Serosurvey for Trichinella in polar bears (Ursus maritimus) from Svalbard and the Barents Sea

The geographic distribution, and the biotic and abiotic predictors of select zoonotic pathogen detections in Canadian polar bears

Increasing Arctic temperatures are facilitating the northward expansion of more southerly hosts, vectors, and pathogens, exposing naïve populations to pathogens not typical at northern latitudes. To understand such rapidly changing host-pathogen dynamics, we need sensitive and robust surveillance tools. Here, we use a novel multiplexed magnetic-capture and droplet digital PCR (ddPCR) tool to assess a sentinel Arctic species, the polar bear (Ursus maritimus; n = 68), for the presence of five zoonotic pathogens (Erysipelothrix rhusiopathiae, Francisella tularensis, Mycobacterium tuberculosis complex, Toxoplasma gondii and Trichinella spp.), and observe associations between pathogen presence and biotic and abiotic predictors. We made two novel detections: the first detection of a Mycobacterium tuberculosis complex member in Arctic wildlife and the first of E. rhusiopathiae in a polar bear. We found a prevalence of 37% for E. rhusiopathiae, 16% for F. tularensis, 29% for Mycobacterium tuberculosis complex, 18% for T. gondii, and 75% for Trichinella spp. We also identify associations with bear age (Trichinella spp.), harvest season (F. tularensis and MTBC), and human settlements (E. rhusiopathiae, F. tularensis, MTBC, and Trichinella spp.). We demonstrate that monitoring a sentinel species, the polar bear, could be a powerful tool in disease surveillance and highlight the need to better characterize pathogen distributions and diversity in the Arctic.

A Review of Circumpolar Arctic Marine Mammal Health-A Call to Action in a Time of Rapid Environmental Change

The impacts of climate change on the health of marine mammals are increasingly being recognised. Given the rapid rate of environmental change in the Arctic, the potential ramifications on the health of marine mammals in this region are a particular concern. There are eleven endemic Arctic marine mammal species (AMMs) comprising three cetaceans, seven pinnipeds, and the polar bear (Ursus maritimus). All of these species are dependent on sea ice for survival, particularly those requiring ice for breeding. As air and water temperatures increase, additional species previously non-resident in Arctic waters are extending their ranges northward, leading to greater species overlaps and a concomitant increased risk of disease transmission. In this study, we review the literature documenting disease presence in Arctic marine mammals to understand the current causes of morbidity and mortality in these species and forecast future disease issues. Our review highlights potential pathogen occurrence in a changing Arctic environment, discussing surveillance methods for 35 specific pathogens, identifying risk factors associated with these diseases, as well as making recommendations for future monitoring for emerging pathogens. Several of the pathogens discussed have the potential to cause unusual mortality events in AMMs. Brucella, morbillivirus, influenza A virus, and Toxoplasma gondii are all of concern, particularly with the relative naivety of the immune systems of endemic Arctic species. There is a clear need for increased surveillance to understand baseline disease levels and address the gravity of the predicted impacts of climate change on marine mammal species.

Epidemiology of Trichinella in the Arctic and subarctic: A review

The finding of Trichinella in the Arctic was foreseen because captive polar bears and arctic foxes had been found infected during the first decades of the 20th century. Human trichinellosis outbreaks were reported to have taken place in 1944 in Franz Josef Archipelago and 1947 in Greenland, and previous outbreaks in Greenland also appeared to have been trichinellosis. Now, it is known that Trichinella parasites thrive in the Arctic and subarctic and pose a risk for public health. We collated the available information, which show that infection prevalences are high in many animal host species, and that outbreaks of human trichinellosis have been described also recently. The species diversity of Trichinella in the Arctic and subarctic is relatively high, and the circulation is in non-domestic cycles with transmission by predation, scavenging and cannibalism. There are also sporadic reports on the synanthropic species Trichinella spiralis in arctic wild mammals with little known or assumed contact to potential synanthropic cycles. In this paper, we summarize the knowledge on epidemiology of Trichinella parasites in the circumpolar Arctic and subarctic regions, and discuss the challenges and solutions for their control.

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Trichinella infection is common in wild animals in the Arctic and subarctic regions.

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The high prevalence of Trichinella infection in some arctic marine mammal species suggests a marine cycle.

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Outbreaks of human trichinellosis have been described, and public health importance still remains obvious.

