DIAGNOSIS OF TUBERCULOSIS IN THE LYMPH NODES OF WILD BOARDS HUNTED IN LA RIOJA COMMUNITY

L E REYES AVILA, O MORENO BUITRAGO, A VERNA, S JIMÉNEZ PALACIOS1, J MEDRANO GÓMEZ2, V PÉREZ, J F GARCÍA MARÍN.

Casa das Artes de Vila Nova de Famalicao. Portugal

Congreso; 12 Annual Meeting of the Portugueses Society of Animal Pathology jointly with 16 Annual Meeting of the Spanish Society Veterinary Pathology; 2004

At present, prevalence of cattle tuberculosis has been reduced significantly due to eradication programs and, in consequence, the role of wildlife as reservoir of the infection has gained attention: In the last years and in some areas of Spain, tuberculosis has been considered as a major disease among wild Mycobacterium Bovis, lesions have been constantly identified in mandibular and retropharyngeal lymph nodes. A diagnostic protocol based on the examination of these lymph nodes was carried out in 101 wild boards coming from more than 30 hunts in La Rioja community. Lymph nodes were carefull trimmed and gross lesions were identified and classified according to caseous necrosis extension (A:miliary; B:nodular; C: diffuse). A total of 24 animals showed pathological changes (A:14; B:5; C:5). Microscopically, two main types of lesion were identified. Type H1 was characterized by the presence of necrosis and mineralization, granulomatous inflammation and repair tissue. This lesion was seen in 10 of the animals, and acid-fast bacilli were identified in all the cases by Ziehl-Neelsen, immunohistochemistry against M. bovis antigens or PCR by the detection of the IS6110 insertion sequence of M. tuberculosis complex, in paraffin-embedded tissue sections. Type H2 lesions were depicted by the presence of “sulfur granules” in the necrotic areas, characterized by colonies of gram- positive bacilli surrounded by a zone of palisading, eosinophilic, club.shaped structures accompanied by an inflammatory exudate formed mainly by neutophils, macrophages, lymphocytes and foreing body giant cells demarcated by a thick fibrous wall. This type appeared in 14 animals and mycobacteria  was not detected in any of them. Type H1 lesions were associated with any of the fross lesions observed whereas H2 forms showed an A pattern. Thos work confirms the importance of wild board as a reservoir of tuberculosis that was identified in a 10% of the cases and points out the importance of infections consisten with Actinomyces spp. (14%) in the retropharyngeal and mandibular lymph nodes. Lesions due to this bacteria could cause difficulties in the gross diagnosis of tuberculosis. The absence of mixed infections due to both pathogens is remarkable