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PubMed1995

Elimination of fox rabies from Belgium using a recombinant vaccinia-rabies vaccine: an update.

To improve both safety and stability of the vaccines used in the field to vaccinate foxes against rabies by the oral route, a recombinant vaccinia virus, expressing the glycoprotein of rabies virus (VVTGgRAB) has been developed. VVTGgRAB innocuity was verified in target species and in domestic animals as well as in numerous wild animal species that could compete with the red fox in consuming vaccine baits in Europe. Oral immunization of foxes, by distributing VVTGgRAB vaccine-baits, was undertaken in the whole of the infected area of Belgium (10,000 km2). Five campaigns of fox vaccination covering the whole infected area were carried out from the autumn of 1989 until 1991. Each time, 150,000 vaccine-baits were dispersed by air at a mean density of 15 per km2. These campaigns induced a drastic decrease in the incidence of rabies and the elimination of the disease from 80% of the initial infected area. Regarding the geographical evolution of rabies in Belgium and in adjacent regions in neighbouring countries, new spatial strategies for bait dispersal were planned for 1992, 1993 and 1994: successive restricted campaigns were carried out along political borders only. These campaigns induced a new decrease of incidence; no rabid foxes could be detected in 1993 in spite of an improved epidemiological surveillance. In 1994, rabies was confirmed again in 13 foxes collected in a region situated close to the French border. These cases demonstrate the persistence of a focus of rabies on the border and justify further restricted campaigns of vaccination.

Administration, Oral↗
PubMed2006

Cs-137 in Arctic foxes (Alopex lagopus) on Svalbard.

This study presents 137Cs muscle activity concentrations in Arctic foxes (Alopex lagopus) from Svalbard over a period of several years and discusses the transfer of 137Cs to Arctic foxes through likely predator--prey relationships. Mean 137Cs activity concentrations and 137Cs Tag values (per trapping season) ranged from 0.51+/-2.76 to 1.32+/-2.89 Bq/kg (w.w.) and 5.1 x 10(-4) to 1.3 x 10(-3)m(2)/kg, respectively. Mean concentration ratios of 137Cs in Arctic foxes compared to probable prey ranged from 1.0 to 7.9. On Svalbard, transfer of 137Cs to Arctic foxes is likely to occur via both marine and terrestrial food chains. The relative contribution of marine and terrestrial food sources to the diet of Arctic foxes may vary by location and by season and may lead to either an increase or decrease in the trophic transfer of 137Cs to Arctic foxes compared to transfer resulting from terrestrial only diets.

Animals↗
PubMed2005

Prevalence of Trichinella larvae and extra-intestinal nematodes in Norwegian red foxes (Vulpes vulpes).

A survey of the parasitic fauna of the Norwegian red fox (Vulpes vulpes) population was carried out in 1994/1995 and 2002-2005. All foxes were killed during the licensed hunting season from October to April and, in total, 393 animals from all regions of the country were examined. The present study details the results of extra-intestinal nematode and Trichinella larvae examinations. All individuals were examined for Trichinella, using routine digestion methods. Parasitological examination of the internal organs of some of the foxes also identified a number of different extra-intestinal nematodes. The following prevalences were identified (number positive/number foxes examined): Trichinella larvae 19/393 (4.8%); Capillaria böhmi (C. böhmi) 88/174 (51%); Capillaria aerophila (C. aerophila) 160/181 (88%); Crenosoma vulpis (Cr. vulpis) 105/181 (58%) and Capillaria plica (C. plica) 81/154 (53%). No evidence of Angiostrongylus vasorum infection was found. The 19 different Trichinella isolates were species typed by PCR and sequence analysis; 18 isolates were identified as Trichinella nativa and one as Trichinella britovi. A wide geographical distribution of the parasites was seen. The following exceptions were recorded: C. böhmi, the prevalence of which was significantly lower in northern Norway (6%) compared to other regions (central Norway, eastern Norway and southern and western Norway; 52-57%). There was a significantly higher prevalence of Trichinella infection in eastern Norway (8.1%), when compared with the rest of the country (0.6%). Cr. vulpis prevalence was significantly higher in central Norway (83%) than in other regions (41-56%). There were no significant differences in age and sex distribution of the parasites with the exception of Cr. vulpis where juvenile foxes had a greater likelihood of infection. The data also indicated that adult foxes were more commonly infected with Trichinella larvae (5.8%) than juveniles (3.3%) (no statistical significance).

Animals↗
PubMed2006

Occurrence of Giardia and Cryptosporidium in Norwegian red foxes (Vulpes vulpes).

