The Arctic as a model for anticipating, preventing, and mitigating climate change impacts on host–parasite interactions

Genomic characterization and virulence gene profiling of Erysipelothrix rhusiopathiae isolated from widespread muskox mortalities in the Canadian Arctic Archipelago

BACKGROUND

Muskoxen are important ecosystem components and provide food, economic opportunities, and cultural well-being for Indigenous communities in the Canadian Arctic. Between 2010 and 2021, Erysipelothrix rhusiopathiae was isolated from carcasses of muskoxen, caribou, a seal, and an Arctic fox during multiple large scale mortality events in the Canadian Arctic Archipelago. A single strain ('Arctic clone') of E. rhusiopathiae was associated with the mortalities on Banks, Victoria and Prince Patrick Islands, Northwest Territories and Nunavut, Canada (2010-2017). The objectives of this study were to (i) characterize the genomes of E. rhusiopathiae isolates obtained from more recent muskox mortalities in the Canadian Arctic in 2019 and 2021; (ii) identify and compare common virulence traits associated with the core genome and mobile genetic elements (i.e. pathogenicity islands and prophages) among Arctic clone versus other E. rhusiopathiae genomes; and iii) use pan-genome wide association studies (GWAS) to determine unique genetic contents of the Arctic clone that may encode virulence traits and that could be used for diagnostic purposes.

RESULTS

Phylogenetic analyses revealed that the newly sequenced E. rhusiopathiae isolates from Ellesmere Island, Nunavut (2021) also belong to the Arctic clone. Of 17 virulence genes analysed among 28 Arctic clone isolates, four genes - adhesin, rhusiopathiae surface protein-A (rspA), choline binding protein-B (cbpB) and CDP-glycerol glycerophosphotransferase (tagF) - had amino acid sequence variants unique to this clone when compared to 31 other E. rhusiopathiae genomes. These genes encode proteins that facilitate E. rhusiopathiae to attach to the host endothelial cells and form biofilms. GWAS analyses using Scoary found several unique genes to be overrepresented in the Arctic clone.

CONCLUSIONS

The Arctic clone of E. rhusiopathiae was associated with multiple muskox mortalities spanning over a decade and multiple Arctic islands with distances over 1000 km, highlighting the extent of its spatiotemporal spread. This clone possesses unique gene content, as well as amino acid variants in multiple virulence genes that are distinct from the other closely related E. rhusiopathiae isolates. This study establishes an essential foundation on which to investigate whether these differences are correlated with the apparent virulence of this specific clone through in vitro and in vivo studies.

Apparent fatal winter tick (Dermacentor albipictus) infestation in captive reindeer (Rangifertarandus)

The winter tick, Dermacentor albipictus (Ixodidae), commonly infests a wide variety of wild and domestic ungulates throughout North America. This one-host-tick infests animals from October to April, with moose (Alces alces) particularly affected. Animals highly infested may present with anemia, tick-induced alopecia, and alterations in thermoregulation, often resulting in death. Mortality from winter tick infestation has been reported in free-ranging woodland caribou (Rangifer tarandus caribou) and captive reindeer in Alberta, Canada. This historic report raises concern about mortality due to D. albipictus in a wider host range, specifically on translocated caribou. The aim of this report was to describe three cases of winter tick infestation in captive reindeer resulting in severe anemia and mortality likely due to the infestation in New Hampshire, northeastern United States (US). Additionally, ticks were screened molecularly for the detection of tick-borne pathogens. At time of necropsy, all three reindeer showed decreased nutritional status, marked submandibular edema, and had heavy D. albipictus infestation. None of the reindeer exhibited alopecia, which is a common clinical manifestation in moose that die from winter tick infestation. No pathogens were detected via qPCR screening. This report highlights the risk that captive cervids face in areas where winter tick is endemic; therefore, the adoption of preventive control measures should be encouraged to reduce the risk of tick infestation and potential death of these animals.

Helminth ecological requirements shape the impact of climate change on the hazard of infection

Outbreaks and spread of infectious diseases are often associated with seasonality and environmental changes, including global warming. Free-living stages of soil-transmitted helminths are highly susceptible to climatic drivers; however, how multiple climatic variables affect helminth species, and the long-term consequences of these interactions, is poorly understood. We used experiments on nine trichostrongylid species of herbivores to develop a temperature- and humidity-dependent model of infection hazard, which was then implemented at the European scale under climate change scenarios. Intestinal and stomach helminths exhibited contrasting climatic responses, with the former group strongly affected by temperature while the latter primarily impacted by humidity. Among the demographic traits, larval survival heavily modulated the infection hazard. According to the specific climatic responses of the two groups, climate change is expected to generate differences in the seasonal and spatial shifts of the infection hazard and group co-circulation. In the future, an intensification of these trends could create new opportunities for species range expansion and co-occurrence at European central-northern latitudes.

Host movement dominates the predicted effects of climate change on parasite transmission between wild and domestic mountain ungulates

Climate change is shifting the transmission of parasites, which is determined by host density, ambient temperature and moisture. These shifts can lead to increased pressure from parasites, in wild and domestic animals, and can impact the effectiveness of parasite control strategies. Understanding the interactive effects of climate on host movement and parasite life histories will enable targeted parasite management, to ensure livestock productivity and avoid additional stress on wildlife populations. To assess complex outcomes under climate change, we applied a gastrointestinal nematode transmission model to a montane wildlife-livestock system, based on host movement and changes in abiotic factors due to elevation, comparing projected climate change scenarios with the historic climate. The wildlife host, Alpine ibex (Capra ibex ibex), undergoes seasonal elevational migration, and livestock are grazed during the summer for eight weeks. Total parasite infection pressure was more sensitive to host movement than to the direct effect of climatic conditions on parasite availability. Extended livestock grazing is predicted to increase parasite exposure for wildlife. These results demonstrate that movement of different host species should be considered when predicting the effects of climate change on parasite transmission, and can inform decisions to support wildlife and livestock health.

Climate change effects on terrestrial parasitic nematodes: Where are the knowledge gaps?

Climate change is expected to affect parasitic nematodes and hence possibly parasite-host dynamics and may have far-reaching consequences for animal health, livestock production, and ecosystem functioning. However, there has been no recent overview of current knowledge to identify how studies could contribute to a better understanding of terrestrial parasitic nematodes under changing climates. Here we screened almost 1,400 papers to review 57 experimental studies on the effects of temperature and moisture on hatching, development, survival, and behaviour of the free-living stages of terrestrial parasitic nematodes with a direct life cycle in birds and terrestrial mammals. Two major knowledge gaps are apparent. First, research should study the temperature dependency curves for hatching, development, and survival under various moisture treatments to test the interactive effect of temperature and moisture. Second, we specifically advocate for more studies that investigate how temperature, and its interaction with moisture, affect both vertical and horizontal movement of parasitic nematodes to understand infection risks. Overall, we advocate for more field experiments that test environmental effects on life-history traits and behaviour of parasitic nematodes in their free-living stages under natural and realistic circumstances. We also encourage studies to expand the range of used hosts and parasitic nematodes because 66% of results described in the available studies use sheep and cattle as hosts and 32% involve just three nematode species. This new comprehension brings attention to understudied abiotic impacts on terrestrial parasitic nematodes and will have broader implications for livestock management, wildlife conservation, and ecosystem functioning in a rapidly warming climate.

Hazard assessment of global warming around the world using GIS

Global warming is among the important environmental problems of the earth. The present research aims to study temperature variations around the world. For this purpose, the monthly temperature data of 178 points from the NOAA site were studied from 1950 to 2019. In this study, the temperature changes were investigated in terms of its increase, decrease, and significance level by the Mann-Kendall method. Geographic Information System (GIS) and interpolation methods were used to determine the changes in temperature in global warming maps. According to the obtained results, except for 3.8% of the designated area, other parts of the world show change toward warmer conditions. Overall, the world's land temperature has increased by 1.08℃ during the study period. Also, about 85% of the designated area shows moderate and severe hazardous conditions in terms of global warming. The spatial analysis showed higher change and hazardous conditions for global warming in mid-longitude and high-latitude close to both poles.

