Comprehensive survey of caseous lymphadenitis in sheep and goats flocks of Iran: Clinical, bacteriological, and molecular insights

Abstract

Caseous lymphadenitis (CLA) is a chronic and highly contagious disease in sheep and goats caused by Corynebacterium pseudotuberculosis, resulting in significant economic losses in the livestock industry. Despite its global prevalence, studies on CLA at the flock level in Iran remain limited. This study aimed to investigate the prevalence and epidemiology of CLA in sheep and goat herds across all 31 provinces of Iran using clinical, bacteriological, and molecular diagnostic methods to inform effective control and management strategies. This cross-sectional study, conducted from 2017 to 2022, investigated CLA prevalence in sheep and goat herds across all 31 provinces of Iran. Using a stratified sampling approach, 120 herds per province were selected and categorized by size into small (<70 animals), medium (70–150 animals), and large (>150 animals) groups, ensuring diverse representation. Clinical examinations and microbiological analyses identified cases, while multiplex PCR confirmed the presence of C. pseudotuberculosis. Statistical methods assessed associations between flock size, species, and age. The study revealed distinct prevalence patterns of CLA across Iranian provinces, with low prevalence (<5 %) observed in over 30 % of flocks, moderate prevalence (5–10 %) in 20–50 %, and high prevalence (>10 %) in less than 15 %. Clinical signs were primarily observed in the prescapular and submandibular lymph nodes, with lesions confirmed by bacteriological and molecular methods. C. pseudotuberculosis was the primary causative agent, with other secondary pathogens occasionally identified. Multiplex PCR successfully confirmed C. pseudotuberculosis in all positive samples. This study highlights the localized prevalence of CLA across Iran, identifying areas of high prevalence that necessitate urgent intervention. The findings underscore the importance of integrating effective vaccination strategies, biosecurity measures, and early detection protocols to manage CLA and reduce its economic impact. Future efforts should prioritize developing and implementing region-specific vaccines and preventive measures in Iranian herds.