Faecal samples from 269 Norwegian wild red foxes (Vulpes vulpes) shot during the hunting season (October-April) in 2002-2004 were examined for the presence of Giardia and Cryptosporidium. Cryptosporidium oocysts were detected in samples from 6 (2.2%) of the foxes, and Giardia cysts in 13 (4.8%) of the foxes. The prevalence of Giardia infection was significantly higher in juvenile male foxes than in adult male foxes, but no other significant differences between age and sex were found. No significant differences in prevalence related to geographical origin of animals were found. Insufficient nucleated Cryptosporidium oocysts were isolated for successful PCR, but genotyping of Giardia duodenalis isolates from seven foxes demonstrated a high degree of heterogeneity amongst them, with all isolates belonging to the zoonotic Assemblages A and B.

Age Factors↗
PubMed1991

Polyglucosan bodies in the central nervous system of a fox.

Polyglucosan bodies (PGB) in the central nervous system of an old male fox, Vulpes vulpes japonica, without neurological signs were examined by light and electron microscopy, lectin histochemistry and immunohistochemistry. Fox PGB were round, slightly-basophilic and PAS-positive structures. Most of the bodies were situated free in the neuropil. Electron microscopically, fox PGB were composed mainly of branching filaments and electron-dense material. Lectin histochemistry revealed that fox PGB contained mannose and galactose in addition to glucose. Fox PGB were immunoreactive for monoclonal antibodies raised against human polyglucosan. These findings indicate that fox PGB are similar to feline ones.

Animals↗
PubMedDate not supplied

Effects of space allowance and earthen floor on welfare-related physiological and behavioural responses in male blue foxes.

Welfare-related physiological and behavioural responses were studied in farm-bred male blue foxes (Alopex lagopus). Three different-sized cages (80-cm long [CL80], 120-cm long [CL120], and 240-cm long [CL240]; each 105-cm wide x 70-cm high) with wire-mesh floors and one enlarged cage (CL240E) with both wire-mesh floor (240-cm long x 105-cm wide x 70-cm high) and earthen floor (80-cm long x 105-cm wide x 70-cm high) were compared. N = 30 males for each group. The experiments lasted from weaning in July to pelting in December. Statistical analyses were based on the models accounting for litter as a block effect. Breaking strength of tibia was highest for foxes having access to both wire-mesh and ground floors (CL240E). Stress-induced hyperthermia was evident during capture and immobilisation. The highest rectal temperature (mean +/- SEM) was found in CL240E (capture: 39.6 +/- 0.09 degrees C, restraint:40.0 +/- 0.09 degrees C) and the lowest in CL80 (capture: 39.1 +/- 0.09 degrees C, restraint: 39.7 +/- 0.09 degrees C). Likewise, capture time (median; interquartile range) in the home cage was highest in CL240E (29; 18 to 44) and lowest in CL80 (12; 9 to 14). During capture, foxes tended to withdraw to the farthest site within the cage. CL240E foxes typically showed the most fear towards human. The most confident animals were found in CL80. The cortisol:creatinine ratio (median; interquartile range) obtained from circadian urine did not reveal statistically significant differences among CL80 (3. 5; 2.6 to 4.1), CL120 (2.3; 1.5 to 3.8) and CL240 (2.3, 1.5 to 3.7). The earthen flooring complicated the urine sampling and conclusions for CL240E (1.7; 1.2 to 2.2). CL240E foxes were the most active and explorative on both wire-mesh- and ground-floored open-field arenas. Altogether, 53% of furs from CL240E were classified as very dirty. Dirtiness of furs in other test groups was slight. In conclusion, the present results did not reveal an unambiguous superiority of any of the studied cage options for well-being of farmed blue foxes.

Animal Husbandry↗
PubMed2001

Cost-efficient vaccination of foxes (Vulpes vulpes) against rabies and the need for a new baiting strategy.

In this study, ecological models, optimisation algorithms and threshold analysis were linked to develop oral-vaccination strategies against rabies in fox populations. It is important that such strategies are cost-efficient and resistant to environmental conditions which would lessen their success. The model validation shows that the ecological models used are suited to predict the proportion of tetracycline- (TC) marked foxes in the course of time. This figure indicates the proportion of foxes which had at least one contact to vaccine baits, and is based on the design of the vaccination strategy (i.e. the number and timing of vaccination campaigns and the number of baits used per square kilometre and campaign). The design of a vaccination strategy also determines the costs. It is the combination of ecological models and optimisation algorithms that helped us to design a vaccination strategy which is capable of achieving a continuous rate of >70% of TC-marked foxes within an analytical horizon of 3 years at low costs. Compared to the standard strategy (baseline comparator), the improved strategy incurs just over half of the cost while almost doubling the number of weeks during which the proportion of TC-marked foxes is >70%. In the improved strategy, June is recommended as the time for bait distribution. The standard strategy, however, avoids summer months (because high temperatures reduce the durability of the baits) which again leads to a reduction of the bait intake by the foxes. Using threshold analysis, we examined the effect of a reduced durability of the baits on the design of the improved vaccination strategy. We concluded that distribution of baits in June was optimal given that the durability of baits is above a threshold of 7 days.