Interactive effects of rising temperatures and urbanisation on birds across different climate zones: A mechanistic perspective

Climate change and urbanisation are among the most pervasive and rapidly growing threats to biodiversity worldwide. However, their impacts are usually considered in isolation, and interactions are rarely examined. Predicting species' responses to the combined effects of climate change and urbanisation, therefore, represents a pressing challenge in global change biology. Birds are important model taxa for exploring the impacts of both climate change and urbanisation, and their behaviour and physiology have been well studied in urban and non-urban systems. This understanding should allow interactive effects of rising temperatures and urbanisation to be inferred, yet considerations of these interactions are almost entirely lacking from empirical research. Here, we synthesise our current understanding of the potential mechanisms that could affect how species respond to the combined effects of rising temperatures and urbanisation, with a focus on avian taxa. We discuss potential interactive effects to motivate future in-depth research on this critically important, yet overlooked, aspect of global change biology. Increased temperatures are a pronounced consequence of both urbanisation (through the urban heat island effect) and climate change. The biological impact of this warming in urban and non-urban systems will likely differ in magnitude and direction when interacting with other factors that typically vary between these habitats, such as resource availability (e.g. water, food and microsites) and pollution levels. Furthermore, the nature of such interactions may differ for cities situated in different climate types, for example, tropical, arid, temperate, continental and polar. Within this article, we highlight the potential for interactive effects of climate and urban drivers on the mechanistic responses of birds, identify knowledge gaps and propose promising future research avenues. A deeper understanding of the behavioural and physiological mechanisms mediating species' responses to urbanisation and rising temperatures will provide novel insights into ecology and evolution under global change and may help better predict future population responses.

Climate change in the Arctic: Testing the poleward expansion of ticks and tick-borne diseases

Climate change is most strongly felt in the polar regions of the world, with significant impacts on the species that live there. The arrival of parasites and pathogens from more temperate areas may become a significant problem for these populations, but current observations of parasite presence often lack a historical reference of prior absence. Observations in the high Arctic of the seabird tick Ixodes uriae suggested that this species expanded poleward in the last two decades in relation to climate change. As this tick can have a direct impact on the breeding success of its seabird hosts and vectors several pathogens, including Lyme disease spirochaetes, understanding its invasion dynamics is essential for predicting its impact on polar seabird populations. Here, we use population genetic data and host serology to test the hypothesis that I. uriae recently expanded into Svalbard. Both black-legged kittiwakes (Rissa tridactyla) and thick-billed murres (Uria lomvia) were sampled for ticks and blood in Kongsfjorden, Spitsbergen. Ticks were genotyped using microsatellite markers and population genetic analyses were performed using data from 14 reference populations from across the tick's northern distribution. In contrast to predictions, the Spitsbergen population showed high genetic diversity and significant differentiation from reference populations, suggesting long-term isolation. Host serology also demonstrated a high exposure rate to Lyme disease spirochaetes (Bbsl). Targeted PCR and sequencing confirmed the presence of Borrelia garinii in a Spitsbergen tick, demonstrating the presence of Lyme disease bacteria in the high Arctic for the first time. Taken together, results contradict the notion that I. uriae has recently expanded into the high Arctic. Rather, this tick has likely been present for some time, maintaining relatively high population sizes and an endemic transmission cycle of Bbsl. Close future observations of population infestation/infection rates will now be necessary to relate epidemiological changes to ongoing climate modifications.

Distribution and prevalence of the myxozoan parasite Tetracapsuloides bryosalmonae in northernmost Europe: analysis of three salmonid species

Global climate change is altering the abundance and spread of many aquatic parasites and pathogens. Proliferative kidney disease (PKD) of salmonids caused by the myxozoan Tetracapsuloides bryosalmonae is one such emerging disorder, and its impact is expected to increase with rising water temperature. Yet, the distribution and prevalence of T. bryosalmonae in Northern Europe remain poorly characterized. Here, we studied 43 locations in 27 rivers in northernmost Norway and Finland to describe T. bryosalmonae infection frequency and patterns in 1389 juvenile salmonids. T. bryosalmonae was discovered in 12 out of 27 rivers (44%) and prevalence ranged from 4.2 to 55.5% in Atlantic salmon and from 5.8 to 75% in brown trout among infected rivers. In sympatric populations, brown trout was more frequently infected with T. bryosalmonae than was salmon. Age-specific parasite prevalence patterns revealed that in contrast to lower latitudes, the infection of juvenile fish predominantly occurs during the second summer or later. Temperature monitoring over 2 yr indicated that the mean water temperature in June was 2.1 to 3.2°C higher in rivers containing T. bryosalmonae compared to parasite-free rivers, confirming the important role of temperature in parasite occurrence. Temporal comparison in T. bryosalmonae prevalence over a 10 yr period in 11 rivers did not reveal any signs of contemporary parasite spread to previously uninfected rivers. However, the wide distribution of T. bryosalmonae in rivers flowing to the Barents Sea indicates that climate change and heat waves may cause new disease outbreaks in northern regions.

Association of Environmental Factors with Seasonal Intensity of Erysipelothrix rhusiopathiae Seropositivity among Arctic Caribou

Several caribou (Rangifer tarandus) populations have been declining concurrently with increases in infectious diseases in the Arctic. Erysipelothrix rhusiopathiae, a zoonotic bacterium, was first described in 2015 as a notable cause of illness and death among several Arctic wildlife species. We investigated epidemiologic and environmental factors associated with the seroprevalence of E. rhusiopathiae in the Arctic and found that seropositivity was highest during warmer months, peaking in September, and was highest among adult males. Summer seroprevalence increases tracked with the oestrid index from the previous year, icing and snowing events, and precipitation from the same year but decreased with growing degree days in the same year. Seroprevalence of E. rhusiopathiae varied more during the later years of the study. Our findings provide key insights into the influence of environmental factors on disease prevalence that can be instrumental for anticipating and mitigating diseases associated with climate change among Arctic wildlife and human populations.

Behaviour is more important than thermal performance for an Arctic host-parasite system under climate change

Climate change is affecting Arctic ecosystems, including parasites. Predicting outcomes for host-parasite systems is challenging due to the complexity of multi-species interactions and the numerous, interacting pathways by which climate change can alter dynamics. Increasing temperatures may lead to faster development of free-living parasite stages but also higher mortality. Interactions between behavioural plasticity of hosts and parasites will also influence transmission processes. We combined laboratory experiments and population modelling to understand the impacts of changing temperatures on barren-ground caribou (Rangifer tarandus) and their common helminth (Ostertagia gruehneri). We experimentally determined the thermal performance curves for mortality and development of free-living parasite stages and applied them in a spatial host-parasite model that also included behaviour of the parasite (propensity for arrested development in the host) and host (long-distance migration). Sensitivity analyses showed that thermal responses had less of an impact on simulated parasite burdens than expected, and the effect differed depending on parasite behaviour. The propensity for arrested development and host migration led to distinct spatio-temporal patterns in infection. These results emphasize the importance of considering behaviour-and behavioural plasticity-when projecting climate-change impacts on host-parasite systems.

Cercariae of a Bird Schistosome Follow a Similar Emergence Pattern under Different Subarctic Conditions: First Experimental Study

The emergence of cercariae from infected mollusks is considered one of the most important adaptive strategies for maintaining the trematode life cycle. Short transmission opportunities of cercariae are often compensated by periodic daily rhythms in the cercarial release. However, there are virtually no data on the cercarial emergence of bird schistosomes from freshwater ecosystems in northern latitudes. We investigated the daily cercarial emergence rhythms of the bird schistosome Trichobilharzia sp. “peregra” from the snail host Radix balthica in a subarctic lake under both natural and laboratory seasonal conditions. We demonstrated a circadian rhythm with the highest emergence during the morning hours, being seasonally independent of the photo- and thermo-period regimes of subarctic summer and autumn, as well as relatively high production of cercariae at low temperatures typical of northern environments. These patterns were consistent under both field and laboratory conditions. While light intensity triggered and prolonged cercarial emergence, the temperature had little effect on cercarial rhythms but regulated seasonal output rates. This suggests an adaptive strategy of bird schistosomes to compensate for the narrow transmission window. Our results fill a gap in our knowledge of the transmission dynamics and success of bird schistosomes under high latitude conditions that may serve as a basis for elucidating future potential risks and implementing control measures related to the spread of cercarial dermatitis due to global warming.

