The tick-borne encephalitis virus (TBEV) is the causative agent of neurological disease in humans, and it is mainly transmitted by the tick Ixodes ricinus in western Europe. In Norway, previous surveillance studies have detected the virus along the coast from Nordland County in the north to the Swedish border in the southeast. However, all human cases of tick-borne encephalitis are restricted to the southernmost part of the country, presenting a significant increase in the incidence in the last decades. The incidence and prevalence of TBEV is consistently linked to climatic factors. We evaluated the monthly variation in prevalence of TBEV during six years, in nymphal and adult ticks from Mandal, southern Norway; a TBEV endemic area with high density of ticks. In addition, we evaluated the relationship between the virus prevalence and the accumulated heat and relative humidity. A marked seasonality of the virus prevalence was observed, peaking in the spring-early summer in nymphs and in summer-early autumn in adult ticks. The accumulated heat correlated positively with the prevalence in nymphs and adults, and the relative humidity correlated negatively with the prevalence in adults. Future research should focus on understanding the impacts of host dynamics, climate change and land use in the circulation of this emerging virus in Norway.

Tick-borne encephalitis virus (TBEV) is a medically important orthoflavivirus endemic across Europe and Asia, transmitted primarily by Ixodes ticks but also through ingestion of unpasteurized milk from infected ruminants. While milk-borne human infections are well documented, experimental evidence for natural mother-to-offspring transmission in livestock remains scarce. Here, we experimentally assessed the potential for lactogenic transmission of TBEV in sheep. Eight ewes were infected subcutaneously with the European subtype TBEV strain Hochosterwitz and co-housed with 16 three-week-old lambs (two per ewe) for an 18-day observation period. Clinical parameters, hematology, and virological and serological profiles were monitored. All animals remained asymptomatic, with no hematological abnormalities. TBEV RNA was detected in ewes’ serum and milk from day one post-infection, and in lamb serum from day five. Virus-specific antibodies emerged in ewes from day four and in lambs from day 13. These findings provide direct experimental evidence that TBEV can be transmitted via milk from ewes to their suckling lambs throughout the lactation period, underscoring a potential but underappreciated route for virus transmission in endemic areas.

Ticks are important vectors of zoonotic pathogens in Europe, but knowledge regarding the presence of Rickettsia spp. and Bartonella spp. in questing Ixodes ricinus in Norway remains limited. This study investigated the occurrence of these bacteria in ticks collected across the Norwegian distribution range of I. ricinus. A total of 564 adult ticks and 3930 nymphs (393 pools) collected in seven counties were analysed by real-time PCR. Rickettsia spp. were detected only in adult ticks, with an overall prevalence of 3.9 % (22/564). Infected ticks were identified in only two counties, Østfold and Agder, with a prevalence of 11.2 and 10.9 %, respectively. Species-specific analysis confirmed R. helvetica in 77.3 % (17/22) of the positive samples. Rickettsia spp. were not detected in any nymph pools. Bartonella spp. were detected in 0.5 % (3/564) of adult ticks, representing the first report of Bartonella spp. in questing I. ricinus in Norway. Infected ticks were found in three counties, Østfold, Telemark, and Nordland. Bartonella spp. were not detected in any nymph pools. These findings demonstrate that Rickettsia spp. and Bartonella spp. are present in questing adult ticks in Norway, highlighting the importance of continued surveillance of emerging tick-borne pathogens in northern Europe.

Tick-borne diseases constitute a major group of emerging vector-borne infections and represent a growing public health concern in many European countries. In Europe, the most clinically significant agents transmitted by Ixodes ricinus are tick-borne encephalitis virus (TBEV) and Borrelia burgdorferi sensu lato, the causative agents of tick-borne encephalitis and Lyme borreliosis, respectively. Ixodes ricinus also serves as a vector for other pathogenic microorganisms, including louping-ill virus (LIV) and Anaplasma phagocytophilum. Various endosymbionts, such as Wolbachia pipientis and Midichloria mitochondrii, are also found in ticks. In this study, we assessed the prevalence of TBEV, LIV, B. burgdorferi s. l., A. phagocytophilum, W. pipientis, and M. mitochondrii in 3437 I. ricinus ticks collected from five locations in Norway. The estimated pool prevalence of TBEV ranged from 0 to 0.4% in nymphs, while the prevalence in adults ranged from 0 to 7.1%. In contrast, no LIV was detected. Borrelia burgdorferi s. l. was detected at all sites, with prevalences ranging from 3.4% to 14.3% (overall prevalence of 5.7%), representing four genotypes (B. afzelii, B. garinii, B. valaisiana and B. burgdorferi sensu stricto). Estimated pooled prevalence of A. phagocytophilum was 5.1% in nymphs, while the overall prevalence in adults was 19.8%. In adult ticks, W. pipientis and M. mitochondrii occurred at overall prevalences of 11.0% and 84.1%, respectively. In only 12.3% of ticks, none of the agents investigated were detected. However, 32.6% of the ticks showed co-occurrence of infectious agents and/or the endosymbionts. Thus, this underscores the need for improved understanding of microbial interactions influencing tick-borne disease outcomes.

