Are you ready for the tick season? Spring dynamic of tick diversity and density in urban and suburban areas.

Abstract

Background: Occurrence of tick-borne diseases (TBD) is often seasonal and associated with seasonal activity of appropriate tick vectors. As seasonal activity of ticks differs, the risk of contracting particular TBD should change between and within seasons. It is of key importance to monitor seasonal dynamic of tick vectors, especially in human-associated habitats. The aim of the current study was to compare activity and density of Ixodes ricinus and Dermacentor reticulatus during spring season in urban and suburban habitats.

Methods: Systematic tick collection by dragging was performed every 1-2 weeks between mid-March and mid-June 2021 at 15 sites: 6 in Warsaw (urban areas) and 9 in suburban areas.

Results: During 178 field collections of ticks, including 131 collections from urban sites and 47 collections from rural areas, 738 ticks (385 adult D. reticulatus and 353 I. ricinus) were collected. Dermacentor reticulatus ticks are found from the beginning of spring, peaking in April and May, and I. ricinus ticks are present from early April, peaking in April and May as well. I. ricinus were abundant in rural and urban areas, including botanical garden and forest kindergarten area. Dermacentor reticulatus were found in urban fallow lands but were not collected in parks. These ticks were abundant in fallow lands, meadow, and mixed forest. DNA of B. burgdorferi s.l. and Rickettsia spp. was identified in ticks from urban areas.

Conclusions: Due to the marked differences in spring dynamic of D. reticulatus and I. ricinus, the sampling effort should be repeated at least three times per season for accurate estimation of tick occurrence (presence/absence) and density. Due to "exchange" of tick species, total tick density remains high through the spring season of activity, which may result in high transmission of tick-borne pathogens (TBPs). Tick densities are dependent on the habitat type and may be low in well-managed agricultural habitats (crop fields, pastures, chicken yard), but high in semi-natural habitats (fallow lands, rural forests). Numerous I. ricinus populations can be maintained in urban green areas such as botanical gardens. Ticks from urban areas can serve as vectors of important TBPs (B. burgdorferi s.l., Rickettsia spp.).