Sublethal effects of parasitism on ruminants can have cascading consequences for ecosystems

Parasitic infections are common, but how they shape ecosystem-level processes is understudied. Using a mathematical model and meta-analysis, we explored the potential for helminth parasites to trigger trophic cascades through lethal and sublethal effects imposed on herbivorous ruminant hosts after infection. First, using the model, we linked negative effects of parasitic infection on host survival, fecundity, and feeding rate to host and producer biomass. Our model, parameterized with data from a well-documented producer–caribou–helminth system, reveals that even moderate impacts of parasites on host survival, fecundity, or feeding rate can have cascading effects on ruminant host and producer biomass. Second, using meta-analysis, we investigated the links between helminth infections and traits of free-living ruminant hosts in nature. We found that helminth infections tend to exert negative but sublethal effects on ruminant hosts. Specifically, infection significantly reduces host feeding rates, body mass, and body condition but has weak and highly variable effects on survival and fecundity. Together, these findings suggest that while helminth parasites can trigger trophic cascades through multiple mechanisms, overlooked sublethal effects on nonreproductive traits likely dominate their impacts on ecosystems. In particular, by reducing ruminant herbivory, pervasive helminth infections may contribute to a greener world.

Improving Widescale Monitoring of Ectoparasite Presence in Northern Canadian Wildlife with the Aid of Citizen Science

Simple Summary

Surveying ticks on wildlife hosts consistently over time and across space presents many challenges. In Yukon, Canada, the winter tick, Dermacentor albipictus, is a blood-feeding parasite that can cause significant losses of hair and blood in moose and other wildlife. The impacts of winter tick infestation in wildlife hosts in this northern region are not well documented. To enhance existing surveillance of winter ticks in Yukon, we implemented a three-year citizen science program, the Yukon Winter Tick Monitoring Project (YWTMP) to engage hunters in the collection of underrepresented moose and caribou samples. Social media, participation incentives, and hide-sampling kits distributed to hunters increased the combined number of annual moose and caribou hide submissions almost 100-fold, and the geographical range of samples by almost 500 km, compared with submission numbers in the previous seven years. Citizen science samples were also used to detect previously unknown infection localities on moose in southeastern Yukon that are spatially separate to known infestations found on elk and deer, helping to build a better picture of infection dynamics on different host animals. Engaging with key demographic groups using structured citizen science programs like the YWTMP can significantly expand sampling efforts in remote areas while maintaining systematic sampling methods to monitor parasites of wildlife health concern.

Abstract

Sampling hides from harvested animals is commonly used for passive monitoring of ectoparasites on wildlife hosts, but often relies heavily on community engagement to obtain spatially and temporally consistent samples. Surveillance of winter ticks (Dermacentor albipictus) on moose (Alces alces) and caribou (Rangifer tarandus caribou) hosts in Yukon, Canada, has relied in part on voluntary submission of hides by hunters since 2011, but few samples were submitted. To enhance sampling efforts on underrepresented moose and caribou hosts, we implemented a three-year citizen science program, the Yukon Winter Tick Monitoring Project (YWTMP), to better engage with hunters in hide sample collection. A combination of in-person and social media outreach, incentivized engagement, and standardized hide sampling kits increased voluntary submissions of moose and caribou hides almost 100-fold since surveillance began. Citizen science samples expanded the northernmost geographic extent of existing sampling efforts for moose by 480 km and for caribou by 650 km to reach 67.5° N latitude. Samples also resulted in new detections of winter ticks on moose hides that are spatially separate to those submitted for other cervids in Yukon. Findings from the YWTMP have provided an essential baseline to monitor future winter tick host–parasite dynamics in the region and highlighted priority areas for ongoing tick surveillance.

Taxa-specific activity loss and mortality patterns in freshwater trematode cercariae under subarctic conditions

Cercarial activity and survival are crucial traits for the transmission of trematodes. Temperature is particularly important, as faster depletion of limited cercarial energy reserves occurs at high temperatures. Seasonal climate conditions in high latitude regions may be challenging to complete trematode life cycle during the 6-month ice-free period, but temperature effects on the activity and survival of freshwater cercariae have not been previously identified. After experimentally simulating natural subarctic conditions during warmer and colder months (13 and 6°C), a statistical approach identifying changes in the tendency of cercarial activity loss and mortality data was used to detect differences in three trematode genera, represented by four taxa (Diplostomum spp., Apatemon spp., small- and large-sized Plagiorchis spp.). A strong temperature-dependent response was identified in both activity loss and mortality in all taxa, with Diplostomum spp. cercariae showing the most gradual changes compared to other taxa. Furthermore, whilst activity loss and mortality dynamics could not be divided into ‘fish- vs invertebrate-infecting cercariae’ groups, the detected taxa-specific responses in relation to life-history traits indicate the swimming behaviour of cercariae and energy allocation among larvae individuals as the main drivers. Cercariae exploit the short transmission window that allows a stable continuance of trematodes’ life cycles in high-latitude freshwater ecosystems.

ASSESSMENT OF VARIATION IN THE DETECTION AND PREVALENCE OF BLOOD PARASITES AMONG SYMPATRICALLY BREEDING GEESE IN WESTERN ALASKA, USA

Haemosporidian parasites may impact avian health and are subject to shifts in distribution and abundance with changing ecologic conditions. Therefore, understanding variation in parasite prevalence is important for evaluating biologically meaningful changes in infection patterns and associated population level impacts. Previous research in western Alaska, US, indicated a possible increase in Leucocytozoon spp. infection between Emperor Geese (Anser canagicus) sampled in 1996 (<1%, n=134) and during 2011-12 (19.9%, 95% confidence interval [CI]: 3.0-36.8%, n=77); however, different detection methods were used for these estimates. Prior research in this same region identified a lack of Leucocytozoon spp. parasites (0%, n=117) in sympatrically breeding Cackling Geese (Branta hutchinsii minima) in 2011. We molecularly screened blood samples collected from sympatrically breeding Emperor and Cackling Geese in western Alaska during additional breeding seasons to better assess temporal and species-specific variation in the prevalence of blood parasites. We found similar prevalence estimates for Leucocytozoon spp. parasites in Emperor Goose blood samples collected in 1998 and 2014, suggesting consistent infection of Emperor Geese with blood parasites at these time points. Using samples from sympatric geese sampled during 2014, we found evidence for a higher incidence of parasites among Emperor Geese (20.3%, 95% CI: 11.8-32.7%) compared to Cackling Geese (3.6%, 95% CI: 1.1-11.0%), reinforcing the previous finding of species-specific differences in infection. Furthermore, we detected Leucocytozoon, Haemoproteus, and Plasmodium spp. blood parasites in unflighted goslings of both species, supporting the possible transmission of these parasites at western Alaska breeding grounds. Our results help to clarify that prevalence of Leucocytozoon spp. parasites have probably remained consistent among Emperor Geese breeding in western Alaska since the late 1990s and that this species may disproportionally harbor Leucocytozoon spp. compared to sympatrically breeding Cackling Geese.

Nonlinear shifts in infectious rust disease due to climate change

Range shifts of infectious plant disease are expected under climate change. As plant diseases move, emergent abiotic-biotic interactions are predicted to modify their distributions, leading to unexpected changes in disease risk. Evidence of these complex range shifts due to climate change, however, remains largely speculative. Here, we combine a long-term study of the infectious tree disease, white pine blister rust, with a six-year field assessment of drought-disease interactions in the southern Sierra Nevada. We find that climate change between 1996 and 2016 moved the climate optimum of the disease into higher elevations. The nonlinear climate change-disease relationship contributed to an estimated 5.5 (4.4-6.6) percentage points (p.p.) decline in disease prevalence in arid regions and an estimated 6.8 (5.8-7.9) p.p. increase in colder regions. Though climate change likely expanded the suitable area for blister rust by 777.9 (1.0-1392.9) km² into previously inhospitable regions, the combination of host-pathogen and drought-disease interactions contributed to a substantial decrease (32.79%) in mean disease prevalence between surveys. Specifically, declining alternate host abundance suppressed infection probabilities at high elevations, even as climatic conditions became more suitable. Further, drought-disease interactions varied in strength and direction across an aridity gradient-likely decreasing infection risk at low elevations while simultaneously increasing infection risk at high elevations. These results highlight the critical role of aridity in modifying host-pathogen-drought interactions. Variation in aridity across topographic gradients can strongly mediate plant disease range shifts in response to climate change.

