Nasal shedding of Mycobacterium tuberculosis in wild boar is related to generalised tuberculosis and concomitant infections

BackgroundWild boar is an important reservoir of Mycobacterium tuberculosis variant bovis, the main causative agent of bovine tuberculosis (bTB). A proportion of tuberculosis (TB)-affected wild boars shed M tuberculosis by nasal route, favouring the maintenance of bTB in a multihost scenario. The aim of this work was to assess if M tuberculosis nasal excretion is influenced by factors commonly associated with high TB prevalence in wild boar.MethodsTB diagnosis and M tuberculosis isolation were carried out in 112 hunted wild boars from mid-western Spain. The association between the presence of M tuberculosis DNA in nasal secretions and explanatory factors was explored using partial least squares regression (PLSR) approaches.ResultsDNA from M tuberculosis was detected in 40.8 per cent nasal secretions of the TB-affected animals. Explanatory factors provided a first significant PLSR X’s component, explaining 25.70 per cent of the variability observed in M tuberculosis nasal shedding. The presence of M tuberculosis in nasal secretions is more probable in animals suffering from generalised TB and mainly coinfected with Metastrongylus species and porcine circovirus type 2, explaining nearly 90 per cent of the total variance of this model.ConclusionMeasures aiming to control these factors could be useful to reduce M tuberculosis shedding in wild boar.