First study on molecular epidemiology of caseous lymphadenitis in slaughtered sheep and goats in Duhok Province, Iraq

Abstract

Background: Caseous lymphadenitis (CLA) is a chronic suppurative bacterial infection caused by Corynebacterium pseudotuberculosis (C. pseudotuberculosis) affecting superficial and internal lymph nodes and internal organs of small ruminants. Aims: Through the use of molecular methods, this study aimed to estimate the prevalence of caseous lymphadenitis and it’s contributing factors as well as the degree of genetic diversity and epidemiological relationships among C. pseudotuberculosis isolates from slaughtered sheep and goats in various districts of Duhok Province, Iraq. Methods: A total of 18836 carcasses (15775 sheep and 3061 goats) were inspected by veterinarians at slaughterhouses (Duhok-Sumel (2453 sheep+627 goats), Zakho (6000 sheep), Bardarash (1117 sheep+379 goats), Amedi (413 sheep+178 goats) and Akre (5792 sheep+1877 goats)) in Duhok Province for detection the prevalence rate of CLA using molecular techniques. Results: The prevalence of the disease was 0.94% and 1.93% in sheep and goats, respectively. Sheep in Duhok-Sumel and goats in Amedi were at the higher risk of infection than the animals in another location, with a prevalence rate of 4.31% and 6.18%, respectively. Sheep and goats of older age were more susceptible. Females were more susceptible than males in all districts except Duhok-Sumel where the reverse was true. ERIC-PCR analysis grouped the bacterial isolates into 11 different genotypes. Maximum Likelihood phylogenetic tree of partial sequences of the 16S rRNA gene sequences of C. pseudotuberculosis revealed no divergent sequences discovered in this study. Conclusion: A strict control program needs to be applied to reduce the entrance of the pathogen from the neighboring countries.