Screening of wild roe deer populations in Sweden 2016-2022 for SARS-CoV-2.

Effective control of zoonotic infectious diseases requires identifying the animal species involved in the infectious cycle as transmitters or reservoirs where the pathogen could persist and evolve, increasing the risk of reintroduction of new variants in humans and animals. Multiple surveillance studies have detected the presence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) or specific antibodies in free-ranging white-tailed deer (Odocoileus virginianus) in North America, being the wild mammal species with the most reported cases of SARS-CoV-2 infection. However, so far, all attempts to detect the infection in European cervids have been unsuccessful. In this study, we demonstrated the presence of specific antibodies against SARS-CoV-2 in European fallow deer (Dama dama) and red deer (Cervus elaphus) in Spain. However, all samples of European roe deer (Capreolus capreolus), taxonomically related to the American white-tailed deer, were seronegative for the virus. We tested 215 serum samples from roe deer (n = 116), red deer (n = 63), and fallow deer (n = 36) collected in eight provinces of central-southern Spain between 2017 and 2022. We first screened sera by a surrogate virus neutralization test (sVNT) ELISA based on the binding of the receptor-binding domain of SARS-CoV-2 to the angiotensin-converting enzyme 2 (ACE2) receptor and then confirmed positive samples by a conventional virus neutralization test (cVNT) against the Alpha, Delta, and Omicron variants. Four fallow deer and two red deer samples were seropositive in both neutralization assays. Four samples of fallow deer and one of red deer, collected in a suburban park near Madrid in February 2022, had antibodies against the Alpha, Delta, and Omicron variants, while a seropositive sample of red deer, collected in a rural area in February 2021, was specific for the Delta variant. All samples collected before the start of the pandemic in Spain were seronegative for sVNT, which also indicates that there are not cross-reactive antibodies potentially elicited by other viruses antigenically related to SARS-CoV-2. The results indicate probable human-to-deer transmission of SARS-CoV-2, but do not clarify whether there was subsequent spread within herds.

SARS-CoV-2's origin should be investigated worldwide for pandemic prevention

We conducted a series of studies in the Dobris Forest, Czech Republic, to determine whether competition between white-tailed deer (Odocoileus virginianus) and sympatric cervid species could limit expansion of the white-tail population. We used grazing time among species as an indication of potential interspecific competition and predicted that grazing time on an open pasture would decrease if deer other than conspecifics were present or entered the pasture. We used 710 observational records in our analyses: 409 for white-tailed deer, 225 for fallow deer (Dama dama), 66 for red deer (Cervus elaphus), and 10 for roe deer (Capreolus capreolus). The time that white-tailed, fallow, and roe deer spent grazing was not affected by whether the pasture was harvested or whether any deer were present when the focal animal entered. We observed a strong tendency for grazing time by red deer to be directly related to the numbers of whitetails or female fallow deer visible before red deer entered the pasture, Grazing time of white-tailed and fallow deer increased if the focal deer was joined by another animal. For white-tailed and fallow deer, the anti-predatory strategy of joining a group may have been balanced by avoiding the most competitive classes of animals. Our results suggest that interspecific cooperative behavior, rather than interspecific competition, occurs among these sympatric cervids.

Wildlife animals may be susceptible to multiple infectious agents of public health or veterinary relevance, thereby potentially forming a reservoir that bears the constant risk of re‐introduction into the human or livestock population. Here, we serologically investigated 493 wild ruminant samples collected in the 2021/2022 hunting season in Germany for the presence of antibodies against the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) and four viruses pathogenic to domestic ruminants, namely, the orthobunyavirus Schmallenberg virus (SBV), the reovirus bluetongue virus (BTV) and ruminant pestiviruses like bovine viral diarrhoea virus or border disease virus. The animal species comprised fallow deer, red deer, roe deer, mouflon and wisent. For coronavirus serology, additional 307 fallow, roe and red deer samples collected between 2017 and 2020 at three military training areas were included. While antibodies against SBV could be detected in about 13.6% of the samples collected in 2021/2022, only one fallow deer of unknown age tested positive for anti‐BTV antibodies, and all samples reacted negative for antibodies against ruminant pestiviruses. In an ELISA based on the receptor‐binding domain (RBD) of SARS‐CoV‐2, 25 out of 493 (5.1%) samples collected in autumn and winter 2021/2022 scored positive. This sero‐reactivity could not be confirmed by the highly specific virus neutralisation test, occurred also in 2017, 2018 and 2019, that is, prior to the human SARS‐CoV‐2 pandemic, and was likewise observed against the RBD of the related SARS‐CoV‐1. Therefore, the SARS‐CoV‐2 sero‐reactivity was most likely induced by another hitherto unknown deer virus belonging to the subgenus Sarbecovirus of betacoronaviruses.