Screening potential insect vectors in a museum biorepository reveals undiscovered diversity of plant pathogens in natural areas

Phytoplasmas (Mollicutes, Acholeplasmataceae), vector-borne obligate bacterial plant parasites, infect nearly 1,000 plant species and unknown numbers of insects, mainly leafhoppers (Hemiptera, Deltocephalinae), which play a key role in transmission and epidemiology. Although the plant-phytoplasma-insect association has been evolving for >300 million years, nearly all known phytoplasmas have been discovered as a result of the damage inflicted by phytoplasma diseases on crops. Few efforts have been made to study phytoplasmas occurring in noneconomically important plants in natural habitats. In this study, a subsample of leafhopper specimens preserved in a large museum biorepository was analyzed to unveil potential new associations. PCR screening for phytoplasmas performed on 227 phloem-feeding leafhoppers collected worldwide from natural habitats revealed the presence of 6 different previously unknown phytoplasma strains. This indicates that museum collections of herbivorous insects represent a rich and largely untapped resource for discovery of new plant pathogens, that natural areas worldwide harbor a diverse but largely undiscovered diversity of phytoplasmas and potential insect vectors, and that independent epidemiological cycles occur in such habitats, posing a potential threat of disease spillover into agricultural systems. Larger-scale future investigations will contribute to a better understanding of phytoplasma genetic diversity, insect host range, and insect-borne phytoplasma transmission and provide an early warning for the emergence of new phytoplasma diseases across global agroecosystems.

Implications of Zoonoses From Hunting and Use of Wildlife in North American Arctic and Boreal Biomes: Pandemic Potential, Monitoring, and Mitigation

The COVID-19 pandemic has re-focused attention on mechanisms that lead to zoonotic disease spillover and spread. Commercial wildlife trade, and associated markets, are recognized mechanisms for zoonotic disease emergence, resulting in a growing global conversation around reducing human disease risks from spillover associated with hunting, trade, and consumption of wild animals. These discussions are especially relevant to people who rely on harvesting wildlife to meet nutritional, and cultural needs, including those in Arctic and boreal regions. Global policies around wildlife use and trade can impact food sovereignty and security, especially of Indigenous Peoples. We reviewed known zoonotic pathogens and current risks of transmission from wildlife (including fish) to humans in North American Arctic and boreal biomes, and evaluated the epidemic and pandemic potential of these zoonoses. We discuss future concerns, and consider monitoring and mitigation measures in these changing socio-ecological systems. While multiple zoonotic pathogens circulate in these systems, risks to humans are mostly limited to individual illness or local community outbreaks. These regions are relatively remote, subject to very cold temperatures, have relatively low wildlife, domestic animal, and pathogen diversity, and in many cases low density, including of humans. Hence, favorable conditions for emergence of novel diseases or major amplification of a spillover event are currently not present. The greatest risk to northern communities from pathogens of pandemic potential is via introduction with humans visiting from other areas. However, Arctic and boreal ecosystems are undergoing rapid changes through climate warming, habitat encroachment, and development; all of which can change host and pathogen relationships, thereby affecting the probability of the emergence of new (and re-emergence of old) zoonoses. Indigenous leadership and engagement in disease monitoring, prevention and response, is vital from the outset, and would increase the success of such efforts, as well as ensure the protection of Indigenous rights as outlined in the United Nations Declaration on the Rights of Indigenous Peoples. Partnering with northern communities and including Indigenous Knowledge Systems would improve the timeliness, and likelihood, of detecting emerging zoonotic risks, and contextualize risk assessments to the unique human-wildlife relationships present in northern biomes.

Entomopathogenic Fungi for Tick Control in Cattle Livestock From Mexico

Ticks are one of the main economic threats to the cattle industry worldwide affecting productivity, health and welfare. The need for alternative methods to control tick populations is prompted by the high prevalence of multiresistant tick strains to the main chemical acaricides and their ecological consequences. Biological control using entomopathogenic fungi (EPF) is one of the most promising alternative options. The objective of this paper is to review the use of EPF as an alternative control method against cattle ticks in Mexico. Metarhizium anisopliae sensu lato (s.l.) and Beauveria bassiana s.l. are the most studied EPF for the biological control of ticks in the laboratory and in the field, mainly against Rhipicephalus microplus; however, evaluations against other important cattle ticks such as Amblyomma mixtum and R. annulatus, are needed. A transdisciplinary approach is required to incorporate different types of tools, such as genomics, transcriptomics and proteomics in order to better understand the pathogenicity/virulence mechanism in EPF against ticks. Laboratory tests have demonstrated the EPF efficacy to control susceptible and resistant/multiresistant tick populations; whereas, field tests have shown satisfactory control efficiency of M. anisopliae s.l. against different stages of R. microplus when applied both on pasture and on cattle. Epidemiological aspects of ticks and environmental factors are considered as components that influence the acaricidal behavior of the EPF. Finally, considering all these aspects, some recommendations are proposed for the use of EPF in integrated control schemes for livestock ticks.

A Peculiar Distribution of the Emerging Nematode Angiostrongylus cantonensis in the Canary Islands (Spain): Recent Introduction or Isolation Effect?

Simple Summary

Angiostrongylus cantonensis, commonly known as the rat lungworm, is considered the leading cause of eosinophilic meningitis in humans. It is an emerging zoonotic parasite, endemic to the temperate and tropical zones of the Far East, Southeast Asia and the Pacific Islands, that has expanded to all continents with the exception of Antarctica. Considering the recent finding of this parasite in rats from the Canary Islands, the aim of this study was to determine its current distribution in these islands in order to highlight the risk sources for angiostrongyliasis in the archipelago. We also analyzed the environmental conditions that could determine distribution. A. cantonensis was detected in only one of the eight islands that constitute this archipelago, i.e., in the north part of the island, which presents better environmental conditions than the south for the parasite to establish itself. This limited distribution could indicate a recent introduction of the parasite in the Canaries or an isolation effect that has not allowed the expansion to the other islands. The presence of A. cantonensis implies risks for humans and other animals that justify the need of control measures to prevent the expansion to other similar areas of the archipelago.

Abstract

Angiostrongylus cantonensis is an emerging zoonotic nematode recognized as the leading cause of eosinophilic meningitis in the word. After its discovery in China, it was recorded in 30 countries worldwide. Recently, it has expanded to new areas such as South America and it has been recently found in the Atlantic island of Tenerife (Canary Islands). In order to characterize the distribution of A. cantonensis in the Canary Islands, the lungs of 1462 rodents were sampled in eight islands of the archipelago over 13 years and were then analyzed for A. cantonensis. Remarkably, the parasite was detected only in Tenerife, in Rattus rattus (19.7%) and Rattus norvegicus (7.14%). They were concretely in the northern part of the island, which had a warmer and more humid climate than the south and main cities. The absence of this nematode in other islands with similar environmental conditions could be explained by an isolation effect or by a recent introduction of the parasite in the islands. Besides, the presence in Tenerife of the most invasive lineage of A. cantonensis reinforced the hypothesis of a recent introduction on this island. This study highlights the need to implement control measures to prevent the expansion to other areas in order to avoid the transmission to humans and other animals.

Linkages between environmental issues and zoonotic diseases: with reference to COVID-19 pandemic

Coronavirus disease (COVID-19) caused by severe acute respiratory syndrome (SARS) coronavirus 2 (SARS-CoV-2) has taken mankind by surprise with various unprecedented impacts on human life around the globe. This zoonotic pandemic is proving to be the most destructive disease outbreaks since decades. The increasing human population and anthropogenic activities have impacted the environment and have direct linkages with the current and other recent outbreaks of zoonotic diseases. Despite having a difference in their origin, major reasons behind the emergence and spread of zoonotic pandemics are related to activities such as habitat fragmentation, deforestation, biodiversity loss, intensive agriculture and livestock farming, uncontrolled urbanization, pollution, climate change and bushmeat hunting and trading. It is important to focus on environmental and climatic factors that are involved in the emergence of such pandemics involving novel human pathogens and viruses in particular. Research and data analysis, particularly in relation to COVID-19, has shown that meteorological factors along with population density and living conditions (particularly in the urban and semi-urban areas) play a crucial role in the intensity, evolution and spread of SARS-CoV-2. This particular virus is novel but coronaviruses have a long history and are known to cause disease outbreaks earlier as well. COVID-19 pandemic provides learning for the future, in particular the importance of environmental sustainability for controlling such outbreaks. A strategic plan can be developed involving policy-makers, organizations, and governments to control the onset and spread of the novel pathogens. This review-based study recommends that prevention of COVID-19 like pandemics from re-occurring is through tackling the issues related to the environment by controlling anthropogenic activities. It will also be important to track the lineage and future evolution course of such human pathogens so as to determine the nexus of environmental and biological factors in the development and spread of novel strains.