BACKGROUND:Borrelia burgdorferi sensu lato (s. l.) and Neoehrlichia mikurensis are the most prevalent pathogenic bacteria found in Ixodes ricinus in Norway. Here we evaluate the prevalence of both bacteria and the density of infected ticks, key factors to assess the human infection risk. The study was performed in one location in southern Norway. RESULTS:An overall prevalence of 12% for B. burgdorferi s. l. and 8% for N. mikurensis was found. The most prevalent B. burgdorferi s. l. genospecies was Borrelia afzelii, followed by Borrelia burgdorferi sensu stricto and Borrelia garinii. The highest density of infected nymphs with B. burgdorferi s. l. was in May and the lowest was in November. In the case of N. mikurensis, the highest density of infected nymphs was found in September and the lowest in November. B. burgdorferi s. l. prevalence was negatively correlated with tick density. CONCLUSIONS:Our results highlight the importance of assessing not only pathogen prevalences but also tick population densities. Extended periods of surveillance in questing ticks are necessary to understand the intricate dynamics of ticks and tick-borne pathogens.

Tick-borne encephalitis virus (TBEV) is an emerging pathogen that initially causes flu-like symptoms and can progress to central nervous system (CNS) infections. Tick-borne encephalitis (TBE) is an endemic disease in southern coastal counties with regular human cases, while the causative agent, TBEV, is prevalent in ticks in most of the coastal regions of Norway. This study was aimed to understand TBEV infection status across Norway including both TBE endemic and non-endemic areas. For this, we analyzed a total of 1940 residual serum samples from 19 counties of Norway (as of 2016). The samples were initially screened by ELISA, followed by virus neutralization tests for TBEV confirmation. We found a similar TBEV seroprevalence of 1.7% in TBE endemic and 1.6% in non-endemic areas. Since TBE cases are only reported from endemic regions, our findings suggest a potential subclinical or asymptomatic infection and underdiagnosis in non-endemic areas. Notably, only 43% of the ELISA-positive samples were confirmed by virus neutralization tests indicating that not all ELISA positives are true TBEV infections. Additionally, 137 samples of patients presenting with symptoms of CNS infections from a non-endemic area were included. Of these samples, 11 ELISA-positive samples were analyzed for cross-reactivity among flaviviruses. Cross-reactivity was detected with Dengue virus, West Nile Virus, and non-specific reactions. This underscores the importance of using multiple diagnostic tests to confirm TBEV infections. None of the patients with CNS infection was found to be TBE positive, and in the whole cohort, we found a low TBEV seroprevalence of 0.7%.

The annual number of tick-borne encephalitis (TBE) cases in Norway has increased dramatically from 1 case in 1998 to 113 in 2023. Characterization of TBE virus (TBEV) genomes from both clinical samples and tick vectors is necessary to understand disease severity and transmission dynamics. However, clinical samples with intact virus are rare because TBE is usually diagnosed by serology in the post-viremic phase, when the viral load is low and undetectable by molecular methods such as polymerase chain reaction (PCR). To date, Mandal-2009 is the only TBEV sequence from Norway with complete virus genome, sequenced directly from the tick vector. We used a combined approach with newly designed overlapping primer pairs and nanopore sequencing together with Sanger sequencing to obtain nearly complete TBEV genomes from both patient and tick samples from Norway. The patient had severe TBE complicated with hemophagocytic lymphohistiocytosis (HLH). The patient and tick samples were collected 16 km apart, from Telemark and Vestfold Counties, respectively. Pairwise genomic comparison showed 99.7 % identity, and phylogenetic analysis revealed that these sequences were closely related to the TBEV strain from Kumlinge in Åland, Finland, rather than to the previously published Norwegian variant Mandal-2009. These findings confirm the existence of novel TBEV variants in the endemic areas of Telemark and Vestfold Counties of Norway. Our findings highlight the need for continuous monitoring and characterization of novel TBEV genomes in Norway and Europe.