In this study, we used a multi-faceted approach to understand patterns of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission and persistence in a wild white-tailed deer (Odocoileus virginianus) population. Serology data indicated transmission of SARS-CoV-2 and persistence during the seven-month sampling period. Traditional disease modelling based on deer-to-deer transmission indicated relatively low prevalence with an R0 of 1.9 and recovery period of 7 days; however, individual-based modelling informed by GPS tracked-movement data captured a potential transmission event. Phylogenetic analyses revealed a recurring pattern of divergent groups of deer-derived sequences with human-derived sequences falling close to each deer-derived cluster. Further, human-derived sequences were frequently sampled months prior to the deer-derived sequences, indicating repeated human to deer spillover. Using multiple types of data as well as both fine and broad scale analyses, we have characterized a pattern of localized outbreaks of SARS-CoV-2 within white-tailed deer populations that are likely recurring due to frequent spillover events. Our results suggest that while deer-to-deer transmission occurs over small spatiotemporal scales, SARS-CoV-2 persistence over longer periods and across larger regions is likely driven by repeated spillover from human populations.

Correspondence has appeared in the literature concerning the relationships between red deer (Cervus elaphus), roe deer (Capreolus capreolus), fallow deer (Dama dama) and some other species, such as Japanese deer (Cervus nippon), which are feral in the British Isles. Competition, described as antipathy or antagonism by various writers, appears to be the most widely accepted mechanism whereby relative abundance of one deer species is often correlated with relative scarcity of others. Other explanations involve geographical limits of distribution, two examples being the relative abundance of fallow deer in the south of England, and of roe deer in the Lake District (Delap 1955, Carne 1955). Carne (1954) has stated that Japanese (syn. sika) and fallow deer are, having been introduced into Britain, a powerful deterrent to the roe; he claims support for this contention from historical records which he considers show that as fallow deer have increased in an area, roe deer have decreased, often to extinction. Having observed in the Lake District of England that fallow deer have never established themselves in forests occupied by roe deer, Carne confirmed (1955) a statement by Delap (1955) that there is antipathy between them. Delap also stated that roe deer and red deer or red deer and fallow deer can 'associate happily', but that antagonism exists between roe deer and fallow deer. However, even co-existence of red deer and roe deer does not appear to be a constant feature; Wildash (1951) records that roe deer are seldom found where red deer are present in any numbers in Austria, that the red deer is a 'natural enemy' of the roe, and also that Austrian foresters could not give any reason for this antipathy. The purpose of this paper is to examine these ideas in the light of further evidence. It will be shown that roe, red and fallow deer are characteristically most numerous at different stages in the development of several British forests; when two or more of these three species are present in the same forest area, the number of each of them increases and decreases in a successional manner, which is related to development of the forest habitat towards a climax of mature trees. Such successional changes of the deer fauna are considered to be similar in nature to the marked changes which were shown to occur to the species composition of the bird fauna when a heathland area in East Anglia was afforested (Lack & Lack 1951).

The risk of viral transmissions from domestic/wild animals to humans is a major public health concern. Humans can also transmit viruses back to domestic and wild animals, acting as a reservoir for virus maintenance and a source of epidemic diseases re-emergence. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), causing COVID-19, likely originated from wildlife and has been evidenced to transmit from humans to captive, domestic and wild animals. White-tailed deer (Odocoileus virginianus) show high SARS-CoV-2 prevalence following human contamination, suggesting they could act as an emerging virus reservoir. We completed recent research on European cervid species by investigating whether SARS-CoV-2 had emerged in longitudinally monitored European roe deer (Capreolus capreolus) populations in direct contact with humans in France. We performed indirect tests (serological enzyme-linked immunosorbent assays and seroneutralization) on sera collected before and after the virus emergence in humans, and direct reverse transcriptase polymerase chain reaction tests on nasal swabs collected in 2022. We also investigated the virus exposure and prevalence in three other cervid species. Enzyme-linked immunosorbent assay tests were positive for 2.20% of sera, pre- and post-pandemic, but seroneutralization and polymerase chain reaction tests were negative. Although one population showed increased seroprevalence post-2020, results suggest that SARS-CoV-2 has not emerged in those populations and that enzyme-linked immunosorbent assay cross-reaction with one or several unidentified circulating coronaviruses is possible.

