First Record of Lyme DiseaseBorreliain the Arctic

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may become a significant problem for these populations, but current observations of parasite presence often lack a historical reference of prior absence.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.

Long-term increases in pathogen seroprevalence in polar bears (Ursus maritimus) influenced by climate change

The influence of climate change on wildlife disease dynamics is a burgeoning conservation and human health issue, but few long-term studies empirically link climate to pathogen prevalence. Polar bears (Ursus maritimus) are vulnerable to the negative impacts of sea ice loss as a result of accelerated Arctic warming. While studies have associated changes in polar bear body condition, reproductive output, survival, and abundance to reductions in sea ice, no long-term studies have documented the impact of climate change on pathogen exposure. We examined 425 serum samples from 381 adult polar bears, collected in western Hudson Bay (WH), Canada, for antibodies to selected pathogens across three time periods: 1986-1989 (n = 157), 1995-1998 (n = 159) and 2015-2017 (n = 109). We ran serological assays for antibodies to seven pathogens: Toxoplasma gondii, Neospora caninum, Trichinella spp., Francisella tularensis, Bordetella bronchiseptica, canine morbillivirus (CDV) and canine parvovirus (CPV). Seroprevalence of zoonotic parasites (T. gondii, Trichinella spp.) and bacterial pathogens (F. tularensis, B. bronchiseptica) increased significantly between 1986-1989 and 1995-1998, ranging from +6.2% to +20.8%, with T. gondii continuing to increase into 2015-2017 (+25.8% overall). Seroprevalence of viral pathogens (CDV, CPV) and N. caninum did not change with time. Toxoplasma gondii seroprevalence was higher following wetter summers, while seroprevalences of Trichinella spp. and B. bronchiseptica were positively correlated with hotter summers. Seroprevalence of antibodies to F. tularensis increased following years polar bears spent more days on land, and polar bears previously captured in human settlements were more likely to be seropositive for Trichinella spp. As the Arctic has warmed due to climate change, zoonotic pathogen exposure in WH polar bears has increased, driven by numerous altered ecosystem pathways.

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.

Evidence for Borrelia bavariensis Infections of Ixodes uriae within Seabird Colonies of the North Atlantic Ocean

The first report of members of the spirochete genus Borrelia in the seabird tick, Ixodes uriae, and seabird colonies occurred during the early 1990s. Since then, Borrelia spp. have been detected in these ticks and seabird colonies around the world. To date, the primary species detected has been Borrelia garinii, with rare occurrences of Borrelia burgdorferi sensu stricto and Borrelia lusitaniae. During our research on Borrelia and I. uriae in seabird colonies of Newfoundland and Labrador, Canada, we have identified Borrelia bavariensis in I. uriae To our knowledge, B. bavariensis has previously been found only in the Eurasian tick species Ixodes persulcatus and Ixodes ricinus, and it was believed to be a rodent-specific Borrelia ecotype. We found B. bavariensis within I. uriae from three seabird colonies over three calendar years. We also reanalyzed B. garinii sequences collected from I. uriae from Eurasian seabird colonies and determined that sequences from two Russian seabird colonies likely also represent B. bavariensis The Canadian B. bavariensis sequences from I. uriae analyzed in this study cluster with previously described sequences from Asia. Overall, this is an important discovery that illustrates and expands the range of hosts and vectors for B. bavariensis, and it raises questions regarding the possible mechanisms of pathogen dispersal from Asia to North America.IMPORTANCE To our knowledge, this is the first documentation of B. bavariensis outside Eurasia. Additionally, the bacterium was found in a marine ecosystem involving the seabird tick I. uriae and its associated seabird hosts. This indicates that the epizootiology of B. bavariensis transmission is much different from what had been described, with this species previously believed to be a rodent-specific ecotype, and it indicates that this pathogen is established, or establishing, much more widely.

