Effects of management, behavior, and scavenging on risk of brucellosis transmission in elk of western Wyoming.


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.

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