Simple SummaryFallow and roe deer are both game species, and therefore it is crucial to monitor their population locally and on a country scale. The method of pellet group count is commonly used for estimating population trends of ungulates; however, in the case of the two species, the misidentification rate can be high due to their similar body size. Our aim was to determine a metrical threshold between pellet groups of roe deer (native species) and fallow deer (alien species) to be applied during fieldwork. We measured the number of feces in the group, the length and width of five randomly selected feces from each pellet group and the length/width ratio. Roe deer pellets were shorter, narrower and less elongated than those of fallow deer; yet, length was found to be the best discriminant. The most accurate threshold was 1.2 cm. The mean number of pellets in a group was lower for roe deer than for fallow deer. A value of 50–52 pellets best differentiated between the two species. We therefore concluded that, on the basis of morphometric measurement, it is possible to distinguish roe and fallow deer feces.The method of pellet group count is commonly used for estimating population trends of ungulates; however, in the case of species of similar body size, the misidentification rate can be high. Our aim was to find a metrical threshold between pellet groups of roe deer (native species) and fallow deer (alien species) to be applied during fieldwork. The study was conducted in spring 2020 and 2021 in central Poland (lowlands) in areas were only roe or fallow deer occurred. We measured the number of feces in the group, the length and width of five randomly selected feces from each pellet group and the length/width ratio. Roe deer pellets were shorter, narrower and less elongated than those of fallow deer; yet, length was found to be the best discriminant. The most accurate threshold was 1.2 cm, i.e., 12–15% of pellets were over/below this value. The mean number of pellets in a group was lower for roe deer (39.6, SE = 1.6) than for fallow deer (64.5, SE = 1.5). A value of 50–52 pellets best differentiated between the two species. To conclude, combining these two measurements could be an objective method to distinguish between pellet groups of the two species.

Antimicrobial resistance (AMR) is a recognised threat to global health. Obtaining data on the prevalence of AMR in environmental bacteria is key to understanding drivers and routes of transmission. Here, 325 Shiga toxin negative deer faecal samples—gathered from across the Scottish mainland—were screened for the presence of AMR Escherichia coli and investigated for potential risk factors associated with AMR occurrence. E. coli with resistance to antimicrobials of clinical health concern, including carbapenems and 3rd generation cephalosporins, were targeted. Ninety-nine percent of samples yielded E. coli, and the prevalence of resistant E. coli at the level of faecal samples was 21.8% (n = 71) for tetracycline, 6.5% (n = 21) for cefpodoxime, 0.3% for ciprofloxacin (n = 1), with no recorded resistance to meropenem. Potential risk factors for tetracycline and cefpodoxime resistance were investigated. The presence of broadleaved woodlands was significantly associated with both AMR phenotypes, which may relate to land use within or around such woodlands. Associated risk factors varied across resistance phenotype and deer species, with proximity or density of horses an indicator of significantly decreased and increased risk, respectively, or tetracycline and cefpodoxime resistance in E. coli from roe deer, but not from red deer. Distance from wastewater treatment plants was a significant risk factor for tetracycline resistance in E. coli from red deer but not from roe deer. Data indicated that AMR E. coli can occur in wild deer populations that are not directly exposed to the selective pressure exerted by antimicrobial treatment. Overall, resistance to critically important antimicrobials was found to be low in the studied population, suggesting no immediate cause for concern regarding human health. Utilising existing culling frameworks, wild deer in Scotland could function well as a sentinel species for the surveillance of AMR in the Scottish environment.

Cryptosporidium spp. and Giardia duodenalis are zoonotic pathogens that cause enteric disease in humans and animals. This study aimed to identify the species/assemblages of Cryptosporidium and Giardia duodenalis in Scottish wild deer populations. Faecal samples (n = 990) were collected from across mainland Scotland from red deer, roe deer, sika deer and fallow deer. The oocysts/cysts were concentrated, DNA was extracted and then analysed by PCR (Cryptosporidium SSU-rRNA and Giardia duodenalis β-giardin, glutamate dehydrogenase (gdh), triosephosphate isomerase (tpi) DNA). All positive PCR amplicons were sequenced to determine Cryptosporidium species and Giardia assemblage. Overall, 12.3 % (122/990) of samples were positive for Cryptosporidium and identified C. ryanae (77/122), C. parvum (22/122) and C. ubiquitum (13/122). Rates of Cryptosporidium infection varied significantly (P = 0.009) between the deer species. Cryptosporidium was also significantly (P = 0.001) more likely to be detected in male deer compared to females and in seasons with high rainfall (P = 0.002). Giardia was detected in 7.9 % (76/962) samples, and sequencing identified assemblage A (62/76), assemblage B (4/76), assemblage D (2/76) and assemblage E (5/76). The assemblages of 3/76 positive samples were unidentifiable. Detection of Giardia was significantly higher (P < 0.001) in roe deer than the other deer species. During this study we also demonstrate that deer calves had significantly higher rates of infection for both Cryptosporidium (P = 0.001) and Giardia (P < 0.001), than other age groups. Co-infection with both pathogens was rare (14/962 samples). These findings confirm that wild Scottish deer harbour both Cryptosporidium and Giardia; however, their role in transmission to humans or livestock remains unclear.

