Abstract
Tick-borne pathogens (TBPs) constitute an emerging public health concern favoured by multidimensional global changes. Amongst these, increase and spread of wild boar (Sus scrofa) populations are of special concern since this species can act as a reservoir of zoonotic pathogens and promote tick abundance. Thus, we aimed to make a first assessment of the risk by TBPs resulting from wild boar and ticks in the vicinity of a highly populated area. Between 2014 and 2016, we collected spleen samples and 2256 ticks from 261 wild boars (out of 438 inspected) in the metropolitan area of Barcelona (MAB; northeast Spain). We morphologically identified four tick species: Hyalomma lusitanicum (infestation prevalence: 33.6%), Dermacentor marginatus (26.9%), Rhipicephalus sanguineus sensu lato (18.9%) and R. bursa (0.2%). Ticks were pooled according to species and individual host. A total of 180 tick pools and 167 spleen samples were screened by real-time PCR and/or reverse line blot hybridization assay for Ehrlichia sp., Anaplasma sp., Babesia sp., Rickettsia sp., Borrelia burgdorferi sensu lato and Coxiella burnetii. Seventy-two out of the 180 tick pools were positive to Rickettsia spp. (minimum prevalence of 8.7%), including Rickettsia massiliae, R. slovaca and R. raoultii. We did not detect Rickettsia spp. in wild boar spleens nor other TBPs in ticks or wild boars. Since the ticks identified can bite humans, and the recorded spotted fever group (SFG) rickettsiae are zoonotic pathogens, there is a risk of SFG rickettsiae transmission for MAB inhabitants. Our results suggest a broader distribution of H. lusitanicum, competent vector for the Crimean-Congo haemorrhagic fever virus than previously known. Wild boar is not a Rickettsia spp. reservoir according to the spleen negative results. However, its abundance could favour tick life cycle and abundance, and its proximity to humans could promote the infection risk by Rickettsia spp.
Highlights
Ticks are the most important vectors of disease transmission to livestock, pets and humans (Jongejan & Uilenberg, 2004), and both the number of tick-borne pathogens (TBPs) and the incidence of tick-borne diseases are increasing globally as a result of multidimensional global changes (Colwell et al, 2011; Dantas-Torres et al, 2012)
The species parasitizing most wild boars was H. lusitanicum (infestation prevalence of 33.6%, 95% confidence interval (CI): 29.3%–38.1%), followed by D. marginatus (26.9%, 95% CI: 23%–31.3%) and R. sanguineus s.l. (18.9%, 95% CI: 16.4%–23.9%), while R. bursa was found on one wild boar (0.2%, 95% CI: 0.01%–1.3%)
Wild boars carry ticks infected with zoonotic Rickettsia species in the metropolitan area of Barcelona (MAB), an area that is home to three million people that live in sympatry with wild boars
Summary
Ticks are the most important vectors of disease transmission to livestock, pets and humans (Jongejan & Uilenberg, 2004), and both the number of tick-borne pathogens (TBPs) and the incidence of tick-borne diseases are increasing globally as a result of multidimensional global changes (Colwell et al, 2011; Dantas-Torres et al, 2012). Tick ecology and TBPs epidemiology are driven by environmental factors including host composition and abundance (James et al, 2013; Randolph, 2004; Ruiz-Fons et al, 2012). Wildlife can display a significant role in TBPs epidemiology, as they can act as reservoirs of human pathogens and increase the tick range and abundance (Dantas-Torres et al, 2012; Varela-Castro et al, 2018). With the increasing number of human-wildlife interactions in densely populated areas, we face new epidemiological scenarios where zoonotic pathogens can spread (Bradley & Altizer, 2007; Fernández-Aguilar et al, 2018)
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