In a warmer Arctic, mosquitoes avoid increased mortality from predators by growing faster

Climate change is altering environmental temperature, a factor that influences ectothermic organisms by controlling rates of physiological processes. Demographic effects of warming, however, are determined by the expression of these physiological effects through predator-prey and other species interactions. Using field observations and controlled experiments, we measured how increasing temperatures in the Arctic affected development rates and mortality rates (from predation) of immature Arctic mosquitoes in western Greenland. We then developed and parametrized a demographic model to evaluate how temperature affects survival of mosquitoes from the immature to the adult stage. Our studies showed that warming increased development rate of immature mosquitoes (Q10 = 2.8) but also increased daily mortality from increased predation rates by a dytiscid beetle (Q10 = 1.2-1.5). Despite increased daily mortality, the model indicated that faster development and fewer days exposed to predators resulted in an increased probability of mosquito survival to the adult stage. Warming also advanced mosquito phenology, bringing mosquitoes into phenological synchrony with caribou. Increases in biting pests will have negative consequences for caribou and their role as a subsistence resource for local communities. Generalizable frameworks that account for multiple effects of temperature are needed to understand how climate change impacts coupled human-natural systems.

The tick Ixodes uriae (Acari: Ixodidae): Hosts, geographical distribution, and vector roles

The seabird tick Ixodes uriae White 1852, has the most extensive geographical distribution of all tick species, including Afrotropical, Australasian, Nearctic, Neotropical and Palearctic Zoogeographic Regions. Additionally, this tick species parasitizes a wide range of seabirds and constitutes a host for several viral and bacterial agents. Considering the current biological knowledge about this tick species, in this article we list localities, hosts, tick-borne microorganisms and viruses transmitted by I. uriae described in the literature and include new geographical records.

Wildlife health in a rapidly changing North: focus on avian disease

Climate-related environmental changes have increasingly been linked to emerging infectious diseases in wildlife. The Arctic is facing a major ecological transition that is expected to substantially affect animal and human health. Changes in phenology or environmental conditions that result from climate warming may promote novel species assemblages as host and pathogen ranges expand to previously unoccupied areas. Recent evidence from the Arctic and subarctic suggests an increase in the spread and prevalence of some wildlife diseases, but baseline data necessary to detect and verify such changes are still lacking. Wild birds are undergoing rapid shifts in distribution and have been implicated in the spread of wildlife and zoonotic diseases. Here, we review evidence of current and projected changes in the abundance and distribution of avian diseases and outline strategies for future research. We discuss relevant climatic and environmental factors, emerging host-pathogen contact zones, the relationship between host condition and immune function, and potential wildlife and human health outcomes in northern regions.

Exploring Diversity among Norwegian Borrelia Strains Originating from Ixodes ricinus Ticks

Characterisation of Borrelia strains from Ixodes ricinus ticks is important in the epidemiological surveillance of vector-borne pathogens. Multilocus sequences analysis (MLSA) is a molecular genotyping tool with high discriminatory power that has been applied in evolutionary studies and for the characterisation of Borrelia genospecies. MLSA was used to study genetic variations in Borrelia strains isolated from I. ricinus ticks collected from the woodlands in Skodje. The results demonstrate that the 50 Borrelia strains were separated into 36 sequence types (STs) that were not previously represented in the MLST database. A distance matrix neighbour-joining tree (bootstrapped 500 iterations) showed four deeply branched clusters, and each deeply branched cluster represented one Borrelia genospecies. The mean pairwise genetic differences confirm the genospecies clustering. The combination of alleles separates the Borrelia strains from northwest Norway from the strains in the MLST database, thus identifying new STs. Although a highly divergent B. afzelii population could be expected, the heterogeneity among the B. garinii strains is more unusual. The present study indicates that the circulation of strains between migrating birds and stationary birds in this coastal region may play a role in the evolution of B. garinii strains.

