Pestivirus Infections in Semi-Domesticated Eurasian Tundra Reindeer (Rangifer tarandus tarandus): A Retrospective Cross-Sectional Serological Study in Finnmark County, Norway

A serological screening for potential viral pathogens among semi-domesticated Eurasian tundra reindeer (Rangifer tarandus tarandus) in Finland

BACKGROUND

Reindeer herding and husbandry is a traditional and important livelihood in Fennoscandia, and about 200,000 semi-domesticated reindeer are herded in Finland. Climatic changes, leading to ice-locked winter pastures, and encroachment of pasture-land have led to changes in reindeer husbandry, increasing the extent of supplementary or full ration feeding, which has become very common in Finland. Keeping reindeer in corrals or gathering them at permanent feeding sites will increase nose-to-nose contact between animals and they may be exposed to poor hygienic conditions. This may impact the epidemiology of infectious diseases, such as viral infections. The aim of this study was to investigate Finnish semi-domesticated reindeer for exposure to viral pathogens. Blood samples were collected from 596 reindeer (358 calves, 238 adults) in 2015, from nine reindeer slaughterhouses, representing most of the reindeer herding regions in Finland. Plasma samples were investigated for antibodies against a selection of known and potential reindeer viral pathogens by using enzyme linked immunosorbent assays (ELISA).

RESULTS

The screening suggested that alphaherpesvirus and gammaherpesvirus (malignant catarrhal fever virus group; MCFV) were enzootic in the reindeer population, with a seroprevalence of 46.5% (range at slaughterhouse level 28.6-64.3%) and 29.0% (range 3.5-62.2%), respectively. Whereas the seroprevalence was significantly higher for alphaherpesvirus among adult reindeer (91.2%) as compared to calves (16.8%), no age difference was revealed for antibodies against gammaherpesvirus. For alphaherpesvirus, the seroprevalence in the northernmost region, having the highest animal density (animals/km²), was significantly higher (55.6%) as compared to the southernmost region (36.2%), whereas the seroprevalence pattern for gammaherpesvirus indicated the opposite, with 8.1% in the north and 50.0% in the south. Four reindeer (0.7%) had antibodies against Pestivirus, whereas no antibodies were detected against Bluetongue virus or Schmallenbergvirus.

CONCLUSIONS

Alphaherpesvirus and gammaherpesvirus (MCFV) seems to be enzootic in the Finnish reindeer population, similar to other reindeer herds in Fennoscandia, whereas the exposure to Pestivirus was low compared to findings in Norway and Sweden. The ongoing changes in the reindeer herding industry necessitate knowledge on reindeer health and diseases that may impact animal welfare and health of reindeer as well as the economy of the reindeer herding industry.

A Screening for Virus Infections among Wild Eurasian Tundra Reindeer (Rangifer tarandus tarandus) in Iceland, 2017-2019

A winter population of around 4000-5000 wild Eurasian tundra reindeer (Rangifer t. tarandus) in the eastern part of Iceland represents descendants from 35 semi-domesticated reindeer imported to Iceland from Finnmark county, Norway, in 1787. While previous studies have indicated that they host fewer parasite species as compared to reindeer in Fennoscandia, little information exists on their exposure to reindeer viral pathogens. The aim of this study was to investigate blood from hunted reindeer for antibodies against alphaherpesvirus and gammaherpesviruses (malignant catarrhal fever viruses, MCFV), pestivirus, bluetongue virus, and Schmallenberg virus, and to investigate nasal and oral mucosal membrane swab samples for the presence of parapoxvirus-specific DNA. Blood samples collected during the hunting seasons in 2017 (n = 40), 2018 (n = 103), and 2019 (n = 138) were tested for viral antibodies using enzyme-linked immunosorbent assays (ELISA). Screening for parapoxvirus DNA was conducted on swab samples from 181 reindeer by polymerase chain reaction (PCR), targeting the B2L and GIF genes. Antibodies against pestivirus were detected in two animals from 2017, and antibodies against MCFV were detected in two reindeer from 2018. No antibodies were detected against the other viruses tested. Parapoxvirus-specific DNA was detected in nasal swab samples from two animals sampled in 2019. This study suggests that the investigated viral infections are either not present or present at a low prevalence only, probably not representing a major health threat to this reindeer population. The lack of exposure to alphaherpesvirus, an enzootic pathogen in most investigated Rangifer populations, was unexpected.