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In this review, we had access to the large amount of Trichinella literature published in the Russian language.

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.

Zoonoses and potential zoonoses of bears

Captive and free-ranging wild bears can carry and transmit several zoonotic pathogens. A review of nearly 90 years of scientific publications concerning confirmed and potential zoonotic diseases that can be present in any of the eight species of bears in the world was conducted. The findings were organized amongst the following disease sections: bacterial, viral, protozoal, mycotic, helminth and arthropod-borne. The most commonly reported pathogens of concern were of parasitic (Trichinella, Toxoplasma) and bacterial (Francisella, Brucella) origin.

International Commission on Trichinellosis: Recommendations on the use of serological tests for the detection of Trichinella infection in animals and humans

Serological methods are widely used for detection of infections in animals and humans. The recommendations provided here take into account the best current methods for the serological detection of Trichinella infection. They are based on current scientific information including unpublished data from laboratories with relevant expertise in this field. These recommendations represent the official position of the International Commission on Trichinellosis (ICT) regarding acceptable methods for the use and interpretation of serology testing for Trichinella infection in animals and humans.

The ICT does not recommend use of serological methods for testing individual carcasses of animals at slaughter for assuring food safety. For detection of human infections, for epidemiological studies in animals and humans, and for monitoring Trichinella infection in swine, the ICT recommends ELISA using excretory/secretory (ES) antigens. These antigens are obtained from the in-vitro maintenance of Trichinella spiralis muscle larvae and are recognized by sera from hosts infected by all Trichinella species and genotypes identified thus far. In most situations, positive results obtained by ELISA should be confirmed by western blot. Serological assays should be properly standardized and validated for their intended purpose. The components of the test that are critical for maintaining suitable performance should be identified and appropriately checked. Users of commercial tests should verify that the test has been adequately evaluated by an independent body. Serology is useful for detecting Trichinella in animals and humans but its limitations need to be taken into account when interpreting the results.

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Trichinella serology is not recommended for testing individual animals to assure food safety.

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Serological assays should be standardized and validated for their intended purpose.

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ELISA using excretory/secretory antigens is the test recommended by the ICT.

The epidemiology of trichinellosis in the Arctic territories of a Far Eastern District of the Russian Federation

Trichinellosis, a zoonotic disease caused by nematodes of the genus Trichinella, is still a public health concern in the Arctic. The aims of this study were to investigate the seroprevalence of anti-Trichinella IgG in aboriginal peoples of two settlements in the Chukotka Autonomous Okrug (Russian Federation) on the Arctic coast of the Bering Sea, and to evaluate the survival of Trichinella nativa larvae in local fermented and frozen meat products. A seroprevalence of 24.3% was detected in 259 people tested by an enzyme-linked immunosorbent assay (ELISA). The highest prevalence was detected among people who consumed traditional local foods made from the meat of marine mammals. Trichinella nativa larvae were found to survive for up to 24 months in a fermented and frozen marine mammal meat product called kopalkhen. Since the T. nativa life cycle can be completed in the absence of humans, it can be expected to persist in the environment and therefore remain a cause of morbidity in the human populations living in Arctic regions.

Trichinella and polar bears: a limited risk for humans

In this review, we identified 63 cases reported since World War II of human trichinellosis linked to the consumption of parasitized polar bear (Ursus maritimus) meat. This low number contrasts to the numerous cases of human trichinellosis related to consumption of the meat of black (U. americanus) or brown bears (U. arctos). The prevalence of Trichinella infection is high in bears, but larval muscular burden is usually lower in polar bears compared to other bear species. Polar bears, therefore, seem to play a limited role in the transmission of trichinellosis to humans, as native residents living in the Arctic traditionally consume well-cooked bear meat, and travellers and foreign hunters have only limited access to this protected species due to the declining polar bear population.

