Caseous Lymphadenitis Outbreak in Dairy Cattle: Clinical Findings, Management, and Autogenous Vaccine Development.

Caseous lymphadenitis (CL), caused by Corynebacterium pseudotuberculosis, typically affects small ruminants but is rarely reported in cattle. This case report describes an outbreak of CL in a dairy herd in southern Portugal, where 55 of 500 animals (11%) were clinically affected. Diagnosis was based on characteristic lesions and laboratory confirmation by bacterial culture and PCR. Control measures included isolation, culling, environmental disinfection, and vector management. An autogenous vaccine was prepared from herd isolates and administered under veterinary supervision. No further clinical cases occurred following vaccination. Although immunological and efficacy assessments were not performed, the apparent control of the outbreak suggests that autogenous vaccination, combined with strict biosecurity, may support disease management in atypical hosts. This report underscores the importance of recognizing C. pseudotuberculosis infections in cattle and highlights the need for further evaluation of autogenous vaccines under controlled conditions.