First detection of Borrelia burgdorferi sensu lato DNA in king penguins (Aptenodytes patagonicus halli)

The hard tick Ixodes uriae parasitises a wide range of seabird species in the circumpolar areas of both Northern and Southern hemispheres and has been shown to be infected with Borrelia burgdorferi sensu lato, the bacterial agents of Lyme borreliosis. Although it is assumed that seabirds represent viable reservoir hosts, direct demonstrations of infection are limited to a single study from the Northern hemisphere. Here, the blood of 50 tick-infested adult king penguins (Aptenodytes patagonicus halli) breeding in the Crozet Archipelago (Southern Indian Ocean) was examined for B. burgdorferi sl exposure by serology and for spirochetemia by in vitro DNA amplification. Four birds were found positive by serology, whereas B. burgdorferi sl DNA was detected in two other birds. Our data therefore provide the first direct proof of Borrelia burgdorferi sl spirochetes in seabirds of the Southern hemisphere and indicate a possible reservoir role for king penguins in the natural maintenance of this bacterium. Although the bacterial genetic diversity present in these hosts and the infectious period for tick vectors remain to be elucidated, our results add to a growing body of knowledge on the contribution of seabirds to the complex epizootiology of Lyme disease and the global dissemination of B. burgdorferi sl spirochetes.

Global ecology and epidemiology of Borrelia garinii spirochetes

Lyme borreliosis (LB) is a tick-transmitted infectious disease caused by Borrelia burgdorferi sensu lato (s. l.). In Europe, three different Borrelia species are the main causative agents of LB: B. burgdorferi sensu stricto (s.s.), Borrelia afzelii, and Borrelia garinii. The latter depends heavily on birds as its main reservoir hosts. In fact, birds can act both as biological carriers of Borrelia and transporters of infected ticks. The seasonal migration of many bird species not only aid in the spread of B. garinii to new foci but also influence the high level of diversity found within this species. B. garinii have been isolated not only from terrestrial birds in Europe, but also from seabirds worldwide, and homology between isolates in these two different infection cycles suggests an overlap and exchange of strains. In addition, it has been shown that birds can maintain and spread B. garinii genotypes associated with LB in humans. This review article discusses the importance of birds in the ecology and epidemiology of B. garinii spirochetes.

Population genetics, taxonomy, phylogeny and evolution of Borrelia burgdorferi sensu lato

In order to understand the population structure and dynamics of bacterial microorganisms, typing systems that accurately reflect the phylogenetic and evolutionary relationship of the agents are required. Over the past 15 years multilocus sequence typing schemes have replaced single locus approaches, giving novel insights into phylogenetic and evolutionary relationships of many bacterial species and facilitating taxonomy. Since 2004, several schemes using multiple loci have been developed to better understand the taxonomy, phylogeny and evolution of Lyme borreliosis spirochetes and in this paper we have reviewed and summarized the progress that has been made for this important group of vector-borne zoonotic bacteria.

Destruction of spirochete Borrelia burgdorferi round-body propagules (RBs) by the antibiotic tigecycline

Persistence of tissue spirochetes of Borrelia burgdorferi as helices and round bodies (RBs) explains many erythema-Lyme disease symptoms. Spirochete RBs (reproductive propagules also called coccoid bodies, globular bodies, spherical bodies, granules, cysts, L-forms, sphaeroplasts, or vesicles) are induced by environmental conditions unfavorable for growth. Viable, they grow, move and reversibly convert into motile helices. Reversible pleiomorphy was recorded in at least six spirochete genera (>12 species). Penicillin solution is one unfavorable condition that induces RBs. This antibiotic that inhibits bacterial cell wall synthesis cures neither the second "Great Imitator" (Lyme borreliosis) nor the first: syphilis. Molecular-microscopic techniques, in principle, can detect in animals (insects, ticks, and mammals, including patients) helices and RBs of live spirochetes. Genome sequences of B. burgdorferi and Treponema pallidum spirochetes show absence of >75% of genes in comparison with their free-living relatives. Irreversible integration of spirochetes at behavioral, metabolic, gene product and genetic levels into animal tissue has been documented. Irreversible integration of spirochetes may severely impair immunological response such that they persist undetected in tissue. We report in vitro inhibition and destruction of B. burgdorferi (helices, RBs = "cysts") by the antibiotic Tigecycline (TG; Wyeth), a glycylcycline protein-synthesis inhibitor (of both 30S and 70S ribosome subunits). Studies of the pleiomorphic life history stages in response to TG of both B. burgdorferi and Treponema pallidum in vivo and in vitro are strongly encouraged.

