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

Necropsy findings, meat control pathology and causes of loss in semi-domesticated reindeer (Rangifer tarandus tarandus) in northern Norway

BACKGROUND

Reindeer herding in Norway is based on traditional Sámi pastoralism with the animals free ranging throughout the year. The animals move over large areas in varying terrain and often in challenging weather conditions. Winter crises, such as difficult grazing conditions caused by icing or large amounts of snow, are survival bottlenecks for reindeer. Calves are especially vulnerable, and many may die from starvation during winter crises. Predation and starvation are the predominant narratives to explain losses, however, carcasses are difficult to find and often little remains after scavenging and decay. Documentation of the causes of death is therefore scarce.

RESULTS

In this study, we investigated the cause of reindeer mortality in Troms and Finnmark, Nordland and Trøndelag during 2017-2019. Necropsies (n = 125) and organ investigation (n = 13) were performed to document cause of death. Body condition was evaluated using visual fat score and bone marrow fat index. A wide range of causes of death was detected. The diagnoses were categorized into the following main categories: predation (n = 40), emaciation (n = 35), infectious disease (n = 20), trauma (n = 11), feeding related disease (n = 5), neoplasia (n = 4), others (n = 6) and unknown (n = 17). Co-morbidities were seen in a number of diagnoses (n = 16). Reindeer herders are entitled to economic compensation for reindeer killed by endangered predators, but a lack of documentation leads to a gap between the amount of compensation requested and what is awarded. An important finding of our study was that predators, during winter, killed animals in good as well as poor body condition. Emaciation was also shown to be associated with infectious diseases, and not only attributable to winter grazing conditions.

CONCLUSIONS

This study highlights the importance of examining dead reindeer to gain knowledge about why they die on winter pasture. The work presented herein also shows the feasibility and value of increased documentation of reindeer losses during winter.

First report of Orthostrongylus sp. (Nematoda: Protostrongylidae) in wild reindeer (Rangifer tarandus) from the Taimyr, Russia: Nearctic parasites in a Palearctic host

First stage larvae of an unknown lungworm (Protostrongylidae) were isolated in the feces of a wild reindeer (Rangifer tarandus) from Taimyr, Russia. Larvae were 365-366 μm long and had a tail spike lacking a dorsal spine. DNA analyses using BLAST showed that nuclear sequences obtained (LSU rDNA, 825 bp and ITS2 rDNA, 395 bp) were highly similar (99.50% and 98.88% identity, respectively) to an isolate of Orthostrongylus macrotis (GenBank: EU595592.1) from North America. It cannot be confirmed whether these larvae represent an uncharacterized species of Orthostrongylus or can be referred to O. macrotis, a species that has historically only been reported from the Nearctic. This is the first report of lungworms attributable to Protostrongylinae in R. tarandus across its vast geographic in the Holarctic.

Pharmacokinetics of a long-acting subcutaneous eprinomectin injection in semi-domesticated reindeer (Rangifer tarandus tarandus) - A pilot study

Reindeer (Rangifer tarandus tarandus) are exposed to the pathogenic parasitic nematode Elaphostrongylus rangiferi during grazing. The severity of disease is dose-dependent. Prophylactic anthelmintic treatment is needed to improve animal health and reindeer herding sustainability. Herds are traditionally only gathered once during the summer, requiring a drug with a persistent effect. In this study we investigated the suitability of long-acting eprinomectin, given as a single subcutaneous injection at 1 mg/kg bodyweight in adult reindeer and calves. Plasma and faeces concentrations were determined using ultra-high performance liquid chromatography high resolution mass spectrometry (UHPLC-HRMS). Plasma concentrations remained above the presumed effect level of 2 ng/mL for 80 days, demonstrating the drug's potential. Pharmacokinetic parameters were compared to other species using allometric scaling. Calves and adults had slightly different profiles. No viable faecal nematode eggs were detected during treatment. Eprinomectin was measurable in the reindeer faeces up to 100 days, which is of environmental concern.

