Veterinary Risk Assessment – Captive Enclosure Release of Eurasian Beaver (Castor fiber) Cors Dyfi Prepared by Dr R CAMPBELL-PALMER BSc(Hons) Zoology MSc (Animal Welfare and Applied Behaviour) PhD Independent Beaver Ecologist ……………………………… Dr ADAM D NAYLOR BVetMed MSc (Wild Animal Health) CertAVP (Zoo Med) DipACZM DipECZM(ZHM) MRCVS EBVS® European Veterinary Specialist in Zoo Health Management American College of Zoological Medicine Board Certified Specialist in Zoological Medicine™ Royal College of Veterinary Surgeons Specialist in Zoological and Wildlife Medicine British and Irish Association of Zoos and Aquaria Veterinary Advisor for Native Species Working Group Royal Zoological Society of Scotland, Veterinary Surgeon …………………………………………………….. & Dr SIMON J GIRLING BVMS (Hons) DZooMed DipECZM(ZHM) CBiol FRSB EurProBiol FRCVS Royal College of Veterinary Surgeons Fellow and Recognised Specialist in Zoo & Wildlife Medicine EBVS European Veterinary Specialist in Zoo Health Management Past-President of the European College of Zoological Medicine Honorary Clinical Associate Professor, University of Glasgow, School of Veterinary Medicine EAZA EEP Veterinary Advisor for Pallas’ cat, Otocolobus manul EAZA EEP Veterinary Advisor for the Red Fronted Macaw (Ara rubrogenys) Veterinary Advisor for the Scottish Wildcat Studbook Royal Zoological Society of Scotland, Head of Veterinary Services ………………………………………………………….. VRA – enclosed beaver release A. Risk assessment Hazard Identification Based on Literature Review As part of the Scottish Beaver Trial, pre-release health screens and post-release monitoring protocols were based on the IUCN guidelines (Woodford, 2001) and incorporated governmental (DEFRA) and public health concerns such as rabies and Giardia spp. infection. A literature search on reported disease in captive and wild beavers was also used to formulate these protocols with the use of CAB ABSTRACTS, BIOSIS and MEDLINE databases (Goodman et al., 2012). The literature search focussed on the Eurasian beaver but also took into accounts diseases reported in the related North American species Castor canadensis and diseases expected to be found in semi-aquatic and terrestrial rodents which had not been reported in the Eurasian beaver but for which there was a theoretical possibility of disease occurring in this species. This was determined in order to cover those diseases which theoretically may occur in the Eurasian beaver but which have yet to be formally reported in peer reviewed literature- thereby providing a more complete hazard identification. These reviews were updated for this work, and additional health studies published since the conclusion of the Scottish Beaver Trial, and specifically relevant to a British context included. It is worth noting a fully peer-reviewed risk assessment following IUCN guidelines for the release of the Eurasian beaver into Britain has already been recently published (Girling et al., 2019c). Risk Assessment and Hazard Identification The aim of this report was to identify the risks of disease in domestic animals, wildlife and people, arising from the enclosed release of a pair or small family group of beavers into a permanent enclosure at the Cors Dyfi reserve. As per the IUCN wildlife disease risk analysis (2014) the identification of the pathogens which may affect the reintroduced species were identified (hazard identification). This extended to include all those pathogens reported in the peer reviewed literature in the Eurasian beaver, the related cousin the North American beaver and other semi-aquatic/related rodents which live in a similar environment and therefore are likely to be exposed to similar pathogens. This was to ensure the widest range of potential pathogens was covered to provide as full a risk assessment as feasible, acknowledging the paucity of peer reviewed publications on disease in the Eurasian beaver. From this a review of the literature, a risk assessment was determined, and each pathogen assessed following the pathway as laid out by the industry standard IUCN guidelines for wildlife reintroduction risk analysis (IUCN, 2014): a). the likelihood of release (of the pathogen) into the area of concern. This was assessed based on whether: Campbell-Palmer, Naylor & Girling, May 2020 2 VRA – enclosed beaver release • the disease has been reported in C. fiber (greater potential impact), C. canadensis (medium potential impact) or other semi-aquatic/related rodent species (lower potential impact) • whether the disease in question can be screened for in the pre-release animal using validated methods which can produce a high degree of sensitivity and specificity (>85%) allowing the exclusion of said beaver from the reintroduction and so meaning the pathogen poses a lesser potential