Mycobacterium microti Infection in Red Foxes in France

Mycobacterium microti, member of the Mycobacterium tuberculosis, complex is known to interfere in the screening and diagnosis of bovine tuberculosis. This pathogen is increasingly detected in the frame of surveillance programs for tuberculosis in livestock and wildlife. Recently, red foxes (Vulpes vulpes) were found infected by Mycobacterium bovis in four French endemic areas. M. microti infection was concomitantly found during this investigation. Rates of infection by M. microti and M. bovis are not different except in one of the four areas (lower prevalence for M. microti in Charente). As for M. bovis infection, none of the infected foxes presented gross TB-like lesions. Infection of red foxes by M. microti seems to occur by ingestion of contaminated food, as mesenteric lymph nodes are mostly infected albeit no fecal excretion could be detected. Red foxes appear to be susceptible to Mycobacterium microti infection but seem to play a role of dead-end host for the transmission of this bacillus.