Association between bacterial otitis and porcine circovirus 2 (PCV2) infection in pigs

The occurrence and bacteriology of purulent otitis in groups of pigs affected by three different clinical conditions are described: postweaning multisystemic wasting syndrome (PMWS), depressed growth (attrition) and normal growth (control). A total of 385 animals, 60-130 days of age, were examined. Diagnosis of PMWS was confirmed by the presence of clinical signs and pathological findings compatible with the disease, and through detection of viral antigens in tissues by immunohistochemistry. From 242 pigs with PMWS, 57 (23.5%) showed purulent lesions in the middle ear. Among 119 pigs with attrition, only 1 (0.7%) presented the lesion. In 24 control pigs, middle ear lesions were not detected. The most frequently isolated agents from the lesions were Arcanobacterium pyogenes (43%), a-hemolytic Streptococci (37.2%) and Pasteurella multocida (27.9%) out of 86 materials. The frequent occurrence of purulent lesions in the middle ear of PMWS affected pigs suggests that PCV2 infection may increase the susceptibility to bacterial otitis. The low occurrence of this disease in piglets with attrition suggests that otitis does not represent a significant cause for depressed growth in pigs from growing and finishing age. The isolation of A. pyogenes, a-hemolytic Streptococci and P. multocida from most of the lesions emphasizes the importance of these organisms as causal agents of otitis media in swine.