Pancreatitis in hyperlipemic mink (Mustela vison)

In both man and animals, inflammatory changes in the pancreas often occur with disturbances in lipid metabolism, including hypertriglyceridemia and an excess of free fatty acids. Hyperlipoproteinemia type I is a human condition caused by a deficiency of lipoprotein lipase. A similar metabolic disturbance that occurs in mink is of considerable comparative interest, as it is also followed by pancreatitis. Pancreatic lesions in hyperlipoproteinemic mink included overt variably sized nodules with hemorrhage and necrosis. These lesions began as intralobular necrosis of exocrine cells and progressed to total lobular destruction, with eventual involvement of interlobular tissue. Remnants of epithelial cells and lipid-filled macrophages were seen in necrotic areas, along with other types of inflammatory cells scattered in a lipid-rich exudate. Granulation tissue developed rapidly in necrotic areas. Additional observations included ductal proliferation, replacement of epithelial cells with fat, and mural arterial thickening, most conspicuously with vacuolated cells and endothelial proliferation. Extravasation of lipid-rich plasma is thought to be a major intensifier of the inflammatory response.     

Pregnancy detection in putatively unmated mink (Mustela vison) by serum progesterone level

The aim of this study was to determine whether blood plasma progesterone is a reliable indicator of pregnancy in mink at an early stage of gestation. We also attempted to establish the threshold value of progesterone as a pregnancy indicator. The analysis was carried out at a production farm on 42 standard female mink aged 1 year, which were grouped both according to the observed success of mating ("mated" and "unmated") and the level of blood serum progesterone measured afterwards ("pregnant" and "nonpregnant"). It was next verified whether a particular female had been assigned to the proper group in the first place. An analysis of accuracy of mating success assessment within the group of unmated females revealed that more than one-third of decisions were wrong, since some females that had been considered unmated ultimately whelped. This suggests that mating supervision by farm workers lacks reliability. A progesterone test for verification of such management decisions should limit the risk of err,or. We suggest that progesterone tests could be carried out using the threshold values 1.9 ng/ml and 20 ng/ml in blood sampled on 25 March and 8 April, respectively, although some level of uncertainty should be taken into account.     

Verrucous endocarditis associated with Streptococcus bovis in mink (Mustela vison)

Between 1998 and 2001, mortalities due to verrucous endocarditis were experienced at several mink farms. Gram-positive cocci were isolated from the endocardium of all the animals examined but not always from other internal organs. Almost all the isolates were identified as Streptococcus bovis and only a few isolates belonged to other Streptococcus species. Typing by pulsed-field gel electrophoresis of a selection of isolates revealed several patterns and several different clones. Attempts to reproduce disease by the injection of cultures of a field isolate into healthy mink failed.     

Immobilization of mink (Mustela vison) with medetomidine-ketamine and remobilization with atipamezole

Four groups of mink were immobilized with medetomidine-HCl (MED) 0.1 mg/kg + ketamine (KET) 5 or 7.5 mg/kg at different ambient temperatures. The induction time, degree of immobilization and analgesia, rectal temperature, heart and respiration rates were recorded at intervals throughout the immobilization period. The animals were then given atipamezole-HCl (ATI) 0.5 mg/kg for reversal at different times after injection of MED/KET and the effects of the antagonist were evaluated.Subcutaneous administration of MED/KET induced complete immobilization in all 20 animals, and the highest dose was considered suitable for major surgery. Prolonged immobilization at low ambient temperatures (–10 to +5°C) caused severe hypothermia in all animals. The mean rectal temperature had dropped to 37.8°C and 32.1°C at 15 and 85 min, respectively, after injection of MED/KET, significantly lower than the corresponding values for animals immobilized at room temperature.Intramuscular administration of ATI 20 or 40 min after injection of MED/KET rapidly remobilized the animals without apparent side-effects. Administration of ATI to animals recovering spontaneously 90 min after injection of MED/KET induced thermogenesis (shivering) in animals immobilized at a low ambient temperature, while no such effect was seen in animals immobilized at room temperature. One hour after injection of ATI, the rectal temperatures of all treated animals had returned to normal and there were no signs of abnormal behaviour.     

