Long-term antibody production and viremia in American mink (Neovison vison) challenged with Aleutian mink disease virus.

BACKGROUND: Selecting American mink (Neovison vison) for tolerance to Aleutian mink disease virus (AMDV) has gained popularity in recent years, but data on the outcomes of this activity are scant. The objectives of this study were to determine the long-term changes in viremia, seroconversion and survival in infected mink. Mink were inoculated intranasally with a local isolate of Aleutian mink disease virus (AMDV) over 4 years (n = 1742). The animals had been selected for tolerance to AMDV for more than 20 years (TG100) or were from herds free of AMDV (TG0). The progenies of TG100 and TG0, and their crosses with 25, 50 and 75% tolerance ancestry were also used. Blood samples were collected from each mink up to 14 times until 1211 days post-inoculation (dpi) and were tested for viremia by PCR and for anti-AMDV antibodies by counter-immunoelectrophoresis (CIEP). Viremia and CIEP status were not considered when selecting replacements. Low-performing animals were pelted and the presence of antibodies in their blood and antibody titer were measured by CIEP, and viremia and viral DNA in seven organs (n = 936) were tested by PCR. RESULTS: The peak incidences of viremia (66.7%) and seropositivity (93.5%) were at 35 dpi. The incidence of viremia decreased over time while the incidence of seroconversion increased. The least-squares means of the incidence of PCR positive of lymph node (0.743) and spleen (0.656) were significantly greater than those of bone marrow, liver, kidneys, lungs and small intestine (0.194 to 0.342). Differences in tolerant ancestry were significant for every trait measured. Incidences of viremia over time, terminal viremia, seropositivity over time, AMDV DNA in organs and antibody titer were highest in the susceptible groups (TG0 or TG25) and lowest in the tolerant groups (TG100 or TG75). CONCLUSION: Previous history of selection for tolerance resulted in mink with reduced viral replication and antibody titer. Viremia had a negative effect and antibody production had a positive effect on survival and productivity.

Breeding parameters on a mink farm infected with Aleutian mink disease virus following the use of methisoprinol.

Aleutian mink disease virus is one of the greatest threats to modern mink farming. The disease reduces fecundity and causes high mortality among kits. The aim of this study was to evaluate the effectiveness of methisoprinol in counteracting the effects of Aleutian disease, both by inhibiting replication of the virus and by mitigating the harmful effects of the disease on the fecundity and weight of infected animals. The study included 300 individuals with confirmed infection, divided according to antibody titres into three experimental groups, which received a 20% methisoprinol solution, and three control groups, which did not receive the immunostimulant. In the mink from the experimental groups, the number of copies of the genetic material of the virus in the spleens and lymph nodes was one order of magnitude lower than in the case of the control groups. Mink receiving the supplement also showed higher fecundity (on average 5.83 in the experimental groups and 4.83 in the control groups), and the weight of their offspring before slaughter was over 200 g higher. Given the lack of effective methods for immunoprophylaxis and treatment, methisoprinol supplementation can be an effective means of counteracting the effects of AMDV on persistently infected farms.

Causes of mortality in farmed mink in the Intermountain West, North America.

The primary causes of mortality were identified in postmortem examination of 339 (90.9%) of 373 farmed mink (Neovison vison; syn. Mustela vison) from January 2009 through June 2014 at the Utah Veterinary Diagnostic Laboratory (Logan, Utah). Mink were raised under farm conditions in the Intermountain West in North America, except for 1 submission of mink from Wisconsin. In the 339 mink where cause(s) of death were established, 311 (91.7%) died from a single disease or condition, whereas 28 (8.3%) had 2 diseases or conditions contributing to death. Where cause(s) of death were evident, 11 diseases accounted for 321 (94.7%) of the diagnoses: bacterial pneumonia (67, 18.8%), Aleutian mink disease (61, 17.7%), mink viral enteritis (56, 16.2%), hepatic lipidosis (28, 8.1%), nutritional myopathy (24, 7%), bacterial enterocolitis (17, 4.9%), bacterial septicemia (16, 4.6%), starvation (15, 4.3%), epizootic catarrhal gastroenteritis of mink (14, 4.1%), pancreatitis (13, 3.8%), and bacterial metritis (10, 2.9%). In 34 (9.1%) animals, a cause of death was not evident. In an additional 16 (4.3%) of the mink, botulism was suspected from clinical history but could not be confirmed by laboratory testing. Control measures for the most common causes of death in farmed mink include testing and removal of positive animals (Aleutian mink disease), vaccination (Pseudomonas aeruginosa pneumonia, mink viral enteritis), avoidance of obesity in mink (hepatic lipidosis), and environmental management, including maintaining clean water cups, floors, feed troughs, cages, feed silos, feed truck tires, workers' shoes, dining areas for farm personnel, leather mink handling gloves, street clothes, and coveralls.

