White-tailed deer at the top of a ridge. Photo credit: John J. Mosesso/NBII.Gov

Sampling locations for landscape genetics and spread of CWD project

Understanding the spread of chronic wasting disease (CWD) is necessary to predict the impact of disease on deer populations and to develop effective strategies for control. Our research goal is to use a landscape genetics approach to characterize the relationship between landscape feature, spatial population genetic structure, and the distribution and potential spread of CWD in white-tailed deer in southern Wisconsin. Our research objectives are three-fold. First, characterize deer spatial genetic structure by using molecular genetic markers to assess genetic diversity and variation on the landscape. From these data we will predict distance, direction, and rates of deer dispersal. Second, identify whether landscape characteristics which explain deer spatial genetic structure over and above geographic distance. We will identify landscape features such as rivers, highways, and habitat types that are associated with genetic connectivity or discontinuity across the study region. Third, we will combine deer spatial genetic structure and landscape characteristics to develop predictive models of CWD spread. Results of this study will be used to help understand the disease dynamics of CWD, the spatial spread of disease and its relationship to deer movement and landscape features, and assist management agencies in developing appropriate management and surveillance strategies for this disease.

Our initial results demonstrated that landscape genetics offers a promising approach for identifying relationships between landscape features and population genetic structure for investigating wildlife disease. Genetic differentiation was correlated with CWD prevalence. The Wisconsin River had a significant influence on gene flow between study area and core-area deer. However, US Highway 18/151, which is relatively recent, did not appear to limit gene flow. Differences in landscape features such as deer density, forest cover and land use can affect deer dispersal and influence the rate at which disease establishes and increases in prevalence locally.

For more information visit http://wildlife.wisc.edu/coop/CWD/CWD_Introduction.html and contact Michael D. Samuel, Wisconsin Cooperative Wildlife Research Unit.

Black-footed ferret. Photo credit: Paul Marinari

Black-tailed prairie dog. Photo credit: Lisa Zolly/NBII.Gov

Plague, caused by the bacterium Yersinia pestis, is a disease of wild rodents that can afflict humans and other mammals.  Prairie dogs in western U.S., are susceptible to plague, (> 90% mortality in afflicted colonies).   Prairie dogs play a critical role,  maintaining biodiversity and integrity of western grasslands stretching from southern Canada to northern Mexico.  The black-tailed prairie dog (once the most abundant mammal in North America) has declined to less than 2% of its former population and sylvatic plague is one of the most serious threats to its continued existence.  The endangered black-footed ferret (Mustela nigripes) depends on prairie dogs as both food sources and to provide habitat (prairie dog burrows).  A captive breeding and recovery program was established for ferrets in 1987 after disease outbreaks nearly eradicated the last known wild population.  Management and recovery of this species is tightly linked to prairie dog survival.  The black-footed ferret is also highly susceptible to plague and may suffer high mortality rates upon infection.  Limiting the incidence of plague infections in prairie dogs and other wild rodents would reduce the incidence and potential of zoonotic transmission of the disease and enhance recovery potential of the black-footed ferret.  One method for controlling disease in free-ranging wildlife is to prevent infection through a targeted oral immunization program.   Recombination techniques were used to insert the capsular antigen (F1) of Y. pestis into an attenuated form of raccoon pox virus.   This vaccine was voluntarily consumed by prairie dogs (Mencher et al., 2004).  Experimental exposure to 130,000 Y. pestis bacteria, a realistic dose in a plague outbreak, resulted in a 56% survival rate of vaccinated animals, while the majority of nonvaccinated controls did not survive.  Research efforts to improve the vaccine and develop a baiting system for mass immunization programs of prairie dogs are ongoing.

For more information view Protecting Black-Footed Ferrets and Prairie Dogs Against Sylvatic Plague (PDF, 699 KB) and contact Tonie E. Rocke, National Wildlife Health Center

Feeding time at an elk feedground in Wyoming - March 2008. Photo credit: Vicki Patrek, USGS

There is a growing need to understand connectivity and movement patterns among elk herds and their parasites across the Greater Yellowstone Ecosystem (GYE). We are developing microsatellite and mitochondrial (mt) deoxyribonucleic acid (DNA) makers to assess connectivity among elk from nine study areas. So far, we have sequenced 695 base pairs (bp) of mtDNA control region from 407 elk. Statistical analyses revealed moderately-high mtDNA differentiation, suggesting limited female-mediated gene flow among study areas. We also genotyped 11 nuclear DNA microsatellites from 80 elk on four study areas. Statistical analyses revealed relatively low genetic differentiation, suggesting moderately high gene flow. The nearly 10-fold higher mtDNA differentiation suggests relatively limited female-mediated gene flow, possibly due to female philopatry. One microsatellite locus in a disease-related gene (IFNG) had relatively high FST (FST = 0.07), suggesting a possible adaptive function of IFNG. Five additional microsatellites were optimized, including three loci in genes with disease-related functions. All 16 microsatellite, mtDNA, and base line data represent important tools for long term, noninvasive monitoring of elk population connectivity across the GYE. To study helminth parasites, we noninvasively sampled 554 fecal deposits during 2007 and 2008 from elk, bison, bighorn sheep, pronghorn, and cattle from across the GYE. We developed an internal transcribed spacer region 2 (ITS-2) nuclear gene sequencing assay for parasite species identification, and a cytochrome oxidase-1 (CO1) mitochondrial assay for assessing parasite gene flow. We produced ITS-2 polymerase chain reaction (PCR) products from 345 individual nematode parasites of ungulate hosts, and identified 223 (88%) to species. Dictyocaulus viviparous lungworms were at moderate prevalence (10-50%) in elk and bison. The most prevalent gastrointestinal (GI) parasite in elk was Spiculopteragia spp., with ~5-10% prevalence. Bison in the GYE appear to commonly be infected with both Cooperia oncophora and Ostertagia ostertagi. Bighorn sheep are commonly infected with Protostrongylus lungworms and Marshallagia GI worms, which were not shared with other wild ungulates in the GYE. These DNA markers and preliminary data provide valuable tools for noninvasive monitoring of parasite transmission across the GYE.

For more information view Viral Tracking of Wildlife Corridors across the Rocky Mountains (PDF, 374 KB) and contact Paul C. Cross at the Northern Rocky Mountain Research Center; Gordon Luikart, Marty Kardos, or Vanessa Ezenwa at the University of Montana, Missoula; or P.J. White at the National Park Service.