Introduction
Bovine tuberculosis (bTB) is a chronic disease caused by members of theMycobacterium tuberculosis complex (MTBC)
(Rodriguez-Campos et al., 2014). MTBC
have been isolated from numerous different domestic and wild animal
species. Recent epidemiological investigations have shown the
fundamental role played by wildlife in the maintenance of the causal
agents of bTB. This results in continuous interspecies transmissions
from wild animals to livestock and vice versa, hindering national and
international eradication programs (Atkins
and Robinson, 2013, Garcia-Jimenez et
al., 2016, Maria et al., 2015,
Nigsch et al., 2018). Badger (Meles
meles ), free–ranging red deer (Cervus elaphus elaphus ) and wild
boar (Sus scrofa ) are the most relevant known wild animals acting
as a reservoir of bTB in Europe, including Great Britain. The ongoing
geographic expansion of wild boar populations have raised concerns
regarding the monitoring of several infectious diseases, including
zoonotic plagues like bTB and hepatitis E
(Gortazar et al., 2008,
Martinelli et al., 2015). Beside the
members of the MTBC and Mycobacterium leprae, the agent that
causes Hansen’s disease, over 180 species of nontuberculous mycobacteria
(NTM) have been described (Gupta et al.,
2018). NTM are commonly encountered in the environment and they have
been isolated from a variety of sources, including water, feed, soil,
dust, aerosol, invertebrates, protozoa or animals
(Falkinham, 2015,
Ghielmetti et al., 2018). Of these, two
species are recognized as true pathogens for humans, namely M.
marinum and M. ulcerans (Johansen
et al., 2020). Nevertheless, more than 60 species of NTM are known to
be opportunistic pathogenic to humans and other mammals, and infections
with these emerging pathogens are now more common than tuberculosis in
industrialized countries (Biet and
Boschiroli, 2014, Griffith et al., 2007,
Tortoli, 2014). Immunocompromised
individuals are highly susceptible to opportunistic NTM infections and
improved laboratory diagnostics have enabled more accurate detection of
fastidious or extremely slow growing species. Despite the increasing
relevance in mycobacterial infections, only restricted information on
the occurrence and their diversity in wildlife is available. Moreover,
although wild boars are among the most widely distributed large mammals
in the world (Oliver et al., 1993), the
literature concerning this species is mainly focused on (i) the presence
of MTBC and (ii) the impact of NTM infections on the prevalence of MTBC
(Boniotti et al., 2014,
Chiari et al., 2016,
Di Marco et al., 2012,
Michelet et al., 2015,
Naranjo et al., 2008,
Richomme et al., 2010,
Santos et al., 2009,
Vicente et al., 2006). Canton Ticino is
the most southern Canton of Switzerland and a large proportion of his
border is shared with Italy. The territory encompasses an area of 2‘812
square kilometre where the majority of the urban area is concentrated in
the flat land and forests cover about one third of the alpine region.
The wild boar presence in the territory has been documented during the
XVI century. Thereafter, it disappeared and it is only since 1981 that
it has been officially sighted again
(Dipartimento Territorio / Finanze e
Economia, 2010). The wild boars are distributed almost exclusively
along flat- and hilly land, with the highest animal density observed in
the southern districts of Mendrisio, Lugano and the lower part of the
Maggia valley (Dipartimento Territorio /
Finanze e Economia, 2010). The population increase is estimated at
100%-180%, consequently the population can theoretically double or
even triplicate in 12 months without control measurements. In order to
regulate this growth, licensed hunters are allowed to hunt the animals
each year in September without sex or hunting bag restrictions. Wild
boar is one of the most hunted mammalians in the Canton of Ticino,
second only to red deer.
Recent studies from Spain, Czech Republic, Brazil and Slovenia
comprehensively evaluated the spectrum of NTM species in black pigs
using molecular methods (Garcia-Jimenez et
al., 2015, Gortazar et al., 2011,
Pate et al., 2016,
Trcka et al., 2006). It is significant to
note that, the latter mentioned publications, describe significant
differences in the spectrum of species isolated. Such differences may
not be exclusively the result of geographic distribution of NTM, but the
advance in molecular techniques and the progress in mycobacterial
characterization led to enormous diagnostic improvements over the past
decades (Tortoli, 2014). It is
noteworthy, that the dissection of the M. avium complex (MAC) in
the mentioned publications was performed at different levels, impeding a
direct comparison of the isolated mycobacteria. The characterization of
NTM from clinical samples is often a challenge for laboratory personal
in routine diagnostic. Because of its rapidness, cost-effectiveness and
high throughput the matrix-assisted laser desorption ionization–time of
flight mass spectrometry (MALDI-TOF MS) technology has nowadays been
integrated in the workflow of numerous diagnostic laboratories
(Alcaide et al., 2018,
Mediavilla-Gradolph et al., 2015,
Murugaiyan et al., 2018). However, the
accuracy achievable at present with genetic approaches remains superior
to the MALDI-TOF-based species identification
(Tortoli, 2014). Therefore, the accuracy
and limitations of this method based on ordinary samples from veterinary
origin should be evaluated. The present research used a panel of NTM
showing a wide range of species isolated from a common source and
verified the consensus grade between sequence analysis and MALDI-TOF.
This study aimed (i) to determine the occurrence and diversity of
mycobacterial species among healthy wild boar hunted in Canton Ticino,
(ii) to identify the geographical distribution of mycobacterial species,
and (iii) to compare two different diagnostic identification approaches
for the genus Mycobacterium .