Revised Disease Risk Analysis for the Conservation Translocation of the Eurasian Beaver (Castor fiber) to England.

Published online
12 Apr 2024
Published by
Natural England
Content type

Common, S. & Sainsbury, A. W. & Donald, H.

Publication language
England & Norway & UK & Nordic Countries


In a disease risk analysis (DRA) on the conservation translocation of free-living beavers from either Norway or Great Britain, or those housed in either fenced enclosures or zoological collections in Great Britain, to England, 96 hazards (89 infectious and seven non-infectious) were evaluated and 26 received detailed analysis. This DRA was an expanded and updated version of one published in 2020 (Donald, Common, and Sainsbury 2021) and analysed an additional 28 hazards, of which four required detailed evaluation. The revision included a new translocation pathway in which beavers held in fenced enclosures, and other captive collections, in Great Britain might be released, in addition to the two pathways previously investigated. This included beavers held in naturalistic, fenced enclosures as well as those held in private and zoological collections. Contact between these beavers and with exotic mammalian species was considered in the risk analysis. Of the 26 hazards assessed in detail, 17 were of high or medium risk of precipitating disease in beavers or sympatric mammals, including people: Echinococcus multilocularis; Leptospira spp.; Yersinia spp.; Toxoplasma gondii (as both a carrier and population hazard); Taenia spp.; persecution; captivity; road traffic collisions; Eimeria spp.; Streptococcus castoreus; Neostichorchis subtriquetrus; Emmonsia crescens; Trichinella spp.; gram- negative bacteria; Brucella spp.; and hantaviruses (Puumala-virus (PUUV) and Saaremaa-virus (SAAV)). Moreover, seven hazards were considered to be of higher risk of precipitating disease if captive beavers from enclosures are chosen for conservation translocation in preference to free-living beavers: Brucella spp.; Echinococcus multilocularis; Trichinella spp.; Toxoplasma gondii (as a carrier and population hazard); Francisella tularensis; Taenia martis and hantaviruses (PUUV and SAAV). In the disease risk analysis employed in this report, which uses World Organisation for Animal Health methods, risk estimation is made prior to consideration of disease risk management, which is evaluated thereafter. Disease risk management measures are employed to reduce the risk level and therefore the risk estimations noted might be reduced when risk management is implemented. Eleven of the 26 hazards are stressor-associated and very careful attention to translocation protocols will be required to reduce the risk from disease precipitated by them. Parasites which are stressor-associated hazards may be commensal, or Beaver specific (for example Neostichorchis subtriquetrus), and therefore are an important component of biodiversity. Therefore, efforts should be made to conserve these parasites following translocation, stress mitigation is the favoured method of management, and prophylactic anti-parasitic treatment must be used with care to prevent elimination of these native parasites.

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