Recurrent outbreak of Streptococcus bovis/Streptococcus equinus complex-associated meningoencephalitis in farmed mink

The Streptococcus bovis/Streptococcus equinus complex (SBSEC) is part of the normal gastrointestinal microflora in animals and humans but is an opportunistic pathogen that has been implicated in meningitis, endocarditis and septicaemia. There is only one report of SBSEC causing disease (endocarditis) in mink. This case report describes two outbreaks of SBSEC infection in farmed mink occurring 1 year apart at the same facility. In both cases, affected mink had neurological signs prior to death and the mortality level was 5,000 (2021) and 500 (2022) out of 100,000 mink. Necropsy findings included hepatomegaly, splenomegaly and congested lungs. Histopathology revealed suppurative meningoencephalitis and neutrophilic inflammation in the lungs, liver and kidneys. Aerobic bacterial culture identified SBSEC isolates in the brain and liver. This is the first report to implicate SBSEC in meningoencephalitis and septicaemia in farmed mink.

Genetic differences in variants of the AMD virus at the site of a disease outbreak

Aleutian Mink Disease Virus (AMDV) results in mink breeding losses due to frequent abortion, low fecundity and high juvenile mortality. Due to the high persistence of pathogen in the environment and lack of causative treatment there is a need for research on alternative methods to eliminate the pathways of the spread of the virus and extinguish current outbreaks. The aim of the study was to investigate molecular variation of AMDV on a farm where mass deaths of mink took place. The material for the research was obtained from a mink farm located in Latvia. Mass deaths had occurred on the farm among symptoms typical of Aleutian disease. Spleen samples were collected from the dead animals during post-mortem examination. Sequencing and bioinformatic analysis made it possible to distinguish the variants occurring in the groups. The presence of the genetic material of the virus was confirmed by PCR and qPCR in each of the spleen samples. The isolates were divided into two main groups: the dominant group A, with more than 83% of all isolates, and group B. Comparison of the variants with the nonpathogenic strain AMDV-G revealed that isolates from group A were more than 95% similar to that strain, whereas the similarity of group B isolates was just over 86%. The average viral load in both groups was 108 copies; no differences in viral load were noted between groups. Testing based on serological analysis produces fairly effective screening results, but these methods do not enable complete elimination of the virus from a population. Only their use in combination with modern testing techniques as tools for identification of vectors and the directions of the spread of the AMD virus can make it possible to block the routes of its spread and to extinguish its current outbreaks.

First Report of Skunk Amdoparvovirus (Species Carnivore amdoparvovirus 4) in Europe in a Captive Striped Skunk (Mephitis mephitis)

Skunk amdoparvovirus (Carnivore amdoparvovirus 4, SKAV) is closely related to Aleutian mink disease virus (AMDV) and circulates primarily in striped skunks (Mephitis mephitis) in North America. SKAV poses a threat to mustelid species due to reported isolated infections of captive American mink (Neovison vison) in British Columbia, Canada. We detected SKAV in a captive striped skunk in a German zoo by metagenomic sequencing. The pathological findings are dominated by lymphoplasmacellular inflammation and reveal similarities to its relative Carnivore amdoparvovirus 1, the causative agent of Aleutian mink disease. Phylogenetic analysis of the whole genome demonstrated 94.80% nucleotide sequence identity to a sequence from Ontario, Canada. This study is the first case description of a SKAV infection outside of North America.

Small but mighty: old and new parvoviruses of veterinary significance

In line with the Latin expression "sed parva forti" meaning "small but mighty," the family Parvoviridae contains many of the smallest known viruses, some of which result in fatal or debilitating infections. In recent years, advances in metagenomic viral discovery techniques have dramatically increased the identification of novel parvoviruses in both diseased and healthy individuals. While some of these discoveries have solved etiologic mysteries of well-described diseases in animals, many of the newly discovered parvoviruses appear to cause mild or no disease, or disease associations remain to be established. With the increased use of animal parvoviruses as vectors for gene therapy and oncolytic treatments in humans, it becomes all the more important to understand the diversity, pathogenic potential, and evolution of this diverse family of viruses. In this review, we discuss parvoviruses infecting vertebrate animals, with a special focus on pathogens of veterinary significance and viruses discovered within the last four years.

