Letter to the editor
An original article has recently been published in Transboundary and
Emerging Diseases entitled ‘Unravelling animal exposure profiles of
human Q fever cases in Queensland, Australia, using natural language
processing’ by Clarck and others (https://doi.org/10.1111/tbed.13565;
Clark et al., 2020), to which we have some comments.
In this paper, the authors applied natural language processing to an
18-year data set of Q fever notifications in Queensland, Australia, to
investigate whether patients belonging to different demographic groups
commonly report different potential exposure pathways. Identifying
potential exposure pathways is necessary to design effective
interventions and aid outbreak prevention.
Q fever is a worldwide zoonosis caused by an obligate intracellular
bacterium, Coxiella burnetii (Angelakis and Raoutl, 2011). With
only anecdotal reports of human-to-human transmission, the epidemiology
of human infections always reflects the circulation of the bacterium in
animal (domestic and wild) reservoirs. The prevalence of Q fever is
highly variable from one country to another, due to mainly
epidemiological and geographical disparities. In areas of endemicity, as
Australia and Spain, Q fever occurs as sporadic cases, usually after
identifiable at-risk activities (farming, slaughterhouse work, or rural
tourism), however, as a rule, it is infected livestock, particularly
goats and sheep, the most important sources of zoonotic Q fever
outbreaks in humans. Nonetheless the origin of several human Q fever
cases continues to be unclear. Besides domestic livestock, a diversity
of possible wildlife reservoirs has been identified through molecular
and serological surveys, including wild mammals, birds and even ticks
(Toledo et al., 2009; Cooper, Stephens, Ketheesan, & Govan, 2013;
González-Barrio and Ruiz-Fons, 2019). Throughout history, wildlife has
been an important source of infectious diseases transmissible to humans.
Today, zoonoses with a wildlife reservoir constitute a major public
health problem, affecting all continents, an example is the SARS-CoV 2
that it has been able to cross the inter-species barrier to emerge as
the most devastating human pandemic of our time. The total number of
zoonoses is unknown, some 1,415 known human pathogens have been
catalogued and 62% are of zoonotic origin (Billinis, 2013). Human
impacts on habitats, biodiversity and climate could be responsible for
changes in the patterns of interaction between domestic animals,
wildlife and humans, allowing wild animals to be involved in the
epidemiology of most zoonoses and thus serving as important reservoirs
for the transmission of zoonotic agents to domestic animals and humans
(González-Barrio and Ruiz-Fons, 2019). These changing patterns may also
be behind the re-emergence of enzootic zoonoses such as Q fever that,
although with a lower pandemic potential, it may become a serious health
problem. Within Europe, Spain has reported the highest number of human Q
fever cases annually since 2016 (0.8 cases per 100.000 population). In
2018, more than a third of the overall number of cases were notified
from Spain (ECDE, 2019). In addition, Spain is the country where more
studies in relation to Q fever have been conducted on wildlife and where
more reservoirs of the bacteria have been confirmed (González-Barrio and
Ruiz-Fons, 2019). In my opinion, these factors combined with the
identification of shared genotypes between wildlife and humans in
Iberian Peninsula (González-Barrio et al., 2016a,b,c) makes it possible
that wild reservoirs, in this case ticks, deer, rabbits and micromammals
(Toledo et al., 2009; González-Barrio et al., 2015a,b) among others, may
play an important role in the increase of Q fever cases in Spain.