Persistent viral shedding during asymptomatic Aleutian mink disease parvoviral infection in a ferret.

A 2-year-old domestic ferret that appeared clinically healthy was repeatedly seropositive for Aleutian mink disease parvovirus (ADV) over a 2-year observation period. Antibody titers, determined by counter-immunoelectrophoresis, ranged from 1024 to 4096. Viral DNA also was identified in serum, urine, feces, and blood cell fractions by polymerase chain reaction analysis. Ultimately, DNA in situ hybridization revealed ADV DNA in histologic sections of various tissues and organs. These data indicate that this asymptomatic ferret was persistently infected with ADV.     

Nonsuppurative meningoencephalitis associated with Aleutian mink disease parvovirus infection in ranch mink.

Severe nonsuppurative meningoencephalitis associated with Aleutian mink disease parvovirus (ADV) infection was observed in adult ranch mink. Brain lesions included severe, locally extensive to coalescing lymphoplasmacytic meningoencephalitis with accompanying gliosis, satellitosis, and mild extension of inflammation into the leptomeninges. ADV was identified in mesenteric lymph node, spleen, brain, and liver of affected mink by polymerase chain reaction techniques. Sequences of the ADV isolate (TH5) revealed 2 unique residues in the region of the viral genome that determines pathogenicity. These findings suggest that certain strains of ADV may preferentially cause disease in the nervous system. ADV infection should be considered in the differential diagnosis of neurologic disorders in mink.     

Antigen distribution in organs of mink with Aleutian disease parvovirus infection

On tissues from naturally infected non-Aleutian mink an immunohistological study was performed using monoclonal antibodies and the immunoperoxidase method. Structural proteins of ADV were demonstrated in cryosections and in ethanol-fixed and paraffin-embedded material which provide antigen detection in a similar amount together with good histological structure. In lymphoid organs viral antigen was restricted to B-cell areas, particularly lymphoid follicles. The pattern of antigen distribution was typical for follicular dendritic cells which are capable to retain immune complexes. Beside macrophages in the interior of lymphoid follicles most likely proliferating B-lymphoblasts reveal nuclear and cytoplasmatic presence of structural proteins indicating viral replication. Cells of the mononuclear phagocyte system such as cells of lymphatic sinuses and hepatic Kupffer cells harbor viral protein in the cytoplasm, probably resulting from phagocytosis of immune complexes. Renal glomeruli were consistently negative for virus antigen whereas in interstitial infiltrates cells resembling macrophages stained positive for ADV structural proteins.     

A survey of Aleutian mink disease virus infection of feral American mink in Nova Scotia

Spleen samples from 14 mink that were trapped in 4 counties of Nova Scotia were tested for the presence of the Aleutian mink disease virus (AMDV) by polymerase chain reaction. Viral DNA was not detected in samples from Kings County (n = 2), but was detected in all the mink sampled from Colchester (n = 2) and Halifax (n = 6) counties, and 3 of 4 mink from Yarmouth County. The high level of AMDV-infected mink in Colchester and Halifax counties may pose a serious threat to the captive mink and wild animal populations. Because treatment of infected free-ranging mink is not an option, AMDV control strategies for the captive mink should be primarily focused on bio-security to protect clean ranches.     

Monitoring chronic infection with a field strain of Aleutian mink disease virus

Aleutian mink disease virus (AMDV) readily spread within farmed mink and causes chronic infections with significant impacts for welfare and economy. In the present study a currently circulating Danish AMDV strain was used to induce chronic experimental infection of farmed mink.PCR was used to detect viral DNA in full blood, organs, faeces and oro-nasal swabs weekly for the first 8 weeks and then biweekly for another 16 weeks after AMDV challenge inoculation of wild type mink. The mink (n = 29) was infected and seroconverted 2–3 weeks after AMDV inoculation and AMDV antibodies persisted during the maximum experimental period of 24 weeks. Viraemia and faecal excretion of viral DNA was detected in the mink (n = 29) at various and intermittent time intervals. Excretion of viral DNA in oro-nasal swabs was detected for 1–8 weeks in 21 mink. This highlights the risk of transmitting AMDV between infected farms.PCR was successfully used to detect viral DNA in organs 8, 16 and 24 weeks after AMDV inoculation with only minor differences between these weeks which is of diagnostic interest.This AMDV challenge model was also used to mimic natural infection of susceptible sapphire mink. Four of 6 sapphire mink were infected indirectly via the AMDV inoculated wild type mink whereas the other 2 sapphire mink remained uninfected.     

Molecular epidemiology of Aleutian mink disease virus in Finland

Aleutian mink disease virus (AMDV) is a parvovirus that causes an immune complex-mediated disease in minks. To gain a more detailed view of the molecular epidemiology of mink AMDV in Finland, we phylogenetically analysed 14 new Finnish strains from 5 farms and all 40 strains with corresponding sequences available in GenBank. A part of the major non-structural (NS1) protein gene was amplified and analysed phylogenetically. A rooted nucleotide tree was constructed using the maximum parsimony method. The strains described in this study showed 86-100% nucleotide identity and were nearly identical on each farm. The ratio of synonymous to non-synonymous substitutions was approximately 2.7, indicating a mild purifying selection. Phylogenetic analysis confirmed that AMDV strains form three groups (I-III), all of which contained Finnish strains. The tree inferred that the three lineages of AMDV have been introduced to Finland independently. The analysis suggested that AMDV strains do not cluster into genotypes based on geographical origin, year of isolation or pathogenicity. Based on these data, the molecular clock is not applicable to AMDV, and within this gene area no recombination was detected.     