Cercarial dermatitis, often called swimmer’s itch, is a non-communicable skin condition caused by bird schistosomes. The host response is characterized by an early type I hypersensitivity reaction and a late phase of cutaneous inflammation, often leading to severe itching. Outbreaks of cercarial dermatitis in recreational waters can significantly impact public health. The aim of this present study was to describe the geographical distribution of reported cercarial dermatitis in Norway from 1980 to the end of 2023. The study is based on random reports obtained from private persons, hospitals, general practitioners and environmental health sectors experiencing the problem. The first case of cercarial dermatitis in Norway was reported back in 1980. In the following years, an increasing number of cases were reported with a clear increase from 2010 and onwards. By the end of 2023 cercarial dermatitis was reported from a total of 414 lakes and 37 rivers. Approximately 81

The distribution range of the taiga tick, Ixodes persulcatus, has increased in the last decade in Northern Europe. We performed samplings at nine locations in Nordland County, east and northeast of Brønnøysund, south of the Arctic Circle in July 2023. Four of 62 ticks collected were identified as I. persulcatus (one female, two males and one nymph), the remaining were identified as Ixodes ricinus (9 females, 2 males and 47 nymphs). This is the first report of I. persulcatus in Norway. Given the importance of I. persulcatus as vector of Borrelia burgdorferi sensu lato and more pathogenic subtypes of the tick-borne encephalitis virus, more research should be done focusing on its distribution, ecology and associated pathogens in Norway.

Ctenolepisma longicaudatum (Escherich, 1905) (Zygentoma, Lepismatidae) is an indoor nuisance and a potential threat to cultural heritage objects. The sustained effect of insecticidal bait application was investigated by collecting old and potentially degraded bait from previously conducted pest control experiments. The collected bait was compared with fresh bait in no-choice laboratory tests. The different insecticidal bait treatments decimated C. longicaudatum populations significantly with no difference between 43-month-old and fresh bait. Across all different levels of degradation 79–97% of the individuals died within 18 days. The study documents a sustained effect of bait and should direct pest control technicians towards a single bait application when managing C. longicaudatum populations. This will reduce the amount of bait used and the number of man-hours needed to decimate or eradicate a local population. The knowledge generated in this study may therefore directly contribute to a reduction of human exposure to harmful pesticidal substances in the indoor environment.

In Norway, tick-borne encephalitis (TBE) has been a mandatory notifiable disease since 1975 (Norwegian Surveillance system for communicable diseases, MSIS).1 According to ECDCs classification, coastal areas in southern Norway (counties of Agder, Vestfold and Telemark) are endemic for TBE. Further, the counties of Østfold, Akershus and Buskerud, and western and northern Norway to Brønnøy municipality are imperiled.2-9

Ixodes ricinus ticks are Scandinavia's main vector for tick-borne encephalitis virus (TBEV), which infects many people annually. The aims of the present study were (i) to obtain information on the TBEV prevalence in host-seeking I. ricinus collected within the Øresund-Kattegat-Skagerrak (ØKS) region, which lies in southern Norway, southern Sweden and Denmark; (ii) to analyse whether there are potential spatial patterns in the TBEV prevalence; and (iii) to understand the relationship between TBEV prevalence and meteorological factors in southern Scandinavia. Tick nymphs were collected in 2016, in southern Scandinavia, and screened for TBEV, using pools of 10 nymphs, with RT real-time PCR, and positive samples were confirmed with pyrosequencing. Spatial autocorrelation and cluster analysis was performed with Global Moran's I and SatScan to test for spatial patterns and potential local clusters of the TBEV pool prevalence at each of the 50 sites. A climatic analysis was made to correlate parameters such as minimum, mean and maximum temperature, relative humidity and saturation deficit with TBEV pool prevalence. The climatic data were acquired from the nearest meteorological stations for 2015 and 2016. This study confirms the presence of TBEV in 12 out of 30 locations in Denmark, where six were from Jutland, three from Zealand and two from Bornholm and Falster counties. In total, five out of nine sites were positive from southern Sweden. TBEV prevalence of 0.7%, 0.5% and 0.5%, in nymphs, was found at three sites along the Oslofjord (two sites) and northern Skåne region (one site), indicating a potential concern for public health. We report an overall estimated TBEV prevalence of 0.1% in questing I. ricinus nymphs in southern Scandinavia with a region-specific prevalence of 0.1% in Denmark, 0.2% in southern Sweden and 0.1% in southeastern Norway. No evidence of a spatial pattern or local clusters was found in the study region. We found a strong correlation between TBEV prevalence in ticks and relative humidity in Sweden and Norway, which might suggest that humidity has a role in maintaining TBEV prevalence in ticks. TBEV is an emerging tick-borne pathogen in southern Scandinavia, and we recommend further studies to understand the TBEV transmission potential with changing climate in Scandinavia.