A SCOPING REVIEW OF THE RANGIFER TARANDUS INFECTIOUS DISEASE LITERATURE: GAP BETWEEN INFORMATION AND APPLICATION

The role and impact of infectious diseases in wildlife population dynamics are increasingly recognized, yet disease information is variably incorporated into wildlife management frameworks. This discrepancy is particularly relevant for Rangifer tarandus (caribou or reindeer), a keystone circumarctic species experiencing widespread population declines. The primary objective of this review was to characterize the available peer-reviewed literature on infectious diseases of Rangifer by using a scoping review methodology. Three databases of peer-reviewed literature-Web of Science, BIOSIS previews, and Scopus-were searched and 695 articles met the criteria for initial review. After screening for relevance and language, 349 articles, published between 1967 and 2020, remained. More than half of the excluded articles (181/346; 52%) were left out because they were not published in English; the majority of these excluded articles (120) were in Russian. From the 349 included articles, 137 (39%) pertained to wild (as opposed to semidomesticated or captive) Rangifer populations. Articles on infectious disease in wild Rangifer were published in 40 different journals across various disciplines; the most common journals were disease and parasitology oriented, accounting for 55% of included articles. Most studies were descriptive (87%), followed by experimental (9%). Of the pathogen taxa investigated, helminths were the most common, comprising 35% of articles. Rangifer subspecies were not equally represented in the literature, with barren-ground caribou (R. t. groenlandicus; n=40) and woodland caribou (R. t. caribou; n=39) having the greatest abundance and diversity of infectious disease information available. Few studies explicitly examined individual or population-level impacts of disease, or related disease to vital population rates, and only 27 articles explicitly related results to management or conservation. Findings from this review highlight an unbalanced distribution of studies across Rangifer ecotypes, a preference for dissemination in disease-specialized publication venues, and an opportunity for investigating population-level impacts that may be more readily integrated into caribou conservation frameworks.

THE FIRST REPORT ABOUT <i>LAPHOSTRONGYLUS RANGIFERI</i> (INVASIVE PARASITIC SPECIES IN REINDEER) IN THE LENINGRAD REGION

is a parasitic nematode specific to reindeer ( ). In the XXth century, reindeer were not found in the Leningrad Region. However, by 2020, several dozen of them were brought from the Murmansk Region and the Yamalo-Nenets Autonomous Okrug and settled in at least seven private menageries. As a result of a study of the feces of 34 imported reindeer carried out in 2018-2021, larvae of nematodes were isolated, whose morphological, morphometric, physiological and biological characteristics corresponded to those of E. rangiferi . The species identification was confirmed by subsequent molecular genetic studies. The discovery of parasite larvae in the feces of the second generation reindeer (born in 2018-2020) indicates the successful completion of the full life cycle of this helminth, which requires a participation of intermediate hosts - terrestrial or freshwater gastropods. A combination of such circumstances as: 1) the appearance of reindeer infested with E. rangiferi in the Leningrad Region; 2) the presence of wild, agricultural and zoo ruminants capable of becoming the definitive hosts for Elaphostrongylus in the Leningrad Region; 3) the spread of the larvae of this parasite as a result of free walking of reindeer in the forest, their lease and resale, the commercial sale of non-disinfected manure; 4) the ability of larvae to maintain viability in feces and infected mollusks for about 2 years, withstanding freezing and drying; 5) high lethality of infested nonspecific hosts due to parasitic encephalomyelitis, pneumonia, etc.; 6) the lack of methods for treating sick animals - endangers the theriofauna of the Leningrad Region.

The First Report of Elaphostrongylus cervi Infection in Two Imported Wapitis (Cervus canadensis) in Slovenia

This study describes two female wapitis (Cervus canadensis) with neurological signs associated with an Elaphostrongylus cervi (E. cervi) infection. The original host of the nematode parasite is the Eurasian red deer (Cervus elaphus), although other cervids and small ruminants may also be affected. The two wapitis imported from Canada were kept in an enclosure with the Slovenian red deer herd. After developing debilitating neurological signs, the wapitis were euthanized and examined for possible causes. A histopathological examination of the brain of the first wapiti revealed severe diffuse perivascular meningoencephalitis with chronic vasculitis, and some cross-sections of nematodes were found in the leptomeninges. A necropsy of the second wapiti revealed severe pachymeningitis and leptomeningitis, where several adult nematode parasites were found. E. cervi was confirmed by molecular methods. The prevalence of E. cervi in the European red deer population is high, but no study has been conducted to assess its prevalence in Slovenia. This was the first confirmation of E. cervi in Slovenia and the first infection with this parasite described in Europe in a wapiti. Elaphostrongylus cervi should also be considered as a differential diagnosis in Europe for all ruminants grazing on pastures frequented by red deer and showing neurological clinical signs.