Endemic Skunk amdoparvovirus in free-ranging striped skunks (Mephitis mephitis) in California

The genus Amdoparvovirus includes the newly discovered skunk amdoparvovirus and the well-characterized Aleutian disease virus which causes significant health impacts in farmed mink worldwide. In 2010-2013, an outbreak of fatal amdoparvovirus-associated disease was documented in free-ranging striped skunks (Mephitis mephitis) from the San Francisco Bay Area of California. To characterize the geographic distribution, earliest occurrence and abundance of this virus, as well as possible impacts on sympatric mustelids of conservation concern, we tested blood samples from skunks throughout California and fishers (Pekania pennanti) from northern California for amdoparvovirus DNA. Amdoparvovirus DNA was detected in 64.8% of sampled skunks (140/216), and test-positive skunks were distributed widely throughout the state, from as far north as Humboldt County and south to San Diego County. The first test-positive skunks were detected from 2004, prior to the 2010-2013 outbreak. No significant spatial or temporal clustering of infection was detected. Although healthy and clinically ill animals tested positive for amdoparvovirus DNA, histopathologic evaluation of a subset from clinically ill skunks indicated that positive PCR results were associated with pneumonia as well as there being more than one inflammatory type lesion. None of 38 fishers were PCR-positive. Given the widespread geographic distribution and lack of a clear epizootic centre, our results suggest the presence of an endemic skunk-associated amdoparvovirus strain or species. However, if the virus is not host-specific, skunks' ubiquitous presence across rural and urban habitats may pose a risk to susceptible domestic and wild species including mustelids of conservation concern such as fishers and Pacific martens (Martes caurina).

Amdoparvovirus Infection in Red Pandas (Ailurus fulgens)

Aleutian mink disease virus is the type species in the genus Amdoparvovirus, and in mink and other Mustelidae can cause either subclinical disease or fatal chronic immune stimulation and immune complex disease. The authors describe a novel amdoparvovirus in the endangered red panda ( Ailurus fulgens), discovered using viral metagenomics. The authors analyzed the prevalence, tissue distribution, and disease association by PCR, in situ hybridization, electron microscopy, and histology in a group of 6 red pandas from a single zoological collection. The study incorporates a fecal shedding survey and analysis of tissues from 4 necropsied animals over a 12-year span. The tentatively named red panda amdoparvovirus (RpAPV) was detected in the feces and/or tissues of all animals tested. At necropsy of 1 geriatric animal, infection was associated with pyogranulomatous peritonitis, pancreatitis, and myocarditis. Other animals had detectable low-level viral nucleic acid in lymph nodes and both oral and intestinal epithelium at the time of necropsy. Full-length genome sequences of RpAPV strains from 2 animals had 12% sequence divergence, demonstrating genetic diversity even among in-contact animals. RpAPV is a persistent infection in this cohort of red pandas, and has variable clinical expression.

Full genetic characterization and epidemiology of a novel amdoparvovirus in striped skunk (Mephitis mephitis)

Amdoparvovirus is a newly defined parvoviral genus that contains four species (Carnivore amdoparvovirus 1-4), including the well-known Aleutian mink disease virus (AMDV). Amdoparvoviruses cause an immune-associated and often lethal wasting syndrome in Mustelidae and Caninae hosts. In this study, we molecularly investigated amdoparvoviruses detected in 44 striped skunks (Mephitis mephitis) found dead in and around Vancouver, British Columbia, Canada. Some of the animals exhibited pathological changes compatible with amdoparvovirus-associated disease. The nearly complete genomic sequence was obtained for seven different strains and our analyses show how this virus, which we named skunk amdoparvovirus (SKAV), should be classified as a separate species within the genus (proposed Carnivore amdoparvovirus 5). We detected co-infections, recombinant genomes, at least three separate viral lineages, and preliminary evidence for geographic segregation of lineages. Furthermore, we proved that similar viruses, only partially characterized in previous studies and labeled as AMDV, circulate in skunks from other distant areas of North America (Ontario and California) and found evidence for spillover events in mink (Neovison vison). Although SKAVs are capable of causing disease in infected animals, a high proportion of sub-clinical infections has been observed, suggesting these animals might act as asymptomatic carriers and pose a threat to wild and captive carnivores. Finally, we highlight the need for more specific diagnostic tests and further molecular investigations to clarify the epidemiology and host- and geographical distributions of amdoparvoviruses in terrestrial carnivores, especially because the whole spectrum of viral diversity in this group is likely still unknown.

Amdoparvoviruses in small mammals: expanding our understanding of parvovirus diversity, distribution, and pathology

Many new viruses have been discovered recently, thanks in part to the advent of next-generation sequencing technologies. Among the Parvoviridae, three novel members of the genus Amdoparvovirus have been described in the last 4 years, expanding this genus that had contained a single species since its discovery, Aleutian mink disease virus. The increasing number of molecular and epidemiological studies on these viruses around the world also highlights the growing interest in this genus. Some aspects of amdoparvoviruses have been well characterized, however, many other aspects still need to be elucidated and the most recent reviews on this topic are outdated. We provide here an up-to-date overview of what is known and what still needs to be investigated about these scientifically and clinically relevant animal viruses.

