Comprehensive pathological insights and molecular detection of caseous lymphadenitis caused by Corynebacterium...

Objectives: Caseous lymphadenitis (CLA) is one of the significant economically important diseases of small ruminants caused by Corynebacterium pseudotuberculosis. Despite the occurrence of CLA worldwide, there are no reports of CLA in slaughtered ruminants in Bangladesh. This study was designed to investigate the pathology and molecular detection of CLA in slaughtered sheep, goats, and cattle in Bangladesh. Materials and Methods: A total of 102 goats, 16 sheep, and 50 cattle were examined at several slaughterhouses in Mymensingh Sadar. Mesenteric lymph nodes, lungs, liver, spleen, and kidneys from animals with suspected internal lesions were evaluated pathologically. Confirmation of C. pseudotuberculosis was performed by polymerase chain reaction (PCR). Results: Gross examination revealed enlarged mesenteric lymph nodes with multiple abscesses containing greenish-yellow caseous material. The spleen exhibited a characteristic onion-skin appearance, commonly associated with CLA. Histopathology revealed caseous necrosis, encapsulated by fibrous tissue, with infiltration of neutrophils and mononuclear cells, along with Gram-positive coccobacilli arranged in Chinese letter patterns. Similar lesions were observed in other visceral organs of goats. PCR detected C. pseudotuberculosis in 29.41% (30/102) goats, 6.25% (1/16) sheep, and 18% (9/50) cattle. Conclusions: To date, it is the first report of internal CLA in slaughtered ruminants in Bangladesh, as confirmed by pathological and molecular findings, and it highlights the importance of slaughterhouse-based surveillance for disease control.