Epizootological Monitoring and Forecast of the Risks Associated with Infections, Transmitted by Ixodidae Ticks, on the Island Russky in 2016 (Primorsk Territory)

Abstract

Species composition and contamination by the causative agents of natural focal infections, notably Ixodes ticks, collected in 2014–2015 on the Island Russky were studied. The total of 817 ticks was collected, including Ixodes persulcatus, I. pavlovskyi, Haemaphysalis concinna, H. japonica douglasi. The most of the nymphs (46 specimens) were observed in I. pavlovskyi. Using immune-enzyme analysis, reliably higher rate of positive findings was revealed in I. pavlovskyi (2.2 %) compared to I. persulcatus (0.5 %) while analyzing individual contamination of two Ixodes species. The pattern of inter-specific distinctions did not changed (I. pavlovskyi – 1.3 %; I. persulcatus – 0.5 %) when investigating tick virus burden by means of polymerase chain reaction. However, in case of comparative evaluation, using the same method, of their contamination with borrelia (I. pavlovskyi – 25.1 %; I. persulcatus – 46.4 %), agents of granulocytic anaplasmosis (I. pavlovskyi – 1.9 %; I. persulcatus – 5.7 %) and monocytic ehrlichiosis (I. pavlovskyi – 1.3 %; I. persulcatus – 7.2 %) I. persulcatus showed higher indicators. Only tick-borne encephalitis RNA and borrelia DNA were revealed in I. pavlovskyi nymphs, whereat their contamination by spirochetes (45.7 %) was authentically higher than of imagoes. The natural focus of tick-borne encephalitis on the Island Russky is estimated now as low-active one. At the same time, of Ixodes tick-borne borreliosis – as active, with significant contamination of the tick nymphs with spirochetes. In terms of high nymph contamination it is supposed that in 2016 the risk of Ixodes tick-borne borrelioses morbidity rate will increase for humans visiting the Island within the period of high vector activity (May– June).