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[Experimental paratuberculosis: pathogenicity of mycobactin-dependent mycobacteria strains to calves]
Abstract:
The pathogenicity for calves of two strains of wood-pigeon mycobacteria isolated in our laboratory, one strain isolated in the United Kingdom, one strain isolated from a Roe-deer in Denmark and three strains of M. paratuberculosis, were compared. Seven groups of four 3 to 4 week-old calves were infected by the intravenous route using 10(6) to 10(9) viable units. They were slaughtered one year after the exposure or earlier if their state required it. The macroscopic and microscopic lesions and cultures from the mesenteric lymph nodes, ileon and caecum were studied. At necropsy, the post-mortem findings were hardly significant. However, the histopathological studies showed lesions identical to the classical aspects of paratuberculosis in cattle, both in animals inoculated with M. paratuberculosis and those inoculated with wood-pigeon mycobacteria. The isolation of the bacteria showed that all animals were infected. The experimental infection was able to reproduce a disease resembling paratuberculosis with M. paratuberculosis (except the strain 2103) and with wood-pigeon mycobacteria, but it has not been able to distinguish the disease caused by M. paratuberculosis from the one caused by wood-pigeon mycobacteria.
Insights
Wood-pigeon mycobacteria cause paratuberculosis-like lesions in calves, similar to Mycobacterium bovis paratuberculosis. This study found no significant differences in disease presentation between the two mycobacterial strains.
Area of Science:
- Veterinary Microbiology
- Pathology
Context:
- Bovine paratuberculosis, caused by Mycobacterium avium subspecies paratuberculosis (MAP), poses significant economic challenges in cattle farming.
- Wood-pigeon mycobacteria have been implicated as potential agents of paratuberculosis-like disease, necessitating comparative pathogenicity studies.
Purpose:
- To compare the pathogenicity of wood-pigeon mycobacteria strains against Mycobacterium paratuberculosis in a calf model.
- To histopathologically and microbiologically assess disease development following experimental infection.
Summary:
- Calves were experimentally infected intravenously with M. paratuberculosis or wood-pigeon mycobacteria strains.
- Histopathological examination revealed lesions consistent with paratuberculosis in calves infected with both types of mycobacteria.
- Bacterial isolation confirmed infection in all animals, and the induced disease was indistinguishable between the two mycobacterial groups.
Impact:
- This research highlights the pathogenic potential of wood-pigeon mycobacteria in inducing paratuberculosis-like disease in calves.
- The findings suggest that differentiating between M. paratuberculosis and wood-pigeon mycobacteria based on clinical or pathological presentation may be challenging.