Tick-borne encephalitis virus (TBEV) is found in Ixodes ricinus ticks throughout the area where viable tick populations exist. In Norway, TBEV is found in I. ricinus from the south coast until Brønnøy municipality in Nordland County and the range of the vector is expanding due to changes in climate, vegetation, host animals and environmental conditions. TBEV might thus have the potential to establish in new areas when I. ricinus expand its geographical distribution. At present, there is little knowledge on the status of the virus in high-altitude areas of inland regions in Norway. It has previously been indicated that reindeer may be an important sentinel species and indicator of the spread of ticks and TBEV in high-altitude regions. In this study, 408 semi-domesticated Eurasian tundra reindeer (Rangifer tarandus tarandus) from eight herds, from Tana in Troms and Finnmark County in northern Norway to Filefjell in Innlandet and Viken Counties in southern Norway, were screened for TBEV antibodies using a commercial enzyme-linked immunosorbent assay (ELISA). We found 16 TBEV reactive reindeer samples by ELISA; however, these results could not be confirmed by the serum neutralization test (SNT). This could indicate that a flavivirusand not necessarily TBEV, may be circulating among Norwegian semi-domesticated reindeer. The results also indicate that TBEV was not enzootic in Norwegian semi-domesticated reindeer in 2013-2015. This knowledge is important as an information base for future TBEV and flavivirus surveillance in Norway.

Abstract 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.

Rodent control is necessary to prevent damage and spread of disease, and the most common pesticides used for urban and rural rodent control are anticoagulant rodenticides. The aim of this present study was to present data on suspected exposure to rodenticides in humans and domestic animals in Norway based on inquiries to the Norwegian Poison Information Centre in the 16-year period from 2005 through 2020. A total of 4235 inquiries regarding suspected exposures to rodenticides were registered in the study period. Of these, 1486 inquiries involved humans and 2749 animals. Second generation anticoagulants were involved in 68% of human exposures and 79% of animal exposures. Dogs were the most frequent species involved in the animal exposures with 93% of the inquiries, while cats were second most frequent involved. Around 50% of the human inquiries concerned children at the age of 0-4 years. Only 2% of the cases were in the age group 10-19 years, while adults comprised 35% of the inquiries. Acute poisonings accounted for almost 100% of the inquiries among both humans and animals. The exposure was accidental in 99% of the animal exposures and in 85% of the human exposures. In humans, only 14 inquiries were regarding occupational related accidents. Misdeed or self-inflicted injury accounted for 15% of the human inquiries and were the cause of 79% of the severe poisonings. Severe poisoning was only assessed in 1% of the cases involving children under 5 years. In contrast, 17% of the inquiries concerning adults (≥20 years) were assessed as severe. Subsequently, to prevent human and animal rodenticide exposure, we urge the use of non-chemical methods such as sanitation, rodent proofing (a form of construction which will impede or prevent rodents access to or from a given space or building) and mechanical traps. Restricting the use of rodenticides to professional pest controllers (or other persons with authorisation), reinforcing high quality education of these persons, and securing compliance of the best codes of practice could be advocated to reduce accidental exposure to rodenticides in humans and animals.