Experimental manipulation of cavity temperature produces differential effects on parasite abundances in blue tit nests at two different latitudes

Although different predictive models forecast that climate change will alter the distribution and incidence of parasitic diseases, few studies have investigated how microclimatic changes may affect host-parasite relationships. In this study, we experimentally increased the temperature inside nest boxes of the blue tit Cyanistes caeruleus during the nestling period at two different latitudes (central Spain and central Germany) to determine its effect on parasite abundance. The two localities have contrasting climate conditions: the southern one in Spain is warmer and drier than the northern one in Germany. Consistent with this, we observed that the parasitic fauna in nests at the two localities differs. The flea species Ceratophyllus gallinae was more abundant in the northern locality, while the blowfly species Protocalliphora azurea and biting midge species of the genus Culicoides were more abundant in the southern one, as were blood parasites. Moreover, dermanyssid mites and blackflies (Simuliidae) were observed only in the southern locality. The temperature inside nest boxes was increased using heat mats placed underneath the nest material during the nestling period (day 3 to day13 post-hatching). Compared with control nests, the average temperature in heated nests increased by 2.24 °C and 1.35 °C at night in Spain and Germany, respectively. Consequently, the average relative humidity in heated versus control nests decreased 4.93 and 0.82 units in Spain and Germany, respectively. The abundance of blowfly pupae in the heated nests was significantly lower than that of control nests at both localities. The abundance of larval fleas was also lower in the heated nests, but only at the Spanish locality. Infection by the blood parasites Haemoproteus/Plasmodium was higher in males attending the heated nests in Germany, and the control nests in Spain. Moreover, both male body mass and nestling wing length were negatively related to the abundance of larval fleas. In conclusion, our results indicate that increased temperature at the nestling stage may affect the fitness of blue tits by altering parasite prevalence rates.

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Temperature increase inside blue tit nest boxes affects ectoparasite abundance at two different localities.

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Blowfly and flea larvae abundances were negatively affected by increase in temperature.

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Male body mass and nestling wing length were negatively related to the abundance of flea larvae.

Emerging infectious disease: An underappreciated area of strategic concern for food security

Emerging infectious diseases (EIDs) increasingly threaten global food security and public health. Despite technological breakthroughs, we are losing the battle with (re)emerging diseases as treatment costs and production losses rise. A horizon scan of diseases of crops, livestock, seafood and food-borne illness suggests these costs are unsustainable. The paradigm of coevolution between pathogens and particular hosts teaches that emerging diseases occur only when pathogens evolve specific capacities that allow them to move to new hosts. EIDs ought to be rare and unpredictable, so crisis response is the best we can do. Alternatively, the Stockholm Paradigm suggests that the world is full of susceptible but unexposed hosts that pathogens could infect, given the opportunity. Global climate change, globalized trade and travel, urbanization and land-use changes (often associated with biodiversity loss) increase those opportunities, making EID frequent. We can, however, anticipate their arrival in new locations and their behaviour once they have arrived. We can 'find them before they find us', mitigating their impacts. The DAMA (Document, Assess, Monitor, Act) protocol alters the current reactive stance and embodies proactive solutions to anticipate and mitigate the impacts of EID, extending human and material resources and buying time for development of new vaccinations, medications and control measures.

Being on Land and Sea in Troubled Times: Climate Change and Food Sovereignty in Nunavut

Climate change driven food insecurity has emerged as a topic of special concern in the Canadian Arctic. Inuit communities in this region rely heavily on subsistence; however, access to traditional food sources may have been compromised due to climate change. Drawing from a total of 25 interviews among Inuit elders and experienced hunters from Cambridge Bay and Kugluktuk in Nunavut, Canada, this research examines how climate change is impacting food sovereignty and health. Our results show that reports of food insecurity were more pronounced in Kugluktuk than Cambridge Bay. Participants in Kugluktuk consistently noted declining availability of preferred fish and game species (e.g., caribou, Arctic char), a decline in participation of sharing networks, and overall increased difficulty accessing traditional foods. Respondents in both communities presented a consistent picture of climate change compounding existing socio-economic (e.g., poverty, disconnect between elders and youth) and health stressors affecting multiple aspects of food sovereignty. This article presents a situated understanding of how climate change as well as other sociocultural factors are eroding food sovereignty at the community-scale in the Arctic. We argue that a communal focus is required to address resilience and adaptation at the local level through programs that protect the local cultural knowledge, traditional ways of life, and indigenous sovereignty to reduce the severities of food insecurity in the Arctic stemming from climate change.

First records of Dermacentor albipictus larvae collected by flagging in Yukon, Canada

Background

The winter tick (Dermacentor albipictus) has garnered significant attention throughout North America for its impact on wildlife health, and especially for moose (Alces alces), where high tick burdens may result in host hair loss, anemia, and can prove fatal. The environmental transmission of D. albipictus larvae to a host is a critical event that has direct impact on infestation success, yet in-field observations of this life stage are lacking. In Yukon, Canada, D. albipictus had previously been found on hosts, but its larval life stage had not been detected in the field, despite previous sampling attempts.

Methods

We sampled for D. albipictus larvae using traditional flagging methods in Ibex Valley and Braeburn, Yukon. Sites were sampled repeatedly for D. albipictus larvae by flagging from late August to end of October in 2018 and late August to end of November 2019.

Results

Larvae of D. albipictus were collected throughout Ibex Valley, at approximate densities ranging from 0.04 to 4236 larvae/100 m². Larvae were present primarily on grassy vegetation on south-facing slopes in the Ibex Valley region and in Braeburn. Highest average larval numbers suggest peak questing activity was towards the end of September and beginning of October, as elsewhere in North America.

Conclusions

To the best of our knowledge, we report the first successful collection of the off-host, larval life stage of D. albipictus by flagging, north of 60° latitude in Yukon, Canada. These new observations provide critical information on the spatial distribution of the host-seeking life stage of D. albipictus and confirm that this species is completing its whole life cycle in southern Yukon. Understanding the environmental conditions where larvae spend their vulnerable period off-host in this northern location can inform both management strategies and projections of future range expansion which may occur with a changing climate.

Questing by Tick Larvae (Acari: Ixodidae): A Review of the Influences That Affect Off-Host Survival

Questing is a host-seeking behavior in which ticks ascend plants, extend their front legs, and wait poised for a chance to attach to a passing host. Hard ticks are ectoparasites of terrestrial vertebrates and because some species vector disease, they are among the most medically important of arthropod pests. All ixodid ticks require blood to survive and reproduce with the number of blood-hosts needed to complete their life cycle varying among species. The vast majority are three-host ticks requiring a different host for each developmental stage: larva, nymph, and adult. A few, including some of the most economically important species, are one-host ticks, that quest only in the larval stage. Questing is a rate-limiting behavior critical to tick survival and disease transmission. For the off-host larval stage, survival is highly dependent on ecological and physiological factors. Yet, off-host larval ecophysiology is often overlooked for the more obvious adult and nymphal tick-host interactions. This review summarizes the literature on ixodid larval questing with emphasis on how specific biotic and abiotic factors affect off-host survival.

Parasites of an Arctic scavenger; the wolverine (Gulo gulo)

Parasites are fundamental components within all ecosystems, shaping interaction webs, host population dynamics and behaviour. Despite this, baseline data is lacking to understand the parasite ecology of many Arctic species, including the wolverine (Gulogulo), a top Arctic predator and scavenger. Here, we combined traditional count methods (i.e. adult helminth recovery, where taxonomy was confirmed by molecular identification) with 18S rRNA high-throughput sequencing to document the wolverine parasite community. Further, we investigated whether the abundance of parasites detected using traditional methods were associated with host metadata, latitude, and longitude (ranging from the northern limit of the boreal forest to the low Arctic and Arctic tundra in Nunavut, Canada). Adult parasites in intestinal contents were identified as Baylisascaris devosi in 72% (n = 39) of wolverines and Taenia spp. in 22% (n = 12), of which specimens from 2 wolverines were identified as T. twitchelli based on COX1 sequence. 18S rRNA high-throughput sequencing on DNA extracted from faeces detected additional parasites, including a pseudophyllid cestode (Diplogonoporus spp. or Diphyllobothrium spp.), two metastrongyloid lungworms (Angiostrongylus spp. or Aelurostrongylus spp., and Crenosoma spp.), an ascarid nematode (Ascaris spp. or Toxocara spp.), a Trichinella spp. nematode, and the protozoan Sarcocystis spp., though each at a prevalence less than 13% (n = 7). The abundance of B. devosi significantly decreased with latitude (slope = -0.68; R² = 0.17; P = 0.004), suggesting a northerly limit in distribution. We describe B. devosi and T. twitchelli in Canadian wolverines for the first time since 1978, and extend the recorded geographic distribution of these parasites ca 2000 km to the East and into the tundra ecosystem. Our findings illustrate the value of molecular methods in support of traditional methods, encouraging additional work to improve the advancement of molecular screening for parasites.

