3.1 Temporal evolution of scientific research
Publications dated from 1979 to 2019 and, overall, the temporal trend in
publication on antimicrobial resistance in wildlife shows a growth in
the number of documents published per year, with an annual percentage
growth rate of 7,2% (Figure 2). The global evolution of literature can
be split into two periods, exhibiting kind of a diauxic growth: from
1979 to 2008, the scientific literature increased slowly (only 47
publications). However, from 2009 to 2019, the growth was steady and
swift; 78% of the research papers were published in the last ten years.
This indicates that this research topic has attracted particular
interest (and perhaps funding) in the last decade, likely a reflex of
the increase of global importance of the AMR subject as more countries
and institutions began to devote themselves to this topic. The maximum
number of documents on AMR in wildlife was published in 2018, with a
total of 20 publications, but 2019 should follow the same trend as the
database was last updated in November, accounting already 17
publications. This rejuvenated interest in AMR research in wildlife can
be attributed to the fact that three of the most cited research in AMR
in wildlife were published in previous years and in relevant journals
(Table 1). Additionally, and perhaps more importantly, since the first
studies regarding antibiotic resistance in wildlife, a discussion
started whether resistance in wildlife was or not related with human use
(Gilliver et al., 1999; Österblad et al., 2001). Gilliver et al. (1999)
detected high prevalence of bacteria with antibiotic resistance from
wild rodents living in rural areas in Wirral, northwest England, in
areas with absent or minimum levels of released antibiotics. Such fact
led Gilliver et al. (1999) to claim that the found prevalence was not
directly a result of anthropogenic impact and that antibiotic use
restrictions would have marginal effect of wildlife reservoirs.
Contrastingly, Österblad et al. (2001) described almost no resistance in
bacteria recovered from moose, deer and voles in pristine areas of
Finland. These two seminal papers brought into debate the effects of
human proximity, highlighting the importance of understanding the role
of wildlife in the ecology of antibiotic resistance. Since then,
research has been focused on untangling the routes of transmission
between humans and wildlife, reinforcing the idea that the same
antimicrobial resistance patterns co-occur in wildlife, livestock and
human populations. For example, beta-lactamases that inactivate the
action of beta-lactam antibiotics (e.g. penicillin), one of the most
important group of antimicrobial agents used in human and veterinary
medicine, are now frequently found in bacterial isolates from wildlife
(Guenther et al., 2011), particularly birds and mammals (Silva et al.,
2011; Goncalves et al., 2013), as well as in livestock and environmental
samples.