An outbreak of toxoplasmosis in farmed mink (Mustela vison S.).

A large Wisconsin mink (Mustela vison) farm experienced an outbreak of toxoplasmosis in the spring of 1999 following an outbreak of canine distemper during the previous fall. Major clinical signs for pregnant females included reduced feed consumption, abortions, and stillborn kits; kits < or =3 weeks old experienced ataxia and mortality. Of 7,800 females, 1,976 (26%) lost their entire litter either from abortion or neonatal mortality. Kit mortality from 7 days to 3 weeks of age was 3,300, and overall kit mortality attributed to the toxoplasmosis outbreak was 10,408. Six neonatal mink kits, 12 3-week-old kits, and 2 adult female mink were submitted to the University of Minnesota Veterinary Diagnostic Laboratory for diagnostic workup. Gross postmortem lesions were limited to empty stomachs (12 of 12 kits) and pale livers (4 of 12 kits) for the 3-week-old kits. Major microscopic lesions included interstitial pneumonia, encephalitis, encephalomalacia, and myocarditis. Toxoplasmosis was diagnosed by microscopic lesions, microscopic lesion distribution, and the detection of Toxoplasma gondii tachyzoites by immunohistochemistry. This is the first detailed report of an outbreak of toxoplasmosis in mink in the United States.     

A syndrome of hereditary tyrosinemia in mink (Mustela vison Schreb.).

A hereditary disease in mink (Mustela vison Schreb.) leading to death when the affected kits are about six weeks old has been investigated. The disorder is inherited as a simple autosomal recessive character. Strongly elevated plasma tyrosine concentration is an outstanding feature of the disease. An enzyme defect in tyrosine aminotransferase (EC 2.6.1.5) or 4-hydroxyphenylpyruvate dioxygenase (EC 1.13.11.27) is considered together with the possibility of a parallel between the disease in mink and the disease tyrosinosis or hereditary tyrosinemia in man.     

Serogroups and antimicrobial susceptibility among Escherichia coli isolated from farmed mink (Mustela vison Schreiber) in Denmark

Escherichia coli is commonly found in outbreaks of diarrhoea in mink during the production season although its role as a primary causal organism remains unclear. The present study was undertaken to determine the serogroups and antimicrobial susceptibility of E. coli isolates from healthy and diarrhoeic mink. Rectal swabs were taken from healthy and diseased animals, on six different farms, once at the onset of disease and again approximately 2 weeks later. The swabs were subjected to bacteriological investigation; a total of 210 E. coli were isolated, 98 from healthy animals and 112 from diseased. All isolates were serotyped and MICs were determined for nine antimicrobial compounds. Non-haemolytic isolates numbered 147, whereas 63 were haemolytic. Both haemolytic and non-haemolytic isolates were isolated from both healthy and diseased animals.A wide range of serogroups was detected, the most frequent being O2 (11.0%), O78 (11.0%), O153 (7.1%), O25 (5.7%), O6 (4.8%), and O15 (4.8%), but diarrhoea was not associated with specific serogroups. All isolates were sensitive to enrofloxacin, neomycin, gentamicin and colistin. In contrast, considerable variations in susceptibility were found among the six mink farms, for tetracycline (0-46.4%, average 21.9), ampicillin (2.9-50.0%, average 23.3), spectinomycin (8.0-35.7%, average 21.9), sulfamethoxazole (8.6-57.7%, average 30.0) and trimethoprim (0-35.7%, average 9.5). Resistance to tetracycline was statistically more prevalent among haemolytic than among non-haemolytic strains.In conclusion, serogrouping and haemolysin testing failed to identify any association with diarrhoeal disease and antimicrobial resistance was highly variable between different mink farms.     

