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.     

Serology and protein electrophoresis for evidence of exposure to 12 mink pathogens in free-ranging American mink (Neovison vison) in Argentina

Background: Basic pathologic characteristics for farmed minks were previously reported worldwide. However, its status in the wild has not been studied in detail.

Objective: Serology and electrophoresis were carried out for evidence of exposure to 12 mink pathogens on two different locations.

Animals and methods: Serology was done in 87 wild minks by reference techniques against Toxoplasma gondii, Encephalitozoon cuniculi, Neospora caninum, Brucella abortus, Mycobacterium bovis, Leptospira interrogans, canine distemper virus (CDV), canine adenovirus (CAV), canine parvovirus (CPV), rabies virus (RV), Influenza A virus (FLUAV) and Aleutian disease virus (ADV). Hypergammaglobulinemia, the ADV main clinical feature, was determined by conventional electrophoresis.

Results: Seventy-one percent of the 87 sera had antibodies against one or more pathogens. ADV accounted for the highest seroprevalence (29%), followed by T. gondii (26%), L. interrogans (14%), M. bovis (12%), B. abortus (9%), N. caninum (3%), CPV (3%) and CDV (2%). Seroprevalence was influenced by location but not sex or age. Additionally, 16% of the seropositive samples for ADV had gammaglobulin levels >40.0 g/L. Antibody titers for CDV and CPV were low and difficult to interpret as almost all these cases had borderline concentrations.

Conclusion: A cautious interpretation of the results is urged as the epidemiological role of the wild mink is largely unexplored for most of these agents. Nevertheless, the information may be clinically relevant..     

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.     

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.     

Immunophenotypic and functional effects of bunker C fuel oil on the immune system of American mink (Mustela vison)

The relationship between exposure to environmental contaminants and immunotoxicity in vulnerable marine species is unknown. In this study, we used American mink (Mustela vision) as a surrogate species for the sea otter to examine the immunotoxic effects of chronic exposure to a low concentration of bunker C fuel oil (500 ppm admixed in the feed for 113-118 days). The mink immune system was monitored over time by flow cytometric analysis for alterations in the immunophenotype of blood lymphocytes and monocytes and by mitogen-stimulated proliferation assays for changes in peripheral blood mononuclear cell function. Fuel oil exposure caused a mild, yet significant (P < 0.05) increase in the absolute numbers of specific peripheral blood lymphocyte subsets (CD3+T cells) and monocytes, an increase in the level of expression of functionally significant cell surface proteins (MHC II, CD18), and an increase in mitogen-induced mononuclear cell proliferative responses. This heightened state of cellular activation along with the increase in specific cell surface protein expression on both the innate and adaptive immune cells is similar to the pro-inflammatory or "adjuvant-like" effect described in laboratory models of polycyclic aromatic hydrocarbon exposure in other species. These results show the benefits of using a controlled laboratory model for detecting and characterizing subtle petroleum oil-induced perturbations in immune responses. In addition this study establishes a framework for studying the effects of environmental petroleum oil exposure on the immune system of free-ranging marine mammals. Expansion of these studies to address biolgical significance is warranted.     

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.     

High feeding intensity increases the severity of fatty liver in the American mink (Neovison vison) with potential ameliorating role for long-chain n-3 polyunsaturated fatty acids

Background

Rapid body fat mobilization, obesity, and an inadequate supply of n-3 polyunsaturated fatty acids (PUFA) have been suggested to play roles in the etiology of fatty liver in the American mink (Neovison vison). This study examined the effects of feeding intensity and dietary fat source on fatty liver induced by fasting. In a multi-factorial design, 3 different fat sources (herring oil, rich in n-3 PUFA, soya oil, rich in n-6 PUFA, and canola oil, rich in n-9 monounsaturated fatty acids) were fed to mink at a low and high feeding intensity for 10 weeks, followed by an overnight or a 5-day fasting treatment to induce fatty liver.

Results

Fasting led to the development of fatty liver with increased severity in the mink fed at the high feeding intensity. The herring oil diet, high in long-chain n-3 PUFA, was found to decrease the severity of fatty liver in the mink at the high feeding intensity.

Conclusion

Preventing excessive weight gain and increasing dietary intake of n-3 long-chain PUFA may help prevent excessive lipid accumulation during prolonged periods of fasting or inappetence by promoting hepatic fatty acid oxidation.     

