Prevalence and molecular investigation of caseous lymphadenitis among the slaughtered sheep at Duhok Abattoirs; experimental infection with Corynebacterium pseudotuberculosis in rabbits

Caseous lymphadenitis is a chronic infection caused by Corynebacterium pseudotuberculosis that affects the lymphatic system, resulting in abscesses in the lymph nodes and internal organs. This study was conducted to determine the prevalence rate of caseous lymphadenitis among slaughtered sheep in Duhok abattoirs, Duhok, Iraq and to investigate to what extend rabbits can develop caseous lymphadenitis just like that in sheep. A total of 1052 carcasses of sheep were randomly selected (939 males and 113 females) and carefully inspected for detection any suspected caseous lymph adenitis. The isolated Corynebacterium pseudotuberculosis from lymph nodes of sheep carcasses were identified by PCR before used in in vivo infection in rabbits. Data revealed that the prevalence rate of caseous lymphadenitis was at 1.9% among the slaughtered sheep and the prevalence rates were higher in females and older ages than that of males and younger ages, respectively. Experimentally infected rabbits developed various clinical signs were ranging from in inappetence to sudden death, mainly during first week of infection. Histopathologically, the infected rabbits developed caseous lymphadenitis and pyogranuloma after a time point of 10 days post-infection. Liver, spleen and lymph nodes of infected rabbits showed caseo-necrotic foci with multiple micro-granulomas with presence of thick pyogenic membrane infiltrated with leukocytic cells; these findings are strictly resemblance to that reported in sheep. The obtained preliminary data of using rabbits as an animal model is promising which will enhance a better understanding the pathogenesis of caseous lymphadenitis in animals.