Spatiotemporal and Ecological Patterns ofMycobacterium microtiInfection in Wild Boar (Sus scrofa)

Abstract

Mycobacterium microti has recently been described as the causative agent of tuberculosis-like lesions in wild boar (Sus scrofa), a reservoir specie of Mycobacterium tuberculosis complex (MTBC) in some European Mediterranean ecosystem. Through a five-year survey on tuberculosis in free-living wild boars, the epidemiological trend of M. microti infections and the host and population risk factors linked with its occurrence were described. Retropharyngeal and mandibular lymph nodes of 3041 hunted wild boars from six different districts were macroscopically inspected. The sex and age of each animal were registered, as well as the animal abundance in each district. Lesions compatible with tuberculosis (190) were collected and analysed using a gyrB PCR-RFLP assay. M. microti was identified directly in 99 tissue samples (Prev = 3.26%; 95% CI: 2.67-3.97%), while neither Mycobacterium bovis, nor other members of the MTBC were detected. The probability of being M. microti positive showed spatio-temporal variability, with 26% of increase of risk of being infected for each year. Moreover, a positive effect of wild boar abundance and age on the prevalence was detected. The generalized increase in the European wild boar population, coupled with its sensitivity to M. microti infection, poses a future concern for the identification and management of MTBC members in wild boar.

Evidence of low prevalence of mycobacterial lymphadenitis in wild boars (Sus scrofa) in Poland

“…Tuberculosis in wild boars has been reported in several European countries such as Spain [3], Italy [4], Portugal [7], Great Britain [5], France [6] and recently in Poland [8]. …”

“…Tuberculosis caused by Mycobacterium bovis or M. caprae in wild boars have been reported most frequently [2, 3, 5–8], while M. microti [4] and non-tuberculous, potentially pathogenic environmental mycobacteria, have been reported less often [9, 10]. …”

Testing Eurasian wild boar piglets for serum antibodies against Mycobacterium bovis

“…In 7-12 month old yearlings (those harvested by hunters in their first autumn-winter season), prevalences reported ranged from 20 to 52% (Vicente et al, 2006(Vicente et al, , 2013Díez-Delgado et al, 2014). Infection of yearling wild boar was also noted in a survey on the MTC member M. microti in Italy (11.11%; Chiari et al, 2015). However, published information refers almost exclusively to wild boar over six months of age, since it is generally based on hunterharvested individuals sampled in autumn and winter.…”

Mycobacterium microti detection in French wildlife

“…Furthermore, the presence of this pathogen has been described more and more often in wildlife in other countries (Schoning and others 2013, Boniotti and others 2014). The European wild boar and the badger seem particularly susceptible to M microti infection, raising concerns about the identification and management of MTBC members in wildlife (Smith and others 2009, Chiari and others 2015). On the one hand, as regards livestock and wildlife bovine TB monitoring, this mycobacterium could interfere with bovine TB diagnosis, especially where its geographic distribution overlaps with that of M bovis .…”