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Combining traditional and molecular methods better captures parasite diversity.

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B. devosi and Taenia spp. distribution extends ca 2000 km East and into the tundra.

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The abundance of B. devosi in wolverines significantly decreases with latitude.

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B. devosi and Taenia spp. abundance is not associated with wolverine host metadata.

Range expansion of muskox lungworms track rapid arctic warming: implications for geographic colonization under climate forcing

Rapid climate warming in the Arctic results in multifaceted disruption of biodiversity, faunal structure, and ecosystem health. Hypotheses have linked range expansion and emergence of parasites and diseases to accelerating warming globally but empirical studies demonstrating causality are rare. Using historical data and recent surveys as baselines, we explored climatological drivers for Arctic warming as determinants of range expansion for two temperature-dependent lungworms, Umingmakstrongylus pallikuukensis and Varestrongylus eleguneniensis, of muskoxen (Ovibos moschatus) and caribou (Rangifer tarandus), in the Canadian Arctic Archipelago from 1980 through 2017. Our field data shows a substantial northward shift of the northern edge of the range for both parasites and increased abundance across the expanded ranges during the last decade. Mechanistic models parameterized with parasites’ thermal requirements demonstrated that geographical colonization tracked spatial expansion of permissive environments, with a temporal lag. Subtle differences in life histories, thermal requirements of closely related parasites, climate oscillations and shifting thermal balances across environments influence faunal assembly and biodiversity. Our findings support that persistence of host-parasite assemblages reflects capacities of parasites to utilize host and environmental resources in an ecological arena of fluctuating opportunity (alternating trends in exploration and exploitation) driving shifting boundaries for distribution across spatial and temporal scales.

Parasite intensity drives fetal development and sex allocation in a wild ungulate

An understanding of the mechanisms influencing prenatal characteristics is fundamental to comprehend the role of ecological and evolutionary processes behind survival and reproductive success in animals. Although the negative influence of parasites on host fitness is undisputable, we know very little about how parasitic infection in reproductive females might influence prenatal factors such as fetal development and sex allocation. Using an archival collection of Dall’s sheep (Ovis dalli dalli), a capital breeder that depends on its body reserves to overcome the arctic winter, we investigated the direct and indirect impacts of the parasite community on fetal development and sex allocation. Using partial least squares modelling, we observed a negative effect of parasite community on fetal development, driven primarily by the nematode Marshallagia marshalli. Principal component analysis demonstrated that mothers with low parasite burden and in good body condition were more likely to have female versus male fetuses. This association was primarily driven by the indirect effect of M. marshalli on ewe body condition. Refining our knowledge of the direct and indirect impact that parasite communities can have on reproduction in mammals is critical for understanding the effects of infectious diseases on wildlife populations. This can be particularly relevant for species living in ecosystems sensitive to the effects of global climate change.

Adaptations, life-history traits and ecological mechanisms of parasites to survive extremes and environmental unpredictability in the face of climate change

Climate change is increasing weather unpredictability, causing more intense, frequent and longer extreme events including droughts, precipitation, and both heat and cold waves. The performance of parasites, and host-parasite interactions, under these unpredictable conditions, are directly influenced by the ability of parasites to cope with extremes and their capacity to adapt to the new conditions. Here, we review some of the structural, behavioural, life history and ecological characteristics of parasitic nematodes that allow them to persist and adapt to extreme and changing environmental conditions. We focus primarily, but not exclusively, on parasitic nematodes in the Arctic, where temperature extremes are pronounced, climate change is happening most rapidly, and changes in host-parasite interactions are already documented. We discuss how life-history traits, phenotypic plasticity, local adaptation and evolutionary history can influence the short and long term response of parasites to new conditions. A detailed understanding of the complex ecological processes involved in the survival of parasites in extreme and changing conditions is a fundamental step to anticipate the impact of climate change in parasite dynamics.

Adult survival in migratory caribou is negatively associated with MHC functional diversity

Genes of the major histocompatibility complex (MHC) are involved in acquired immunity in vertebrates. Only a few studies have investigated the fitness consequences of MHC gene diversity in wild populations. Here, we looked at the association between annual survival and body mass and MHC-DRB exon 2 (MHC-DRB) genetic diversity, obtained from high-throughput sequencing, in two declining migratory caribou (Rangifer tarandus) herds. To disentangle the potential direct and general effects of MHC-DRB genetic diversity, we compared different indices of diversity that were either based on DNA-sequence variation or on physicochemical divergence of the translated peptides, thereby covering a gradient of allelic-to-functional diversity. We found that (1) body mass was not related to MHC-DRB diversity or genotype, and (2) adult survival probability was negatively associated with point accepted mutation distance, a corrected distance that considers the likelihood of each amino acid substitution to be accepted by natural selection. In addition, we found no evidence of fluctuating selection over time on MHC-DRB diversity. We concluded that direct effects were involved in the negative relationship between MHC functional diversity and survival, although the mechanism underlying this result remains unclear. A possible explanation could be that individuals with higher MHC diversity suffer higher costs of immunity (immunopathology). Our results suggest that genetic diversity is not always beneficial even in genes that are likely to be strongly shaped by balancing selection.

Infection with brainworm (Elaphostrongylus rangiferi) in reindeer (Rangifer tarandus ssp.) in Fennoscandia

Sami reindeer herders have considerable traditional knowledge about a neurological reindeer disease resembling elaphostrongylosis, but the causative agent was not identified prior to the description of the brainworm Elaphostrongylus rangiferi in Russia in 1958. Elaphostrongylosis was quickly recognised as a serious cause of reindeer morbidity and mortality. The ecology, epidemiology and pathophysiology of the disease were studied in Sweden and Norway during the 1960s and in particular the 1970s to 1990s. In Finland, elaphostrongylosis was not recognised as an important disease for Finnish reindeer husbandry, even though the presence of brainworm infection has been documented. Brainworm has an indirect lifecycle with snail and slug intermediate hosts. The free-living L1 larvae have extremely good freeze tolerance and can survive > 360 days at − 80 °C in water (solid ice). Even though reindeer brainworm is clearly well adapted to the Arctic chill, the lifecycle stages outside the reindeer final host are sped up at warmer environmental temperatures. Arctic summer temperatures are close to the developmental threshold of the parasite in the intermediate gastropod hosts (8–10 °C), and the parasite has typically had a 2-year life cycle. Disease outbreaks generally occur during the winter following the infection of reindeer with infected snails and slugs during the summer and autumn. Warmer summers result in faster development of brainworm larvae in the intermediate hosts. Clinical symptoms have been seen reported as early as August, such as in the outbreak in Trøndelag, Norway in 2018. The reindeer brainworm is also a cause of conflict between reindeer herders and small ruminant farmers, because it can cause severe disease in goats and sheep, which share pasture with reindeer. Many knowledge gaps remain if we wish to successfully predict and mitigate for large-scale outbreaks in a future with a predicted warmer, wetter and wilder climate.

Reduced immune responsiveness contributes to winter energy conservation in an Arctic bird

Animals in seasonal environments must prudently manage energy expenditure to survive the winter. This may be achieved through reductions in the allocation of energy for various purposes (e.g. thermoregulation, locomotion, etc.). We studied whether such trade-offs also include suppression of the innate immune response, by subjecting captive male Svalbard ptarmigan (Lagopus muta hyperborea) to bacterial lipopolysaccharide (LPS) during exposure to either mild temperature (0°C) or cold snaps (acute exposure to −20°C), in constant winter darkness when birds were in energy-conserving mode, and in constant daylight in spring. The innate immune response was mostly unaffected by temperature. However, energy expenditure was below baseline when birds were immune challenged in winter, but significantly above baseline in spring. This suggests that the energetic component of the innate immune response was reduced in winter, possibly contributing to energy conservation. Immunological parameters decreased (agglutination, lysis, bacteriostatic capacity) or did not change (haptoglobin/PIT54) after the challenge, and behavioural modifications (anorexia, mass loss) were lengthy (9 days). While we did not study the mechanisms explaining these weak, or slow, responses, it is tempting to speculate they may reflect the consequences of having evolved in an environment where pathogen transmission rate is presumably low for most of the year. This is an important consideration if climate change and increased exploitation of the Arctic would alter pathogen communities at a pace outwith counter-adaption in wildlife.

