Superspreaders are disproportionately responsible for the infections of other hosts. Perhaps the best-known human superspreader was Typhoid Mary, who caused 53 deaths due to Salmonella bacteria transmission. Although the frequency of "Typhoid Marys" is unclear, they are probably not rare. Superspreading is implicated in the rapid expansion of SARS (Sudden Acute Respiratory Syndrome) and HIV across the globe. For most infectious diseases, 20% of hosts cause 80% of infections. The goal of this research is to determine whether glucocorticoids, major vertebrate stress hormones that have been implicated in disease transmission, are involved in superspreading. Stress hormones could impact superspreading by affecting how parasites (or vectors, such as mosquitos and biting flies) choose hosts on which to feed, how hosts resist or tolerate parasites, or how hosts transmit parasites to other hosts or vectors. Surprisingly, there has never been a systematic study of the effects of stress hormones on all aspects of one complex host-vector-parasite system. This knowledge gap is significant and deserves attention because many anthropogenic and natural factors alter stress hormone regulation, and these factors are increasingly important in the context of global change. By knowing how and when stress hormones affect host-parasite interactions, we may become better able to predict and control zoonotic disease outbreaks.
Intellectual merit: To investigate the role of stress hormones in superspreading, interactions among zebra finches (ZEFI), Culex pipiens mosquitos, and West Nile virus (WNV) will be studied. WNV was chosen because it has decimated some songbird populations and is thought responsible for more than 33,000 human infections and 1150 deaths. ZEFI and Culex were chosen because their genomes have been sequenced, providing opportunities for strong experimental approaches. Stress hormones are predicted to impact i) ZEFI behavior to Culex exposure, ii) Culex blood-feeding preference on ZEFI, iii) ZEFI resistance to WNV infection, iv) ZEFI tolerance of WNV infection, and/or v) ZEFI competency to transmit WNV to Culex. Ultimately, data will be used to determine directly when stress hormones have the largest impacts, information valuable for human and wildlife populations.
Broader impacts: In animals, superspreading appears important for the transmission of several zoonotic diseases (infections that spill from animal into human populations) such as West Nile virus and some hantaviruses. In the context of global change, basic research on understanding superspreading has significant societal value because zoonotic diseases are predicted to become more prevalent. Collaboration with the Tampa Museum of Science and Industry, which attracts more than one million guests annually, will include the development of a Science Works Theater that helps the public understand disease ecology. Training workshops for Hillsborough County high school teachers will also be held, providing teachers tools to train incipient scientists in modern disease biology. For USF students, about 40% of whom come from under-represented backgrounds, robust learning experiences will be provided. Individuals on the project will learn animal husbandry, minor surgeries, how to work in a high-security infectious disease research facility, modern lab assays, data analysis, and scientific writing.
