No Need for Raised Temperatures Over “Beaver Fever”: Low Prevalence of Giardia in Wild Scottish Beavers (Castor Fiber)

Eurasian beavers (Castor fiber) were reintroduced to Scotland, UK, after more than two centuries of extinction. Giardia spp. are important protozoal parasites causing waterborne gastroenteritis in humans, with the zoonosis known as “beaver fever” in North America, raising public health concerns in Scotland. Using a rapid enzyme immunochromatographic assay (SNAP Giardia, IDEXX Laboratories, Inc) for soluble Giardia antigen, we tested 274 live wild beavers trapped for translocation (2019–25) and 26 wild beavers found dead. Prevalence was 1.83% (n=5/274) in live beavers (95% confidence interval, 0.6–4.21), with no clinical illness observed. Beavers that were positive for Giardia antigen on testing were treated and retested as negative before translocation. Prevalence was highest in kits at 3.7% (n=3/81) and lowest in adults at 0.71% (n=1/140), but the difference did not reach statistical significance. One dead adult female tested positive, with no evidence of disease and death was attributed to sepsis from bite wounds. Wild Eurasian beavers in Scotland currently do not appear to pose a notable Giardia infection risk to humans or animals, especially compared with the higher prevalence in local domestic animals.