A Screening for Virus Infections in Eight Herds of Semi-domesticated Eurasian Tundra Reindeer (Rangifer tarandus tarandus) in Norway, 2013-2018

Background: Previous serological screenings have indicated that Eurasian semi-domesticated tundra reindeer (Rangifer tarandus tarandus) in Finnmark, Northern Norway, are exposed to alphaherpesvirus, gammaherpesvirus and pestivirus. Alphaherpesvirus (i.e., Cervid herpesvirus 2; CvHV2) has been identified as the transmissible component of infectious keratoconjunctivitis (IKC). Limited knowledge exists on the presence and prevalence of virus infections in other herding regions in Norway, which are hosting ~67,000 semi-domesticated reindeer and have contact with other species and populations of wildlife and livestock than those present in Finnmark. Methods: Blood samples (n = 618) were obtained over five winter seasons (2013-2018), from eight different herds representing summer pasture districts in Tana, Lakselv, Tromsø, Lødingen, Hattfjelldal, Fosen, Røros, and Filefjell, distributed from North to South of the reindeer herding regions in Norway. Blood samples were investigated for specific antibodies against five viral pathogen groups, alphaherpesvirus, gammaherpesvirus (viruses in the malignant catarrhal fever group; MCFV), pestivirus, bluetongue virus (BTV), and Schmallenberg virus (SBV), by using commercial multispecies serological tests (ELISA). In addition, swab samples obtained from the nasal mucosal membrane from 486 reindeer were investigated by PCR for parapoxvirus-specific DNA. Results: Antibodies against aphaherpesvirus and MCFV were found in all eight herds, with a total prevalence of 42% (range 21-62%) and 11% (range 2-15%), respectively. Anti-Pestivirus antibodies were detected in five of eight herds, with a total prevalence of 19% (range 0-52%), with two of the herds having a particularly high seroprevalence. Antibodies against BTV or SBV were not detected in any of the animals. Parapoxvirus-specific DNA was detected in two animals representing two different herds in Finnmark. Conclusions: This study confirmed that alphaherpesvirus and MCFV are enzootic throughout the geographical reindeer herding regions in Norway, and that pestivirus is present in most of the herds, with varying seroprevalence. No exposure to BTV and SBV was evident. This study also indicated that semi-domesticated reindeer in Finnmark are exposed to parapoxvirus without disease outbreaks being reported from this region.

Screening of Eurasian Tundra Reindeer for Viral Sequences by Next-Generation Sequencing

Reindeer husbandry is essential for the livelihood and culture of indigenous people in the Arctic. Parts of the herding areas are also used as pastures for farm animals, facilitating potential transmission of viruses between species. Following the Covid-19 pandemic, viruses circulating in the wild are receiving increased attention, since they might pose a potential threat to human health. Climate change will influence the prevalence of infectious diseases of both humans and animals. The aim of this study was to detect known and previously unknown viruses in Eurasian tundra reindeer. In total, 623 nasal and 477 rectal swab samples were collected from reindeer herds in Fennoscandia, Iceland, and Eastern Russia during 2016–2019. Next-generation sequencing analysis and BLAST-homology searches indicated the presence of viruses of domesticated and wild animals, such as bovine viral diarrhea virus, bovine papillomavirus, alcephaline herpesvirus 1 and 2, deer mastadenovirus B, bovine rotavirus, and roe deer picobirnavirus. Several viral species previously found in reindeer and some novel species were detected, although the clinical relevance of these viruses in reindeer is largely unknown. These results indicate that it should be possible to find emerging viruses of relevance for both human and animal health using reindeer as a sentinel species.