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 (Sindbis, Chikungunya), Flaviviridae (West Nile, Usutu, Dengue), and Peribunyaviridae (Inkoo, Batai, Tahyna). The principal focus of this study was Inkoo (INKV) and Sindbis (SINV) virus circulating in Norway because there is a knowledge gap regarding reservoirs and transmission. Therefore, we aimed to determine the prevalence of SINV and INKV in mosquitoes and seroprevalence of INKV in semi-domesticated Eurasian tundra reindeer ( Rangifer tarandus tarandus ). Methods: In total, 213 pools containing about 25 mosquitoes each and 480 reindeer sera were collected in eight Norwegian reindeer summer pasture districts during 2013-2015. The mosquito pools were analysed for INKV and SINV RNA, with reverse transcriptase (RT)-real time quantitative PCR (RT-qPCR), and pyrosequencing. Reindeer sera were analysed for INKV-specific IgG by Indirect Immunofluorescence Assay (IIFA) and Plaque Reduction Neutralization Test (PRNT). Results: Aedes spp. were the most dominant species among the collected mosquitoes. Two of the mosquito 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%. IgG seroprevalence in reindeer revealed 60% positive for INKV by IIFA. Of the 55 borderline reindeer sera, 24% were positive on cytopathic effect (CPE)-neutralization test. Among 80% of 60 reindeer sera analysed with PRNT for INKV had a titre ≥ 20, and there was no cross-reactivity with the closely related Tahyna virus (TAHV) and Snow Shoe Hare virus (SSHV). None of the analysed mosquito pools were positive for SINV. Conclusions: The occurrence and prevalence of INKV in Aedes mosquitoes and its high seroprevalence among semi-domesticated reindeer in Norway indicate that further studies are required for monitoring this virus. SINV was not detected in the mosquitoes in this study, however, human cases of SINV infection have yearly been reported from Rjukan. Therefore, it is essential to investigate SINV among human population. Our findings are important to raise awareness regarding the geographical distribution of these mosquito-borne viruses in Northern Europe.

The tick-borne encephalitis virus (TBEV), a zoonotic flaviviral infection, is endemic in large parts of Norway and Eurasia. Humans are mainly infected with TBEV via bites from infected ticks. In Norway, the main geographical distribution of ticks is along the Norwegian coastline from southeast (~59°N) and up to the southern parts of Nordland County (~65°N). In this study, we collected ticks by flagging along the coast from Østfold County to Nordland County. By whole-genome sequencing of the mitochondrial genome of Ixodes ricinus, the phylogenetic tree suggests that there is limited phylogeographic structure both in Norway and in Europe. The overall TBEV prevalence is 0.3% for nymphs and 4.3% for adults. The highest estimated TBEV prevalence in adult ticks was detected in Rogaland and Vestfold County, while for nymphs it is highest in Vestfold, Vest-Agder and Rogaland. The present work is one of the largest studies on distribution and prevalence of TBEV in ticks in Scandinavia, showing that the virus is wider distributed in Norway than previously anticipated.

Tick-borne pathogens cause diseases in animals and humans, and tick-borne disease incidence is increasing in many parts of the world. There is a need to assess the distribution of tick-borne pathogens and identify potential risk areas. We collected 29,440 tick nymphs from 50 sites in Scandinavia from August to September, 2016. We tested ticks in a real-time PCR chip, screening for 19 vector-associated pathogens. We analysed spatial patterns, mapped the prevalence of each pathogen and used machine learning algorithms and environmental variables to develop predictive prevalence models. All 50 sites had a pool prevalence of at least 33% for one or more pathogens, the most prevalent being Borrelia afzelii, B. garinii , Rickettsia helvetica , Anaplasma phagocytophilum, and Neoehrlichia mikurensis . There were large differences in pathogen prevalence between sites, but we identified only limited geographical clustering. The prevalence models performed poorly, with only models for R. helvetica and N. mikurensis having moderate predictive power (normalized RMSE from 0.74–0.75, R 2 from 0.43–0.48). The poor performance of the majority of our prevalence models suggest that the used environmental and climatic variables alone do not explain pathogen prevalence patterns in Scandinavia, although previously the same variables successfully predicted spatial patterns of ticks in the same area.

Ticks carry pathogens that can cause disease in both animals and humans, and there is a need to monitor the distribution and abundance of ticks and the pathogens they carry to pinpoint potential high risk areas for tick-borne disease transmission. In a joint Scandinavian study, we measured Ixodes ricinus instar abundance at 159 sites in southern Scandinavia in August-September, 2016, and collected 29,440 tick nymphs at 50 of these sites. We additionally measured abundance at 30 sites in August-September, 2017. We tested the 29,440 tick nymphs in pools of 10 in a Fluidigm real-time PCR chip to screen for 17 different tick-associated pathogens, 2 pathogen groups and 3 tick species. We present data on the geolocation, habitat type and instar abundance of the surveyed sites, as well as presence/absence of each pathogen in all analysed pools from the 50 collection sites and individual prevalence for each site. These data can be used alone or in combination with other data for predictive modelling and mapping of high-risk areas.