Detection of Wood Mice (Apodemus sylvaticus) Carrying Non-Tuberculous Mycobacteria Able to Infect Cattle and Interfere with the Diagnosis of Bovine Tuberculosis

Abstract

Mycobacterial infections caused by the Mycobacterium tuberculosis complex (MTC) and non-tuberculous mycobacteria (NTM) are of great medical and veterinary relevance. The aim of this research was to study whether small mammals play a role in the epidemiology of mycobacterioses. Four samplings of 100 traps were performed in each of three cattle farms with previous history of tuberculosis or NTM between 2017 and 2018. A total of 108 animals belonging to seven species were trapped, classified, and necropsied, and tissues were submitted to microbiological and molecular methods for mycobacteria identification. The wood mouse (Apodemus sylvaticus) was the most abundant species (87%). No MTC was detected but six different NTM were identified (M. intracellulare, M. avium subsp. paratuberculosis, M. gordonae, M. celatum, M. fortuitum, and a not determined Mycobacterium sp.), showing a prevalence of 6.5%. No significant association was found between mycobacteria prevalence and the analyzed factors. Although a role in the epidemiology of MTC could not be attributed to small mammals, A. sylvaticus carries NTM that could be pathogenic or interfere with the diagnosis of tuberculosis. According to our results, there is a risk of NTM transmission at the wildlife–livestock interface through potential indirect contacts between small mammals and cattle.

Mycobacterium microti: Not Just a Coincidental Pathogen for Cats

“…Hence the relevance of isolating opportunistic pathogens such as M. nebraskense and M. lentiflavum from wildlife is unclear. Only recently, a study in Spain tried to identify small mammals, mainly Apodemus sp., as the source of NTM infection in cattle which can lead to cross-reactive responses that can interfere with the diagnosis of tuberculosis ( 56 ). The authors identified six different NTMs ( M. intracellulare, M. avium subsp.…”

“…It is not clear whether these mycobacteria are able to colonize the mice or only pass through the animals. However, the movement of these animals leads to further spread ( 56 ) and may be problematic for livestock animals. The virulence of NTMs, including M. lentiflavum , in mice has been compared to the virulence of M. intracellulare and reported as lower ( 57 ).…”

Interaction Patterns between Wildlife and Cattle Reveal Opportunities for Mycobacteria Transmission in Farms from North-Eastern Atlantic Iberian Peninsula

“…MTC infection among wild mammals from this region has been detected in wild boar (1.12%) and red deer (2.40%) [ 22 ]. Several species of NTM able to infect cattle and interfere with the diagnosis of bovine tuberculosis have been also detected in wood mice [ 18 ] and other wild species from the study area (Varela-Castro, unpublished data: wild boar, red deer, roe deer, badgers, foxes and stone martens).…”

“…Almost half of the MTC-positive cattle of the last ten years in the Basque Country were detected in farms A and C and NTM were also detected in these farms, while in farm B only M. avium subsp. avium was detected [ 18 ]. Farms A and B are dairy farms and farm C is a fighting bull farm.…”

“…However, eradication has not been accomplished yet. In spite of the absence of a mandatory NTM surveillance program, NTM-infected cattle have also been detected in these regions during the national TB eradication campaigns among cattle showing false positive reactions to the tuberculin skin test [ 17 , 18 ]. The interactions between cattle and competent cohabiting wild hosts could contribute to this epidemiological picture of Atlantic Iberian Peninsula.…”