The biogeography of the caribou lungworm, Varestrongylus eleguneniensis (Nematoda: Protostrongylidae) across northern North America

Varestrongylus eleguneniensis (Nematoda; Protostrongylidae) is a recently described species of lungworm that infects caribou (Rangifer tarandus), muskoxen (Ovibos moschatus) and moose (Alces americanus) across northern North America. Herein we explore the geographic distribution of V. eleguneniensis through geographically extensive sampling and discuss the biogeography of this multi-host parasite. We analyzed fecal samples of three caribou subspecies (n = 1485), two muskox subspecies (n = 159), and two moose subspecies (n = 264) from across northern North America. Protostrongylid dorsal-spined larvae (DSL) were found in 23.8%, 73.6%, and 4.2% of these ungulates, respectively. A portion of recovered DSL were identified by genetic analyses of the ITS-2 region of the nuclear rDNA or the cytochrome oxidase c subunit I (COI) region of the mtDNA. We found V. eleguneniensis widely distributed among caribou and muskox populations across most of their geographic prange in North America but it was rare in moose. Parelaphostrongylus andersoni was present in caribou and moose and we provide new geographic records for this species. This study provides a substantial expansion of the knowledge defining the current distribution and biogeography of protostrongylid nematodes in northern ungulates. Insights about the host and geographic range of V. eleguneniensis can serve as a geographically extensive baseline for monitoring current distribution and in anticipating future biogeographic scenarios under a regime of accelerating climate and anthropogenic perturbation.

Diagnosing bovine parafilariosis: utility of the cytochrome c oxidase subunit 1 gene and internal transcribed spacer region for PCR detection of Parafilaria bovicola in skin biopsies and serohemorrhagic exudates of cattle

Background

Parafilaria bovicola (Nematoda: Filariidae) causes cutaneous bleedings in bovine species. Flies serve as intermediate hosts. In recent years, reports on bovine parafilariosis have become more frequent, corroborating the necessity of reliable diagnostic interventions especially since no molecular or serological test has been available. We aimed to establish a polymerase chain reaction assay to detect DNA of P. bovicola in flies, skin biopsies and serohemorraghic exudates of bleeding spots.

Methods

PCRs targeting the cytochrome c oxidase subunit 1 (cox1) gene and the internal transcribed spacer region (ITS) of the ribosomal RNA gene cluster were evaluated for their diagnostic sensitivity as well as performance and specificity on biopsy and serohemorrhagic exudate samples from P. bovicola-infected cattle.

Results

Using serohemorrhagic exudates (n = 6), biopsies (n = 2) and flies (n = 1), the PCR targeting the cox1 gene resulted in a gel band of almost 700 bp. Cloning, sequencing, and removal of primer sequences yielded a 649-bp fragment of the P. bovicola cox1 gene. The PCR targeting the ITS region showed a band of about 1100 bp. Cloning, sequencing, and removal of primer sequences resulted in a 1083 bp stretch of the P. bovicola ITS region. Testing samples from presumably affected animals, the cox1-PCR resulted in bands with the expected size and they were all confirmed as P. bovicola by sequencing. In contrast, the ITS-PCR proved to be less sensitive and less specific and additionally amplified the ITS region of Musca domestica or buttercup DNA. When analysing for sensitivity, the cox1-PCR yielded visible bands up to 2 ng of genomic DNA, whereas the ITS-PCR produced bands up to 3 ng. In a plasmid dilution series, the minimum number of target DNA copies was 10² for the cox1-PCR and 10¹ in the ITS-PCR.

Conclusions

The evaluated cox1-PCR enables reliable detection of P. bovicola DNA in skin biopsies and serohemorrhagic exudates. This PCR and, to a limited extent, the ITS-PCR, may help evaluate different therapeutic approaches. Furthermore, the cox1-PCR may be useful for epidemiological studies on the geographical distribution of P. bovicola. Further understanding of the epidemiology of this parasite will help develop and implement effective control strategies.

Already at the bottom? Demographic declines are unlikely further to undermine genetic diversity of a large Arctic ungulate: muskox, Ovibos moschatus (Artiodactyla: Bovidae)

Low genetic diversity is associated with low fitness and evolutionary potential, yet the demographic and life-history traits of some species contribute to low genetic diversity, without empirical evidence of negative impacts on fitness. Modelling past and future trajectories of genetic diversity under different demographic scenarios can provide insight into how genetic variation might impact population fitness. The muskox is an Arctic species that has undergone multiple population bottlenecks and, although populations have rebounded repeatedly, two large populations have recently declined by &gt; 50%. It is unclear how these demographic patterns influence muskox genetic diversity and fitness. We compared the genetic diversity of Canadian muskox populations undergoing opposing population trends. Genotyping 84 mainland and 244 Victoria Island individuals at ten microsatellite loci revealed low genetic variation (Victoria Island, mean allelic richness 1.66, expected heterozygosity 0.16; mainland, mean allelic richness 2.58, expected heterozygosity 0.41), with no evidence of further reductions in diversity subsequent to recent demographic declines. Bayesian modelling showed that a 1900s bottleneck contributed to the lack of diversity in contemporary populations, and forward-in-time simulations suggested little effect on genetic diversity over the next 100 years. Muskoxen might have reached a genetic diversity minimum, and additional research will be needed to determine their capacity to adapt to rapid changes in selective pressures in a rapidly changing Arctic.

Multi-pathogen serological survey of migratory caribou herds: A snapshot in time

Pathogens can impact host survival, fecundity, and population dynamics even when no obvious disease is observed. Few baseline data on pathogen prevalence and diversity of caribou are available, which hampers our ability to track changes over time and evaluate impacts on caribou health. Archived blood samples collected from ten migratory caribou herds in Canada and two in Greenland were used to test for exposure to pathogens that have the potential to effect population productivity, are zoonotic or are emerging. Relationships between seroprevalence and individual, population, and other health parameters were also examined. For adult caribou, the highest overall seroprevalence was for alphaherpesvirus (49%, n = 722), pestivirus (49%, n = 572) and Neospora caninum (27%, n = 452). Lower seroprevalence was found for parainfluenza virus type 3 (9%, n = 708), Brucella suis (2%, n = 758), and Toxoplasma gondii (2%, n = 706). No animal tested positive for antibodies against West Nile virus (n = 418) or bovine respiratory syncytial virus (n = 417). This extensive multi-pathogen survey of migratory caribou herds provides evidence that caribou are exposed to pathogens that may have impacts on herd health and revealed potential interactions between pathogens as well as geographical differences in pathogen exposure that could be linked to the bio-geographical history of caribou. Caribou are a keystone species and the socio-economic cornerstone of many indigenous cultures across the North. The results from this study highlight the urgent need for a better understanding of pathogen diversity and the impact of pathogens on caribou health.

Prevalence and genetic characterization of Giardia spp. and Cryptosporidium spp. in dogs in Iqaluit, Nunavut, Canada

There are few epidemiologic studies on the role of dogs in zoonotic parasitic transmission in the Circumpolar North. The objectives of this study were to: (a) estimate the faecal prevalence of Giardia spp. and Cryptosporidium spp. in dogs; (b) investigate potential associations between the type of dog population and the faecal presence of Giardia spp. and Cryptosporidium spp.; and (c) describe the molecular characteristics of Giardia spp. and Cryptosporidium spp. in dogs in Iqaluit, Nunavut. We conducted two cross-sectional studies in July and September 2016. In July, the team collected daily faecal samples for 3 days from each of 20 sled dogs. In September, the team collected three faecal samples from each of 59 sled dogs, 111 samples from shelter dogs and 104 from community dogs. We analysed faecal samples for the presence of Giardia spp. and Cryptosporidium spp. using rapid immunoassay and flotation techniques. Polymerase chain reaction (PCR) and sequencing of target genes were performed on positive faecal samples. Overall, the faecal prevalence of at least one of the target parasites, when one faecal sample was chosen at random for all dogs, was 8.16% (CI: 5.52-11.92), and for Giardia spp. and Cryptosporidium spp., prevalence was 4.42% (CI: 2.58-7.49) and 6.12% (CI: 3.88-9.53), respectively. The odds of faecal Giardia spp. in sled dogs were significantly higher than those in shelter and community dogs (OR 10.19 [CI: 1.16-89.35]). Sequence analysis revealed that 6 faecal samples were Giardia intestinalis, zoonotic assemblage B (n = 2) and species-specific assemblages D (n = 3) and E (n = 1), and five faecal samples were Cryptosporidium canis. Giardia intestinalis is zoonotic; however, Cryptosporidium canis is rare in humans and, when present, usually occurs in immunosuppressed individuals. Dogs may be a potential source of zoonotic Giardia intestinalis assemblage B infections in residents in Iqaluit, Nunavut, Canada; however, the direction of transmission is unclear.

