Feral Mink Research Articles

The possible impact of escaped captive American mink (Neogale vison) on the population of feral mink in Denmark.

The Danish feral mink (Neogale vison) population can be divided into wild-born and captive-born mink newly escaped from a farm. The impact of the captive-born mink on the population of feral population is unknown. Captive-born mink has lately been estimated to make up 25-30% of the feral mink population. In December 2020 Danish mink farms were decommissioned until January 2023. The aim of this study was to: 1) Examine whether a supplementation of farmed mink into the feral mink population influence the population growth and extinction rate of the feral mink, 2) Investigate which parameters affect the viability in feral mink populations the most. The age and mortality of 351 mink and the reproduction of 85 adult females culled by hunters from 2019-2022 were determined in three distinct geographic areas of Denmark (Jutland, Zealand, and Bornholm). VORTEX simulations were used to model the population viability and to simulate the impact of a supplementation of captive-born mink into the wild population. Simulations show that changes by 30% in the parameters: fecundity, percentages of breeding females and mortality influenced population size influenced the final population size significantly. The initial population size and inbreeding did not affect the population growth significantly. The simulations showed that the mink population in the regions of Jutland and Zealand could go extinct within 15 to 30 years without any supplementation of captive-born mink to the feral population. The population on Bornholm will however remain stable with current levels of mortality and reproduction even without supplementation of captive mink.

A microbial tale of farming, invasion and conservation: on the gut bacteria of European and American mink in Western Europe

One of the threats that the critically endangered European mink (Mustela lutreola) faces throughout its relict range, including the occidental population, is the impact of the American mink (Mustela vison) invasion in its natural habitat. We aimed to explore the differences in microbiota and genetic diversity between European and American mink to test phylosymbiosis theory. We investigated the gut microbiota composition of European and American mink in controlled environments (captive breeding compounds and fur farms respectively) to account for the impact of the environment on gut bacterial composition. We compared them to the gut microbiota of both mink species in the natural environment across habitats. Our exploratory results showed differences between free-ranging and captive individuals, with more extreme changes in American mink compared to European mink. However, feral American mink from a long-established population exhibited gut bacterial composition closer to the free-ranging native species compared to more recently established feral populations. This result could be explained by dietary shifts in the area sampled based on prey availability through different landscape, but also to a lesser extent due to greater genetic differentiation. This exploratory work contributes to the scarce literature currently available on the dynamics between gut microbiota and mammal invasion.

Diet of Free Ranging American Mink (Neovison vison) in Denmark.

Non-native American mink (Neovison vison) is a widely spread predator in Denmark. The feral population in mainland Denmark consists of captive-born mink that escaped from fur farms and wild mink born in nature, whereas the population on Bornholm is almost all wild-born mink. In this study, the diets of feral mink in mainland Denmark and on the island of Bornholm are analyzed. The aim of this study was to examine (1) whether the diet of the larger captive-born mink differs from that of the smaller wild-born mink, (2) assess the regional variations between the diets of mink in mainland Denmark and on Bornholm, and (3) investigate the seasonal variation in the diet composition of mink. The stomach contents of 364 mink (243 wild-born and 114 captive-born) culled in the years 2019-2022 were analyzed. Of these, 203 mink were from mainland Denmark, and 154 were from Bornholm. No significant differences were found between the diets of captive-born mink and wild-born mink or the mink found in mainland Denmark and on the island of Bornholm. Significantly more empty stomachs were found during spring than during the summer and autumn, suggesting a bottleneck in the diet during spring.

A potential threat to the Pampas Biome: the introduction of American mink, Neovison vison (Schreber, 1777) in Uruguay

ABSTRACT The American mink (Neovison vison) has been introduced for fur farming into several countries around the world. In southern South America, although invasive populations have established in Argentina and Chile, no feral minks have been recorded in the Pampas Biome to date. We report a potentially new biological invasion in Uruguay, presenting observations, pictures and a museum specimen of feral minks in the locality Melilla, Montevideo Department, which probably escaped or were released from a local fur farm. We obtained 35 mink records between 2010 and 2020, mostly close to the fur farm, within a 2.5 km radius. Our report provides the northernmost mink records in South America, being the first in the Pampas Biome. American mink is a feared invader in most of the sites where it has been introduced, and therefore these new records are important mainly to plan and apply management interventions.