Aleutian disease serology, protein electrophoresis, and pathology of the European mink (Mustela lutreola) from Navarra, Spain.

The European mink, Mustela lutreola, has suffered a dramatic decline in Europe during the 20th century and is one of the most endangered carnivores in the world. The subpopulation of European mink from Navarra, Spain, estimated to number approximately 420, represents approximately two thirds of the total number of mink in Spain. Aleutian Disease Virus (ADV) is a parvovirus with a high degree of variability that can infect a broad range of mustelid hosts. The pathogenesis of this virus in small carnivores is variable and can be influenced by both host factors (e.g., species, American mink genotype, and immune status) and viral strain. A cross-sectional study was conducted during the pre-reproductive period of February-March 2004 and 2005 and the postreproductive period of September-December 2004. Mink were intensively trapped along seven rivers that were representative of the European mink habitat in Navarra. Antibody counter immunoelectrophoresis against ADV was performed on 84 European mink blood samples. All the samples were negative. Protein electrophoresis was performed on 93 plasma samples. Nine of those samples (9.6%) had gamma globulin levels exceeding 20% of the total plasma protein. Complete necropsies were performed on 23 cadavers of European mink collected in the area between 2000 and 2005. Seventeen of the mink (74%) had traumatic and hemorrhagic lesions compatible with vehicular impact injuries. Although there were no histopathologic lesions associated with ADV, this study documents the first description of a naturally occurring canine distemper virus infection in a European mink. In addition, pulmonary adiaspiromycosis in three European mink from Spain was reported.

Detection of Aleutian disease antibodies in feral American mink in southern England.

Fourteen of 27 American mink (Mustela vison) trapped in the upper Thames region were positive for anti-Aleutian disease antibodies. This demonstration of the occurrence of this viral disease in a feral American mink population suggests that it could threaten populations of at least two protected mustelids, the otter (Lutra lutra) and the polecat (Mustela putorius), and may also play a role in the apparent decline of local mink populations in Britain.

Melatonin reduces mortality from Aleutian disease in mink (Mustela vison).

Aleutian disease (AD) results from a persistent parvoviral infection that results in marked hypergammaglobulinemia and immune complex mediated lesions of the kidney, liver, lungs and, arteries. Melatonin protected both a wild type or demi strain and a demi/dark crossed strain of mink from AD. The biogenic amine also afforded protection against other non-diagnosed diseases naturally found on mink farms when it was available from a subcutaneously-placed reservoir. Some genetic strains of mink apparently differed in the resistance of mink to the virus and in the protective ability of melatonin. The demi strain was the most resistant followed by pastels, mahogany, darks, and those strains with the double recessive Aleutian gene. The protective action of melatonin appeared to result from melatonin's ability to scavenge free radicals, but it could also be due to the induction of antioxidant enzymes or to the modulation of immunity. Melatonin also protected mink against distemper.

Comparative pathogenicity of four strains of Aleutian disease virus for pastel and sapphire mink.

Information was sought on the comparative pathogenicity of four North American strains (isolates) of Aleutian disease virus for royal pastel (a non-Aleutian genotype) and sapphire (an Aleutian genotype) mink. The four strains (Utah-1, Ontario [Canada], Montana, and Pullman [Washington]), all of mink origin, were inoculated intraperitoneally and intranasally in serial 10-fold dilutions. As indicated by the appearance of specific antibody (counterimmunoelectrophoresis test), all strains readily infected both color phases of mink, and all strains were equally pathogenic for sapphire mink. Not all strains, however, regularly caused Aleutian disease in pastel mink. Infection of pastel mink with the Utah-1 strain invariably led to fatal disease. Infection with the Ontario strain caused fatal disease nearly as often. The Pullman strain, by contrast, almost never caused disease in infected pastel mink. The pathogenicity of the Montana strain for this color phase was between these extremes. These findings emphasize the need to distinguish between infection and disease when mink are exposed to Aleutian disease virus. The distinction has important implications for understanding the natural history of Aleutian disease virus infection in ranch mink.