The MA-ELISA was subsequently evaluated using serum samples from two farms with pigs known to be infected with MA. Bacteriological examination of the sub-maxillary and mesenteric lymph nodes showed that 56 % (103/184) and 35 % (41/117) of the pigs, respectively were positive for MA in these farms. In the first farm, 16 % (29/184) of the pigs tested positive in MA-ELISA and 31 % (57/184) by pathological examination. On the contrary, in the second farm, more pigs tested positive 17 % (15/117) in MA-ELISA with 8 % (9/117) positivity by pathological examination. Taking the results on both farms together, the sensitivity of the MA-ELISA was 14 % and the specificity 83 % , whereas the sensitivity of the pathological examination was 31 % and the specificity 86 % .
For practical reasons use of a serological test as the MA-ELISA may be preferred over pathological or bacteriological examinations. Our studies in experimentally infected and negative “field” sera indicate that the MA-ELISA is significantly more specific and more sensitive than detection by classical pathological examination. However, the studies in two MA infected farms show a variable picture with pathological examination overall performing better. Study in a wider range of “positive” farms will be needed to provide a more comprehensive view of the quality of both tests for detection of MA in infected farms. At the same time further optimization of MA-ELISA with use of lipid antigens from a broader range of serotypes may improve its performance in the face of infections with different MA serotypes.