Effects of Family Housing on Behaviour,Plasma Cortisol and Performance in Adult Female Mink (Mustela vison)

Various behavioural, physiological and production-related parameters were examined in 200 adult female pastel and pearl mink either family housed in three-room cages with no weaning or housed singly in one-room cages after normal weaning procedures. Scanning observations of behaviour and use of the cages were performed in the nursing period and several parameters related to reproduction were registered. The adult female mink were weighed when kits were 16 weeks old (September) and again at pelting time (November). Blood samples were collected from all adult female mink in September at which time the teat condition and fur damage were evaluated. After pelting, bite marks on the leather side of the skin were counted, fur damage was graded after severity and the fur size was measured. Some positive consequences of being family housed were revealed. The familyhoused adult female mink showed a lower level of stereotypes and a higher level of defensiveness and curiosity than the adult female mink in one-room cages during the nursing period. In September and November, family-housed adult females were heavier than singly housed adult females. However, most of the physiological or production-related parameters pointed in a negative direction for familyhoused adult female mink. Reproductive success was somewhat reduced, although not significantly. Plasma cortisol levels were elevated in September, indicating higher levels of stress in these females. They showed a generally poor teat condition in September, with a high proportion of swollen or bitten teats. A high proportion of these adult females showed fur damage in both September and November, and a high number of bite marks was found on the leather side of the skins of these females, indicating that family housing had a high cost for the adult female mink. In conclusion, there seem to be some benefits, at least on the behavioural level, in keeping adult female mink in three-room cages during the nursing period, but both physiological and production-related parameters indicated that the welfare of the adult female mink was threatened if she was continuously cohoused with her litter past the normal age of weaning.     

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.     

Effects of dietary protein levels on digestibility of nutrients and growth rate in young female mink (Mustela vison)

This study investigated digestibilities of nutrients and feed efficiency in female mink at the different dietary protein levels during the mink growth period. Effects of dietary protein on growth performance of minks were also measured. Sixty 45‐day‐old healthy female minks were randomly assigned to 6 treatment groups with 10 animals in each group. Animals were fed diets varying in protein levels: 28% (Group I), 30% (Group II), 32% (Group III), 34% (Group IV), 36% (Group V) and 38% (Group VI), respectively. The digestibilities of key nutrients were determined on Day 14 after initiating the experiment and the last 3 days. From the beginning of the study, body weight and feed intake were weighed and recorded every other week in order to calculate the average daily bodyweight gain and the feed efficiency. The trial had demonstrated that nitrogen intake was greatly significantly different, which was affected by dietary protein levels (p < 0.001). Growth performance of minks was impaired when dietary protein level was at 28%. When dietary protein level was at 34%, minks had the best daily gains, feed efficiency, and digestibilities of some key nutrients.     

Composition of individual nucleobases in diets containing different products from bacterial biomass grown on natural gas, and digestibility in mink (Mustela vison)

The objectives of the present study were to quantify the amount of nucleic acids, to examine the nucleobase composition and to determine the digestibility of individual nucleobases in diets containing various products from bacterial biomass grown on natural gas, including autolytic and hydrolytic fractions, using mink (Mustela vison) as a model animal. The diets consisted of cod fillet (control), commercial basic BioProtein, and five experimentally produced autolytic and hydrolytic fractions of the bacterial protein meal as protein sources. Each diet was assigned to four adult male mink, housed individually in cages equipped for controlled feeding and quantitative collection of faeces. Faeces were collected for 4 days, and the individual nucleobases in diet and faeces were analysed by HPLC after hydrolysis using HClO(4). The content of nucleobases in the diets containing bacterial protein meal was 37% to 205% higher than in the control diet. The nucleobase-nitrogen in the control diet amounted to 4.3% of the total nitrogen content, whereas the experimental bacterial protein diets contained from 7.4% to 17.4% of the total N content in the form of nucleic acids. The various methods used to produce the bacterial protein fractions clearly affected both the amount of nucleic acids and the molar proportions of the individual nucleobases. The average digestibility of the nucleobases was 95%, and all the individual nucleobases were highly digestible. Uracil showed the highest digestibility (on average 96.8%), whereas thymine showed the lowest digestibility (on average 93.6%).     