Validation of a cell culture bioassay for detection of petroleum exposure in mink (Mustela vison) as a model for detection in sea otters (Enhydra lutris)

OBJECTIVE: To validate a luciferase bioassay, which is based on a recombinant mouse hepatoma cell line, for the detection of exposure to petroleum in mustelid species. ANIMALS: 122 American mink (Mustela vison) and 15 sea otters (Enhydra lutris). PROCEDURES: Mink were exposed to Bunker C fuel oil or Alaska North Slope crude oil externally as a single exposure or internally via low dose concentrations in their ration for 6 months. Serum samples were analyzed for cytochrome P450 1A1 induction by quantification of luciferase activity in the bioassay. Mink liver specimens were also evaluated for cytochrome P450 1A1 induction by quantification of ethoxyresorufin-o-deethylase activity. Serum collected from exposed and unexposed sea otters was also analyzed using the luciferase bioassay. RESULTS: Serum samples from mink externally exposed to petroleum had significantly increased luciferase activities at 1 week after exposure. Serum samples taken at later time points or from mink exposed to either product in the ration did not cause significant luciferase induction. Samples from otters exposed to petroleum had significantly higher luciferase induction as compared with samples from otters not exposed to petroleum at 2 and 8 years after the spill. Cytochrome P450 1A1 activity in liver specimens collected from mink that were internally exposed through diet was significantly increased at the conclusion of our study. CONCLUSION AND CLINICAL RELEVANCE: The luciferase bioassay is a sensitive and specific method for determining recent exposure to petroleum in mink. The lack of luciferase activity in serum samples collected from mink greater than 1 week after experimental exposure was likely attributable to lower overall petroleum exposure in our trial, compared with natural exposures.     

Investigations into shaking mink syndrome: an encephalomyelitis of unknown cause in farmed mink (Mustela vison) kits in Scandinavia.

An apparently novel neurological disease clinically characterized by shaking, tremors, seizures, staggering gait, and ataxia was first observed in farmed mink kits in Denmark in 2000 and subsequently in Sweden, Denmark, and Finland in 2001, and again in Denmark in 2002. Lymphoplasmacytic encephalomyelitis was found in the affected kits. The lesions were most severe in the brainstem and cerebellum and consisted of neuronal degeneration and necrosis, neuronophagia, focal and diffuse gliosis, perivascular cuffs formed by lymphocytes, plasma cells and macrophages, and segmental loss of Purkinje cells. Testing was conducted to determine the cause of the disease, including general virological investigations (virus culture, negative-staining electron microscopy, immunoelectron microscopy, polymerase chain reaction for herpesviruses, adenoviruses, pestiviruses, and coronaviruses), tests for specific viral diseases (canine distemper, Borna disease, Louping ill, West Nile virus infection, tick-borne encephalitis, Aleutian disease), tests for protozoa (Toxoplasma gondii, Neospora caninum, Encephalitozoon cuniculi), bacteria (general culture, listeria, Clamydophila psittaci), and intracerebral inoculation of neonatal mice. The results of all these investigations were negative. One group of 3 mink kits inoculated intracerebrally with brain homogenate of affected mink developed clinical signs and histological lesions similar to those observed in naturally infected mink. Based on the histopathological features, it is postulated that the disease is caused by a yet unidentified virus.     

Late development of homoeothermy in mink (Mustela vison) kits -- a strategy for maximum survival rate