Pathologic features and molecular identification of parelaphostrongylosis in a sitatunga (Tragelaphus spekii)

We report the pathologic features, local inflammatory response immunophenotype, and molecular identification results of cerebral nematodiasis in a young sitatunga (Tragelaphus spekii) from Texas. To the authors' knowledge, this is the first report of cerebral nematodiasis by Parelaphostrongylus tenuis in a sitatunga, a bovid species introduced into the USA, and the first characterization of the local inflammatory response immunoprofile in this condition. A molecular identification method based on formalin-fixed and paraffin-embedded-polymerase chain reaction was described. These results contribute to knowledge on geographical distribution and host spectrum of P. tenuis, and highlight the relevance of this nematodiasis in naïve translocated or introduced bovid species into endemic areas.

Occurrence of faecal endoparasites in reindeer (Rangifer tarandus) in two grazing areas in northern Norway

Background

Semi-domesticated reindeer represent an important livestock industry and livelihood for a proportion of the human population in northern Fennoscandia. Reindeer husbandry is considered an extensive animal husbandry, where the animals are kept mostly on natural pastures, although sometimes kept in fenced areas for shorter periods. These reindeer may harbour a variety of parasites that may affect animal health and production. The relatively limited close contact between herds and owners gives limited opportunities for diagnosis and treatment of diseases in general. Furthermore, the effects of subclinical parasitism in livestock are commonly expressed as a reduction in productivity rather than clinical disease and mortality. Thus, specific knowledge of endoparasites and parasitic infections in these herds is scarce. This study investigated the occurrence of various endoparasites in reindeer by analysis of a total of 114 faecal samples from winter-slaughtered reindeer from two different grazing areas in Troms and Finnmark, Norway.

Results

Using a McMaster method, a Baermann technique, and a direct immunofluorescent antibody test, the following parasites were identified in the faecal samples with the occurrence data given as percentages: Strongylid eggs (62%), Nematodirinae spp. eggs (24%), Capillaria sp. eggs (42%) and Moniezia spp. eggs (17%), Dictyocaulus spp. larvae (14%) protostrongylid larvae (40%), Eimera spp. oocysts (23%), and Giardia duodenalis cysts (5%). Cryptosporidium oocysts were not detected. Parasite eggs, oocysts, and cysts were quantified.

Molecular analysis revealed G. duodenalis sub-assemblage AI, a potentially zoonotic genotype not previously reported in reindeer from this region. Morphological analyses of Eimeria oocysts identified two species, Eimeria mayeri and Eimeria rangiferis, and molecular analyses of the cytochrome C oxidase I (coi) gene and 18 s rRNA (18SSU) gene of Eimeria confirmed the presence of Eimeria species that are specific to reindeer.

Conclusions

A high prevalence, but low burden, of endoparasites was detected in samples from these semi-domesticated reindeer. The samples were collected during winter, when adult gastrointestinal parasites usually produce only low numbers of transmission stages. Therefore, together with the low number of samples, detailed and definitive conclusions regarding parasite status of semi-domesticated reindeer are avoided. Nevertheless, these data provide a snapshot overview of parasite occurrence in a semi-domesticated animal group vulnerable to the various environmental changes to which they are exposed.

Post-Translational Protein Deimination Signatures in Plasma and Plasma EVs of Reindeer (Rangifer tarandus)

Simple Summary

Reindeer are an important wild and domesticated species of the Arctic, Northern Europe, Siberia and North America. As reindeer have developed various strategies to adapt to extreme environments, this makes them an interesting species for studies into diversity of immune and metabolic functions in the animal kingdom. Importantly, while reindeer carry natural infections caused by viruses (including coronaviruses), bacteria and parasites, they can also act as carriers for transmitting such diseases to other animals and humans, so called zoonosis. Reindeer are also affected by chronic wasting disease, a neuronal disease caused by prions, similar to scrapie in sheep, mad cows disease in cattle and Creutzfeldt-Jakob disease in humans. The current study assessed a specific protein modification called deimination/citrullination, which can change how proteins function and allow them to take on different roles in health and disease processes. Profiling of deiminated proteins in reindeer showed that many important pathways for immune defenses, prion diseases and metabolism are enriched in deiminated proteins, both in plasma, as well as in plasma extracellular vesicles. This study provides a platform for the development of novel biomarkers to assess wild life health status and factors relating to zoonotic disease.

