Submitted to: Journal of Wildlife Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2009
Publication Date: 10/1/2009
Citation: Luikart, G., Beja-Pereira, A., Chen, S., Bricker, B.J. 2009. DNA Genotyping Suggests Recent Brucellosis Outbreaks in the Greater Yellowstone Area Originated from Elk. Journal of Wildlife Diseases. 45(4):1174-1177. Interpretive Summary: Brucellosis is a bacterial disease that causes cattle to abort. Recently, the disease has been eradicated, for the most part, from livestock in the United States. However, occasionally infected cattle are found. This same disease can be found in some of the elk and bison of the Greater Yellowstone Area. It is suspected that diseased elk and/or bison may be responsible for recent outbreaks of brucellosis in cattle from the Greater Yellowstone Area. In this paper, we use DNA fingerprinting to compare bacterial strains from bison, elk and cattle. With a computer analysis program to reconstruct the ancestry of the isolates, we found that the cattle infections most likely originated from diseased elk. These data tell us that diseased elk are a greater problem for ranchers than bison and that prevention of the disease in cattle should focus on keeping cattle separated from diseased elk.
Technical Abstract: Brucellosis is a disease caused by bacteria of the genus Brucella. Brucella species infect a variety of livestock animals and humans world wide. In the United States, the disease with the greatest economic impact is caused by Brucella abortus in cattle. Although the disease has been mostly eradicated from American livestock, new infections are occasionally found. Since the disease is also found in elk and bison of the Greater Yellowstone Area, these reservoir hosts have been implicated as the source of recent outbreaks in cattle from this region. Until recently, there have been no methods available to prove the source of infection. A new method for generating DNA fingerprints of Brucella strains provides the opportunity for detailed genetic comparisons among strains. The DNA fingerprint markers have accelerated mutation rates, and therefore continuously change and evolve. As a result, by the time an outbreak is discovered, the fingerprint pattern of the outbreak strain may be somewhat different from the pattern of the source strain. In this paper, a computer algorithm is used to construct networks among the selected strain haplotypes. By analyzing the number of mutation steps between strains, genetic relationships are inferred. The data show that the strains from two recent outbreaks in cattle are genetically much closer to local elk strains than to bison strains of B. abortus.