The objective of this study was to establish the age at which mink kits develop functional homoeothermy. The investigation was based on the hypothesis that in this species with very immature neonates, late development of homoeothermy may be an adaptation to economize with energy. Measurements of heat production (HE) by means of indirect calorimetry lasting 3 h were performed on neonatal kits and kits from 1 to 54 days of age. Both single kits and groups of 4-5 huddling kits were kept at 15 degrees C (L) or 30 degrees C (H) [from 35 days onwards at 25 degrees C (H)]. Animals were weighed before and after the experiments and evaporative water losses (EWL) were calculated. When exposed to L temperature, single kits responded with a very low HE until 29 days of age, and groups of kits until 14 days of age. It was not until they reached an age of approximately 6 weeks that single kits showed a clear thermoregulatory response to the L temperature by increased HE, whereas groups of kits showed increased HE from 29th day onwards. When kept at H temperature, HE was low initially, but all kits showed elevated HE at 8 days of age, and the metabolic rate was similar for single kits and kits huddling in groups. Evaporative water losses was higher among single than among groups of kits and slightly lower but more variable for animals at L than at H temperature. It was concluded that mink kits develop functional homoeothermy at an age of close to 6 weeks and that the failure of very young kits to thermoregulate is an adaptation mechanism in order to economise with their very limited body energy reserves.     

Economic profit from increased litter size,body weight and pelt quality in mink (Mustela vison)

Economic benefits of improving litter size, body weight (i.e. pelt length) and pelt quality were estimated in mink. Effects of the size of the litter in which the kit was born, on pelt length and pelt quality, were also assessed. The traits were recorded during a selection experiment involving the traits litter size, body weight and underfur density. Skins originating from litters of ≥10 kits tended to be smaller and sold at a lower price, compared with pelts from smaller litters. Litter size did not seem to affect fur quality. Pelt quality score decreased with increasing September weight. Pelts of animals with September weights of < 2000 g and pelting weights of < 2300 g had a lower sales price than pelts of heavier animals. Pelt quality had only a small effect on the price The highest economic gain was achieved by increasing litter size. The net revenue from each extra kit per litter was, in Swedish Kronor, SEK 70, 122 and 170 at an average sales price of SEK 150, 200 and 250, respectively.     

Energy intake and milk production in mink (Mustela vison)--effect of litter size.

Energy intake and milk production were measured in 12 mink dams raising litters of 3, 6 and 9 kits one to four weeks post partum by means of balance experiments and measurements of milk intake of the kits by the water isotope dilution technique. The dams were fed ad libitum on a conventional wet mink diet (DM: 323 g/kg; CP: 173 g/kg; ME: 4.4 MJ/kg). Milk samples collected from dams with corresponding litter sizes and lactation weeks, and body composition of kits nursed by these dams, were analysed for content of DM, ash, N and fat. The ME and drinking water consumption were higher in dams nursing 9 kits than in dams nursing 3 kits. The N and water balances as well as the live weight of dams were not affected by litter size. Daily milk production was higher in dams nursing 9 kits than in dams nursing 3 kits. The DM, N and fat content of the milk increased during lactation, but were not affected by litter size. Individual kit live weight was higher in litters of 3 than in litters of 6 and 9 kits four weeks post partum. The DM and fat content of the kits were lowest in kits from litters of 9 kits, whereas these kits had the highest protein content. Daily ME for maintenance of kits and the efficiency of utilisation of ME in milk for body gain were estimated to 356 kJ/kg0.75, kp approximately 0.53 and kf approximately 0.71, respectively. In conclusion, daily milk production increased with increasing litter size, but not in proportion to the number of kits, indicating that milk production limits the growth rate of the young. In the fourth week of lactation, milk production was not different between dams nursing 6 or 9 kits, indicating a maximum capacity.     

Immunohistochemical detection and localization of new type gosling viral enteritis virus in paraformaldehyde-fixed paraffin-embedded tissue