Abstract

The reindeer (caribou) Rangifer tarandus is a Cervidae in the order Artiodactyla. Reindeer are sedentary and migratory populations with circumpolar distribution in the Arctic, Northern Europe, Siberia and North America. Reindeer are an important wild and domesticated species, and have developed various adaptive strategies to extreme environments. Importantly, deer have also been identified to be putative zoonotic carriers, including for parasites, prions and coronavirus. Therefore, novel insights into immune-related markers are of considerable interest. Peptidylarginine deiminases (PADs) are a phylogenetically conserved enzyme family which causes post-translational protein deimination by converting arginine into citrulline in target proteins. This affects protein function in health and disease. Extracellular vesicles (EVs) participate in cellular communication, in physiological and pathological processes, via transfer of cargo material, and their release is partly regulated by PADs. This study assessed deiminated protein and EV profile signatures in plasma from sixteen healthy wild female reindeer, collected in Iceland during screening for parasites and chronic wasting disease. Reindeer plasma EV profiles showed a poly-dispersed distribution from 30 to 400 nm and were positive for phylogenetically conserved EV-specific markers. Deiminated proteins were isolated from whole plasma and plasma EVs, identified by proteomic analysis and protein interaction networks assessed by KEGG and GO analysis. This revealed a large number of deimination-enriched pathways for immunity and metabolism, with some differences between whole plasma and EVs. While shared KEGG pathways for whole plasma and plasma EVs included complement and coagulation pathways, KEGG pathways specific for EVs were for protein digestion and absorption, platelet activation, amoebiasis, the AGE–RAGE signaling pathway in diabetic complications, ECM receptor interaction, the relaxin signaling pathway and the estrogen signaling pathway. KEGG pathways specific for whole plasma were pertussis, ferroptosis, SLE, thyroid hormone synthesis, phagosome, Staphylococcus aureus infection, vitamin digestion and absorption, and prion disease. Further differences were also found between molecular function and biological processes GO pathways when comparing functional STRING networks for deiminated proteins in EVs, compared with deiminated proteins in whole plasma. This study highlights deiminated proteins and EVs as candidate biomarkers for reindeer health and may provide information on regulation of immune pathways in physiological and pathological processes, including neurodegenerative (prion) disease and zoonosis.

Modeling Thermal Suitability for Reindeer (Rangifer tarandus ssp.) Brainworm (Elaphostrongylus rangiferi) Transmission in Fennoscandia

The brainworm, Elaphostrongylus rangiferi, is a nematode which causes neurological disorders (elaphostrongylosis) in reindeer (Rangifer tarandus ssp.). Favorable climatic conditions have been inferred as the cause of sporadic outbreaks of elaphostrongylosis in Norway, supported by positive associations between observed outbreaks/intensity of infection and summer temperatures in the previous years. Climate warming which results in increased transmission of E. rangiferi therefore presents a risk to the health of semi-domesticated and wild reindeer in Fennoscandia (Norway, Sweden, and Finland), the health of co-grazing small ruminants, and the livelihoods of indigenous Sámi herders. As a first step toward developing climate change impact assessments for E. rangiferi, a degree-day model was developed for larval development in a range of gastropod hosts and applied to historic weather data. Predictions were validated by statistical and qualitative comparison against historic parasitological and outbreak records. The model predicted an overall increase in thermal suitability for E. rangiferi, which was statistically significant in the north and along the Scandinavian mountain ranges, where reindeer density is highest. In these regions annual cumulative temperature conditions are suitable for larval development within a single year, potentially changing E. rangiferi epidemiology from a 2-year transmission cycle to a 1-year transmission cycle. This is the first mechanistic model developed for E. rangiferi and could be used to inform veterinary risk assessments on a broad spatial scale. Limitations and further developments are discussed.