Biting insects in a rapidly changing Arctic

First detection of a cervidpoxvirus in Europe-disease occurrence in semi-domesticated Eurasian tundra reindeer (Rangifer tarandus tarandus) in Norway and Sweden

Globally, there are six millions of Rangifer spp., including both wild and semi-domesticated populations. Reindeer herding with Eurasian tundra reindeer (Rangifer tarandus tarandus) is central to the Fennoscandian Sámi people. Commencing in 2018, a novel disease presenting with periorbital lesions was reported in reindeer in multiple locations in Norway and Sweden, as individual cases and outbreaks. Lesions were also seen on the genitals, nostrils, and ears of affected reindeer, in combination with lethargy. Necropsy findings included lesions with crusts on the eyelids, vulva, and anus, along with moderately swollen lymph nodes, liver, and spleen. Histological examination of the eyelid lesions showed a disrupted epidermis with necrotic squamous epithelium and inflammation. Shotgun sequencing of samples from outbreaks yielded a partial draft genome of a virus related to Deerpox virus W-848-83 (currently known as Cervidpoxvirus muledeerpox) in genus Cervidpoxvirus. Cervidpoxviruses have previously only been detected in Capreolinae in North America. An in-house qPCR targeting the cervidpoxvirus virion core protein gene was designed and showed the presence of viral-specific DNA in multiple organs, with the highest load in skin lesions. RNAscope in situ hybridization detected viral transcripts in the epithelium of the eye lesions. Transmission electron microscopy analysis revealed the presence of intracytoplasmic poxvirus-like particles with characteristic morphology within the lesions. In vitro infection in Madin-Darby bovine kidney epithelial cells demonstrated cytopathic effect. It is unknown whether the emergence of this disease in semi-domesticated reindeer in Norway and Sweden is due to ecosystem changes facilitating altered disease dynamics, or if the virus has been recently introduced.

IMPORTANCE

This study documents the first detection of a Cervidpoxvirus in Europe, causing disease in semi-domesticated reindeer in Norway and Sweden. It identifies the causative agent and describes the disease characteristics of this previously unknown condition in reindeer, advancing our understanding of how this virus impacts reindeer health and welfare. Given the cultural and ecological importance of reindeer herding in Fennoscandia, understanding this disease is crucial for safeguarding the livelihoods of Sámi communities. Additionally, the study raises important questions about the role of ecosystem changes, climate-driven insect dynamics, and potential reservoir hosts in facilitating disease outbreaks. These findings underscore the broader implications of environmental change on animal health and highlight the need for continued research to mitigate risks posed by emerging infectious diseases (EIDs).

Metagenomic analysis of mosquitoes from Kangerlussuaq, Greenland reveals a unique virome

Climate change is dramatically affecting vector ecology in extreme environments such as the Arctic. However, little is known about the current status of viruses of arthropod vectors located in such northerly locations. As part of a field survey on the role of wildlife in international movement of zoonotic pathogens, we sampled mammalophilic mosquitoes near the settlement of Kangerlussuaq, Greenland in July 2022 and July 2023 to investigate their virome. The majority of mosquitoes were identified as either Aedes impiger or Aedes nigripes. Metagenomic analysis of RNA extracted from species pools detected a number of novel RNA viruses belonging to a range of different virus families, including Flaviviridae, Orthomyxoviridae, Bunyavirales, Totiviridae and Rhabdoviridae. However, the sequence identities when compared to previously published, were as low as 34% at the amino acid level. Furthermore, a comparison of virome diversity between Aedes species emphasises the uniqueness of both Aedes impiger and Aedes nigripes from this secluded ecosystem. It also highlights the need to better understand the viromes of potential pathogen vectors as the impacts of climate change are experienced in such northerly ecosystems.

Widespread geographic distribution of filarioid nematodes in caribou (Rangifer tarandus sspp.) in Canada

