Establishment of Reference Intervals for Serum Amyloid A and Haptoglobin in Free-Ranging Barren-Ground Caribou (Rangifer tarandus granti), and Herd Health Implications.

Barren-ground caribou of the subspecies Rangifer tarandus granti are distributed throughout Alaska, USA, and the Yukon, Canada. The acute phase response is an innate immune response activated due to inflammatory stimulus, resulting in changing levels of acute phase proteins, including haptoglobin (Hp) and serum amyloid A (SAA). Haptoglobin and SAA are used as indicators of inflammation in domestic species, with several studies demonstrating their use in wildlife. In this study, banked serum samples from apparently clinically normal free-ranging barren-ground caribou (reference group) were used to establish reference intervals (RI) for Hp and SAA in caribou. These RIs were compared with additional samples from a declining herd with ongoing Brucella suis biovar 4 transmission. The RIs for Hp and SAA with 90% upper confidence intervals were 0.12-1.03 (0.08-1.27) mg/mL and 0.10-18.44 (0.10-31.00) mg/L, respectively. The SAA levels in the declining herd were found to be significantly elevated from the reference group (P=0.009), whereas no difference was found in Hp levels between the two herds (P=0.389). Meanwhile, SAA and Hp levels in animals with B. suis biovar 4 titers ≥1:80 were significantly elevated from the reference group (SAA P<0.001; Hp P=0.178). The results of our study indicate that SAA and Hp hold promise in monitoring the overall herd health of caribou in Alaska.