Inkoo and Sindbis viruses in blood sucking insects, and a serological study for Inkoo virus in semi-domesticated Eurasian tundra reindeer in Norway.

BACKGROUND: Mosquito-borne viruses pose a serious threat to humans worldwide. There has been an upsurge in the number of mosquito-borne viruses in Europe, mostly belonging to the families Togaviridae, genus Alphavirus (Sindbis, Chikungunya), Flaviviridae (West Nile, Usutu, Dengue), and Peribunyaviridae, genus Orthobunyavirus, California serogroup (Inkoo, Batai, Tahyna). The principal focus of this study was Inkoo (INKV) and Sindbis (SINV) virus circulating in Norway, Sweden, Finland, and some parts of Russia. These viruses are associated with morbidity in humans. However, there is a knowledge gap regarding reservoirs and transmission. Therefore, we aimed to determine the prevalence of INKV and SINV in blood sucking insects and seroprevalence for INKV in semi-domesticated Eurasian tundra reindeer (Rangifer tarandus tarandus) in Norway. MATERIALS AND METHODS: In total, 213 pools containing about 25 blood sucking insects (BSI) each and 480 reindeer sera were collected in eight Norwegian reindeer summer pasture districts during 2013-2015. The pools were analysed by RT-PCR to detect INKV and by RT-real-time PCR for SINV. Reindeer sera were analysed for INKV-specific IgG by an Indirect Immunofluorescence Assay (n = 480, IIFA) and a Plaque Reduction Neutralization Test (n = 60, PRNT). RESULTS: Aedes spp. were the most dominant species among the collected BSI. Two of the pools were positive for INKV-RNA by RT-PCR and were confirmed by pyrosequencing. The overall estimated pool prevalence (EPP) of INKV in Norway was 0.04%. None of the analysed pools were positive for SINV. Overall IgG seroprevalence in reindeer was 62% positive for INKV by IIFA. Of the 60 reindeer sera- analysed by PRNT for INKV, 80% were confirmed positive, and there was no cross-reactivity with the closely related Tahyna virus (TAHV) and Snowshoe hare virus (SSHV). CONCLUSION: The occurrence and prevalence of INKV in BSI and the high seroprevalence against the virus among semi-domesticated reindeer in Norway indicate that further studies are required for monitoring this virus. SINV was not detected in the BSI in this study, however, human cases of SINV infection are yearly reported from other regions such as Rjukan in south-central Norway. It is therefore essential to monitor both viruses in the human population. Our findings are important to raise awareness regarding the geographical distribution of these mosquito-borne viruses in Northern Europe.

Ixodes ricinus and Borrelia prevalence at the Arctic Circle in Norway.

The distribution limit of Ixodes ricinus ticks in northwestern Europe (Brønnøy, Norway, 1° south of the Arctic Circle), has been known since the 1930s. To reconfirm this finding and extend studies in the areas adjacent to the Arctic Circle (66°33' N), ticks were collected from dogs and cats in 8 districts in northern Norway from 64°56' N to 68°48' N. We detected 549 I. ricinus, 244 (44%) of them in Brønnøy district, and 305 (range 6-87 ticks) in 7 districts in the northern part of the study area. The prevalence of Borrelia in these ticks was determined by real-time PCR. In the Brønnøy district (65°28' N, 12°12' E), 29% of the I. ricinus were Borrelia spp.-positive, and the species B. afzelii was nearly twice as prevalent as B. garinii and/or B. valaisiana. In the study area north of Brønnøy district, only 12 (4%) of the collected ticks contained Borrelia spp. In conclusion, tick occurrence and Borrelia prevalence are high in the Brønnøy district. In contrast, I. ricinus occurrence and Borrelia prevalence are low further north across the Arctic Circle in Norway.

Fennoscandian distribution of an important parasite of cervids, the deer ked (Lipoptena cervi), revisited.

The deer ked [Lipoptena cervi (L. 1758) (Dipt., Hippoboscidae)] is a blood-sucking ectoparasite of cervids. The species has been resident in Sweden for more than two centuries, whereas in Finland ( approximately 50 years) and Norway ( approximately 30 years), it has established itself relatively recently. L. cervi may cause serious health problems in its natural hosts, act as a vector for zoonotic diseases, and pose a socioeconomic threat to forest-based activity. In this paper, we review the distribution and former expansion of the species in Fennoscandia. The current distribution of L. cervi appears bimodal, and the geographical range expansion of the species shows notable differences across Fennoscandia. The western population in Norway and Sweden has its northern edge of range at respective latitudes of 61 degrees N and 62 degrees N, whereas the eastern population in Finland reaches 65 degrees N. The future expansion of L. cervi is dependent on several interdependent extrinsic and intrinsic factors. International multidisciplinary collaboration is needed to achieve a synthesis on the factors affecting expansion rates and to understand the effects of L. cervi on wildlife, human health, and the rural societies of Fennoscandia.

Transport of ticks by migratory passerine birds to Norway.

Ticks can be transported over large distances and across geographical barriers by avian hosts. During the spring migrations of 2003 to 2005, 9,768 passerine birds from 4 bird observatories along the southern coastline of Norway were examined for ticks. Altogether, 713 birds carried a total of 517 larvae and 1,440 nymphs. The highest prevalence of tick infestation was observed in thrushes and dunnock (Prunella modularis). The degree of tick infestation varied during each season, between localities, and from year to year. Blackbirds (Turdus merula) caught in localities with many ticks had greater infestation than those from localities with few or no ticks, suggesting local tick recruitment. A similar study performed during 1965­1970 involving 2 of the bird observatories in the present study found ticks on 4.2% of birds, while we found infestation of 6.9% at the same localities (P < 0.001). With the exception of 10 nymphs and 1 larva, the predominant tick was Ixodes ricinus. Seven nymphs of Hyalomma rufipes and 1 larva of Dermacentor sp. were also found. No species of Dermacentor had previously been found in Norway.