Tick species diversity and population dynamics of Ixodes ricinus in Galicia (north-western Spain).

Ticks are the major arthropod vectors of animal and human pathogens in Europe; thus, information of tick species and their phenology allows identifying those areas and periods involving a high risk of exposure to particular tick-borne pathogens. In order to assess the diversity of exophilic tick species in north-western Spain, questing ticks were collected by flagging in 17 different locations; ticks were microscopically and molecularly identified at the 16S rDNA loci. In addition, phenology of questing ticks in the same region was studied in representative sampling areas of three different ecological regions, where ticks were monthly collected in 300-m transects during two complete years. The possible influence of different climate variables on the normalized accumulated fraction of nymphal and adult Ixodes ricinus was assessed using a generalized linear mixed model (GLMN). I. ricinus was the most frequently and widely distributed tick species; Dermacentor marginatus, Dermacentor reticulatus, Ixodes frontalis and Ixodes acuminatus were sporadically found. Nymphs were the most commonly collected stage. Both nymphs and adults of I. ricinus presented a unimodal activity pattern; density showed a peak in late spring-early summer whereas the lowest levels were found at late summer-early autumn. GLMN showed that both nymphal and adult I. ricinus phenology was directly associated with the accumulated temperature, photoperiod and average daily maximum temperature and inversely associated with average daily maximum relative humidity. This information could be used to predict the annual periods associated with a higher exposure and risk of transmission of pathogens and to complete the global map of distribution of tick species.