ANTIDOG IgG SECONDARY ANTIBODY SUCCESSFULLY DETECTS IgG IN A VARIETY OF AQUATIC MAMMALS

Serological tests play an important role in the detection of wildlife diseases. However, while there are many commercial assays and reagents available for domestic species, there is a need to develop efficient serological assays for wildlife. In recent years, marine mammals have represented a wildlife group with emerging infectious diseases, such as influenza, brucellosis, and leptospirosis. However, with the exception of disease-agent-specific assays or functional assays, few reports describe the use of antibody detection assays in marine mammals. In an indirect enzyme-linked immunoassay (EIA) or an immunofluorescence assay, antibody is detected using an antitarget species secondary conjugated antibody. The sensitivity of the assay depends on the avidity of the binding reaction between the bound antibody and the detection antibody. A commercial polyclonal antidog IgG conjugated antibody was tested in an EIA for its ability to sensitively detect the IgG of seven marine mammals including sea otter ( Enhydra lutris ), polar bear ( Ursus maritimus ), grey seal ( Halichoerus grypus ), harbor seal ( Phoca vitulina ), northern elephant seal ( Mirounga angustirostris ), California sea lion ( Zalophus californianus ), Pacific walrus ( Odobenus rosmarus ) and one freshwater mammal: Asian small-clawed otter ( Aonyx cinerea ). With the exception of Asian small-clawed sea otters, the detection of IgG in these marine mammals either exceeded or was nearly equal to detection of dog IgG. The use of the tested commercial antidog IgG antibody may be a valid approach to the detection of antibody response to disease in sea mammals.

A Review of Infectious Agents in Polar Bears (Ursus maritimus) and Their Long-Term Ecological Relevance

Disease was a listing criterion for the polar bear (Ursus maritimus) as threatened under the Endangered Species Act in 2008; it is therefore important to evaluate the current state of knowledge and identify any information gaps pertaining to diseases in polar bears. We conducted a systematic literature review focused on infectious agents and associated health impacts identified in polar bears. Overall, the majority of reports in free-ranging bears concerned serosurveys or fecal examinations with little to no information on associated health effects. In contrast, most reports documenting illness or pathology referenced captive animals and diseases caused by etiologic agents not representative of exposure opportunities in wild bears. As such, most of the available infectious disease literature has limited utility as a basis for development of future health assessment and management plans. Given that ecological change is a considerable risk facing polar bear populations, future work should focus on cumulative effects of multiple stressors that could impact polar bear population dynamics.

Serological signature of tick-borne pathogens in Scandinavian brown bears over two decades

BACKGROUND

Anthropogenic disturbances are changing the geographic distribution of ticks and tick-borne diseases. Over the last few decades, the tick Ixodes ricinus has expanded its range and abundance considerably in northern Europe. Concurrently, the incidence of tick-borne diseases, such as Lyme borreliosis and tick-borne encephalitis, has increased in the human populations of the Scandinavian countries.

METHODS

Wildlife populations can serve as sentinels for changes in the distribution of tick-borne diseases. We used serum samples from a long-term study on the Scandinavian brown bear, Ursus arctos, and standard immunological methods to test whether exposure to Borrelia burgdorferi sensu lato, the causative agent of Lyme borreliosis, and tick-borne encephalitis virus (TBEV) had increased over time. Bears had been sampled over a period of 18 years (1995-2012) from a southern area, where Ixodes ricinus ticks are present, and a northern area where ticks are uncommon or absent.

RESULTS

Bears had high levels of IgG antibodies against B. burgdorferi sensu lato but not TBEV. Bears at the southern area had higher values of anti-Borrelia IgG antibodies than bears at the northern area. Over the duration of the study, the value of anti-Borrelia IgG antibodies increased in the southern area but not the northern area. Anti-Borrelia IgG antibodies increased with the age of the bear but declined in the oldest age classes.

CONCLUSIONS

Our study is consistent with the view that ticks and tick-borne pathogens are expanding their abundance and prevalence in Scandinavia. Long-term serological monitoring of large mammals can provide insight into how anthropogenic disturbances are changing the distribution of ticks and tick-borne diseases.

Advancing nematode barcoding: a primer cocktail for the cytochrome c oxidase subunit I gene from vertebrate parasitic nematodes

Although nematodes are one of the most diverse metazoan phyla, species identification through morphology is difficult. Several genetic markers have been used for their identification, but most do not provide species-level resolution in all groups, and those that do lack primer sets effective across the phylum, precluding high-throughput processing. This study describes a cocktail of three novel primer pairs that overcome this limitation by recovering cytochrome c oxidase I (COI) barcodes from diverse nematode lineages parasitic on vertebrates, including members of three orders and eight families. Its effectiveness across a broad range of nematodes enables high-throughput processing.