The objective of this paper is to report the prevalence and distribution of lesions of caseous lymphadenitis (CL) in hair sheep slaughtered in an abattoir in the state of Paraíba, northeastern Brazil. From 1,466 sheep slaughtered, 236 (15.9%) had gross lesions similar to that of CL. The prevalence was higher in females, 17.9% (135/754), than in males, 13.8% (101/732). Ninety seven (36.3%) out of 268 lesions were localized in the prescapular lymph node, 22.4% (60/268) in the parotideal, and 20.9% (56/268) in the prefemoral. Only 70 (26.1%) out of 268 lesions suggestive of CL were detected during ante mortem examination. Caseous lymphadenitis-like lesions were observed in all flocks examined from different municipalities in the states of Paraíba, Pernambuco and Bahia. Cultures and histologic examination were performed in samples from 51 lesions. Corynebacterium pseudotuberculosis was isolated in 74.5% (43/51) samples, Staphylococcus aureus in 7.8% (4/51) samples, Escherichia coli in 2% (1/51), and in 5.9% (3/51) samples cultures were negative. Histologic findings in 11 lymph nodes showed all characteristic lesions of caseous lymphadenitis: central area of necrosis formed by concentric lamellae, with large bacterial colonies and mineralization, surrounded by an inflammatory exudate with epithelioid macrophages and few neutrophils; lymphocytes and plasma cells were observed in the next layer, and fibrous tissue was surrounding the whole lesion. Lesions in the other 32 lymph nodes showed most, but not all lesions characteristic of the disease. Giant cells were observed in 21 lymph nodes. Histologic lesions in lymph nodes from which S. aureus was isolated were similar as those of CL. These findings suggest that CL lesions are characteristic, but not pathognogmonic, because they can be confused with lesions caused by other pyogenic bacteria or tuberculosis; therefore bacteriologic examination is necessary for the diagnosis of the disease.
Caseous lymphadenitis; sheep; Corynebacterium pseudotuberculosis; ante mortem examination; post mortem examination