Lack of resistance against the tick Ixodes ricinus in two related passerine bird species

Although many wild bird species may act as reservoir hosts for tick-transmitted diseases and/or support long-distance dispersal of infected ticks, to date no research has been done on the extent to which songbirds may acquire resistance to ixodid ticks. Here we investigate whether two passerine species belonging to the family Paridae, the blue tit (Cyanistes caeruleus) and the great tit (Parus major), are able to acquire resistance after repeated infestations with Ixodes ricinus nymphs. As blue tits are less frequently exposed to I. ricinus in the wild than great tits, we expected I. ricinus to be less adapted towards the blue tit's resistance mechanisms. Over the three infestation sessions we observed consistently high tick attachment rates and yields, high engorgement weights, and short engorgement and moulting durations, indicating that neither of the two songbird species is able to mount effective immune responses against I. ricinus nymphs after repeated infestations. As a consequence of the lack of resistance, birds were unable to prevent the direct harm (acute blood depletion) caused by tick feeding. Birds compensated the erythrocyte loss without reduction in general body condition (body mass corrected for tarsus length). The lack of resistance suggests that I. ricinus has a long co-evolutionary history with both avian hosts, which enables the tick to avoid or suppress the host's resistance responses.

Complex population structure of Lyme borreliosis group spirochete Borrelia garinii in subarctic Eurasia

Borrelia garinii, a causative agent of Lyme borreliosis in Europe and Asia, is naturally maintained in marine and terrestrial enzootic cycles, which primarily involve birds, including seabirds and migratory passerines. These bird groups associate with, correspondingly, Ixodes uriae and Ixodes ricinus ticks, of which the latter species may bite and transmit the infection to humans. Studies of the overlap between these two natural cycles of B. garinii have been limited, in part due to the absence of representative collections of this spirochete's samples, as well as of the lack of reliable measure of the genetic heterogeneity of its strains. As a prerequisite for understanding the epidemiological correlates of the complex maintenance of B. garinii, the present study sought to assess the diversity and phylogenetic relationships of this species' strains from its natural hosts and patients with Lyme borreliosis from subarctic Eurasia. We used sequence typing of the partial rrs-rrl intergenic spacer (IGS) of archived and prospective samples of B. garinii from I. uriae ticks collected predominantly on Commander Islands in North Pacific, as well as on the islands in northern Sweden and arctic Norway. We also typed B. garinii samples from patients with Lyme borreliosis and I. ricinus ticks infesting migratory birds in southern Sweden, or found questing in selected sites on the islands in the Baltic Sea and Lithuania. Fifty-two (68%) of 77 B. garinii samples representing wide geographical range and associated with I. ricinus and infection of humans contributed 12 (60%) of total 20 identified IGS variants. In contrast, the remaining 25 (32%) samples recovered from I. uriae ticks from a few islands accounted for as many as 10 (50%) IGS types, suggesting greater local diversity of B. garinii maintained by seabirds and their ticks. Two IGS variants of the spirochete in common for both tick species were found in I. ricinus larvae from migratory birds, an indication that B. garinii strains are exchanged between different ecological niches. Notably, B. garinii variants associated with I. uriae ticks were found in each of the six clusters, representing two phylogenetic lineages of this species identified among the studied samples. Our findings suggest that B. garinii in subarctic Eurasia comprises two partially overlapping populations with different levels of genetic heterogeneity, presumably, due to distinctive selective pressures on the spirochete in its marine and terrestrial enzootic cycles.