The Scottish Beaver Trial: Veterinary Monitoring of the Knapdale Beaver Population 2009-2014
Total Page：16
File Type：pdf, Size：1020Kb
The Scottish Beaver Trial: Veterinary Monitoring of the Knapdale Beaver Population 2009-2014 Gidona Goodman DVM MSc (Wild Animal Health) MRCVS Exotic Animal and Wildlife Unit, R(D)SVS University of Edinburgh Page 2 of 20 The Scottish Beaver Trial: Veterinary Monitoring of the Knapdale Beaver Population 2009-2014 Gidona Goodman DVM MSc (Wild Animal Health) MRCVS Exotic Animal and Wildlife Unit, R(D)SVS, University of Edinburgh Summary Sixteen Norwegian wild-caught beavers (Castor fiber) were released in Scotland between 2009 and 2010 as part of the five year Scottish Beaver Trial. All animals underwent a thorough clinical examination and were screened for a variety of animal and human pathogens. No significant pathogens were isolated that precluded any animal for release. Post-release health monitoring continued from 2010 to 2014 through trapping and visual observations. As a result of this monitoring one animal was removed from the trial due to poor body condition. Two animals died shortly after release; one with circulatory failure and one for which the cause of death was not determined. Two kits died, most likely due to predation. Body weights of adult beavers post-release remain within the expected weight range for Norwegian beavers. The University of Edinburgh, Goodman G. 2014. The Scottish Beaver Trial: Veterinary Monitoring of the Knapdale Beaver Population 2009-2014. [email protected] Page 3 of 20 Table of Contents Page 1. Introduction 4 1.1 Background 4 1.2 Objectives 4 2. Methodology and results 4 2.1 Pre-release health monitoring 4 2.1.1 Quarantine 4 2.1.2 Health assessment 5 2.1.3 Pathogen screening 6 2.2 Release of animals in to the wild 6 2.3 Post-release health monitoring 7 2.3.1 Health assessment 7 2.3.2 Post-release removal from the trial 8 3. Discussion 8 3.1 General discussion 8 3.2 Results 9 4. Health monitoring beyond the trial 10 5. Further release of beavers to the wild 10 5.1 Key points 10 6. References 11 Appendix A Scottish beaver Trial Family Tree 13 Appendix B Body weight and tail thickness of selected individual 14 beavers over the trial period Appendix C Health screen results of beavers released into Knapdale 17 2008-2014 Page 4 of 20 1. Introduction 1.1 Background In 2008 the Scottish Government granted a licence to the Scottish Wildlife Trust and the Royal Zoological Society of Scotland to conduct a five year trial on the reintroduction of the Eurasian beaver (Castor fiber) in Knapdale on the west coast of Scotland. Beavers have been extinct in Scotland since the 16th century due to hunting. This is the first controlled and licensed release of a wild mammal into the UK. In May 2009 eleven beavers (three families) trapped originally in Norway were released at Knapdale, followed by another five animals in 2010. 1.2 Objectives Scottish Natural Heritage (SNH) is coordinating the independent monitoring programme to assess the impacts of the Scottish Beaver Trial. SNH is leading a number of monitoring projects in collaboration with various independent monitoring partners. Beaver health is one of the elements being monitored independently by the Royal (Dick) School of Veterinary Studies. Veterinary input was provided by the author prior to the start of trial and throughout the five year period, to provide veterinary support and fulfil the following objectives: 1. Ensure animal welfare at all stages of the trial. 2. Ensure that reintroduced animals are fit and healthy for release. 3. Ensure no diseases of risk to livestock, wildlife or of risk to humans are introduced with the beavers. The veterinary involvement, guidelines and testing to meet the above objectives varied as the trial entered the different phases; pre-release, initial release and post- release. The report structure reflects these different phases. 2. Methodology and results The methodology and results of the beaver health monitoring from 2009-2014 are summarised in three different phases. 1. Pre-release when the beavers were in captivity during statutory quarantine and awaiting the results of health tests. 2. Release phase, which includes the days surrounding the release phase. 3. Post-release until the end of the trial duration. 2.1 Pre-release health monitoring 2.1.1 Quarantine Wild beavers were trapped in Norway, transported to the UK by air and placed in specially designated quarantine facilities. UK legislation at the time required imported beavers to be placed in approved rabies quarantine facilities for six months. Full details on the quarantine facilities and monitoring of animals during this period can be found in the SBT 2014 publication: The Scottish Beaver Trial: the story of the first licensed release of beavers into the wild in the UK (In press). Despite the beavers being housed in purpose built facilities, the main mortalities occurred during the quarantine period, with the deaths of six animals. No common cause of death was identified. Four animals had signs of infection or inflammation. Page 5 of 20 One adult female had an