of identification of M. hyosynoviae antibodies in the herd experiencing lameness downstream compared to the two non-affected herds warrants investigation into the role that antibody production could play against lameness development. In conclusion, this study provides information on potential windows of opportunity to induce an immune response against M. hyosynoviae.