Ticks and the city - are there any differences between city parks and natural forests in terms of tick abundance and prevalence of spirochaetes?

Abstract

Background Ixodes ricinus ticks are commonly encountered in either natural or urban areas, contributing to Lyme disease agents Borreliella [(Borrelia burgdorferi (sensu lato)] spp. and Borrelia miyamotoi enzootic cycles in cities. It is an actual problem whether urbanization affects pathogen circulation and therefore risk of infection. The aim of the study was to evaluate main tick-borne disease risk factors in natural, endemic areas of north-east (NE) Poland (Białowieża) and urban areas of central Poland (Warsaw), measuring tick abundance/density, prevalence of infection with spirochaetes and diversity of these pathogens in spring-early summer and late summer-autumn periods between 2012 and 2015.MethodsQuesting I. ricinus ticks were collected from three urban sites in Warsaw, central Poland and three natural sites in Białowieża, NE Poland. A total of 2993 ticks were analyzed for the presence of Borreliella spp. and/or Borrelia miyamotoi DNA by PCR. Tick abundance was analyzed by General Linear Models (GLM). Prevalence and distribution of spirochaetes was analyzed by Maximum Likelihood techniques based on log-linear analysis of contingency tables (HILOGLINEAR). Species typing and molecular phylogenetic analysis based on the sequenced flaB marker were carried out.ResultsOverall 4617 I. ricinus ticks were collected (2258 nymphs and 2359 adults). We report well established population of ticks in urban areas (10.1 ± 0.9 ticks/100 m2), as in endemic natural areas with higher mean tick abundance (16.5 ± 1.5 ticks/100 m2). Tick densities were the highest in spring-early summer in both types of areas. We observed no effect of the type of area on Borreliella spp. and B. miyamotoi presence in ticks, resulting in similar prevalence of spirochaetes in urban and natural areas [10.9% (95% CI: 9.7–12.2%) vs 12.4% (95% CI: 10.1–15.1%), respectively]. Prevalence of spirochaetes was significantly higher in the summer-autumn period than in the spring-early summer [15.0% (95% CI: 12.8–17.5%) vs 10.4% (95% CI: 9.2–11.6%), respectively]. We have detected six species of bacteria present in both types of areas, with different frequencies: dominance of B. afzelii (69.3%) in urban and B. garinii (48.1%) in natural areas. Although we observed higher tick densities in forests than in maintained parks, the prevalence of spirochaetes was significantly higher in the latter [9.8% (95% CI: 8.6–11.0%) vs 17.5% (95% CI: 14.4–20.5%)].ConclusionsSurprisingly, a similar risk of infection with Borreliella spp. and/or B. miyamotoi was discovered in highly- and low-transformed areas. We suggest that the awareness of presence of these disease agents in cities should be raised.Electronic supplementary materialThe online version of this article (10.1186/s13071-017-2391-2) contains supplementary material, which is available to authorized users.

Urban rodent reservoirs of Borrelia spp. in Warsaw, Poland

“…Given that other research carried out in the city of Warsaw, at sites from suburban areas towards the urban core, documented a [25][26][27]), the occurrence of infected vertebrates considered to be tick hosts and a competent reservoir for this bacterium was expected in our study in the Warsaw habitat. These animals not only participate in pathogen perpetuation, but also infect consecutive tick generations.…”

Questing Ixodes ricinus ticks (Acari, Ixodidae) as a vector of Borrelia burgdorferi sensu lato and Borrelia miyamotoi in an urban area of north-eastern Poland

“…Such a low population density must be associated with the specimen collection sites located in typical recreational areas and not connected with large forest complexes, which considerably limits the accessibility of mediumsize and large I. ricinus hosts. Limiting access to hosts has also been identified as a factor which reduced the density of I. ricinus ticks in parks in Warsaw by half compared to a large forest complex situated within the administrative boundaries of the city (Kowalec et al 2017). Apart from the tick abundance, the risk of contracting TBDs is affected by human behaviour patterns, which bring people in contact with the habitats resided by ticks (Kilpatrick et al 2017;Randolph and EDEN-TBD sub-project team 2010;Rizzoli et al 2014).…”

Lyme Disease Frontiers: Reconciling Borrelia Biology and Clinical Conundrums

“…Vector-competent ticks, such as I. scapularis, and I. pacificus in North America, and I. ricinus in Europe, acquire the pathogen from the reservoir during a blood meal, and can then transmit the spirochete to a new host during a subsequent feed [15]. Although Lyme is often considered a disease acquired in nature, compelling investigations suggest that a high proportion of human tick encounters occur in residential areas [16], and although the tick density in urban green spaces is generally lower than in natural forests, the prevalence of Borrelia can be higher [17]. Adventitious ticks introduced by migratory birds, for example, may also establish new populations [18][19][20].…”