| Summary: | Between December 2010 and January 2011 a number (n=20) of cases were submitted to the Slaughterhouse Support Service (Servei de Suport a Escorxadors, SESC-CReSA), consisting of grossly nodular granulomatous and caseous lesions in pig carcasses from five different farms. Lesions involved lymph nodes, lungs, liver and spleen.
Histopathological examination showed multifocal to coalescent, granulomatous and necrotizing splenitis, hepatitis, pneumonia and lymphadenitis. The presence of acid-fast bacilli in some cases revealed that it was a mycobacteriosis.
Bacteriological analysis was performed to confirm the diagnosis and identify the aetiological agent (to rule out it was from the M. tuberculosis complex mycobacteria, which includes species causing human and animal tuberculosis). The identification of culture isolates by PCR confirmed the growth of M. avium complex. Further sequencing analysis determined it was M. avium. subsp. avium.
The most likely source of the outbreak was considered to be the feed which shared the five farms, which might have been contaminated with M. avium subsp. avium (common pathogen in poultry and other birds). The fact that most of the animals presented a clear involvement of abdominal viscera is consistent with an oral route of infection.
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