Camelidae and Cervidae Caseous Lymphadenitis Study Guide

Overview and Clinical Importance

Caseous lymphadenitis (CLA) is a chronic, contagious bacterial infection caused by Corynebacterium pseudotuberculosis. While traditionally recognized as a major disease of small ruminants, CLA has emerged as a significant health concern in both Old World and New World camelids, as well as various cervid species. In camelids, the disease presents unique challenges due to its insidious nature and preference for internal organ involvement, making diagnosis particularly difficult. The disease causes substantial economic losses through mortality, reduced productivity, carcass condemnation, and culling of affected animals.

Etiology and Pathogen Characteristics

Causative Agent

Corynebacterium pseudotuberculosis is a Gram-positive, non-motile, facultatively anaerobic, pleomorphic coccobacillus belonging to the Actinomycetaceae family. The organism is closely related to C. diphtheriae and C. ulcerans, sharing similar mycolic acid content in the cell wall that contributes to environmental persistence.

Biovar Classification

Two distinct biovars exist based on nitrate reduction ability: