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.

Neuropathologic features of Aleutian disease in farmed mink in Ireland and molecular characterization of Aleutian mink disease virus detected in brain tissues.

A neuropathologic survey was conducted on mink brains from the 5 licensed mink farms in Ireland. The survey was part of a transmissible spongiform encephalopathy surveillance study. Aleutian disease (AD) was present on 4 of the 5 farms (80%). Neuropathologic features of nonsuppurative meningoencephalitis were common in mink from the 4 affected farms but were absent in the mink from the fifth farm, which was free of AD. The meningoencephalitis was characterized by infiltrates of lymphocytes and plasma cells, which were present in meninges, perivascular spaces, and the brain parenchyma. Fibrinoid necrotizing arteritis was seen in 11 mink brains, all of which were obtained from a single farm. Aleutian mink disease virus (AMDV) sequences for the capsid protein VP2 were obtained from brain samples from all affected farms. Although containing previously unreported amino acid residues, similarities with European and North American isolates were observed in the hypervariable regions within VP2, suggesting Irish AMDV is related to those isolates. The predicted amino acid residues, suspected of conferring pathogenicity at certain positions of the VP2 sequence, were present in the viral nucleic acid sequences.

Aleutian mink disease virus and humans.

Reports of a possible relationship between Aleutian mink disease parvovirus (AMDV) and human infection are rare. However, 2 mink farmers with vascular disease and microangiopathy similar to that in mink with Aleutian disease were found to have AMDV-specific antibodies and AMDV DNA. These findings raise the suspicion that AMDV may play a role in human disease.

Infection with Aleutian disease virus-like virus in a captive striped skunk.

CASE DESCRIPTION: A 5-month-old captive female striped skunk (Mephitis mephitis) was evaluated because of lethargy, signs of depression, azotemia, and erythema of the skin around the eyes. CLINICAL FINDINGS: Antemortem diagnostic tests revealed renal disease but failed to identify an etiologic agent. A diagnosis of severe nonsuppurative interstitial nephritis was made on the basis of results of histologic examination of renal biopsy specimens. TREATMENT AND OUTCOME: The skunk was administered isotonic fluids SC daily and later every other day because of the handling-related stress. Because of the skunk's deteriorating condition, it was euthanized after 24 days of supportive care. Aleutian disease was diagnosed on the basis of positive results of a PCR assay that targeted the DNA from Aleutian disease virus (ADV); positive results for ADV were also obtained by use of plasma counterimmunoelectrophoresis and an ELISA. Genetic sequencing of the 365-base pair PCR product revealed 90% sequence identity with mink ADV. CLINICAL RELEVANCE: In the skunk of this report, infection with a skunk-specific parvovirus resulted in clinical signs and pathologic changes similar to those associated with ADV infection in mink. For skunks with signs of renal failure, differential diagnoses should include parvovirus infection. In confirmed cases of infection with this ADV-like virus, appropriate quarantine and biosecurity measures should be in place to prevent spread to other susceptible animals within a zoological collection.

Immunohistochemical detection of 3 viral infections in paraffin-embedded tissue from mink (Mustela vison): a tissue-microarray-based study.

Immunohistochemical (IHC) assays were developed and tested for the detection of 3 viral infections in archived paraffin-embedded mink tissue. Specimens had been obtained from mink with diagnoses of acute Aleutian disease (AD), mink parvoviral enteritis (MVE), or canine distemper (CD) made by means of routine diagnostic procedures. To improve the efficiency and reduce the costs of IHC analyses, tissue microarray (TMA) technology was used. Representative cores 2 mm in diameter from each tissue specimen and from positive- and negative-control specimens were collected in a TMA block. Immunohistochemical reactions to viral antigens were assessed and graded. Positive reactions were found in 91% of the 32 specimens from mink with AD, 53% to 80% of the 60 specimens from mink with MVE, and all 66 of the specimens from mink with CD. To validate the use of TMAs, the IHC methods were applied to whole-mount paraffin-embedded sections of 10 of the positive specimens for each disease, together with whole-mount sections of small intestine and lung tissue from 2 healthy mink. The IHC grading of the TMA cores and the whole-mount sections from the same animal corresponded completely. These results suggest that IHC demonstration of viral antigen allows rapid and reliable diagnosis of the 3 viral infections in mink and is a potential supplement to histologic diagnostic procedures. The TMA technique proved useful for screening large numbers of samples for expression of specific viral antigens, while reducing overall costs.

Reduced severity of histopathological lesions in mink selected for tolerance to Aleutian mink disease virus infection.

The objective of this study was to measure the effect of selection for tolerance on the severity of the Aleutian disease (AD) lesions in mink. Sensitivity and specificity of antibody detection in the blood by counter-immunoelectrophoresis (CIEP) relative to the presence of Aleutian mink disease virus (AMDV) in the spleen by PCR in naturally infected farmed mink were also estimated. Carcasses of 680 sero-positive (CIEP-P) black mink from 28 farms in Nova Scotia, Canada, and from 132 sero-negative (CIEP-N) mink from 14 of these farms were collected at pelting time. A total of 116 of the CIEP-P mink were from three farms where animals have been selected for tolerating AD for almost 20years. The severity of the AD lesions was assessed by histopathological examination of kidneys, lungs, heart, brain and liver on a scale of 0 to 4. Sensitivity and specificity of CIEP relative to PCR were 0.97 and 0.85, respectively, and 16.5% of CIEP-N mink were PCR positive, which could be one of the reasons for the failure of virus eradication by CIEP in Canada. The CIEP-N and tolerant CIEP-P animals had 9.39 and 6.23 greater odds of showing lower lesion severity, respectively, than the CIEP-P animals (P<0.01). The CIEP-N mink had a slightly higher chance (P=0.07) of showing lower lesion severity (odds ratio 1.51) compared with tolerant CIEP-P mink. The results suggested that tolerant mink had significantly reduced severity of AD lesions despite having anti-viral antibodies and carrying the virus.

Progression of experimental chronic Aleutian mink disease virus infection.

BACKGROUND: Aleutian mink disease virus (AMDV) is found world-wide and has a major impact on mink health and welfare by decreasing reproduction and fur quality. In the majority of mink, the infection is subclinical and the diagnosis must be confirmed by serology or polymerase chain reaction (PCR). Increased knowledge based on a systematically description of clinical signs, pathology and histopathology might be a tool to reduce the risk of infection from subclinically infected mink to AMDV free herds. The aim of this study was to give a histopathological description of the progression of a chronic experimental infection with a currently circulating Danish strain of AMDV, Saeby/DEN/799.1/05. These results were compared with the pathogenesis of previously published AMDV stains. RESULTS: This experimental AMDV infection resulted in only decreased appetite and soft or discolored feces, primarily within the first 8 weeks after AMDV inoculation. Gross pathology revealed few and inconsistent findings mainly associated with the liver, spleen and kidneys. The majority of the AMDV inoculated wild type mink (n = 41) developed various histopathological changes consistent with AMDV infection in one or more organs: infiltrations of mononuclear cells in liver, kidney and brain, reduced density of lymphocytes and increased numbers of plasma cells in lymph nodes and spleen. Natural infection, as occurred in the sentinel sapphire mink (four of six mink), progressed similar to the experimentally inoculated mink. CONCLUSIONS: Experimental AMDV inoculation mainly resulted in subclinical infection with unspecific clinical signs and gross pathology, and more consistent histopathology appearing at any time after AMDV inoculation during the 24 weeks of observation. Thus, the observed histopathology substantiates AMDV infection and no correlation to time of inoculation was found. This confirms that diagnosing AMDV infection requires serology and/or PCR and the Saeby/DEN/799.1/05 AMDV strain results in histopathology consistent with other AMDV strains.

Glomerular lesions in Aleutian disease of mink (Mustela vison): a morphological and differential morphometrical study.

A morphological and morphometrical study has been carried out on glomerular lesions in mink with spontaneous Aleutian disease, using the WHO classification for Systemic Lupus Erytematous Nefritis. 154 renal samples from sick animals and 10 samples from uninfected mink were processed by routine histopathological techniques and metacrylate inclusions. The samples were studied quantitatively with an automatic image analyzer. 5 forms of glomerulonephritis (GN) were identified: mesangial glomerulonephritis (n = 13), focal and segmental GN (n = 10), diffuse GN (n = 99), membranous GN (n = 12) and advanced sclerosing GN (n = 10) and were associated with the degree of interstitial plasmocytosis. Glomerule morphometry was shown to be an excellent method for identifying the type of lesion, while it quantified the participation of various glomerular elements in the lesion.

Analyses of leucocytes in blood and lymphoid tissues from mink infected with Aleutian mink disease parvovirus (AMDV).

