THE ROLE OF MUSCID FLIES IN BOVINE PATHOGEN DISSEMINATION

Mastitis and enteritis are two of the most common diseases affecting dairy cows in the United States and worldwide. They are also some of the most costly diseases to the dairy industry. Diverse bacteria can cause mastitis and include contagious pathogens like Staphylococcus aureus and Streptococcus agalactiae that are spread from cow to cow during milking, as well as environmental organisms like Escherichia coli, Streptococcus spp., and Klebsiella spp., among others, which are found throughout the habitat of dairy cows and can establish opportunistic infections. Similarly, the bacterial organisms implicated in enteritis, E. coli and Salmonella spp., are spread from direct contact or from environmental reservoirs. While much attention has been focused on developing novel intervention and treatment strategies to manage the impact of these pathogens on cow health and production, relatively little is known about their epidemiology. Understanding how these pathogens persist in the environment and are transmitted to susceptible cows is therefore an area of high research priority.The long-term goal of this research is to determine the capacity of flies (Diptera: Muscidae) to transmit disease-causing bacteria to dairy cows. Dairy farms are popular breeding grounds for a number of biting and non-biting fly species that have recurring opportunities to acquire and transmit environmental pathogens throughout their life cycle. As larvae, flies require a microbe-rich substrate such as cow manure to complete development. In a typical commercial dairy barn setting, adult female flies deposit their eggs on both managed manure piles and fresh pats or slurries of manure. Cow manure is rich in undigested carbohydrates, proteins, and other nutrients, and both adult male and female flies opportunistically ingest nutrient-rich manure. Female flies are also anautogenous and can use manure, animal secretions, and other bodily fluids (e.g., blood) to provide the necessary proteins for egg development.Due to their life-long association with substrates rich with microbes, high mobility, and gregariousness, flies have been implicated as potential vectors for various pathogens in humans and other animals. Ingestion by flies could enhance pathogen survival and dissemination by providing a protected niche for pathogen proliferation and facilitating pathogen persistence in the environment via continuous shedding in fly feces. Flies could also disseminate bacteria present on the external surfaces of their bodies. However, few studies have examined the capacity of flies to transmit disease-causing bacteria to dairy cows. I propose to address this knowledge gap through two supporting objectives:(Obj. 1) Characterize the prevalence of clinically relevant bacterial taxa in flies and their breeding environments; and(Obj. 2) Experimentally assess the ability of dairy cow pathogens to be disseminated by fly hosts.