To determine the distribution and localization of new type gosling viral enteritis virus (NGVEV) in paraformaldehyde-fixed paraffin-embedded tissues of experimentally infected goslings, for the first time, an immunohistochemical (IHC) staining method was reported. Anti-NGVEV polyclonal serum was obtained from the rabbits immunized with purified NGVEV antigen, which was extracted by caprylic-ammonium sulphate method and purified through High-Q columns anion exchange chromatography. Three-day-old NGVEV-free goslings were orally inoculated with NGVEV-CN strain suspension as infection group and phosphate buffered saline solution (PBS) as control group, respectively. The tissues were collected at sequential time points between 0.5 and 720 h post inoculation (PI), and prepared for IHC staining and ultra-structural observation. The positive immunoreactivity could be readily detected in the lymphoid and gastrointestinal organs of infected goslings as early as 48 h PI, in the liver, kidney, pancreas and myocardium from 72 h, and in the cerebrum and cerebellum from 96 h, while it was hardly detected in the respiratory organs at any time. The positive staining reaction could be detected in NGVEV-infected goslings until 600 h PI, and no positive staining cell could be observed in the controls. The highest levels of viral antigen were found in the bursa of Fabricius (BF), thymus, proventriculus, gizzard and intestine tract, moreover, the liver, kidney, spleen, myocardium and pancreas were intensively and widely stained. The target cells had a ubiquitous distribution, especially included the epithelial cells, endothelial cells, superficial and crypt mucosal cells, glandular cells, fibrocytes, macrophages and lymphocytes, which served as the principal sites for antigen localization. The ultra-structural observation by transmission electron microscope (TEM) further indicated that NGVEV particles could be widely detected in the lymphoid and digestive organs of infected goslings from 72 h PI onwards. This work may be useful not only for offering a possibility of routine diagnosis of NGVE, but also for better understanding of the pathogenesis of the disease.     

Cholecystitis in otters (Lutra lutra) and mink (Mustela vison) caused by the fluke Pseudamphistomum truncatum

Between 1988 and 2004, postmortem examinations were carried out on 445 otters found dead, mostly as a result of road traffic accidents, in southern and south-west England. Thickened, shrunken gall bladders were observed in 10 cases, the first in 2000 and the others between February 2002 and August 2004. A digenean fluke, Pseudamphistomum truncatum, was found in the gall bladders of three cases and also in three of seven American mink examined. Nine of the 10 otters and all the mink came from a localised area of Somerset, indicating that the fluke has become established in the local fish population. P. truncatum has not been recorded previously in Britain, and the results suggest that it has been introduced recently, possibly in imported fish.     

Molecular and morphometric study of metacercariae and adults of Pseudamphistomum truncatum (Opisthorchiidae) from roach (Rutilus rutilus) and wild American mink (Mustela vison)

The presence of metacercariae and adults of the trematode Pseudamphistomum truncatum in roach and mink, respectively, was recorded in Lake Fure North of Copenhagen, Denmark. This zoonotic digenean opisthorchiid represents a threat to humans due to its ability to infect the biliary system following ingestion of inadequately processed infected fish. Therefore precise species identification of infective metacercariae in fish used for human consumption is essential. Due to the relatively limited information on metacercarial identity obtained by morphometric studies a series of molecular techniques were used to link the larval parasite in fish with the un-equivocally diagnosed adults in the biliary system of the mink. By the use of carefully selected polymerase chain reaction (PCR) primers and subsequent sequencing of the ITS region from both metacercariae and adults full sequence identity of both metacercariae and adults were confirmed. The presence of this parasitosis in fish from a lake used for both commercial and recreational fisheries call for hygienic alerts in order to prevent accidental human infection with this opisthorchiid.     

Bacterial diskospondylitis associated with posterior paresis/paralysis in North American farmed mink (Mustela vison)

Posterior paresis/paralysis in farmed mink is responsible for significant morbidity and mortality, with individual farms reporting the loss of as many as 700 animals each year. Although this disease has been recognized by North American mink farmers for approximately 40 years, there are few published reports focusing on this entity. The objective of this study was to investigate the etiology and pathogenesis of the disease. Complete necropsy examinations were done on 40 clinically affected mink, ranging from 7 to 10 weeks of age, and on three normal animals in the same age range from two mink farms. Thirty-two of the 40 clinically affected animals had an isolated vertebral lesion characterized by bone lysis and proliferation that usually was centered on an intervertebral disk space in the midthoracic area. An inflammatory reaction, composed primarily of neutrophils, was present within the vertebral sections in 25 of the 40 affected animals (62.5%), and the presence of gram-positive cocci was confirmed in 8 of 10 animals (80%) in which bacterial organisms were observed histologically. Bacterial cultures from 15 affected animals yielded Streptococcus sp. from the intervertebral disk space in 13 of 15 (86.7%) animals and from heart blood in 6 of 8 (75%). A farm visit revealed no history or evidence of traumatic wounds as a source of infection in these animals, and the diet appeared to be adequate for skeletal development. We conclude that posterior paresis/paralysis in farmed mink is associated with bacterial diskospondylitis, likely occurring secondary to bacteremia/septicemia.     