Mink were infected with Aleutian Mink Disease Parvovirus (AMDV) and sacrificed at monthly intervals after infection. During this time humoral immune responses and leucocyte numbers in blood, mesenteric lymph node, spleen and thymus were monitored. Serum hypergammaglobulinaemia was observed together with elevated antibody responses to AMDV NS1 and VP1/2 proteins. In blood, a highly significant increase in CD8+ lymphocytes was observed. However, (presumed)CD4+ cells defined as CD3+CD8- cells, and B lymphocytes remained relatively constant throughout the study. The (presumed)CD4+/CD8+ ratio decreased significantly from greater than 2 to less than 0.5 and MHC-II+ blood leucocytes increased significantly during infection, a large proportion of these being CD8+. Similar changes were observed in the mesenteric lymph node and spleen. Immunohistology of lymph nodes showed a massive expansion of the paracortical area due to increased numbers of CD8+ cells. The staining intensity of B lymphocytes in lymph nodes with a CD79a reactive monoclonal antibody was decreased in the late infection, indicating a possible greater number of plasma cells. Thymic involution was observed during the AMDV infection, although relative increases in CD3high (presumed)CD4+ and CD3highCD8+ single positive cells were observed. These increases were countered by a corresponding reduction in the CD3low(presumed)CD4+CD8+ double positive cell population. Immunohistology of the thymus in normal mink showed that most of the matured CD3+ T cells were present in the inner medulla, while only few CD3+ cells could be found in the outer cortex. In severely infected mink the thymic structural organisation vanished, and CD3+ cells were found throughout the organ.

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.

Intrapulmonary lymphoid tissue in mink infected with Aleutian disease virus.

Pulmonary lymphoid tissue was studied histologically in mink infected experimentally and naturally with Aleutian disease virus, an infection characterised by systemic lymphoid tissue hyperplasia. Lymphoid tissue hyperplasia was observed in the lamina propria of the bronchial tree, in perivascular tissue, in interlobular septae and subpleurally by day 42 after experimental aerosol infection. Four forms of pulmonary lymphoid tissue were recognised: lymphoepithelial nodules or bronchus-associated lymphoid tissue; lymphoid clusters; lymph nodes and diffuse lymphoid tissue. The cel components of these pulmonary reactions were indistinguishable from those seen in the kidney and the liver of the same experimental animals, except for lymphoepithelial nodules which have a specialised association with respiratory epithelium. Pulmonary lymphoid tissue hyperplasia was a significant feature of experimental aerosol infection with Aleutian disease virus but not of natural infections with this virus.

Spontaneous Aleutian disease in a ferret.

A 3-year-old female ferret died five days after admission to a veterinary clinic for treatment of acute dyspnea and posterior paresis. Blood chemistry showed no hypergammaglobulinemia. Histopathological examination revealed mild to severe inflammatory infiltrates, composed mostly of plasma cells, in multiple organs. Lesions were especially severe in the kidneys, where focal segmental membranous glomerulopathy was also present. In the liver, in addition to lymphocytic and plasmacytic infiltration in periportal areas, dilatation and proliferation of the bile ducts were seen. On analysis of PCR products, using primers directed against the gene encoding Aleutian disease (AD) viral capsid and formalin-fixed kidney samples, we detected a single band of about 400 bp, specific to the AD virus.

Progression of Aleutian disease in natural and experimentally induced infections of mink.

OBJECTIVE: To study temporal changes in amounts of viral DNA in blood leukocytes over long periods, and to determine whether severity of the disease is greater in experimentally induced, compared with natural, infection. ANIMALS: 18 naturally and 6 experimentally infected black mink; 26 naturally infected brown mink. PROCEDURE: Polymerase chain reaction amplification to detect viral DNA in blood and counter-immune electrophoresis to detect serum antibody were performed at regular intervals. RESULTS: In naturally infected black mink, amounts of viral DNA were initially high, but after the appearance of antibody, viral DNA fluctuated and, in some instances, was undetectable. In other mink, small amounts of viral DNA were infrequently detected during the course of the infection. Amounts of viral DNA in leukocytes in late stages of the disease correlated with renal lesions in brown mink, but black mink had more severe lesions associated with smaller amounts of viral DNA. Severity of the disease was not enhanced in experimentally inoculated black mink. CONCLUSIONS: After infection, leukocyte viral DNA is initially present in large amounts, but, in most mink, decreases markedly in association with the appearance of antibody. There is no difference in the progression and severity of the disease between black mink infected experimentally or naturally. Transmission of the disease may be enhanced by use of contaminated toenail clippers for blood collection.