infected anal gland and colitis. No pathogens were isolated from either organ. Escherichia coli was isolated from the intestine and liver of a male kit with an inflammatory reaction in the small intestines. One adult female had a meningitis/encephalitis but no significant bacteria were cultured. An adult male had osteomyelitis of the coccygeal vertebra (Arcanobacterium pyogenes isolated) and liver necrosis. In two animals no primary cause could be identified, this included an autolysed female kit from which no pathogens were isolated and a juvenile female in poor body condition with severe intestinal parasitism. In view of these mortality events occurring while in captivity, a case was made to the Scottish government veterinary advisors to allow for a reduced quarantine period and to import the beavers under the Rabies (Importation of Dogs, Cats and Other Mammals) (England) (Amendment) Order 2004 which permits the import of rodents to zoos and research institutes without rabies quarantine. The probability of these animals being infected with rabies was negligible as Norway’s mainland was considered rabies-free. Subsequently, four animals were allowed into Scotland following veterinary certification by an official Norwegian Food and Safety (Mattilsynet) veterinarian declaring them rabies-free. They were held in Norway for a month to complete other health tests prior to direct transfer to Scotland. 2.1.2 Health assessment All animals were examined thoroughly under general anaesthesia about a month prior to release (Fig. 1). This allowed for a detailed clinical examination. The clinical examination followed normal veterinary practices and included examination of the head (eyes, ears and teeth), skin, fur and tail (for ectoparasites and injuries), abdominal palpation, auscultation and cardiac evaluation. All animals were weighed and a subcutaneous microchip was inserted, or previous placement confirmed, under the skin at the back of the neck. The gender of each animal was also confirmed using one or more methods such as palpation of the baculum (or penis) or the color and viscosity of the anal gland secretions. Blood samples were taken to verify that haematological and biochemical blood values were within the normal range for this species and to check that there was no underlying disease (see 2.1.3). Figure 1. Auscultation of a beaver under general anaesthesia. Page 6 of 20 2.1.3 Pathogen screening The list of potential diseases included in the pre-release health screens were based on the International Union of Conservation of Nature guidelines (IUCN) for rodents published by Woodford (2000) and incorporated governmental (Department of Environment, Food and Rural Affairs) and public health concerns such as rabies, giardiasis and tularaemia. A literature search on reported diseases in captive and wild beavers was also used to complete the list using CAB ABSTRACTS, BIOSIS and MEDLINE databases. Appendix C summarises the health screen results per individual animal. Faecal samples were submitted for bacterial enteric pathogens. Salmonella spp., Campylobacter spp., Clostridium spp. and Yersinia spp. were specifically requested. Faecal samples also underwent floatation with saturated salt solution for nematodes and sedimentation for trematodes. Faecal samples were screened for Giardia spp. and Cryptosporidium spp. Serology was used to screen for antibodies to Franciscella tularensis and Leptospira spp. All animals were negative for zoonotic enteric bacterial pathogens such as Campylobacter spp. Salmonella and Yersinia spp. Neither Giardia spp. nor Cryptosporidium spp. were detected. All animals were seronegative for Franciscella tularensis antibodies. In our program five animals were seropositive for Leptospira spp. antibodies. This included the serovars L. saxkoebing, L. canicola, L. copenhageni, L. icterohaemorrhagiae, L. autumnalis and L. javanica. Numerous helminths were identified in the faecal samples. In eight animals Travassosius rufus and beaver fluke (Stichorchis subtriquetrus) were the most commonly identified parasites. The Norwegian beavers were not deemed at risk of being infected with Echinococcus multilocularis as Norway was considered E. multilocularis free at the time. There was also no ante-mortem diagnostic test available although a novel serological test is being developed (Gottstein et al. 2014). Haematology and biochemistry results were within normal reference range for Eurasian beavers (Girling et al. Pers. Comm). This phase of the report has also been published in a peer-reviewed scientific journal (Goodman et al. 2012). 2.2 Release of animals into the wild In May 2009 three families (eleven individuals) were released to three separate lochs within the Knapdale trial site (see Appendix A family tree). This was followed by the release of five additional animals in 2010. Animals were assessed visually prior to release for normal breathing rhythm and pattern, body condition and demeanour. Only animals deemed fit were released into the wild. The number of people at the release site was limited and beaver individuals were observed visually post-release.