The Finding of the Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2) in a Wild Eurasian River Otter (Lutra lutra) Highlights the Need for Viral Surveillance in Wild Mustelids.

Animals have been involved in the three known outbreaks of severe respiratory syndromes due to coronaviruses (years 2005, 2012, and 2019). The pandemic nature of the SARS-CoV-2 outbreak increases the likelihood of infection from humans of susceptible animal species that, thus, could become secondary viral hosts and even disease reservoirs. We present evidence of spillover infection of wild mustelids by reporting the presence of SARS-CoV-2 in a Eurasian river otter found near a water reservoir in the Valencian Community (Spain). We detected the virus using two different commercial RTqPCR assays on RNA extracted from the nasopharynx (swabbing) and from lung tissue and mediastinal lymph node homogenates. The corresponding samples from two additional otters from distant sites tested negative in identical assays. The diagnosis in the positive otter was confirmed by two-tube RT-PCR assay in which RNA was first retrotranscribed, and then specific regions of the spike (S), nucleocapsid (N), and ORF10 genes were separately amplified from the produced cDNA, followed by electrophoretic visualization and Sanger sequencing. The sequences of the amplified products revealed some non-synonymous changes in the N and ORF10 partial sequences, relative to the consensus sequence. These changes, identified already in human patient samples, point to human origin of the virus, although their specific combination was unique. These findings, together with our previous report of SARS-CoV-2 infection of feral American mink, highlight the need for SARS-CoV-2 surveillance of wild or feral mustelids to evaluate the risk that these animals could become SARS-CoV-2 reservoirs.

Detection of Anti-Leishmania infantum Antibodies in Wild European and American Mink (Mustela lutreola and Neovison vison) from Northern Spain, 2014-20.

The European mink (Mustela lutreola) is listed as a critically endangered species because of ongoing population reduction from habitat degradation and the effects of introduced species, such as American mink (Neovison vison). This small, fragmented population becomes vulnerable to many other threats, including diseases. Leishmaniosis is a zoonotic disease caused by the protozoan parasite Leishmania infantum found in the Mediterranean area, which affects many mammals, including wild small mammals. Furthermore, clinical disease caused by L. infantum has recently been described in other mustelids. To assess the exposure to Leishmania sp. infection in mink species in northern Spain, blood samples from 139 feral American mink and 42 native European mink from north Spain were evaluated for Leishmania sp. infection using enzyme-linked immunosorbent assays against Leishmania spp. antibodies, with 52.4% of American mink and 45.3% of European mink being found seropositive. This finding raises questions regarding how the disease may affect these species and the potential repercussions for conservation efforts. Despite a high seroprevalence being observed in wild mink of both species in this study, association with clinical or pathologic signs of disease has yet to be elucidated.

American mink (Neovison vison) preying on hatchery and wild brown trout (Salmo trutta) juveniles in semi‐natural streams

AbstractPredator–prey interactions are one of the main ecological factors influencing the structure of fish communities. The impact of wading and diving semi‐aquatic predators on riverine fish populations is poorly known. We studied the effect of feral American mink predation on brown trout juveniles during winter in two experiments conducted in semi‐natural streams (length 26 m, width 1.5 m).In the first experiment, we compared the vulnerability of age‐1+ hatchery (length 142 ± 16 mm, average ±SD) and wild (112 ± 8 mm) brown trout of similar genetic origin in sympatry and allopatry. In the second experiment we used age‐0+ brown trout (79 ± 5 mm), increased habitat heterogeneity by addition of fine wood, and compared those to treatments without fine wood addition.Hatchery fish were more vulnerable to mink predation than their wild counterpart, and the predation rate increased with increasing body size among the hatchery trout. Predation by mink on wild trout was higher in sympatric than in allopatric treatments suggesting that stocking of hatchery fish may increase predation on wild conspecifics. Increased habitat heterogeneity resulted in reduced predation rate.The results show that a large size of hatchery fish in small streams was a negative trait, which was opposite to the mainstream observations of salmonid stockings made directly of feeding areas in lakes and oceans. Adding habitat heterogeneity was found important for habitat enhancements in streams with mammalian predators.We highlight the importance of taking all the habitats during the life cycle of migratory fish into account in management decisions and carefully considering whether using hatchery fish to support wild populations in streams.

Assessment of Aleutian mink disease virus (AMDV) prevalence in feral American mink in Iceland. Case study of a pending epizootiological concern in Europe.

