HISTOPATHOLOGICAL AND MOLECULAR STUDIES ON CASEOUS LYMPHADENITIS IN SHEEP AND GOATS IN DUHOK CITY, IRAQ

Caseous lymphadenitis is an infectious bacterial disease of sheep and goats caused by Corynebacterium pseudotuberculosis. This study is aimed to estimate the frequency of caseous lymphadenitis in sheep and goats and to compare with the results of bacteriological analysis, histopathology and molecular diagnosis of suspected cases. In this study, 22 (2.1%) suspected cases of caseous lymphadenitis were diagnosed clinically from 1090 sheep and goats slaughtered at Duhok abattoir. The study showed grossly affected mediastinal lymph node was congested and highly oedematous compared to other lymph nodes. Histopathological examination showed presence of abscess in the centre of affected mediastinal lymph node. Based on standard bacteriological methods, Corynebacterium pseudotuberculosis was the only causative agent isolated from all suspected cases. The confirmation was performed by amplification of the target genes of Corynebacterium pseudotuberculosis including 16S rRNA, rpoB and pld. The results showed successful amplification of 16S rRNA, rpoB and pld among all suspected cases. Overall, the results of this study showed that the Corynebacterium pseudotuberculosis is still the main causative agent of CLA in sheep and goats. The results also revealed molecular and histopathological studies together could be used to identify Corynebacterium pseudotuberculosis directly from cases of CLA from sheep and goats. Further studies including study of virulence genes and antimicrobial susceptibility together with phylogenetic analyses are recommended to be done in the future for better understanding of the epidemiology of this pathogen in Duhok city.