Efficacy of Single Calfhood Vaccination of Elk With Brucella Abortus Strain 19

Abstract

Brucellosis has been eradicated from cattle in the states of Wyoming, Montana, and Idaho, USA. However, free‐ranging elk (Cervus elaphus) that use feedgrounds in the Greater Yellowstone Area (GYA) and bison (Bison bison) in Yellowstone and Grand Teton national parks still have high seroprevalence to the disease and have caused loss of brucellosis‐free status in Wyoming. Management tools to control or eliminate the disease are limited; however, wildlife vaccination is among the methods currently used by wildlife managers in Wyoming. We conducted a controlled challenge study of single calfhood vaccination. Elk calves, caught in January and February of 1999 and 2000 and acclimated to captivity for 3 weeks, were randomly assigned to control or vaccinate groups. The vaccinate groups received Brucella abortus vaccine strain 19 (S19) by hand‐delivered intramuscular injection. Calves were raised to adulthood and bred at either 2.5 or 3.5 years of age for 2000 and 1999 captures, respectively. Eighty‐nine (44 controls, 45 vaccinates) pregnant elk entered the challenge portion of the study. We challenged elk at mid‐gestation with pathogenic B. abortus strain 2308 by intraconjunctival instillation. Abortion occurred in significantly more (P = 0.002) controls (42; 93%) than vaccinates (32; 71%), and vaccine protected 25% of the vaccinate group. We used Brucella culture of fetus/calf tissues to determine the efficacy of vaccination for preventing infection, and we found that the number of infected fetuses/calves did not differ between controls and vaccinates (P = 0.14). Based on these data, single calfhood vaccination with S19 has low efficacy, will likely have only little to moderate effect on Brucella prevalence in elk, and is unlikely to eradicate the disease in wildlife of the GYA.

Status of Brucellosis in Free-Ranging Elk and Bison in Wyoming

“…Brucellosis was first detected in wild elk in 1930 (Murie, 1951) and, currently, appears to be well established in elk and bison in the GYE portions of Wyoming, Montana, and Idaho, USA (Tunnicliff and March, 1935;Thorne et al, 1997;Aune et al, 2002;Etter and Drew, 2006;United States Animal Health Association, 2006). Suspected B. abortus transmissions from elk to cattle in the GYE triggered Wyoming, Idaho, and Montana, USA, to lose their brucellosis Class Free cattle status in 2004, and 2008, respectively (Cross et al, 2007. During 2008, another infection was detected in Wyoming from a single cattle herd, threatening that state's newly regained Class Free status.…”

“…Transmission of brucellosis typically occurs orally when susceptible animals contact infected aborted fetuses, fetal membranes and fluids, or uterine discharges (Thorne, 2001). Supplemental winter feeding of elk congregates animals on feedgrounds from November through April, overlapping the period of peak brucellosis transmission from February through June (Roffe et al, 2004;Cross et al, 2007). Maichak et al (2009) documented that up to 12% of elk attending feedgrounds contacted pseudo-aborted elk fetuses placed on feedground sites.…”

Probable causes of increasing brucellosis in free‐ranging elk of the Greater Yellowstone Ecosystem

“…Supplemental feeding began at some locations as early as 1910 to limit elk impacts on agricultural land and maintain elk populations despite shrinking native winter range (Smith 2001). Feedgrounds are intended to minimize contact between elk and cattle during winter, but they also increase the concentration of elk between November and April, and the transmission of Brucella abortus among elk is most likely between February and June (Roffe et al 2004). The low seroprevalence of brucellosis, historically, in the unfed elk populations of the GYE has fostered an apparent consensus that B. abortus is not self-sustaining in elk populations that do not concentrate on artificial feeding grounds or share winter range with bison (Cheville et al 1998).…”

Culling wildlife hosts to control disease: mountain hares, red grouse and louping ill virus

“…2007). Management aimed at reducing contact between elk and cattle, only increased elk aggregation, the prevalence of brucellosis amongst elk, and the risk of transmission to cattle (Roffe et al. 2004).…”