水貂阿留申病病毒分子生物学研究进展

水貂阿留申病病毒是一种在水貂中广泛存在的重要病原体.该病毒属阿留申病毒属,主要编码4种蛋白(结构蛋白VP1、VP2和非结构蛋白NS1、NS2).VP1蛋白在协助病毒产生感染性方面起着重要作用;VP2蛋白是该病毒的主要免疫原性抗原,能体外中和病毒;NS1和NS2对病毒在宿主细胞中的复制起重要的调节作用.该病毒的分子生物学诊断技术主要有核酸杂交技术、PCR和基因芯片检测技术.     

Pregnancy rate and foetal mortality in Aleutian disease virus infected mink

It is well known observation that farms contaminated with Aleutian Disease (AD) virus on an average have a lower breeding result than not infected farms. In the Danish eradication programme a farm may be registered as an A-farm, if a number of conditions are fullfilled. Among the conditions are yearly testings by countercurrent immuno-electrophoresis of all breeders or certain groups of these. The testing is carried out by the laboratory of the Danish Fur Breeder’s Association. Starting with the testing of 30.000 samples in 1976 the number of tests were 2.9 millions in 1986. The number of A-farms was more than 1,500 out of 4236 in 1986. The A-farms had in 1986 608,116 breeders with an average breeding result of 4.81 compared to the not tested farms that have an average of 4.37 kits per mated female. While the number of breeders has increased from 1.0 million in 1980 to 2.1 million in 1986, the percentage of infertile females has in the same period decreased from 14.7 to 10.9 with an average breeding result increasing from 4.09 to 4.69 (Anon. 1986).     

Mechanisms contributing to the virus persistence in Aleutian disease

In this review published results and further studies concerning the persistence of Aleutian disease virus (ADV) isolate SL3 are presented. By Southern blot and in situ hybridization with strand-specific RNA probes focal replication of ADV-DNA was demonstrated in spleen, mesenteric lymph nodes, sporadically in mononuclear cells of the peripheral blood and bone marrow cells. These findings further support the concept of the lymphotropism of ADV. All cell culture-adapted ADV strains appear to have a ts-defect. Our in vitro studies indicate that the ADV isolate G(orham) induced the synthesis of comparable amounts of viral replicative DNA and viral proteins VP1 and VP2 at the non-permissive temperature of 37 degrees C. However, the viral progeny DNA synthesis was about threefold less at 37 degrees C compared to the permissive temperature of 32 degrees C. These findings suggest that the reduced level of viral progeny DNA at 37 degrees C accounts for the reduced production of infectious ADV. Finally, we provided experimental evidence that the apparent lack of neutralizing antibodies in AD is due to the masking of critical viral epitopes by cellular phospholipids.     

Diversity and stability of Aleutian mink disease virus during bottleneck transitions resulting from eradication in domestic mink in Denmark

Aleutian mink disease (plasmacytosis) virus (AMDV) in domestic mink (Neovison vison) has been subject to eradication in Denmark since 1976. In 2001, approximately 5% of Danish mink farms were still infected and all were located in the northern part of the peninsula of Jutland. In the present study a total of 274 Danish isolates of AMDV collected during the two seasons of 2004 and 2005 were characterized by partial sequencing of the coding region of the non-structural (NS) proteins. Older AMDV isolates from Denmark, available, were also included. The Danish isolates represent a very homogenous cluster compared with Swedish, Finnish and Dutch isolates and seem to represent a minor fraction of the genetic diversity previously found in Denmark. Stability of nucleotide deviations reveals that the purifying selection of bottlenecks imposed on the AMDV population in Denmark by the stamping out policy for more than 6 years exceeds the rate of mutation driven diversity. Among the isolates from farms in northern Jutland two distinct types could be identified and within each of them a number of sub-types which were all useful in tracking spread of infections. Infection at a farm the preceding season was a predisposing risk parameter for disease outbreak at a farm, and strain identity substantiates the suggestion that inadequate disinfection is involved in the recurrence of outbreaks. In cases of new introductions to farms it is indicated that contact including transport between farms played a most significant role.     

Histopathologic and immunohistochemical lesions in liver of mink infected with Aleutian disease virus

Parvovirus of Aleutian disease causes mainly damage to kidneys, but immune complexes deposition and damage may occur also in other organs. In mink farms of Latvia the liver dystrophy or hepatic lipidosis of mink is widely distributed. The goal of this study was to examine probability of liver damage and regeneration of mink infected with Aleutian disease virus. Liver injury was assessed histologically. The mink liver demonstrated inflammation of liver parenchyma and foci of fatty liver. In immunohistochemistry, during liver regeneration the matrix metalloproteinases MMP-9, vascular endothelial growth factor and beta-defensin 2 expressions were lower, but MMP-2 and nerve growth factor receptor p75 expression was increased.     

Aleutian disease in the ferret

Ferrets inoculated with Aleutian disease (AD)-infective material of mink origin harbored the infective agent for at least 136 days after inoculation. In contrast, hamsters given a similar inoculum of infective material no longer harbored the infective agent at 21 days postinoculation. During the infective period, neither ferrets nor hamsters had any detectable illness. However, in certain ferrets, massive periportal lymphocytic infiltrates were observed. A survey of ferrets from different ranches revealed similar lymphocytic infiltrates only in ferrets raised on a ranch which had AD-infected mink.