impact. b). the likelihood that domestic animals or humans would be exposed to the pathogen once it was released and the contrast with whether the pathogen was already endemic in the area of release. c). the consequences of any such exposure on domestic animals or humans. The risk was clearly greater if the pathogen was a known zoonosis or domestic animal pathogen Using the above three assessments for each potential pathogen, the disease risk to domestic animals and humans was categorised to one of the following definitions for qualitative risk assessment, based on European Food Safety Authority (EFSA, 2006) and World Organisation for Animal Health (OIE, 2012). These assessments are described below in the Summary of Risks section and depicted in Table 3. which includes incidence in Eurasian and North American beavers as well as other rodents and whether the organism is a pathogen for other species and a zoonosis. Table 1. Risk level categorisation for disease transference to domestic animals or humans. Risk level Definition Negligible Event is so rare, does not merit consideration Very low Event is very rare, but cannot be excluded Low Event is rare, but does occur Medium Event occurs regularly High Event occurs very often Very high Event occurs almost certainly • Risk Pathways This veterinary risk assessment will assess all disease risk scenarios for completeness, though the key consideration of any risk pathway is the source of the beavers used, to mitigate for the majority of risks presented the significant mitigation is to only use either Scottish or UK captive-bred individuals. Therefore, this veterinary risk assessment assumes throughout that this does not refer to direct imports from Europe and refers only to beavers sourced either from wild-born Scottish animals from the Tayside Campbell-Palmer, Naylor & Girling, May 2020 3 VRA – enclosed beaver release catchment trapped under the SNH Beaver Mitigation Scheme, or responsibly captive bred (as supposed to just captive held) animals in the UK. The assumption is therefore that the beavers bred in the UK, first or subsequent generations, making the risk of introducing non-UK pathogens which are significant zoonoses or domestic animal pathogens (e.g. Echinococcus multilocularis) negligible. This enclosed project would be situated within the Cors Dyfi Nature Reserve (grid ref SN 703 984), owned by Montgomeryshire Wildlife Trust. The reserve is a lowland peat bog, but it has scrubbed up with willow over the years, therefore the aim would be to utilise the beavers as a habitat restoration tool. Outside of the reserve the immediate neighbouring land-use includes a caravan park and extensive sheep grazing areas. Surveys by the wildlife trust have documented that the reserve is habitat for otter, badger, fox, birds of prey, and parts of the reserve are grazed by small numbers of water buffalo during the summer months. Following release, the beaver, as per other native mammals could be subject to exposure to common wildlife pathogens. It should be noted that much of Dyfi catchment site is designated with various conservation statuses such as SSSI and SPA’s, and includes a national nature reserve. The predominant surrounding neighbouring land-use, away from the river stem is rough-sheep grazing. Therefore, direct and regular contact with livestock is unlikely to occur. The most commonly reported potential pathogen in a British context of beavers screened to date is infection with Leptospira spp. although this appears to be significantly linked to areas of increased human activity, strongly geographically linked to loamy clay soils and an extensive study indicates the Eurasian beaver is not a reservoir host (Girling et al., 2019a). There is no evidence to date of wild-living beaver in Britain being significant hosts for sheep fluke and no cases of bovine tuberculosis (Mycobacterium bovis) have been reported (Goodman et al., 2012, 2017). • A Summary of the risk factors See Appendix 1. Haematological parasites In Europe, the most common blood parasites found in rodents are Anaplasma phagocytophilum, Bartonella spp., Haemobartonella spp., Babesia microti, Trypanosoma spp., and Hepatozoon spp. Generally, there tends to be a low prevalence or total absence of haemoparasites in rodents (Wiger, 1979; Healing, 1981). Exceptions include haemoparasite infection rates of 76.9% in Polish common voles (Microtus arvalis), principally Haemobartonella and Bartonella spp. (Pawelczyk et al., 2004). Bajer et al. (2001) suggested bank voles (Clethrionomys glareolus) from the same area displayed Campbell-Palmer, Naylor & Girling, May 2020 4 VRA – enclosed beaver release haemoparasite incidence of 81.9%. Bown et al., (2003) believe that the field vole acts as the main reservoir for Anaplasma