BackgroundRecurring escapes or deliberate releases and subsequent infiltration or establishment of feral populations by individuals from fur farms have been commonly noted since the beginning of fur industry expansion. Once animals have invaded ecosystems adjacent to source farms escapees can change the demography of the feral populations through hybridization, outbreeding depression, competition and spreading of various pathogens which can decimate wild populations. In our study, we aimed to assess spread of Aleutian mink disease virus (AMDV) in the feral population of American mink (Neovison vison) in Iceland. The additional objective was to elucidate whether basic morpho-anatomical parameters (i.e., Fulton’s condition factor or spleen to body weight ratio) might be used as a preliminary indicator of AMDV infection.MethodsAmerican mink (n = 164) were captured by professional hunters in 8 regions of Iceland. The detection of AMDV in the spleen of male and female individuals was based on PCR amplification of an NS1 gene fragment.ResultsWe confirmed AMDV presence in 23.8% (n = 39) of collected samples with no significant difference in infection rate between males and females. Additionally, we revealed that the prevalence of virus in the feral population was higher closer to fur farms. However, the countrywide prevalence and direction of AMDV distribution needs to be further investigated. Comparison of condition indices in non-infected and infected animals showed significant deterioration of body and spleen parameters in the latter group. Therefore, the application of basic measurements of the American mink may be used to evaluate the health status of individuals in terms of pathogen infection.ConclusionsThe study shed a new light on prevalence and distribution of AMDV in the feral population of American mink in Iceland and the results might be successfully applied to develop models to infer dynamics of various pathogens, even those latently transmitted by disease-free animals.

Diversity and transmission of Aleutian mink disease virus in feral and farmed American mink and native mustelids.

Aleutian mink disease virus (AMDV), which causes Aleutian disease, is widely spread both in farmed mink and wild mustelids. However, only limited data are available on the role of wild animals in AMDV transmission and spread. Our aim was to shed light on AMDV transmission among wild mustelids and estimate the effect of intense farming practices on the virus circulation by studying AMDV prevalence and genetic diversity among wild mustelids in Poland. We compared AMDV seroprevalence and proportion of PCR-positive individuals in American mink, polecats, otters, stone martens, and pine martens and used the phylogenetic analysis of the NS1 region to study transmission. In addition, we used a metagenomic approach to sequence complete AMDV genomes from tissue samples. In eastern Poland, AMDV seroprevalence in wild mustelids varied from 22 per cent in otters to 62 per cent and 64 per cent in stone martens and feral mink, respectively. All studied antibody-positive mink were also PCR positive, whereas only 10, 15, and 18 per cent of antibody-positive polecats, pine martens, and stone martens, respectively, were PCR positive, suggesting lower virus persistence among these animal species as compared to feral mink. In phylogenetic analysis, most sequences from feral mink formed region-specific clusters that have most likely emerged through multiple introductions of AMDV to feral mink population over decades. However, virus spread between regions was also observed. Virus sequences derived from farmed and wild animals formed separate subclusters in the phylogenetic tree, and no signs of recent virus transmission between farmed and wild animals were observed despite the frequent inflow of farmed mink escapees to wild populations. These results provide new information about the role of different mustelid species in AMDV transmission and about virus circulation among the wild mustelids. In addition, we pinpoint gaps of knowledge, where more studies are needed to achieve a comprehensive picture of AMDV transmission.

First Description of SARS-CoV-2 Infection in Two Feral American Mink (Neovison vison) Caught in the Wild.

