Central Appalachian Regional Education and Resource Center (CARERC)

Current Projects

Avian-Livestock Links in the Demography of Zoonotic Bacteria and Their Implications for Farmworker Health

Zoonotic disease occurs when humans come into close contact with the normal reservoirs or vectors of disease-causing pathogens. Farms provide multiple opportunities for exposure of workers to pathogens carried by livestock, and possibly by wildlife associated with livestock. The demography of pathogens in livestock is likely influenced by interactions with wildlife, including birds, yet little is known about the factors affecting these interactions. This pilot study will explore the role of avian-livestock interactions in the demography of disease-causing bacteria in the agricultural landscape.

The research term will longitudinally sample house sparrows (Passer domesticus), livestock (goats, horses, and cows), and possible transmission areas (e.g., water or feed bins) for several types of disease-causing bacteria on UK’s North Farm. The results will provide initial findings on prevalence, spatial and temporal dynamics, and possible transmission mechanisms. These findings are expected to inform the development of more extensive studies of the factors leading to movement of bacteria among birds, livestock, and humans.

Specific Aims

  1. To document spatial and temporal patterns of disease-causing bacteria of potential risk to humans and the association between prevalence in free-living house sparrows and in three species of livestock (goats, horses, and cows).
  2. To test alternative hypotheses for possible transmission between birds and livestock: (a) transmission occurs, possibly symmetrically, through joint use of water or food dispensers; (b) transmission occurs asymmetrically, possibly through birds foraging in and around livestock feces, and livestock though contaminated feed or water.
  3. To assess bacterial demography in birds by surveying multiple age classes, sampling individuals repeatedly, and monitoring the movement of birds among locations.

The study will be conducted on the University’s Agricultural Research Station (North Farm) located on the north side of Lexington, Kentucky. Sampling will begin in April and continue through the summer of 2014. House sparrows at the farm have been studied by Dr. Westneat since 1992, and there is an established nest-box population across a large portion of the farm. Most of these birds are individually marked and their life history is known – a major advantage for understanding the particular mechanisms by which bacteria may be transmitted and for understanding the demography of these bacteria within birds. The marked sparrows are associated with spatially distinct livestock activities. Fourteen breeding pairs are in close proximity to cattle, and a different 14 pairs are closely associated with goats and horses. More than 100 additional pairs have variable overlap with horse operations at the farm.

The research team will obtain bacterial samples in several ways: Adults will have a cloacal swab (sample of cloacal bacteria) whenever caught (periodically done for other reasons). Nestlings at some focal nests will have a cloacal swab taken at 10 days of age, the time when UK research biologists handle them for banding. Some focal individuals at locations with strong associations to particular livestock will have fecal samples taken periodically by placing clean paper on the top of the nest box. The birds regularly perch there and defecate, allowing researchers to collect a fresh sample from a known individual at a specified date and time. Pathogens known to be potentially harmful to humans and thus of interest in this study include Salmonella spp., Escherichia coli, and Corynebacterium spp.

Livestock will be sampled by fecal grab (goats, cattle) or free catch (horses) by the personnel normally responsible for animal husbandry. The research team will take periodic samples from feed and water bins, and from fresh feces.

The study seeks to answer three questions:

  1. What potentially zoonotic bacteria are found in both livestock and sparrows at the same locations?
  2. Might these bacteria be transferred in both directions and what might be the mechanism?
  3. How might the spatial and temporal demography of zoonotic bacteria be affected by the demography of associated sparrows?

The researchers will use the answers to these questions to refine additional studies to learn about potential farm worker exposure and to generate a predictive model of risk.

For more information contact:
David F. Westneat, Ph.D.
Department of Biology
101 Morgan Building
University of Kentucky
Lexington, KY 40506-0225
Phone: 859-323-9499