Effects of Management, Behavior, and Scavenging on Risk of Brucellosis Transmission in Elk of Western Wyoming

Abstract

Brucellosis is endemic in elk (Cervus elaphus nelsoni) using winter feedgrounds of western Wyoming, USA presumably because of increased animal density, duration of attendance, and subsequent contact with aborted fetuses. However, previous research addressed antibody prevalence rather than more direct measures of transmission and did not account for elk behavior or scavenging in transmission risk. Throughout March and early April 2005-07, we monitored 48 sets of culture-negative, pseudoaborted elk fetuses, placentas, and fluids (fetal units, FUs) on one winter free-ranging (WFR) location and four sites (Feedline, High Traffic, Low Traffic, Adjacent) associated with four feedgrounds. "At-risk" elk (total elk within 5 m of FU) and proportions of elk sniffing and contacting FUs were highest on Feedlines and decreased toward Low Traffic sites. We did not observe elk investigating FUs Adjacent to feedgrounds or on the WFR location. At-risk elk on Feedline and High Traffic sites decreased throughout the sampling period, whereas proportions of elk investigating FUs were correlated positively to at-risk elk among all sites within feedgrounds. At-risk elk and proportions of elk investigating FUs were correlated with total feedground elk density and population only on High Traffic and Low Traffic sites. Proportions of sex/age groups (female, juvenile, male) investigating FUs did not differ from background populations. Females, however, spent more time (mean [SE], 21.07 [3.47] sec) investigating FUs than juveniles (14.73 [3.53] sec) and males (10.12 [1.45] sec), with positive correlation between total investigations and time spent investigating per female. Eight species of scavengers consumed FUs, removing FUs faster on feedgrounds than WFR locations and reducing proportions of elk that investigated FUs. Our results suggest that 1) reduction of elk density and time attending feedgrounds, particularly on Feedlines; and 2) protection of scavengers on and adjacent to feedgrounds would likely reduce intraspecific transmission risk of brucellosis.

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

“…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. In bison, animals concentrate because of their gregarious herd structure, greatly increasing the potential for contact with infected, aborted materials, perpetuating brucellosis in free-ranging herds (Cheville et al, 1998).…”

Evidência molecular de Brucella sp. em Ozotoceros bezoarticus (veado campeiro) do Pantanal Sul-Mato-Grossense

“…para bovinos nos Estados Unidos da América (EUA). Por outro lado, alguns autores consideram a brucelose um problema significativo em alces (Cervus elhapus) e em bisão (Bison bison) no Park Nacional Yellowstone (Ryan et al 1997, Etter & Drew 2006, Conner et al 2008, Maichak et al 2009, Olsen & Tatum 2010, Olsen 2010. Diagnósticos sorológicos de Brucella spp.…”

“…Diagnósticos sorológicos de Brucella spp. em alces tem revelado baixa prevalência de soros reativos, isto pode ser devido a severidade da doença que acaba sendo fatal, ou uma inerente resistência a doença e ou uma baixa a exposição à doença (Honour 1993, Maichak et al 2009). Porém, em infecções experimentais foi possível verificar que a brucelose foi fatal em alces (Honour 1993).…”

Emergence of Diseases From Wildlife Reservoirs

“…35 This behavioral difference between the bison and elk probably explains the maintenance host role of bison and the absence of brucellosis in most elk populations in North America. 1,4,6 In southern portions of the GYA, however, approximately 23,000 elk receive supplemental feed on state and federal feedgrounds, 20 a mitigation strategy designed to keep elk from seeking cattle feedlines. The winter feeding maintains increased density of elk above the natural carrying capacity of the habitat, however, and feeding grounds provide a site for elk to congregate daily with increased exposure to infectious abortions and discharge on feedstuffs.…”