Simple SummaryCOVID-19 is one of the most important pandemics in recent history. It is an emerging infectious disease, probably of animal origin. Several domesticated and non-domesticated animals are naturally susceptible to SARS-CoV-2 infection, including Mustelidae, of which mink is the first species identified to suffer from this infection. We report herein the detection of the SARS-CoV-2 RNA in lymph node tissue from two feral American mink (Neovison vison) trapped in the wild in the Valencian Community (Eastern Spain) during invasive species trapping campaigns.Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causal agent of COVID-19, is considered a pathogen of animal origin that is mainly transmitted from human to human. Several animal species can be naturally or experimentally infected by SARS-CoV-2, with compelling evidence that mink is highly susceptible to SARS-CoV-2 infection. Human-to-mink infection cases have been reported and there are also suggestions that mink-to-human infection occurs. Mink infections have been reported to date only on fur farms, except for one infected free- ranging wild mink near a Utah (USA) fur farm, which suggests a transmission pathway from farms to wild mink. We now report the detection of SARS-CoV-2 in 2 of 13 feral dark brown American mink (Neovison vison) trapped in the Valencian Community (Eastern Spain), during an invasive species trapping campaign. They were trapped in riverbeds in sparsely inhabited rural areas known to harbor self-sustained feral mink populations. The closest fur farm is about 20 km away. SARS-CoV-2 RNA was detected by two-step RT-PCR in these animals’ mesenteric lymph nodes and was confirmed by sequencing a 397-nucleotide amplified region of the S gene, yielding identical sequences in both animals. A molecular phylogenetic analysis was run on this sequence, which was found to correspond to the consensus SARS-CoV-2 sequence from Wuhan. Our findings appear to represent the first example of SARS-CoV-2 acquired in the wild by feral mink in self-sustained populations.

Prevalence of Toxoplasma gondii and Cryptosporidium in Feral and Farmed American Mink (Neovison vison) in Denmark

To investigate the prevalence of Cryptosporidium spp. infection and Toxoplasma gondii antibodies in farmed and feral mink in Denmark. We examined meat juice from 235 feral mink and 306 farmed mink for T. gondii antibodies, and faecal samples from 113 feral mink and 166 farmed mink for Cryptosporidium oocyst excretion. Meat juice was analysed using a commercial indirect enzyme-linked immunosorbent assay and oocyst excretion was identified by a modified Ziehl-Neelsen method. All farmed mink tested sero-negative, while 53.6% of feral mink were T. gondii sero-positive. The probability of being sero-positive for T. gondii was not associated with recent escapes from farms (p = 0.468), but was significantly higher for male feral mink (64.2%) than female feral mink (42.5%) (p = 0.0008). Only one feral mink and four farmed mink (2.4%) excreted Cryptosporidium oocysts. Farmed mink were all T. gondii sero-negative, whereas approximately half the feral mink were sero-positive. Cryptosporidium prevalence in farmed and feral mink were low. Overall, the public health risk of transmission of these two parasites via mink in Denmark is low.

Current and historical nephric and hepatic mercury concentrations in terrestrial mammals in Poland and other European countries

The long-term anthropogenic release of mercury (Hg) into the environment has led to contamination of the biosphere, with all forms of Hg showing toxic effects and the ability to accumulate in organisms. Since the 1970s, efforts have been made in Western Europe to reduce Hg emissions and for the economic use of Hg, leading to a reduction in Hg exposure to humans and entire ecosystems. The purpose of this research was to present the total mercury (THg) burden in three mustelids (the piscivorous Eurasian otter and American mink, and the invertebrativorous European badger) inhabiting north-western Poland (mostly floodplains) and other European countries (literature data). Moreover, we wanted to investigate whether reductions in the environmental Hg burden in Europe have resulted in reductions in liver and kidney levels in wild terrestrial mammals (Eurasian otter, wild boar, red deer, roe deer, cervids, leporids, rodents, and ecotrophic groups: piscivorous mustelids, non-mustelids whose diets include aquatic prey, canids and other carnivores, omnivores, herbivores), between samples collected before and after 2000. We revealed significantly higher nephric THg levels in roadkilled than in trapped American minks. As roadkilled piscivorous mustelids from the same floodplain had similar hepatic and nephric THg concentrations, we suggest that the European research on Hg ecotoxicology should more often use alien American mink instead of the protected Eurasian otter. Badgers inhabiting Polish and other European floodplains bioaccumulated higher amounts of THg than those from other areas, and as such, may be recommended as bioindicator of mercury soil contamination. Our analysis of abundant data on mammalian hepatic and nephric THg concentrations (excluding non-piscivores mustelids) showed that in 12 of 21 cases, Hg concentrations had dropped significantly since 2000. This data signals a reduction in Hg contamination in terrestrial mammals, such as the Eurasian otter, and may be reason for cautious optimism.

High Genetic Diversity of an Invasive Alien Species: Comparison between Fur-Farmed and Feral American Mink (Neovison vison) in China.

