SREL Reprint #3658

Spatial variation in direct and indirect contact rates at the wildlife-livestock interface for informing disease management

Anni Yang1,2, Raoul K. Boughton3, Ryan S. Miller4, Bethany Wight3, Wesley M. Anderson3,
James C. Beasley5, Kurt C. VerCauteren2, Kim M. Pepin2, and George Wittemyer1

1Department of Fish, Wildlife, and Conservation Biology, Colorado State University,
Fort Collins, CO, 80523, USA
2National Wildlife Research Center, United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services, 4101 Laporte Avenue, Fort Collins, CO, 80521, USA
3Wildlife Ecology and Conservation, Range Cattle Research and Education Center, University of Florida,
3401 Experiment Station, Ona, FL, 33865, USA
4Center for Epidemiology and Animal Health, United States Department of Agriculture, Animal and Plant Health Inspection Service, Veterinary Service, 2150 Centre Avenue, Fort Collins, CO, 80526, USA
5Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA, USA 6Savannah River Ecology Laboratory, Warnell School of Forestry and Natural Resources,
University of Georgia, PO Drawer E, Aiken, SC, 29802, USA

Abstract: Little is known about disease transmission relevant contact rates at the wildlife-livestock interface and the factors shaping them. Indirect contact via shared resources is thought to be important but remains unquantified in most systems, making it challenging to evaluate the impact of livestock management practices on contact networks. Free-ranging wild pigs (Sus scrofa) in North America are an invasive, socially-structured species with an expanding distribution that pose a threat to livestock health given their potential to transmit numerous livestock diseases, such as pseudorabies, brucellosis, trichinellosis, and echinococcosis, among many others. Our objective in this study was to quantify the spatial variations in direct and indirect contact rates among wild pigs and cattle on a commercial cow-calf operation in Florida, USA. Using GPS data from 20 wild pigs and 11 cattle and a continuous-time movement model, we extracted three types of spatial contacts between wild pigs and cattle, including direct contact, indirect contact in the pastoral environment (unknown naturally occurring resources), and indirect contact via anthropogenic cattle resources (feed supplements and water supply troughs). We examined the effects of sex, spatial proximity, and cattle supplement availability on contact rates at the species level and characterized wild pig usage of cattle supplements. Our results suggested daily pig-cattle direct contacts occurred only occasionally, while a significant number of pig-cattle indirect contacts occurred via natural resources distributed heterogeneously across the landscape. At cattle supplements, more indirect contacts occurred at liquid molasses than water troughs or molasses-mineral block tubs due to higher visitation rates by wild pigs. Our results can be directly used for parameterizing epidemiological models to inform risk assessment and optimal control strategies for controlling transmission of shared diseases.

Keywords: Contact rates, Indirect contact, Cattle supplement, Wildlife-livestock interface, Wild pigs

SREL Reprint #3658

Yang, A., R. K. Boughton, R. S. Miller, B. Wight, W. M. Anderson, J. C. Beasley, K. C. VerCauteren, K. M. Pepin, and G. Wittemyer. 2021. Spatial variation in direct and indirect contact rates at the wildlife-livestock interface for informing disease management. Preventive Veterinary Medicine 194: 105423.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).