The Role of Coprophagous Insects in the Epidemiology of Human Pathogens in Agricultural Systems

Cryptosporidium parvum and Giardia duodenalis are important zoonotic pathogens that are responsible for several human health concerns, ranging from massive outbreaks in general populations to high death rates in immunosuppressed patients. Most major outbreaks have been linked with runoff from agricultural lands, but most epidemiological details relevant to these settings are poorly understood. In 2004, we began to study the role of manure-feeding flies as mechanical vectors of these important human pathogens, based on a set of study sites in the southeastern United States. We found that three families of flies carry the pathogens within and between different areas, and deposit the viable infectious agents on surfaces where humans might become infected. During the summer of 2006, we will expand our study to examine the potential role of other insects, especially dung beetles, in moving the infectious cysts and oocysts of these pathogens within various agricultural and sylvatic settings. We are especially interested in how dung beetles might affect maintenance of pathogens in pasturelands as a result of their habit of burying contaminated fecal material. We will trap beetles from the Berry College dairy, beef, and equine facilities, as well as from pastures grazed heavily by wild deer. In collaboration with colleagues at the Johns Hopkins University School of Public Health, we will use modern techniques of immunofluorescent labeling of tissue extracts to determine whether pathogens are present, and in what relative amounts, on beetles and in vertical soil profiles where beetles bury fecal material from infected animals. We will use in situ DNA hybridization technology to determine viability of the pathogens. Based on the data we collect, we hope to provide a basis for a more comprehensive understanding of how these pathogens are maintained and ultimately transmitted in these complex ecosystems.