Intolerance amongst deer species at feeding: Roe deer are uneasy banqueters

Dictyocaulus nematode worms live as parasites in the lower airways of ungulates and can cause significant disease in both wild and farmed hosts. This study represents the first population genetic analysis of large lungworms in wildlife. Specifically, we quantify genetic variation in Dictyocaulus lungworms from wild deer (red deer, fallow deer and roe deer) in Hungary, based on mitochondrial cytochrome c oxidase subunit 1 (cox1) sequence data, using population genetic and phylogenetic analyses. The studied Dictyocaulus taxa display considerable genetic diversity. At least one cryptic species and a new parasite–host relationship are revealed by our molecular study. Population genetic analyses for Dictyocaulus eckerti revealed high gene flow amongst weakly structured spatial populations that utilise the three host deer species considered here. Our results suggest that D. eckerti is a widespread generalist parasite in ungulates, with a diverse genetic backround and high evolutionary potential. In contrast, evidence of cryptic genetic structure at regional geographic scales was observed for Dictyocaulus capreolus, which infects just one host species, suggesting it is a specialist within the studied area. D. capreolus displayed lower genetic diversity overall, with only moderate gene flow compared to the closely related D. eckerti. We suggest that the differing vagility and dispersal behaviour of hosts are important contributing factors to the population structure of lungworms, and possibly other nematode parasites with single-host life cycles. Our findings are of relevance for the management of lungworms in deer farms and wild deer populations.

Distribution of Lesions in Red and Fallow Deer Naturally Infected with Mycobacterium bovis

Management of populations of rare predators is impossible without knowledge of the number and density of their main prey species. In the Southwest Primorskiy Province, the world’s only wild population of the Far Eastern leopard has been preserved, and the area is also part of the range of the Amur tiger. The main hunting objects of these rare predators are ungulates: sika deer, roe deer, wild boar. In 2019, a new ungulate species for Primorskiy Krai and Russia – the water deer – was discovered here. The aim of the work is to study the number and density of wild ungulates in the range of the Far Eastern leopard, to assess the dynamics of changes that have occurred in the populations over 3 years. Materials from two full-scale aerial surveys conducted in 2019 and 2023 were used to estimate the number and density of wild ungulates in the Southwest of Primorskiy Province. The survey routes covered the entire Russian part of the range of the Far Eastern leopard with an area of 571,000 ha, including hunting grounds and protected areas of national and provincial levels. Both surveys were conducted using the same methodology and under as identical conditions as possible. In 2019, the total length of the routes was 1104.8 km and 1298 sika deer, 264 roe deer, 301 wild boar and 11 water deer were encountered. In 2023, 1666 sika deer, 151 roe deer, 71 wild boar and 19 water deer were registered along 999.6 km. Since 2019, sika deer numbers have increased by 25 % to 28.9 thousand individuals at a density of 50.5 ind/1000 ha. Favorable conditions for population growth are created by highly productive oak-broadleaf forests, lack of stable snow cover in winter, as well as additional winter foraging and improvement of anti-poaching work on protected areas. At the same time, the roe deer number and density declined twofold, and by 2023 here was 2.8 thousand individuals at a density of 4.8 ind/1000 ha. The main reasons for the population decline are competitive relationships with sika deer, as well as hunting and poaching pressure outside the specially protected natural areas. As a result of the outbreak of African swine fever, the number of wild boar in the Southwest Primorskiy Province has decreased more than 4 times in three years to 1.3 thousand individuals at a density of 2.3 ind/1000 ha. Water deer population in the south part of the study area was doubled in three years and totaled about 300 individuals at a density of 2.8 ind/1000 ha. Despite the depression of wild boar and roe deer populations, due to the growth of sika deer numbers, the total population of wild ungulates in 2023 remained at the level of 33 thousand animals, which provides prey for the growing populations of the Far Eastern leopard and Amur tiger. The number of sika deer in the study area reached a historical maximum. The population growth indicates that the south-west of Primorskiy Province has the most favorable conditions for this species. With the increasing population of sika deer, roe deer will continue to be displaced from forested areas into open habitats. It is likely that the core roe deer population will remain in rare forests and meadow habitats in the south of Khasanskiy District. It is not known whether the ban on wild boar hunting announced in Primorskiy Province will affect the recovery of the population of this species. The prognosis for the outcome of the disease and the recovery of animal numbers is currently unclear. The rapid growth of the water deer population in the Russian part of its range is not surprising. The combination of favourable environmental factors is complemented by early puberty and high fertility of animals.

Natural infections of SARS-CoV-2 increased in animals: How should humans interactwith animals?