Aleutian mink disease virus in striped skunks (Mephitis mephitis): evidence for cross-species spillover

Aleutian mink disease virus (AMDV) causes a parvovirus infection, initially characterized in American mink (Neovison vison), that may have harmful effects on wild populations of susceptible animals. In North America, where American mink are native, the origin, host range, and prevalence of AMDV in wild species is not clear. We studied striped skunks (Mephitis mephitis) and raccoons (Procyon lotor) to determine whether species sympatric with mink are potential reservoirs in the transmission of AMDV to wild mink and mink farms. Antibodies to AMDV were detected in 41% of skunk serum samples (143/347) and AMDV nucleic acids were detected in 32% (14/40) of skunk spleen samples by PCR, indicating that AMDV exposure and infection were frequent in skunks. We detected no AMDV antibodies in 144 raccoon blood samples. Phylogenetic analysis revealed a newly identified AMDV haplogroup consisting of isolates from Ontario skunks and a free-ranging domestic mink from Ontario. Our findings of frequent AMDV infection in skunks, close genetic similarity between skunk and mink AMDV isolates, and evidence of AMDV transmission from skunks to mink support the hypothesis that skunks may be acting as alternative hosts and reservoirs of AMDV to wild mink through cross-species virus spillover.

Aleutian Disease: An Emerging Disease in Free-Ranging Striped Skunks (Mephitis mephitis) From California

Aleutian disease virus (ADV, Amdovirus, Parvoviridae) primarily infects farmed mustelids (mink and ferrets) but also other fur-bearing animals and humans. Three Aleutian disease (AD) cases have been described in captive striped skunks; however, little is known about the relevance of AD in free-ranging carnivores. This work describes the pathological findings and temporospatial distribution in 7 cases of AD in free-ranging striped skunks. All cases showed neurologic disease and were found in a 46-month period (2010-2013) within a localized geographical region in California. Lesions included multisystemic plasmacytic and lymphocytic inflammation (ie, interstitial nephritis, myocarditis, hepatitis, meningoencephalitis, pneumonia, and splenitis), glomerulonephritis, arteritis with or without fibrinoid necrosis in several organs (ie, kidney, heart, brain, and spleen), splenomegaly, ascites/hydrothorax, and/or encephalomalacia with cerebral microangiopathy. ADV infection was confirmed in all cases by specific polymerase chain reaction and/or in situ hybridization. The results suggest that AD is an emerging disease in free-ranging striped skunks in California.

Aleutian mink disease virus in furbearing mammals in Nova Scotia, Canada

Background

Aleutian mink disease virus (AMDV) is widespread among ranched and free-ranging American mink in Canada, but there is no information on its prevalence in other wild animal species. This paper describes the prevalence of AMDV of 12 furbearing species in Nova Scotia (NS), Canada.

Methods

Samples were collected from carcasses of 462 wild animals of 12 furbearing species, trapped in 10 NS counties between November 2009 and February 2011. Viral DNA was tested by PCR using two primer pairs, and anti-viral antibodies were tested by counterimmunoelectrophoresis (CIEP) on spleen homogenates.

Results

Positive PCR or CIEP samples were detected in 56 of 60 (93.3%) American mink, 43 of 61 (70.5%) short-tailed weasels, 2 of 8 (25.0%) striped skunks, 2 of 11 (18.2%) North American river otters, 9 of 85 (10.6%) raccoons, and 2 of 20 (10.0%) bobcats. Samples from six fishers, 24 coyotes, 25 red foxes, 58 beavers, 45 red-squirrels and 59 muskrats were negative. Antibodies to AMDV were detected by CIEP in 16 of 56 (28.6%) mink and one of the 8 skunks (12.5%). Thirteen of the mink were positive for PCR and CIEP, but three mink and one skunk were CIEP positive and PCR negative. Positive CIEP or PCR animals were present in all nine counties from which mink or weasel samples were collected.

Conclusions

The presence of AMDV in so many species across the province has important epidemiological ramifications and could pose a serious health problem for the captive mink, as well as for susceptible wildlife. The mechanism of virus transmission between wildlife and captive mink and the effects of AMDV exposure on the viability of the susceptible species deserve further investigation.

Implementation and validation of a sensitive PCR detection method in the eradication campaign against Aleutian mink disease virus

Aleutian mink disease virus (AMDV) is a severe progressive disease causing multiple different clinical syndromes in mink. In Denmark, the disease is notifiable and under official control. The control programme, based on serological screening, has confined successfully AMDV to the northern part of Denmark. However, re-infections and new introductions of virus into farms require a confirmatory virological test to verify the positive test results of single animals and ultimately to investigate disease transmission. A one step PCR amplifying a 374-base fragment of the NS1 gene of AMDV was compared to the counter-current immune electrophoresis (CIE) routinely used in the serological screening programme. Mink organs (n=299) obtained from 55 recently infected farms and 8 non-infected farms from 2008 to 2010 were tested by PCR, and the results were found to have a high correlation with the serological status of the mink. The relative diagnostic sensitivity of the PCR was 94.7%, and the relative diagnostic specificity was 97.9% when read in parallel with the CIE. PCR positive samples were sequenced and phylogenetic analysis revealed high similarity within the analysed AMDV strains and to AMDV strains described previously.