Electrolyte composition of mink (Mustela vison) erythrocytes and active cation transporters of the cell membrane

Red blood cells from mink (Mustela vison) were characterized with respect to their electrolyte content and their cell membranes with respect to enzymatic activity for cation transport. The intra- and extracellular concentrations of Na+, K+, Cl-, Ca2+ and Mg2+ were determined in erythrocytes and plasma, respectively. Plasma and red cell water content was determined, and molal electrolyte concentrations were calculated. Red cells from male adult mink appeared to be of the low-K+, high-Na+ type as seen in other carnivorous species. The intracellular K+ concentration is slightly higher than the extracellular one and the plasma-to-cell chemical gradient for Na+ is weak, though even the molal concentrations may differ significantly. Consistent with the high intracellular Na+ and low K+ concentrations, a very low or no ouabain-sensitive Na+, K(+)-ATPase activity and no K(+)-activated pNPPase activity were found in the plasma membrane fraction from red cells. The Cl- and Mg2+ concentrations expressed per liter cell water were significantly higher in red cells than in plasma whereas the opposite was the case with Ca2+. The distribution of Cl- thus does not seem compatible with an inside-negative membrane potential in mink erythrocytes. In spite of a steep calcium gradient across the red cell membrane, neither a calmodulin-activated Ca(2+)-ATPase activity nor an ATP-activated Ca(2+)-pNPPase activity were detectable in the plasma membrane fraction. The origin of a supposed primary Ca2+ gradient for sustaining of osmotic balance thus seems uncertain.     

Glucose metabolism and regulation in lactating mink (Mustela vison)--effects of low dietary protein supply.

Eighteen lactating mink raising litters of 6 to 7 kits were fed ad libitum from parturition on diets with 32% of ME derived from protein and decreasing fat:carbohydrate ratios [high fat:low carbohydrate (HFLC): 67:1, medium fat:medium carbohydrate (MFMC): 52:16, low fat:high carbohydrate (LFHC): 37:31]. Four weeks post partum the dams were fitted with a jugular vein catheter, and the experiment started with a 3 hours fasting period, after which the dams were fed 210 kJ ME of the experimental diets. Blood samples were collected 10 and 5 min before feeding and 30, 60, 90, 120, 150 and 180 min postprandially. Two hours postprandially a single dose of 50 microCi U-14C-labelled glucose was administered to each dam and blood samples were collected 5, 10, 20, 30, 45 and 60 min after the tracer administration. Plasma concentrations of glucose and insulin 30 to 120 min postprandially were higher in dams fed the LFHC diet, than in dams fed the HFLC diet, values for dams fed the MFMC diet being intermediate. Plasma glucagon concentrations were not significantly affected by dietary treatment. The glucagon:insulin ratios decreased postprandially in all dams, the response being significant in dams fed the LFHC diet. Plasma concentrations of urea were not significantly affected by dietary treatment. Plasma FFA concentrations tended to increase postprandially in dams fed the HFLC diet. Glucose turnover rates were approximately 4.0% per min in all dams, irrespective of dietary treatment. However, the daily glucose flux was lower in dams fed the HFLC diet than in dams fed the LFHC diet, and tended to be lower than in dams fed the MFMC diet. In conclusion, a dietary protein supply of 32% of ME simultaneously with a carbohydrate supply of 16% or 31% of ME had no adverse effects on glucose homeostasis or glucose metabolism in lactating mink.