Determination of Corynebacterium pseudotuberculosis prevalence and antimicrobial susceptibility pattern of isolates from lymph nodes of sheep and goats at an organic export abattoir, Modjo, Ethiopia

Corynebacterium pseudotuberculosis is the causative agent of caseous lymphadenitis, a suppurative abscessation in the superficial and internal lymph nodes and internal organs of small ruminants. This study was conducted on the superficial lymph nodes and carcasses of 768 small ruminants slaughtered at a slaughterhouse during the study period; 82 had abscesses or caseous lymphadenitis. The most frequent sites of abscesses in goats were the prescapular (34, 5.54%) and prefemoral lymph nodes (24, 3.91%) respectively. Similar patterns were observed in sheep. The prevalence of caseous lymphadenitis was found to be significantly higher in adult than in young animals, in both species (P < 0.05). The age-wise prevalence rates of lesions on post-mortem inspection, at 95% CI, were 2.7% (2.3-3.1%) and 3.1% (2.8-3.4%) in young sheep and goats, respectively, and 24.4% (17.4-31.4%) and 27.5% (23.8-31.2%) in adult sheep and goats respectively. Corynebacterium pseudotuberculosis isolates were recovered from 72% (59/82) of animals found to have post-mortem evidence of abscesses. The Coryne. pseudotuberculosis isolates were susceptible to the antibiotics norfloxacin, tetracycline, doxycyline HCl and kanamycine; however, resistance was observed against ampicillin, clindamycin and doxycyline HCl. In conclusion, this study reported the magnitude of the problem in the country for the first time and the authors recommend a thorough investigation of wider study areas.