Non-purulent arthritis in Danish slaughter pigs. I. A study of field cases

The pathology and microbiology of non-purulent arthritis in Danish slaughter pigs were studied in order to draw up an updated picture of the disease. Samples of one or more joints, their regional lymph nodes and the heart were collected from 101 arthritic pigs, totalling 137 joints, 86 lymph nodes and 96 hearts (group I). For another selected group including 25 pigs (group II), the preliminary diagnosis of mycoplasmic arthritis, based on the appearance of the corresponding regional lymph node, was assessed versus the appearance of the joint fluid. A total of 44 samples were examined. More than 70% of all joint samples in both groups were sterile. Erysipelothrix rhusiopathiae was isolated from 7% of the joints and Mycoplasma hyosynoviae from 9%. A contamination flora was isolated in 17% of the samples. Very few of the lymph nodes (5%) were infected, and none of the hearts were. In group-II M. hyosynoviae was isolated from 8% of the joints. From the remainder the isolates were contamination flora or low numbers of non-specific bacteria. The gross pathological changes of the lymph nodes and joints of the E. rhusiopathiae cases differed notably from those of the M. hyosynoviae cases. The pathological features of the lymph nodes, in particular, were type specific. This suggests that these features may be used to differentiate between the two types of arthritis. Considering the high number of sterile samples, it is necessary to test this hypothesis in greater detail. A programme is outlined to elucidate the zoonotic and hygienic consequences of a proposed alternative handling and removal procedures for the two types of arthritis at slaughter.