Simple SummaryThe American mink (Neovison vison) is one of the best-known and most widespread invasive species in China and worldwide. To investigate the genetic characteristics and increase comprehension of the invasiveness process for this species, we compared the genetic characteristics of farmed and feral populations in northeastern China using mitochondrial DNA sequences and microsatellite loci. We found a relatively high diversity among the feral populations that was as high as that of the farmed mink. This demonstrated that high genetic diversity promotes the invasiveness and rapid evolution in the wild.Genetic characteristics play an important role in alien species for achieving high adaptation and rapid evolution in a new environment. The American mink (Neovison vison) is one of the best-known and most widespread invasive species that has successfully invaded the Eurasian mainland over quite a short period, including most parts of northeastern China. However, genetic information on farmed and feral American mink populations introduced in China is completely lacking. In this study, we combined mitochondrial DNA sequences and polymorphic microsatellites to examine the genetic divergence and genetic diversity of farmed and feral American mink populations. Our results suggest that there is admixture of individuals of different genetic characteristics between farmed and feral populations of mink. Furthermore, the genetic diversity of both farmed and feral American mink populations was high, and no bottleneck or population expansion was detected in most of the populations. These findings not only highlight the genetic characteristics of American mink in northeastern China but also contribute to the general understanding of the invasiveness of farmed species.

Estimation of the Age and Reproductive Performance of Wild-Born and Escaped Mink (Neovison vison) Caught in the Wild in Denmark.

Simple SummaryPrevious studies of wild caught mink in Denmark showed that 30–80% had recently escaped from farms. Therefore, it is debated whether a self-sustaining feral mink population is established in Denmark or whether the population rests upon a continuous contribution of captive-born farm mink. Knowledge regarding the reproduction and mortality of mink adapted for living in the wild is important for the management of feral mink. In this study, we separated wild-born from captive-born mink caught in the wild in Denmark. To be able to age the mink in this study, an age determination model for mink was developed based on the width of the pulp cavity. The mean litter size of wild-born female mink was 7.6 (range: 5–11 kits). The annual turnover of mink caught in the wild was estimated to be 66%, and the yearly mortality was 69%; thus, the population of wild-born mink is slightly declining. The results confirmed that the wild-born mink population in Denmark is reproducing and self-sustaining without a continuous influx of captive-born mink escaped from farms. The effect of escaped mink on the wild mink population will depend on the currently unknown ability of captive mink to survive in the wild.The feral mink population in Denmark consists of two groups of animals: mink born in the wild and mink that have recently escaped from farms. The aims of this study were to: (1) estimate the reproductive performance and mortality of the Danish mink born in the wild (wild-born) and mink escaped from farms (captive-born); (2) discuss the likelihood of a self-sustaining population of wild-born mink in Denmark; and (3) model the relationship between the pulp cavity width and the age of mink. During 2018, 247 wild caught mink were sent for necropsy at the Danish National Veterinary Institute. Based on body length, 112 were determined as captive-born and 96 as wild-born. The mean litter size ± SE of wild-born females was 7.6 ± 0.9 (range: 5–11 kits) and for captive-born females 5.9 ± 0.9 (range: 1–10 kits). The relationship between age (in months) of mink and pulp cavity width was highly significant. Individuals with a pulp cavity width of >35% were younger than one year. Based on fecundity, the turnover of the mink population was estimated to be 66%, and the yearly mortality was estimated at 69%. Hence, the population is slightly declining. In conclusion, a feral reproducing mink population in Denmark persists without a continuous influx of captive-born mink from farms.

How Selective Breeding Has Changed the Morphology of the American Mink (Neovison vison)-A Comparative Analysis of Farm and Feral Animals.

