Tick Borne Encephalitis

Tick-borne encephalitis (TBE) is the medically most common tick-borne viral disease in Europe and Asia. The TBE virus (TBEV) is a member of the family Flaviviridae. Transmission mainly to humans occurs by ticks of the Family Ixodidae, mainly the castor bean tick (Ixodes ricinus) in Europe and the taiga tick (Ixodes persulcatus) in Asia. Rarely TBEV is also transmitted by contaminated milk of infected ungulates (goat, sheep, cow). The clinical course of TBE is variable and may range from subclinical to fatal encephalomyelitis. Probably host and viral factors are involved in the pathogenesis of disease. So far, no specific treatment of the disease is available. The only effective prevention of TBE is vaccination. A number of different vaccines are available worldwide. In Europe two vaccines are licensed which contain inactivated European subtype TBEV. Probably the European vaccines protect also against infections with other subtypes of TBEV.

THE ABUNDANCE OF BORRELIA INIXODID TICKS OF BAIKAL REGION

Ixodid ticks (n=3714) from natural foci of Baikal Region (Irkutsk Region and Republic of Buryatia) have been examined for pathogenic Borrelia DNA during 2013-2010. On average 40.9 % of the samples were positive for Borrelia markers during the survey period; the range of variantion was – 32–55 %. The increasing of infection rate in ticks is traced in multi-year trends. During the ticks’ activity season, maximal infection rates have been noted at the end of the season (60 %), minimal – at the very beginning of the season (28,6 %) and on the peak of vectors’ abundance (36-39 %). The significant geographical, species and age differences have been detected in Borrelia infection rate of Ixodid ticks. Borrelia DNA have been detected considerably more often in taiga tick (the main vector of Ixodid tick borrelioses in Siberia) and in its nymphs more often, than in adult ticks. There was no difference in the infection rate of male and female ticks, and also between ticks, collected from the vegetation and from human and animals. The ratio og genotyped Borrelia species had been as follows: 64.2 % – B. garinii, 21,7 % – B. afzelii, 14,2 % – B. miyamotoi. Key words: Ixodid ticks, pathogenic Borrelia, PCR, genotyping, Baikal Region.

Impact of climate change on ticks and tick-borne infections in Russia.

This expert opinion considers only the most significant aspects of the impact of climate change on ticks and tick-borne diseases in Russia. Attention is focused on the species that are most widespread in the extratropical part of the northern hemisphere: the taiga tick, Ixodes persulcatus, and the European forest tick, I. ricinus, which are hosts and vectors of tick-borne encephalitis (TBE) virus and Borrelia spirochaetes, agents of ixodid tickborne borrelioses (ITBBs), i.e. of Lyme and Lyme-like diseases.

First records of tick-borne pathogens in populations of the taiga tick Ixodes persulcatus in Sweden

Background The common tick Ixodes ricinus and the taiga tick I. persulcatus are the main tick vectors of Borrelia spirochaetes, TBE virus (TBEV) and of several other zoonotic pathogens in the western and eastern areas, respectively of the Palaearctic region. Recently, populations of the taiga tick were, for the first time, detected in northern Sweden. This prompted us to investigate if they harbour human pathogens. Methods A total of 276 I. persulcatus ticks (136 males, 126 females and 14 nymphs) and one I. ricinus nymph was collected by the cloth-dragging method in northern Sweden in July–August 2015 and May–July 2016. In addition, 8 males and 10 females of I. persulcatus were collected from two dogs (16 and 2 ticks, respectively) in two of the localities. All ticks were microscopically and molecularly identified to developmental stage and species and screened for B. burgdorferi (sensu lato), B. miyamotoi, Anaplasma phagocytophilum, Rickettsia spp., Neoehrlichia mikurensis, Babesia spp. and TBEV using real-time PCR followed by species identification by sequencing the PCR-products of conventional PCR assays. Results Of the ticks collected by the cloth-dragging method, 55% (152/277) were positive for Borrelia. There was no significant difference between the proportions of Borrelia-infected nymphs (33%, 5/15) and Borrelia-infected adult ticks (56%, 147/262), and no significant difference between the proportions of Borrelia-infected males (54%, 74/136) and Borrelia-infected females (58%, 73/126). Three different Borrelia species were identified. Borrelia afzelii was the predominant species and detected in 46% of all Borrelia-infected ticks followed by B. garinii, 35%, B. valaisiana, 1%, and mixed infections of different Borrelia species, 1%; 17% of all Borrelia-infections were untypeable. One I. persulcatus female contained Rickettsia helvetica, and one nymph contained Rickettsia sp. Of the 277 ticks analysed, all were negative for A. phagocytophilum, Babesia spp., Borrelia miyamotoi, N. mikurensis and TBEV. The ticks collected from the two dogs were negative for all pathogens examined except for Borrelia spp., that was detected in 5 out of 16 ticks removed from one of the dogs. Conclusions To our knowledge, this is the first time that I. persulcatus from Sweden has been analysed for the presence of tick-borne pathogens. The examined tick populations had a low diversity of tick-borne pathogens but a high prevalence of B. burgdorferi (s.l.).

Ixodes persulcatus [Schulze 1930] (Acari: Ixodidae) in eastern Finland

Data concerning the occurrence and abundance of the taiga tick Ixodes persulcatus in eastern Finland (North Karelia and Kainuu regions) are presented. Sampling was carried out in May 2008 and June 2009, around the University of Joensuu Mekrijärvi Research Station and the City of Kuhmo. In 2008 and 2009, the abundance of adult taiga ticks in the first study area was 0.17 and 0.13 ticks per flag-km, respectively. Only a single I. persulcatus specimenwas found in the second study area (abundance was 0.02 specimens per flag-km). All ticks (635 specimens) collected from cats and dogs in south-eastern Finlandwere identified as Ixodes ricinus.