Genetic parameters for fur quality graded on live animals and dried pelts of American mink (Neovison vison)

Fur quality and skin size are integral qualities in the mink industry and are main determinants of sales price and subsequent income for mink fur producers. Parental animals of future generations are selected based on quality grading from live animals, but selection response is obtained from dried skins sold after pelting. In this study, we evaluated traits assessed during live grading and pelt traits examined on dried skins to determine correlation between live and pelt traits. Grading traits and body weight were measured during live animal grading for 9,539 Brown American mink, and pelt quality traits and skin size were evaluated on 8,385 dried mink skins after pelting. Data were sampled from 2 yearly production cycles. Genetic parameters were estimated using the REML method implemented in the DMU package. Heritabilities and proportions of litter variance were calculated from estimated variance components for all traits, and genetic and phenotypic correlations between all traits were estimated in a series of bivariate analyses. Heritability estimates for live grading traits ranged from 0.06 to 0.28, heritability estimates for pelt quality traits ranged from 0.20 to 0.30, and finally heritability estimates for body size traits ranged from 0.43 to 0.48. Skin size and body weight were regarded as different traits for the two sexes and were therefore analysed for each sex separately. Genetic correlations between grading traits exhibited a range of 0.30–0.99 and genetic correlations between pelt quality traits ranged from 0.38 to 0.86. Genetic correlations between quality, wool density and silky appearance evaluated during live animal grading and on dried skin after pelting were 0.74, 0.41 and 0.33, respectively. Skin size and body weight were negatively correlated with pelt quality traits and ranged from −0.55 to −0.25. Using standard selection index theory and combined information from both live grading and skin evaluation increase of reliability of selection ranged from 0.6% to 14%. Due to moderate genetic correlations between traits evaluated during live grading and on dried skins, and negative correlations between pelt quality traits and body size, we concluded that traits should be selected simultaneously.     

Detection of Bartonella sp. and a novel spotted fever group Rickettsia sp. in Neotropical fleas of wild rodents (Cricetidae) from Southern Brazil

The Neotropical region shows a great diversity of fleas, comprising more than 50 genera. The importance of the study of fleas is linked to their potential role as disease vectors. The aim of this study is to investigate the presence of Rickettsia spp. and Bartonella spp. in Neotropical fleas collected from wild rodents in Southern Brazil. From 350 rodents captured, 30 were parasitized by fleas. A total of 61 fleas belonging to two genera and six different species were collected (Craneopsylla minerva minerva, Polygenis occidentalis occidentalis, Polygenis platensis, Polygenis pradoi, Polygenis rimatus, and Polygenis roberti roberti). In 13 % of fleas of three different species (C. minerva, P. platensis, and P. pradoi) Rickettsia sp. DNA was found. Phylogenetic analysis of concatenated sequences of gltA, htrA, and ompA genes showed that Rickettsia sp. found in rodent fleas (referred as strain Taim) grouped together with Spotted Fever Group Rickettsia. In reference to Bartonella spp., five genotypes were identified in seven fleas of two species (C. minerva and P. platensis) and in five rodent spleens. Also, 207 frozen samples of wild rodents were screened for these pathogens: while none was positive for Rickettsia spp.; five rodent spleens were PCR-positive for Bartonella spp.. Herein, we show the detection of potential novel variants of Bartonella sp. and Rickettsia sp. in fleas collected of wild rodents from Southern Brazil. Further studies are needed to fully characterize these microorganisms, as well as to improve the knowledge on the potential role of Neotropical flea species as diseases vectors.     

Molecular characterization of Mycobacterium tuberculosis complex (MTBC) isolated from cattle in northeast and northwest China

We studied throat swabs and corresponding serum samples collected from 1067 protein purified derivative (PPD)-tuberculin skin test (TST) positive cattle from different regions of China. The 1067 throat swabs were inoculated onto modified Löwenstein–Jensen medium for the isolation and culture of Mycobacteria. Acid-fast bacilli were identified using traditional biochemical methods, polymerase chain reaction (PCR) amplification and multiplex PCR. They were distinguished as Mycobacterium tuberculosis complex (MTBC) and non-tuberculous mycobacteria (NTM) strains. An indirect Enzyme-Linked Immunosorbent Assay (ELISA) was applied to detect specific antibodies against bovine TB (bTB). Correlations among the ELISA, bacteriology and TST were analyzed and compared. Spoligotyping and variable number tandem repeats–mycobacterial interspersed repetitive unit (VNTR–MIRU) analysis were used to genotype the MTBC. In total, 111 strains of Mycobacteria were cultured from the 1067 throat swab samples, including 43 stains of MTBC (14 strains of Mycobacterium bovis and 29 of Mycobacterium tuberculosis) and 68 strains of NTM. Thirty-eight MTBC strains and four NTM strains were isolated from 72 throat swab samples that the ELISA determined were antibody positive; five MTBC strains and 64 NTM strains were isolated from 995 throat swab samples that were antibody negative on the ELISA. The positive isolation rates of MTBC and NTM were 38.7% (43/111) and 61.3% (68/111), respectively. The concordance rate of cultured MTBC with a positive result on the indirect ELISA for antibody was 52.8% (38/72), which was much higher than the positive rate for TST (4.0%; 43/1067). Genotyping of the 43 strains of MTBC isolated, using spoligotyping and VNTR–MIRU, showed that the 43 isolates had 26 genotypes; 16 strains had a unique genotype. Two groups of six strains and two strains, respectively, showed the same spoligotyping pattern, and belonged to the Beijing family and Beijing-like family, respectively. Combined application of spoligotyping and VNTR–MIRU typing would improve the molecular epidemiological investigation and monitoring of the etiology of bTB in China.     