Simple SummaryDecades of selective breeding carried out on fur farms have changed the morphology, behavior and other features of the American mink, thereby differentiating farm and feral animals. The uniqueness of this situation is not only that we can observe how selective breeding phenotypically and genetically changes successive generations, but also that it enables a comparison of farm minks with their feral counterparts. Such a comparison may thus provide valuable information regarding differences in natural selection and selective breeding. In our study, we found significant morphological differences between farm and feral minks as well as changes in body shape: trapezoidal in feral minks and rectangular in farm minks. Such a clear differentiation between the two populations over a period of several decades highlights the intensity of selective breeding in shaping the morphology of these animals and gives an indication of the speed of phenotypic changes and the species’ plasticity. This also suggests that the selective forces (selective breeding vs. natural selection) acting upon body dimensions of minks vary between feral and farm populations.In this study, we performed a comparative analysis of the morphological traits between feral (n = 43) and farm (n = 200) individuals of the American mink in Poland to address the question of how multigenerational intensive selective breeding has morphologically differentiated these two populations. Nine body measurements and two proportion coefficients were obtained using adult individuals. The significance of differences between population means was assessed using the Wilcoxon test for independent samples, while the Kruskal–Wallis test was used to compare sex-population groups. Spearman’s correlation coefficients between measurements were estimated for each population. We also performed Principal Component Analysis (PCA) to identify the variables that were most closely correlated with variation in the trait measurements and to investigate the morphological differences between farm and feral minks. We found that the farm minks exhibited significantly higher mean values for eight out of eleven studied traits. Moreover, significant changes in forelimb length, with no concomitant changes in hindlimb length, were accompanied by differences in body shape: trapezoidal in feral minks and rectangular in farm minks. The PCA suggested an almost complete separation of the two populations and indicated that sexes were quite separate; farm males in particular constitute a wholly discrete cluster. Such a clear differentiation between the two populations and sexes over a period of several decades highlights the intensity of selective breeding in shaping the morphology of these animals.

Digestive tract nematode infections in non-native invasive American mink with the first molecular identification of Molineus patens.

Parasites may negatively affect hosts condition, especially when infection intensity is high. Species introduced to a new habitat are often less exposed to a parasite pressure but may accumulate parasites in time. American mink (Neovison vison) introduced to Europe, Asia, and South America is an example of such invasive species. We analysed nematode prevalence and digestive tract infection intensity in 796 feral American mink from Poland. The analyses were performed separately for stomach, duodenum, small intestine and large intestine. Parasite species identification was performed using molecular methods based on highly conserved nuclear 18S rRNA gene and supplemented with morphological analysis. In total, we collected 26,852 nematodes and 98.6% of them were isolated from mink stomachs. We found positive association between infection intensity in stomach and other parts of digestive tract. Nematode prevalence was estimated at 63.8% and average infection intensity per one American mink at 52.9 (range from 1 to 1118). If the stomach results were theoretically and intentionally omitted the prevalence was 5 times lower (12.7%) and infection intensity 14 times lower (3.7; range 1–50). We identified two nematode species in digestive tracts of American mink: Aonchotheca putorii and Molineus patens. The 18S rRNA gene sequence of Molineus patens has been reported for the first time. The results showed that Aonchotheca putorii is a dominating nematode in the invasive American mink and that it inhabits stomach intensively and preferably.

Aleutian mink disease: Spatio-temporal variation of prevalence and influence on the feral American mink.

Pathogens are one of the factors driving wildlife population dynamics. The spread of pathogens in wildlife is currently highly related to the transmission of pathogens from farmed animals, which has increased with the constant development of farming. Here, we analysed the spatio‐temporal variation in the prevalence of Aleutian mink disease virus (AMDV) antibodies in feral American mink (Neovison vison) populations in Poland (1,153 individuals from nine sites) in relation to mink farming intensity. AMDV was detected in feral mink at all study sites and the prevalence ranged from 0.461 in the northern region to 0.826 in the western region. Mink males and adults were infected more often than females and subadults; the infection was also more frequent during the mink breeding season than during non‐breeding. The prevalence of AMDV changed non‐linearly in consecutive years and the peak of prevalence was every 3–4 years. The predicted AMDV prevalence was low at sites where the number of farmed mink was also low and increased linearly with the increase in the number of mink kept on farms. The predicted AMDV prevalence at sites with low mink farming intensity strongly varied between years, whereas at sites with high mink farming intensity, the predicted prevalence did not change significantly. AMDV infection affected the mink's body condition and caused an increase in the size of the spleen, liver and kidneys. This study shows that Aleutian mink disease strongly affects feral mink but the spatio‐temporal variation of its prevalence is complex and partly related to the transmission of the virus from farmed mink to feral populations. The study highlights the complexity of AMDV circulation in feral mink populations and implicates a potential spillover of the virus to native species.