The caribou (Rangifer tarandus sspp.) is a keystone wildlife species in northern ecosystems that plays a central role in the culture, spirituality and food security of Indigenous People. The Arctic is currently experiencing an unprecedented rate of climate change, including warming temperatures and altered patterns of precipitation. These environmental changes can facilitate the transmission of arthropod-borne parasites, such as filarioid nematodes. Filarioids are an important cause of morbidity and occasional mortality in Rangifer in Fennoscandia, however, much of the ecology and epidemiology of these parasites in caribou in North America, including Canada, remains unknown. We aimed to determine the parasitic diversity and geographic distribution of filarioid nematodes in three Canadian designatable units (DU) of caribou (barren-ground, boreal and Dolphin & Union) from Northwest Territories, Nunavut and Newfoundland & Labrador. Genomic DNA extracted from 768 blood samples was screened for filarioid nematodes using real-time PCR. The positive samples were Sanger sequenced to identify the parasite present. Based on the sequencing results, we identified Setaria yehi and Onchocerca cervipedis s.l. We then standardized a TaqMan probe based duplex droplet digital PCR (ddPCR) protocol for the simultaneous detection of S. yehi and O. cervipedis s.l. Based on real-time PCR results, 8/768 samples were positive. Setaria yehi and O. cervipedis s.l. were present in 4 separate samples (0.5%) each. Using ddPCR, 68/192 samples were positive (35.4%). Setaria yehi DNA was detected in 57/192 positive samples (29.7%), O. cervipedis s.l. DNA was present in 22/192 samples (11.5%) and 11/192 samples (5.7%) had co-infections. Setaria yehi was detected in all three DUs tested. Onchocerca cervipedis s.l. were found in barren-ground and boreal caribou, but not from the Dolphin and Union caribou. Through this broad-based survey and through developing and implementing advanced molecular methodologies, we have documented the apparent distribution and diversity of S. yehi and O. cervipedis s.l. in parts of three Canadian DUs of caribou. The knowledge gained from this study provides baseline data and methodology for the further elucidation of the epidemiology of these parasites in North America.

Climate change and health in the Arctic

AIM

Adverse human-driven environmental change, including the climate, is having an increasing impact on the Arctic environment and its ecosystems. There has been immense interest in understanding the health risks related to climate change in the Arctic region. In this article, we review recent evidence related to climate change and its impacts on the health of the Arctic population.

METHODS

We summarize current evidence related to primary, secondary and tertiary health effects in the Arctic. We explore a broad range of effects on health including increased exposure to extreme weather, impacts from changes in water quality, air quality, contaminant exposure, food systems and patterns of infectious diseases. We also briefly discuss mental health effects in the Arctic. We conclude by examining further challenges and opportunities for research in this field and advocate the need for adaptation options in the Arctic.

RESULTS

We find that there is a large amount of literature that is focusing on the human health effects in the Arctic but there are still research gaps in terms of understanding these compared with those at lower latitudes. We point out the need for filling several of these knowledge gaps to project future health effects of climate change in the Arctic.

CONCLUSIONS

There is a need for integrated adaptation strategies in the Arctic that fully account for the health impacts and consider indigenous perspectives.

A taste of space: Remote animal observations and discrete-choice models provide new insights into foraging and density dynamics for a large subarctic herbivore

Competition for resources and space can drive forage selection of large herbivores from the bite through the landscape scale. Animal behaviour and foraging patterns are also influenced by abiotic and biotic factors. Fine-scale mechanisms of density-dependent foraging at the bite scale are likely consistent with density-dependent behavioural patterns observed at broader scales, but few studies have directly tested this assertion. Here, we tested if space use intensity, a proxy of spatiotemporal density, affects foraging mechanisms at fine spatial scales similarly to density-dependent effects observed at broader scales in caribou. We specifically assessed how behavioural choices are affected by space use intensity and environmental processes using behavioural state and forage selection data from caribou (Rangifer tarandus granti) observed from GPS video-camera collars using a multivariate discrete-choice modelling framework. We found that the probability of eating shrubs increased with increasing caribou space use intensity and cover of Salix spp. shrubs, whereas the probability of eating lichen decreased. Insects also affected fine-scale foraging behaviour by reducing the overall probability of eating. Strong eastward winds mitigated negative effects of insects and resulted in higher probabilities of eating lichen. At last, caribou exhibited foraging functional responses wherein their probability of selecting each food type increased as the availability (% cover) of that food increased. Space use intensity signals of fine-scale foraging were consistent with density-dependent responses observed at larger scales and with recent evidence suggesting declining reproductive rates in the same caribou population. Our results highlight potential risks of overgrazing on sensitive forage species such as lichen. Remote investigation of the functional responses of foraging behaviours provides exciting future applications where spatial models can identify high-quality habitats for conservation.

