Ticks and serosurvey of anti-Rickettsia spp. antibodies in wild boars (Sus scrofa), hunting dogs and hunters of Brazil

Abstract

Background Rickettsia bacteria are responsible for diseases in humans and animals around the world, however few details are available regarding its ecology and circulation among wild animals and human populations at high transmission risk in Brazil. The aim of this study was to investigate the occurrence of ticks and Rickettsia spp. in wild boars, corresponding hunting dogs and hunters. Methods Serum samples and ticks were collected from 80 free-range wild boars, 170 hunting dogs and 34 hunters from southern and central-western Brazil, from the Atlantic Forest and Cerrado biomes, respectively, between 2016 and 2018. Serum samples were tested by indirect immunofluorescent-antibody assay (IFA) to detect IgG antibodies against Rickettsia rickettsii , Rickettsia parkeri , Rickettsia bellii , Rickettsia rhipicephali and Rickettsia amblyommatis . Tick species were identified by morphological taxonomic keys, as previously described. A total of 164 ticks including A . sculptum , A . brasiliense and A . aureolatum were tested in PCR assays for Spotted Fever Group (SFG) Rickettsia spp. Results A total of 58/80 (72.5%) wild boars, 24/170 (14.1%) hunting dogs and 5/34 (14.7%) hunters were positive (titers ≥ 64) to at least one Rickettsia species. A total of 669/1,584 (42.2%) ticks from wild boars were identified as Amblyomma sculptum , 910/1,584 (57.4%) as Amblyomma brasiliense , 4/1,584(0.24%) larvae of Amblyomma spp. and 1/1,584 (0.06%) nymph as Amblyolmma dubitatum . All 9 ticks found on hunting dogs were identified as Amblyomma aureolatum and all 22 ticks on hunters as A . sculptum . No tested tick was positive by standard PCR to SFG Rickettsia spp. Conclusions The present study was the concomitant report of wild boar, hunting dog and hunter exposure to SFG rickettsiae agents, performed in two different Brazilian biomes. Wild boar hunting may increase the risk of human exposure and consequently tick-borne disease Wild boars may be carrying and spreading capybara ticks from their original habitats to other ecosystems. Further studies can be required to explore the ability of wild boars to infecting ticks and be part of transmission cycle of Rickettsia spp.

Spotted fever group Rickettsiae in Dermacentor marginatus from wild boars in Italy

“…These findings suggest that in rural and peri-urban contexts (i.e., wooded landscapes and hunting areas), hikers/wild boar hunters and hunting dogs may be exposed to D. marginatus , which is commonly retrieved infesting humans and dogs in southern Italy (Otranto et al, 2014). Accordingly, a seroepidemiological survey conducted in Brazil reports that 14.1% of hunting dogs and 14.7% of hunters were exposed to at least one Rickettsia species (Kmetiuk et al, 2019). Again, the period in which the incidence of R. slovaca infection in humans is higher (Raoult et al, 2002;Parola et al 2009) overlaps the boar hunting season (i.e., October to December), suggesting a direct relationship between the risk of Rickettsia spp.…”

From the Approach to the Concept: One Health in Latin America-Experiences and Perspectives in Brazil, Chile, and Colombia

“…Research groups in Brazil have also been applying One Health as a practical tool to solve problems such as zoonoses in different populations and their contact animals, taking advantage of the SUS, which allows comprehensive human-animal sampling. In such scenarios, wild boars, hunting dogs, and hunters have been surveyed in Brazil for vector-borne, waterborne, and foodborne diseases, for the first time worldwide (21). Moreover, One Health research and outreach community projects with community leaders toward Brazilian social classes vulnerability have provided interesting results in animal hoarders, homeless, incarcerated, indigenous, slum, low-income, and traditional island populations in their environments (22)(23)(24)(25).…”

Serosurvey for Pseudorabies (Aujeszky's Disease) in Free-Range Wild Boars (Sus scrofa) of Brazil

“…Although a concomitant study in Colombia sampling 58 collared peccaries and 15 wild boars, showed no positive cases (Montenegro et al 2018), De Castro et al (2014 detected PRV by PCR in spleen samples of all 10 collared peccaries and all three white lipped peccaries sampled from central-western and northern Brazil, using primers designed against swine pseudorabies variant. Such overlap has been confirmed in the Atlantic Forest biome by wild boars infested with the adult and nymph stages of ticks (Amblyomma brasiliense), which use collared peccaries as primary hosts in humid forests (Kmetiuk et al 2019). In the Cerrado biome, peccary habitat destruction and fragmentation has been related to wild boar occurrence (Silveira and Pacheco 2018).…”

“…In Brazil, wild boars have been classified as an exotic invasive species, originated from Eurasian wild boars and their hybrids, and nationwide hunting is officially permitted as a strategy for population control and eradication (Kmetiuk et al 2019). Due to their highly adaptive capacity, wild boars have invaded all six Brazilian biomes, including the Atlantic Forest and Cerrado of central-western, southwestern, and southern Brazil (Kmetiuk et al 2019). Although PRV infection is reportedly established in wild boars elsewhere, no study has been conducted in free-ranging wild boars of Brazil.…”

“…The single male wild boar seropositive found in this study might indicate PRV circulation in degraded areas of centralwestern Brazil, although at a much lower prevalence than in the Pantanal biome. Nonetheless, geographical overlap of native peccaries and invasive wild boars has been described in both Brazilian biomes, the Atlantic Forest and Cerrado (Silveira and Pacheco 2018;Kmetiuk et al 2019).…”