Parasites of seabirds: A survey of effects and ecological implications

Parasites are ubiquitous in the environment, and can cause negative effects in their host species. Importantly, seabirds can be long-lived and cross multiple continents within a single annual cycle, thus their exposure to parasites may be greater than other taxa. With changing climatic conditions expected to influence parasite distribution and abundance, understanding current level of infection, transmission pathways and population-level impacts are integral aspects for predicting ecosystem changes, and how climate change will affect seabird species. In particular, a range of micro- and macro-parasites can affect seabird species, including ticks, mites, helminths, viruses and bacteria in gulls, terns, skimmers, skuas, auks and selected phalaropes (Charadriiformes), tropicbirds (Phaethontiformes), penguins (Sphenisciformes), tubenoses (Procellariiformes), cormorants, frigatebirds, boobies, gannets (Suliformes), and pelicans (Pelecaniformes) and marine seaducks and loons (Anseriformes and Gaviiformes). We found that the seabird orders of Charadriiformes and Procellariiformes were most represented in the parasite-seabird literature. While negative effects were reported in seabirds associated with all the parasite groups, most effects have been studied in adults with less information known about how parasites may affect chicks and fledglings. We found studies most often reported on negative effects in seabird hosts during the breeding season, although this is also the time when most seabird research occurs. Many studies report that external factors such as condition of the host, pollution, and environmental conditions can influence the effects of parasites, thus cumulative effects likely play a large role in how parasites influence seabirds at both the individual and population level. With an increased understanding of parasite-host dynamics it is clear that major environmental changes, often those associated with human activities, can directly or indirectly affect the distribution, abundance, or virulence of parasites and pathogens.

Besnoitia tarandi in Canadian woodland caribou - Isolation, characterization and suitability for serological tests

In the present study, we report the first in vitro isolation of Besnoitia tarandi from North America and the second of B. tarandi at all. The parasite was isolated directly from the skin of a Canadian woodland caribou from the migratory ecotype. The animal belonged to the Leaf River Herd, in Northern Quebec, Canada. The isolate was designated Bt-CA-Quebec1. Sequencing of the 3'-end of the 18S rRNA gene, the complete sequence of the ITS1 and the 5'-end of the 5.8S rRNA gene of Bt-CA-Quebec1 revealed only minor differences to rDNA gene fragments of B. besnoiti. In contrast, the patterns for the microsatellite loci Bt-20 and Bt-21 varied substantially from those reported for B. besnoiti and B. bennetti. Surprisingly, the typing results in the loci Bt-6 and Bt-7 differed between Bt-CA-Quebec1 and results obtained for skin samples from caribou of the Canadian regions of Nunavut and the Northwest Territories reported by other investigators. This indicates that differences might exist among B. tarandi in caribou from different regions in Canada. Mice (γ-interferon knockout) intraperitoneally inoculated with 1.2 × 106 or 1.5 × 106 bradyzoites mechanically released from skin tissue cysts fell ill 8, 9 or 18 days post inoculation. GKO mice inoculated with 3.0 × 104 tachyzoites isolated from the peritoneal cavity of a bradyzoites-inoculated mouse became ill earlier, i.e. 5 days post inoculation. Lung was the predilection site in all mice. Bt-CA-Quebec1 tachyzoites rapidly grew in MARC-145 cells and were used for antigen production. Comparative Western blot analyses revealed only a few differences between B. tarandi Bt-CA-Quebec1 and B. besnoiti Evora antigen when probed with sera collected from chronically infected caribou. Due to its fast growth in vitro, the Bt-CA-Quebec1 isolate may represent an interesting antigen source to establish B. tarandi-specific serological tools and to study the biology of this parasite species further.

Rodent population cycle as a determinant of gastrointestinal nematode abundance in a low-arctic population of the red fox

We analyzed an 11-year time series (2005-2015) of parasite abundance for three intestinal nematode species in the red fox (Vulpes vulpes) as a function of the multi-annual rodent population cycle in low-arctic Norway, while correcting for other potential covariates that could influence prevalence and abundance. Rodents are paratenic and facultative intermediate hosts for the two Ascarididae species Toxascaris leonina and Toxocara canis, respectively and key prey for the red fox. Still the relative importance of indirect transmission through rodents and direct transmission through free-living stages is unclear. Abundance of these Ascarididae species in individual red foxes (N = 612) exhibited strongly cyclic dynamics that closely mirrored the 4-year rodent cycle. Negative binomial models provided evidence for a direct proportional increase in Ascarididae abundance with rodent density suggesting that predator functional response to rodent prey is the key transmission mechanism. In contrast, no cycles and constantly very low abundance were apparent for Uncinaria stenocephala - a third nematode species recorded without paratenic or intermediate stages.

HEALTH SURVEY OF BOREAL CARIBOU (RANGIFER TARANDUS CARIBOU) IN NORTHEASTERN BRITISH COLUMBIA, CANADA

Boreal woodland caribou (Rangifer tarandus caribou) are listed as threatened across Canada, and a basic understanding of their health status is lacking. From December 2012 to April 2013, we investigated multiple health indices for adult female boreal caribou (n=163) captured from seven herds in NE British Columbia, Canada. Health indices included physical characteristics, physiologic and trace mineral status, exposure to or infection with selected pathogens, and measures of chronic stress and inflammation, including serum amyloid A, haptoglobin, and hair cortisol concentration. Key findings were exposure to the bacterium Erysipelothrix rhusiopathiae in 14% of individuals, mild to severe hair loss associated with winter tick (Dermacentor albipictus) infestations in 76% of caribou from December to early February and 81% from late February to early April, and evidence of trace mineral deficiencies with 99% and 34% of individuals deficient in copper and selenium, respectively. Seroprevalence for exposure to selected pathogens was: alphaherpesvirus (63%), pestivirus (1%), Besnoitia spp. (60%), and Neospora caninum (2%). All animals were seronegative to Brucella spp. and Toxoplasma gondii. Mycobacterium avium ssp. paratuberculosis was not detected in any fecal samples. Parasite eggs or larvae, including Parelaphostrongylus andersoni (36%), Skrjabinema spp. (1%), Strongyle-type eggs (11%), Moniezia-type eggs (8%), and nematodirines (3%), were detected on fecal examination, but at low intensity. Blood biochemistry values and hair cortisol concentrations were within ranges previously reported in Rangifer tarandus sspp. Some significant differences among herds were noted, including antler morphology, exposure to Besnoitia spp., and concentrations of serum amyloid A, copper, cobalt, manganese, and iron.

Impact of recent and future climate change on vector-borne diseases

Climate change is one of the greatest threats to human health in the 21st century. Climate directly impacts health through climatic extremes, air quality, sea-level rise, and multifaceted influences on food production systems and water resources. Climate also affects infectious diseases, which have played a significant role in human history, impacting the rise and fall of civilizations and facilitating the conquest of new territories. Our review highlights significant regional changes in vector and pathogen distribution reported in temperate, peri-Arctic, Arctic, and tropical highland regions during recent decades, changes that have been anticipated by scientists worldwide. Further future changes are likely if we fail to mitigate and adapt to climate change. Many key factors affect the spread and severity of human diseases, including mobility of people, animals, and goods; control measures in place; availability of effective drugs; quality of public health services; human behavior; and political stability and conflicts. With drug and insecticide resistance on the rise, significant funding and research efforts must to be maintained to continue the battle against existing and emerging diseases, particularly those that are vector borne.