Administration, Oral↗
PubMed2000

ELISA test for rabies antibody titration in orally vaccinated foxes sampled in the fields.

The assessment of the efficacy of rabies oral vaccination campaigns requires the titration of specific antibodies in the target species. Unfortunately, in Continental Europe, most fox serum samples are in fact "body fluids" taken from cadavers and the lack of a validated titration method for these poor quality sera made it impossible to survey and compare the efficacy of various oral vaccination protocols used by the different European teams. By using ready to use microplates sensitised with rabies virus glycoprotein purchased from a manufacturer and applying a simple and rapid ELISA technique on field fox sera, we obtained antibody quantitation highly correlated with seroneutralising antibody titres measured with a seroneutralisation test on cell culture. We obtained, with fox sera sampled in the same area, the same distribution of high, medium and low titres within all categories of serum quality (from high to very poor quality) and therefore conclude that this ELISA test allows a reliable titration even with highly contaminated body fluids. This test was shown to be equally capable of detecting rabies antibodies in serum samples taken from foxes vaccinated with an highly attenuated rabies virus (the SAG2 double mutant of the Street Alabama Dufferin strain) or with the VRG, the Vaccinia recombinant glycoprotein. Additionally, a strong correlation was demonstrated between titres given by this ELISA (or by the seroneutralisation test) and protection against challenge of foxes orally vaccinated with SAG2 vaccine baits. In view of this validation, this simple and reliable test is proposed for sero-surveying foxes following rabies oral vaccination campaigns.

Administration, Oral↗
PubMed2002

Survey for Trichinella spp. in red foxes (Vulpes vulpes) in Belgium.

Concurrently with a survey for Echinococcus multilocularis in the red fox (Vulpes vulpes) in Flanders, northern Belgium, serological and parasitological analyses for Trichinella spp. were carried out from 1996 to 1999. Muscle samples from foxes in Wallonia, southern Belgium, were obtained during a survey for rabies and alveolar echinococcosis from 1998 to 2000. In muscle samples from tongue, diaphragm, hindlegs and tail of 179 Flemish foxes no larvae were found by trichinoscopy. Serum and muscle juice of, respectively 176 and 26 animals were examined using an ELISA for the detection of antibodies against excretory-secretory (ES) antigen. There were eight (4.5%) positive sera, but no positive muscle juice samples. All muscle samples from 639 foxes in Wallonia proved to be negative for larvae in artificial digestion. Serum and muscle juice of 130 and 478 foxes, respectively were examined in ES-ELISA. There were 61 (46.9%) positive sera and 90 (18.8%) positive muscle juice samples. A comparison between 88 serum and muscle juice samples of the same foxes showed that only half of the serum-positive animals were detected using muscle juice. However, for establishing the true meaning of these results, a more profound epidemiological study on the vulpine population in Belgium is necessary.

Animals↗
PubMed2005

Molecular epidemiology of rabies in northern Colombia 1994-2003. Evidence for human and fox rabies associated with dogs.

During the period 2000-2003, wild grey foxes (Urocyon cinereoargenteus) in northern Colombia became infected with rabies. In order to derive phylogenetic relationships between rabies viruses isolated in foxes, dogs and humans in this region, 902 nt cDNA fragments containing the G-L intergenic region and encoding the cytoplasmic domain of protein G and a fragment of protein L were obtained by RT-PCR, sequenced and compared. Phylogenetic analysis showed that rabies viruses isolated in foxes, dogs and humans belonged to a single genetic variant. Speculative analysis together with epidemiological data indicated that rabies in foxes may have been due to contact with rabid dogs. Rabies transmission between dogs, wild foxes and humans may happen in natural conditions in northern Colombia. This finding is the first to suggest dog-to-fox rabies transmission in South America, and provides another example of dog rabies variants being able to successfully colonize wildlife hosts.

Animals↗
PubMed2006

Remarkable findings concerning PBDEs in the terrestrial top-predator red fox (Vulpes vulpes).