Henneguya corruscans n. sp. (Myxozoa,Myxosporea, Myxobolidae), a parasite of Pseudoplatystoma corruscans (Osteichthyes,Pimelodidae) from the Paraná River,Brazil: A morphological and morphometric study

This paper describes the parasite Henneguya corruscans n. sp. which infects the gills of Pseudoplatystoma corruscans Spix and Agassiz, 1829 found in the Paraná River, Brazil. The parasites belong to the interlamellar-epithelial type as defined by Molnár (2002) [Molnár, K., 2002. Site preference of fish myxosporeans in the gills. Dis. Aquat. Org. 48, 197–207]. The spores examined had thin, smooth walls with symmetric valves; the total length of the spores was 27.6 (25–29) μm. The spore body was ellipsoidal in frontal view and biconvex in lateral view and they measured 14.3 (13–15) μm long by 5 μm wide and 4 μm in thickness. The polar capsules were small and elongated, equally sized, with a rounded posterior extremity and tapering anteriorly, and they corresponded more or less the half the length of the spore body; they were 6.8 (6–7) μm long by 2 μm wide, and the polar filament formed 5–6 coils obliquely to the axis of the polar capsule. The tail was 13.7 (12–15) μm long and bifurcated shortly after the end of the spore body. The importance of the infection for the farming of P. corruscans is discussed.     

Molecular identification,morphological characterization and new insights into the ecology of larval Pseudoterranova cattani in fishes from the Argentine coast with its differentiation from the Antarctic species,P. decipiens sp. E (Nematoda: Anisakidae)

Larvae of the genus Pseudoterranova constitute a risk for human health when ingested through raw or undercooked fish. They can provoke pseudoterranovosis in humans, a fish-borne zoonotic disease whose pathogenicity varies with the species involved, making their correct specific identification a necessary step in the knowledge of this zoonosis. Larvae of Pseudoterranova decipiens s.l. have been reported in several fish species from off the Argentine coasts; however, there are no studies dealing with their specific identification in this region. Here, a genetic identification and morphological characterization of larval Pseudoterranova spp. from three fish species sampled from Argentine waters and from Notothenia coriiceps from Antarctic waters was carried out. Larvae were sequenced for their genetic/molecular identification, including the mitochondrial cytochrome c oxidase subunit II (mtDNA cox2), the first (ITS-1) and the second (ITS-2) internal transcribed spacers of the nuclear ribosomal DNA, and compared with all species of the P. decipiens (sensu lato) species complex (sequences available in GenBank). Further, adults of Pseudoterranova spp. from the definitive host, the southern sea lion, Otaria flavescens, from Argentine and Chilean coasts were sequenced at the same genes. The sequences obtained at the ITS-1 and ITS-2 genes from all the larvae examined from fish of Argentine waters, as well as the adult worms, matched 100% the sequences for the species P. cattani. The sequences obtained at mtDNA cox2 gene for Antarctic larvae matched 99% those available in GenBank for the sibling P. decipiens sp. E. Both MP and BI phylogenetic trees strongly supported P. cattani and P. decipiens sp. E as two distinct phylogenetic lineages and depicted the species P. decipiens sp. E as sister taxon to the remaining taxa of the P. decipiens complex. Larval morphometry was similar between specimens of P. cattani from Argentina, but significantly different from those of P. decipiens sp. E, indicating that larval forms can be distinguished based on their morphology. Pseudoterranova cattani is common and abundant in a variety of fish species from Chile, whereas few host species harbour these larvae in Argentina where they show low levels of parasitism. This pattern could arise from a combination of factors, including environmental conditions, density and dietary preferences of definitive hosts and life-cycle pathways of the parasite. Finally, this study revealed that the life-cycle of P. cattani involves mainly demersal and benthic organisms, with a marked preference by large-sized benthophagous fish.