California Serogroup Viruses in a Changing Canadian Arctic: A Review

The Arctic is warming at four times the global rate, changing the diversity, activity and distribution of vectors and associated pathogens. While the Arctic is not often considered a hotbed of vector-borne diseases, Jamestown Canyon virus (JCV) and Snowshoe Hare virus (SSHV) are mosquito-borne zoonotic viruses of the California serogroup endemic to the Canadian North. The viruses are maintained by transovarial transmission in vectors and circulate among vertebrate hosts, both of which are not well characterized in Arctic regions. While most human infections are subclinical or mild, serious cases occur, and both JCV and SSHV have recently been identified as leading causes of arbovirus-associated neurological diseases in North America. Consequently, both viruses are currently recognised as neglected and emerging viruses of public health concern. This review aims to summarise previous findings in the region regarding the enzootic transmission cycle of both viruses. We identify key gaps and approaches needed to critically evaluate, detect, and model the effects of climate change on these uniquely northern viruses. Based on limited data, we predict that (1) these northern adapted viruses will increase their range northwards, but not lose range at their southern limits, (2) undergo more rapid amplification and amplified transmission in endemic regions for longer vector-biting seasons, (3) take advantage of northward shifts of hosts and vectors, and (4) increase bite rates following an increase in the availability of breeding sites, along with phenological synchrony between the reproduction cycle of theorized reservoirs (such as caribou calving) and mosquito emergence.

Combining deep sequencing and conventional molecular approaches reveals broad diversity and distribution of fleas and Bartonella in rodents and shrews from Arctic and Subarctic ecosystems

BACKGROUND

Bartonella are intracellular bacteria that are transmitted via animal scratches, bites and hematophagous arthropods. Rodents and their associated fleas play a key role in the maintenance of Bartonella worldwide, with > 22 species identified in rodent hosts. No studies have addressed the occurrence and diversity of Bartonella species and vectors for small mammals in Arctic and Subarctic ecosystems, which are increasingly impacted by invasive species and climate change.

METHODS

In this study, we characterized the diversity of rodent fleas using conventional PCR targeting the mitochondrial cytochrome c oxidase II gene (COII) and Bartonella species in rodents and shrews (n = 505) from northern Canada using conventional PCR targeting the ITS (intergenic transcribed spacer) region and gltA (citrate synthase) gene. Metagenomic sequencing of a portion of the gltA gene was completed on a subset of 42 rodents and four rodent flea pools.

RESULTS

Year, total summer precipitation the year prior to sampling, average minimum spring temperature and small mammal species were significant factors in predicting Bartonella positivity. Occurrence based on the ITS region was more than double that of the gltA gene and was 34% (n = 349) in northern red-backed voles, 35% (n = 20) in meadow voles, 37% (n = 68) in deer mice and 31% (n = 59) in shrews. Six species of Bartonella were identified with the ITS region, including B. grahamii, B. elizabethae, B. washoensis, Candidatus B. rudakovii, B. doshiae, B. vinsonii subsp. berkhoffii and subsp. arupensis. In addition, 47% (n = 49/105) of ITS amplicons had < 97% identity to sequences in GenBank, possibly due to a limited reference library or previously unreported species. An additional Bartonella species (B. heixiaziensis) was detected during metagenomic sequencing of the gltA gene in 6/11 rodents that had ITS sequences with < 97% identity in GenBank, highlighting that a limited reference library for the ITS marker likely accounted for low sequence similarity in our specimens. In addition, one flea pool from a northern red-backed vole contained multiple species (B. grahamii and B. heixiaziensis).

CONCLUSION

Our study calls attention to the usefulness of a combined approach to determine the occurrence and diversity of Bartonella communities in hosts and vectors.

Herbivores in Arctic ecosystems: Effects of climate change and implications for carbon and nutrient cycling

Arctic terrestrial herbivores influence tundra carbon and nutrient dynamics through their consumption of resources, waste production, and habitat-modifying behaviors. The strength of these effects is likely to change spatially and temporally as climate change drives shifts in herbivore abundance, distribution, and activity timing. Here, we review how herbivores influence tundra carbon and nutrient dynamics through their consumptive and nonconsumptive effects. We also present evidence for herbivore responses to climate change and discuss how these responses may alter the spatial and temporal distribution of herbivore impacts. Several current knowledge gaps limit our understanding of the changing functional roles of herbivores; these include limited characterization of the spatial and temporal variability in herbivore impacts and of how herbivore activities influence the cycling of elements beyond carbon. We conclude by highlighting approaches that will promote better understanding of herbivore effects on tundra ecosystems, including their integration into existing biogeochemical models, new applications of remote sensing techniques, and the continued use of distributed experiments.

