Document Type : Original Articles
Authors
1
Department of clinical sciences, Faculty of Veterinary Medicine, Ferdowsi University of Mashhad, Mashhad-Iran
2
Department of Clinical Studies, School of Veterinary Medicine, Ferdowsi University of Mashhad. Mashhad- Iran
3
Department of Pathobiology, Faculty of Veterinary Medicine, Ferdowsi University of Mashhad, Mashhad-Iran
10.22092/ari.2025.368988.3596
Abstract
Caseous lymphadenitis (CLA), a chronic bacterial disease caused by Corynebacterium pseudotuberculosis, significantly impacts small ruminant health and productivity worldwide, causing economic losses through reduced wool and milk yields, reproductive issues, and carcass condemnation. Despite its importance, CLA’s prevalence and microbial dynamics remain underexplored in Iran, where small ruminants are vital to rural economies. This study assessed the prevalence, clinical manifestations, and bacteriological profile of CLA in Khorasan Razavi province, northeast Iran, to inform regional control strategies and address potential zoonotic risks. We examined 15 flocks totaling 4,733 animals (4,640 sheep, 93 goats) through clinical inspections and microbiological analysis of pus samples from affected lymph nodes. The results revealed a lymphadenitis prevalence of 11.59% (95% CI: 10.58–12.66%), with 8.62% of sheep (400/4,640) and 8.60% of goats (8/93) affected, varying across flocks from 0% to 28.57%. Submandibular lymph nodes were most commonly affected (51.35%), followed by retropharyngeal (18.02%) and parotid (15.32%) nodes, with peak incidence in the 2–3-year age group (38.24%), likely linked to shearing practices. Bacteriological analysis of 102 pus samples identified C. pseudotuberculosis in 19.6% (20/102) of cases, characterized by small, dry, white colonies with β-hemolysis on Columbia blood agar. A diverse microbial profile included Actinobacillus spp. (7.8%), Trueperella pyogenes (3.9%), and novel isolates like Acinetobacter spp. and Yersinia spp. (1.0% each), with 43.14% of samples sterile, suggesting chronicity or sampling challenges. These findings indicate CLA’s complex etiology, extending beyond a single pathogen and influenced by local husbandry practices. The study underscores CLA’s economic burden and zoonotic potential, given rare but documented human cases. Integrated control measures—enhanced molecular diagnostics, recombinant phospholipase-D (PLD) vaccine trials, and improved biosecurity—are urgently needed. Future research should prioritize genomic strain typing and environmental reservoir analysis to refine CLA management in northeast Iran, offering insights applicable to similar agroecosystems globally
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