Protides of the Mustelidae: immunoresponse of mustelids to Aleutian mink disease virus.

Members of North American Mustelidae were tested for their response to inoculation with 10(6) infective doses of Aleutian disease virus. In subfamily Mustelinae, 3 species in the genus Mustela (M vision, M erminea, and M putorius) and 2 species in genus Martes (Ma pennanti and Ma americana) responded immunologically with some features resembling Aleutian disease in mink. In subfamily Mephitinae, only Mephitis mephitis responded, and others of the subfamily did not, nor did members of subfamilies Melinae and Lutrinae. The responses observed ranged from development of detectable antibody levels determined by counterimmunoelectrophoresis to histopathologic changes typical of Aleutian disease.

Comparison of the lesions of Aleutian disease in mink and hypergammaglobulinemia in ferrets.

Gross and microscopic lesions of Aleutian disease (AD) in mink and hypergammaglobulinemia in ferrets were compared. Both conditions were characterized by widespread proliferation of plasma cells, but proliferation was more prominent in mink infected with AD. Arteritis did not occur in hypergammaglobulinemic ferrets. Minimal or no glomerular alterations occurred in infected ferrets, but were severe in mink infected with AD. Bile duct proliferation was more prominent in diseased mink. Tissue alterations suggested that AD in Aleutian genotype mink is more rapidly progressive than is AD in ferrets, causing overt clinical disease and death. In contrast, hypergammaglobulinemia in ferrets appeared to progress more slowly, with little clinical evidence of disease. This is probably the result of a paucity of glomerular lesions in ferrets. Possible mechanisms to explain the differences in the development of lesions are discussed.

Effect of a valine residue at codon 352 of the VP2 capsid protein on in vivo replication and pathogenesis of Aleutian disease parvovirus in mink.

OBJECTIVE: To determine whether a group of 3 genetic differences in the nonstructural protein (NS1) or 1 genetic difference in the structural protein (VP2) of Aleutian disease parvovirus (ADV) is responsible for an increase in the in vivo replication and pathogenicity of G/U-8, a chimera of ADV-G (nonpathogenic) and ADV-Utah (pathogenic), compared with G/U-10. ANIMALS: 32 eight-month-old female sapphire mink (Mustela vison). PROCEDURE: Chimeric viruses were constructed, propagated in vitro, and used to inoculate mink. Antiviral antibody responses, presence of serum viral nucleic acid, and serum gamma globulin concentrations were monitored for 120 days following inoculation. Histologic examination of the liver, kidneys, spleen, and mesenteric lymph nodes was performed after necropsy. RESULTS: A chimera containing only the 3 amino acid substitutions in NS1 did not elicit measurable responses indicative of replication or pathogenicity in inoculated mink. Serum antiviral antibody responses, frequency of detection of viral nucleic acid in serum, gamma globulin response, and histologic changes in mink inoculated with chimeras containing a valine residue at codon 352 (352V) of VP2 capsid were increased, compared with values from mink inoculated with chimeric viruses that did not contain 352V. CONCLUSIONS AND CLINICAL RELEVANCE: A valine residue at codon 352 in the VP2 capsid protein of ADV affects in vivo viral replication and pathogenicity. This amino acid may be part of an incompletely defined pathogenic determinant of ADV. Further characterization of the pathogenic determinant may allow future development of focused preventive and therapeutic interventions for Aleutian disease of mink.

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.

Parvovirus-associated syndrome (Aleutian disease) in two ferrets.

There is a paucity of information regarding natural Aleutian disease, caused by a parvovirus in ferrets. With the increasing popularity of ferrets as household pets and laboratory animals, and with the advent of a USDA-approved rabies vaccine, the occurrence and the etiopathogenesis of naturally acquired diseases in ferrets needs to be documented. We present the clinical and laboratory findings associated with Aleutian disease in 2 domestic ferrets, one with the chronic wasting form of the disease and one with the central nervous system form.

Suspected Aleutian disease in a wild otter (Lutra lutra).

Clinical and pathological observations of a naturally occurring disease in a British wild otter (Lutra lutra) are reported. Systemic lymphoreticular proliferative changes with plasmacytosis, glomerulonephritis, arteritis and biliary hyperplasia closely resembled the pathological changes in Aleutian disease of mink (Mustela vison). Feral mink provided a possible source of infection.