In the present study, we have analyzed muscle, liver, and adipose tissue of 33 red foxes from Belgium for their content of polybrominated diphenyl ethers (PBDEs). Median sums of seven tri- to hepta-BDEs (BDE 28, BDE 47, BDE 99, BDE 100, BDE 153, BDE 154, and BDE 183) were 2.2, 2.4, and 3.4 ng/g lipid weight in adipose tissue, liver, and muscle, respectively. These levels were lower than those found in various species of voles and mice, the main prey species of the red fox. This is probably related to the high capacity of the foxes to metabolize and eliminate lower brominated congeners. BDE 209 generally dominated the PBDE congener profiles in the red fox samples. In samples containing BDE 209, this congener contributed, on the average, approximately 70% to the total PBDE content. BDE 209 was measured in concentrations as high as 760 ng/g lipid weight in the liver, but the detection frequency was not more than 40%. In animals with the highest BDE 209 levels, this congener was detected in muscle, liver, as well as in adipose tissue. Other abundant congeners were BDE 153 and BDE 47, which prevail in other terrestrial species. The particular PBDE congener profile observed in the red fox resembles that seen in grizzly bears from Canada, but differs from those previously reported for terrestrial avian species. Our data confirms unambiguously that BDE 209 does bioaccumulate in terrestrial top predators, such as the red fox.

Adipose Tissue↗
PubMed2006

[Echinococcus multilocularis in Grisons: distribution in foxes and presence of potential intermediate hosts].

The southern border of the European endemic area of Echinococcus multilocularis runs along the alpine crest. This endemic transition area was analysed in the canton Grisons on a small spatial scale. A total of 543 foxes originating from 10 areas north and 4 areas south of the main alpine divide were investigated. Parasites were isolated using the sedimentation and counting technique on intestinal contents. The mean prevalence of E. multilocularis was 6.4% with significant differences between different areas. In the southern valleys, only foxes from the Val Müstair were infected (14.3%). On the northern side of the main alpine divide, prevalences varied between 0 and 40%. The predation habits of foxes on potential intermediate hosts was investigated by means of stomach content analyses (n=530). Rodents of the genera Microtus/Pitymys were found in 19.6% of fox stomachs, Clethrionomys glareolus in 8.0% and Arvicola terrestris in 0.4%. A small scale analysis based on a 10 x 10 km grid suggested that the predation rate on the genera Microtus/Pitymys significantly correlated with the prevalence of E. multilocularis in foxes (Spearman's r = 0.51). Hence, E. multilocularis appears to occur in the alpine study area on a very small spatial scale. These local sources of infection may persist for decades. This may partly explains why, during the last 34 years, some human cases of alveolar echinococcosis occurred in areas of the Canton Grisons where the parasite is presently endemic in foxes. No such human cases have been recorded in other areas free of E. multilocularis.

Animals↗
PubMed1997

A non-epistatic interaction of agouti and extension in the fox, Vulpes vulpes.

Agouti and extension are two genes that control the production of yellow-red (phaeomelanin) and brown-black (eumelanin) pigments in the mammalian coat. Extension encodes the melanocyte-stimulating hormone receptor (MC1R) while agouti encodes a peptide antagonist of the receptor. In the mouse, extension is epistatic to agouti, hence dominant mutants of the MC1R encoding constitutively active receptors are not inhibited by the agouti antagonist, and animals with dominant alleles of both loci remain darkly pigmented. In the fox the proposed extension locus is not epistatic to the agouti locus. We have cloned and characterized the MC1R and the agouti gene in coat colour variants of the fox (Vulpes vulpes). A constitutively activating C125R mutation in the MC1R was found specifically in darkly pigmented animals carrying the Alaska Silver allele (EA). A deletion in the first coding exon of the agouti gene was found associated with the proposed recessive allele of agouti in the darkly pigmented Standard Silver fox (aa). Thus, as in the mouse, dark pigmentation can be caused by a constitutively active MC1R, or homozygous recessive status at the agouti locus. Our results, demonstrating the presence of dominant extension alleles in foxes with significant red coat colouration, suggest the ability of the fox agouti protein to counteract the signalling activity of a constitutively active fox MC1R.

Agouti Signaling Protein↗
PubMed2006

Inheritance of litter size at birth in farmed arctic foxes (Alopex lagopus, Canidae, Carnivora).