Seroprevalence of Echinococcus spp. and Toxocara spp. in Invasive Non-native American Mink

Invasive non-native species can become reservoirs of zoonotic pathogens and cause their spread during colonization, increasing the risk of zoonoses transmission to both wild hosts and humans. American mink (Neovison vison) are considered an important invasive mammal species responsible for carrying endoparasites. The aim of our study was to evaluate the role of feral American mink as a possible transmission vector of Echinococcus spp. and Toxocara spp. in wildlife. We analysed the frequency of American mink exposure to both parasites, the spatial distribution in Poland, and the variability over time on the basis of specific antibody presence using ELISA and Western blot. Alimentary tract analyses revealed that American mink do not serve as definitive hosts for these parasites. Altogether, 1100 American mink were examined. The average seropositivity for American mink was 14.2% for echinococcosis and 21.7% for toxocarosis; dual-seropositivity was detected in only 6.0%. Seroprevalence of both parasites differed between study sites and significantly increased over time in Toxocara spp. Thus, our study revealed that free-living American mink are exposed to parasites and likely to be involved in the maintenance of both Echinococcus spp. and Toxocara spp. in the wild as paratenic hosts.

Methods for the identification of farm escapees in feral mink (Neovison vison) populations.

In Denmark, American mink (Neovison vison) have been bred for their fur since the mid-1920s. Mink escaping from farms may supply the feral population. Often, it is of biological and management interest to separate the population of feral mink (i.e. mink caught in the wild) in two groups: 1) mink born on farms i.e., escapees, and 2) mink born in the wild. In this study, two methods were used for separating feral mink into the two groups: a) Comparison of body length of farmed mink and feral mink, and b) Presence of a biomarker (tetracycline: an oral antibiotic used on mink farms). A total of 367 wild caught mink (from the mainland of Denmark and the island of Bornholm), and 147 mink from farms, collected during the period 2014–2018, were used for the analysis of body length. For the testing of tetracycline (TC) as a biomarker, 78 mink from farms where there was knowledge about TC treatment (with or without) were examined for fluorescent markings in the canine teeth. Results from both univariate analyses and Gaussian mixture model analysis demonstrated clear divisions between the mean body length (mean ± S.E., range) of farmed males (52.1 cm ± 0.4, 48–68) and farmed females (mean 44.0 ± 0.2, 40–50), and between farmed mink and wild caught mink. Mixture analysis identified two groups within each sex of the wild caught mink, one assigned to farmed mink (born in captivity) and another group of smaller mink suspected of being born in the wild. On Bornholm, the mean (±SD, range) length of males born in the wild was 43.7cm (± 0.3, 36–57) and for females 37.5cm (± 0.3, 32–45). The mean length (±SD, range) of males born in the wild in the mainland of Denmark was 42.5cm (± 2.3, 36–46) and for females 36.1cm (± 1.0, 34–37). Among the feral mink from mainland Denmark, 28.4% of males and 21.6% of females were identified as escapees, while 0% of the males and 1% of the females were identified as escapees among the wild caught mink on Bornholm. Eight percent of mink from farms using tetracycline were false negatives, while no false positives were found among mink from farms not using TC. TC fluorescence was found in five of 217 mink caught in the wild equivalent to 22% escapees in mainland Denmark. No TC markings were found in mink caught in the wild on Bornholm. In conclusion, both methods a) the body length of mink, and b) fluorescent biomarkers in canine teeth are considered as useful tools to identifing mink that have escaped from farms.

Genetic diversity of ranch and feral American mink (Neovison vison Schreber, 1777) in Poland in relation to the natural population of the species

In Poland, the number of feral mink (Neovison vison) and the size of the fur-farming industry are growing. There is a concern that the gene pool of the wild living mink is being infiltrated by that of ranch animals. Three populations were analyzed: Polish ranch mink, feral animals from Poland, and, they were for the first time in Poland, compared with wild individuals from North America. The breeding history of the species and the main ways of introducing the American mink into new areas on different continents were considered. The final research included analysis of the polymorphism of 12 Mustelidae-specific microsatellite loci. It showed a similar level of genetic diversity in all the investigated populations. The research revealed the existence of geographically-specific subpopulations of feral mink in Poland, characterized by different origins, and indicated a small degree of introgression between Polish ranch and wild living populations in the past although the assignment simulation makes it clear that they are genetically distinct groups. The results are in accordance with previously reported models of colonization of Poland by this species and help to explain the influence of anthropogenic factors on the current status of this invasive species. Mixing of two separate genetic pools from the native range in Poland is a newly identified factor, shaping the genetic structure of ranch and feral populations of Neovison vison.