Elk feedground projects reduced seroprevalence, now in monitoring stageWritten by Saige
Pinedale – “If we can lower the prevalence of brucellosis in the elk, we can reduce the risk of transmission of the disease from elk to cattle,” says brucellosis biologist Brandon Scurlock of the Wyoming Game and Fish Department.
“About 22 percent of elk that use feed grounds show antibodies to brucellosis, meaning they have been exposed to the bacteria – they don’t necessarily have the disease,” says Scurlock. “In the northwest, we’re seeing an increasing trend in the native wintering elk, but in terms of feed ground elk, the sero-prevalence has been stable or slightly decreasing.”
When Wyoming lost its brucellosis-free status, research was implemented for both wildlife and cattle. One pilot project and top recommendation of the Brucellosis Coordination Team was the test and slaughter project, which is in the monitoring stage right now.
“They recommended that we conduct the project on all three feed grounds in the Pinedale elk herd unit,” explains Scurlock. “We erected large portable corral traps on the feedgrounds and tested as many yearling and older female elk as we could capture. Those testing seropositive were slaughtered at a USDA facility in Idaho.”
Following slaughter, the meat was returned to Wyoming and distributed to the Salvation Army.
The five-year project began in 2006 and recently concluded, with 2011 being the first year that no elk were slaughtered.
“It was effective at reducing seroprevalence in the population,” says Scurlock. “At the Muddy Creek feed ground, seroprevalence dropped from 37 percent to five percent in the course of five years.”
“However, it was a pilot project that the task force recommended,” continued Scurlock. “It cost over $1 million to implement and is likely not very feasible on a broad scale. We did learn some valuable information and saw prevalence decrease, so we are monitoring the elk now.”
Monitoring efforts will continue for several years to determine if the test and slaughter project will provide long-term results, or if the decrease in prevalence is simply a short-term solution.
Scurlock also mentions that elk are vaccinated with Strain 19 of the bacteria to help them fight the Brucella infections better.
The vaccine doesn’t prevent infection, but rather works to prevent abortions and, as a result, reduces transmission of brucellosis.
Scurlock comments, “We have been monitoring the efficacy of Strain 19 vaccination program since 1989 by bleeding elk and looking at the serology.”
A new method of monitoring vaccination efficacy is through the use of vaginal implant transmitters (VITs). VITs are implanted into pregnant elk.
“When those transmitters are expelled, you can track abortions and normal births,” says WGFD wildlife disease specialist Hank Edwards.
“We started using the VITs to see if there is a difference in abortion rate between vaccinated and unvaccinated elk,” explains Scurlock. “It doesn’t appear to have an affect on seroprevalence – vaccinated animals have the same prevalence as unvaccinated animals, but we are trying to see if there is a difference in abortion rates.”
Scurlock further explains that the vaccine is expensive, and vaccinating elk is a labor-intensive process.
“We don’t want to continue vaccinating unless we see a benefit,” says Scurlock.
Edwards adds that some work is being done to improve vaccines for elk.
“One of the research projects going on at the Sybille Research Facility is to determine which adjuvants work best with elk and the vaccine,” says Edwards. “An adjuvant is something added to a vaccine to enhance the immune response. This project is being done in conjunction with Steve Olson at the National Animal Disease Center.”
Other research is being done to develop a better vaccine. The opening of the Bio-Safety Level 3 lab in the Wyoming State Vet Laboratory will facilitate continuing research. This new lab will allow research with the Brucella bacteria directly.
VITs are also used to determine the location and timings of abortions. In combination with GPS collars, WGFD biologists are able to look at elk contact with aborted fetuses.
“We are trying to see when and where the elk are aborting so we can develop management strategies to reduce chances of contact with the fetus,” says Scurlock. “We have been doing that since 2006 on 17 of 23 feeding grounds.”
In a “Target Feedground Project,” the WGFD is also using flexible management strategies and changing feeding styles to reduce contact with aborted fetuses.
“The most contact occurs when a fetus is expelled right on the feed line, as compared to off a feed line,” says Scurlock. “We determined that using experimental culture-negative fetuses and game cameras.”
By identifying that less contact is made away from feed lines, Scurlock notes that the use of low-density feeding will reduce population density when elk are on feed and should reduce contact and transmission of the bacterium.
The same project has identified that most VITs are expelled in March and April, allowing the WGFD some other management options.
“We are looking at truncating the feeding season,” says Scurlock. “If we can get elk off feed grounds earlier in the year, by February for instance, they won’t be concentrated and we can reduce brucellosis that way.”
Brucellosis on feed grounds and in areas of high-density elk is perhaps more predictable than the occurrence of the disease in and around the Cody and Meeteetse areas. In cooperation with Montana State University, a research project is in progress with the goal of identifying why brucellosis has established in the area.
“Angela Brennan with MSU has been working for the last two years or better trying to figure out what has changed in the Cody region that has allowed brucellosis become established,” says Edwards. “We have some theories, and are in the process of looking at that question, but we can’t definitively point our finger at any one cause – we don’t have any concrete answers yet.”