Natural populations of the arctic fox (Alopex lagopus, Canidae, Carnivora) differ drastically in their reproductive strategy. Coastal foxes, which depend on stable food resources, produce litters of moderate size. Inland foxes feed on small rodents, whose populations are characterized by cycling fluctuation. In the years with low food supply, inland fox populations have a very low rate of reproduction. In the years with high food supply, they undergo a population explosion. To gain insight into the genetic basis of the reproductive strategy of this species, we performed complex segregation analysis of the litter size in the extended pedigree of the farmed arctic foxes involving 20,665 interrelated animals. Complex segregation analysis was performed using a mixed model assuming that the trait was under control of a major gene and a large number of additive genetic and random factors. To check the significance of any major gene effect, we used Elston-Stewart transmission probability test. Our analysis demonstrated that the inheritance of this trait can be described within the frameworks of a major gene model with recessive control of low litter size. This model was also supported by the pattern of its familial segregation and by comparison of the distributions observed in the population and that expected under our model. We suggest that a system of balanced polymorphism for litter size in the farmed population might have been established in natural populations of arctic foxes as a result of adaptation to the drastic fluctuations in prey availability.

Animals↗
PubMedDate not supplied

Ecology and epidemiology of fox rabies.

Although fox rabies has been reported in every country that has foxes, current foci of fox rabies are limited to Europe and North America. The fox rabies virus has unique characteristics that seem to be the result of adaptation through successive passages, i.e., high pathogenicity for the fox, excretion in saliva of a high proportion of infected animals, and low frequency of postinfection immunity. The spread of fox rabies is greatly favored by the characteristics of the genus Vulpes--ubiquity, broad diet, prolific nature, and its particular ethology and ecology. Animals may be immunized by oral vaccination, but natural mechanisms that also can terminate outbreaks are discussed.

Animals↗
PubMed2000

Invading parasites cause a structural shift in red fox dynamics.

The influence of parasites on host life histories and populations is pronounced. Among several diseases affecting animal populations throughout the world, sarcoptic mange has influenced many carnivore populations dramatically and during the latest epizootic in Fennoscandia reduced the abundance of red fox by over 70%. While the numerical responses of red fox populations, their prey and their competitors as well as clinical implications are well known, knowledge of how sarcoptic mange affects the structure of the dynamics of red fox populations is lacking. Integrating ecological theory and statistical modelling, we analysed the long-term dynamics (1955-1996) of 14 Danish red fox populations. As suggested by the model, invading sarcoptic mange significantly affected direct and delayed density dependence in red fox dynamics and concomitant shifts in fluctuation patterns were observed. Our statistical analyses also revealed that the spatial progressive spread of mange mites was mirrored in the autocovariate structures of red fox populations progressively exposed to sarcoptic mange.

Animals↗
PubMed2006

Evaluation of a serological test (indirect ELISA) for the diagnosis of sarcoptic mange in red foxes (Vulpes vulpes).

Sarcoptic mange occurs in many parts of the world and is common in populations of domestic and wild canids, including red foxes (Vulpes vulpes). In recent years, an indirect antibody enzyme-linked immunosorbent assay (ELISA), with higher sensitivity and specificity than traditional diagnostic methods, has been successfully applied in the diagnosis of sarcoptic mange in dogs. The same ELISA has also demonstrated specific antibodies to Sarcoptes scabiei in experimentally infected red foxes. The aim of this study was to evaluate the indirect ELISA when used to detect antibodies to S. scabiei in field sera from Swedish red foxes. One cohort of both infected and non-infected red foxes (cohort 1; n = 88), and one cohort of apparently non-infected foxes (cohort 2; n = 67) were examined for skin lesions and presence of S. scabiei by thorough visual examination at autopsy and skin scrapings. Samples of blood-tinted body liquid from the abdomen or thorax cavity were collected and analysed by the indirect ELISA. The relative sensitivity and specificity of the ELISA at different cut-offs (OD values) were estimated by comparing the test results to the infection status as determined by examination and skin scrapings. The highest combination of relative sensitivity and specificity, calculated based on cohort 1, was 95.4 and 100.0%, respectively. These estimates were constant for cut-offs 0.150-0.225, which included the cut-off based on the mean plus three standard deviations of test results from cohort 2 (0.165). It is concluded that this test can be useful in diagnosis and epidemiological studies of S. scabiei infection in red foxes.

Animals↗
PubMed1976

Food caching by red foxes and some other carnivores.

Food caching by the red fox, Vulpes vulpes, may safeguard surplus food for future consumption. Because of practical difficulties involved in observation the extent to which the fox making a cache, or any other fox, can utilise the hoard was not known. This problem is tackled through extended observation, using unfra-red binoculars, on wild foxes (some of which were radio-tagged), together with experiments involving hand-reared tame foxes, either walked on a long leash or free and radio-tagged. The results demonstrate the fox's ability to rediscover its caches and shed light on the adaptive significance of the behaviour, which is then dsicussed in the context of food safeguarding by other carnivores.

Animals↗