Survival and reproduction in Arctic caribou are associated with summer forage and insect harassment

Investigators have speculated that the climate-driven “greening of the Arctic” may benefit barren-ground caribou populations, but paradoxically many populations have declined in recent years. This pattern has raised concerns about the influence of summer habitat conditions on caribou demographic rates, and how populations may be impacted in the future. The short Arctic summer provides caribou with important forage resources but is also the time they are exposed to intense harassment by insects, factors which are both being altered by longer, warmer growing seasons. To better understand the effects of summer forage and insect activity on Arctic caribou demographic rates, we investigated the influence of estimated forage biomass, digestible energy (DE), digestible nitrogen (DN), and mosquito activity on the reproductive success and survival of adult females in the Central Arctic Herd on the North Slope of Alaska. We tested the hypotheses that greater early summer DN would increase subsequent reproduction (parturition and late June calving success) while greater biomass and DE would increase adult survival (September–May), and that elevated mosquito activity would reduce both demographic rates. Because the period when abundant forage DN is limited and overlaps with the period of mosquito harassment, we also expected years with low DN and high harassment to synergistically reduce caribou reproductive success. Examining these relationships at the individual-level, using GPS-collared females, and at the population-level, using long-term monitoring data, we generally found support for our expectations. Greater early summer DN was associated with increased subsequent calving success, while greater summer biomass was associated with increased adult survival. Mosquito activity was associated with reductions in adult female parturition, late June calving success, and survival, and in years with low DN, had compounding effects on subsequent late June calving success. Our findings indicate that summer nutrition and mosquito activity collectively influence the demographic rates of Arctic caribou, and may impact the dynamics of populations in the future under changing environmental conditions.

Migratory vertebrates shift migration timing and distributions in a warming Arctic

Climate warming in the Arctic has led to warmer and earlier springs, and as a result, many food resources for migratory animals become available earlier in the season, as well as become distributed further northwards. To optimally profit from these resources, migratory animals are expected to arrive earlier in the Arctic, as well as shift their own spatial distributions northwards. Here, we review literature to assess whether Arctic migratory birds and mammals already show shifts in migration timing or distribution in response to the warming climate. Distribution shifts were most prominent in marine mammals, as expected from observed northward shifts of their resources. At least for many bird species, the ability to shift distributions is likely constrained by available habitat further north. Shifts in timing have been shown in many species of terrestrial birds and ungulates, as well as for polar bears. Within species, we found strong variation in shifts in timing and distributions between populations. Ou r review thus shows that many migratory animals display shifts in migration timing and spatial distribution in reaction to a warming Arctic. Importantly, we identify large knowledge gaps especially concerning distribution shifts and timing of autumn migration, especially for marine mammals. Our understanding of how migratory animals respond to climate change appears to be mostly limited by the lack of long-term monitoring studies.

Critical summer foraging tradeoffs in a subarctic ungulate

Summer diets are crucial for large herbivores in the subarctic and are affected by weather, harassment from insects and a variety of environmental changes linked to climate. Yet, understanding foraging behavior and diet of large herbivores is challenging in the subarctic because of their remote ranges. We used GPS video-camera collars to observe behaviors and summer diets of the migratory Fortymile Caribou Herd (Rangifer tarandus granti) across Alaska, USA and the Yukon, Canada. First, we characterized caribou behavior. Second, we tested if videos could be used to quantify changes in the probability of eating events. Third, we estimated summer diets at the finest taxonomic resolution possible through videos. Finally, we compared summer diet estimates from video collars to microhistological analysis of fecal pellets. We classified 18,134 videos from 30 female caribou over two summers (2018 and 2019). Caribou behaviors included eating (mean = 43.5%), ruminating (25.6%), travelling (14.0%), stationary awake (11.3%) and napping (5.1%). Eating was restricted by insect harassment. We classified forage(s) consumed in 5,549 videos where diet composition (monthly) highlighted a strong tradeoff between lichens and shrubs; shrubs dominated diets in June and July when lichen use declined. We identified 63 species, 70 genus and 33 family groups of summer forages from videos. After adjusting for digestibility, monthly estimates of diet composition were strongly correlated at the scale of the forage functional type (i.e., forage groups composed of forbs, graminoids, mosses, shrubs and lichens; r = 0.79, p < .01). Using video collars, we identified (1) a pronounced tradeoff in summer foraging between lichens and shrubs and (2) the costs of insect harassment on eating. Understanding caribou foraging ecology is needed to plan for their long-term conservation across the circumpolar north, and video collars can provide a powerful approach across remote regions.