MCA: Eavesdropping vectors and disease transmission in mixed-species assemblages

Gettysburg College, Gettysburg PA

Investigators

Abstract

Many infectious diseases are spread via intermediary organisms, or “vectors”, such as mosquitoes or bats. These vectors can be attracted to, and feed on, multiple host species, each differing in their susceptibility to infection and their ability to transmit pathogens to others. Often, these host species are found in mixed-species assemblages, such as the choruses of frogs, where multiple species congregate around the same ponds to find mates. Understanding how the behavior of disease vectors in mixed-species assemblages influences disease transmission is essential to assess evolutionary responses to disease, to guide conservation efforts, and to inform public health interventions. For example, vectors often use odor, visual, or sound cues to locate their hosts and can be more strongly attracted to an assemblage by the cues of some hosts or can show preferences for specific host species within an assemblage. Mathematical models predict that this sort of differential attraction strongly influences disease transmission dynamics and overall infection levels within a community. This study will integrate insights from sensory and disease ecology to determine how the cue-oriented foraging behavior of fly-vectors mediates the spread of trypanosome infections and disease transmission within a tropical frog community. The project will include binational research internships for undergraduate students, will produce undergraduate teaching modules on parasite diversity and the sensory ecology of disease vectors, and will result in a pictorial guide to frog-infecting parasites of central Panama, to facilitate future research on these poorly understood species. When signaling to attract mates, animals often form mixed-species assemblages. These attract disease vectors that exploit sexual signals to identify and locate hosts. How the behavior of these eavesdropping vectors shapes the dynamics of wildlife disease is, however, poorly understood. Previous work demonstrates that frog species can vary greatly in their attractiveness to eavesdropping frog-biting midges, and that calling in proximity to heterospecific signalers can increase or decrease the risks experienced by individual frogs. These frog-biting midges are thought to be the key vector in the transmission of trypanosomal infections, nearly ubiquitous to anurans worldwide. This study will investigate eavesdropping vector mediated transmission of trypanosome infection in mixed-species frog choruses. To accomplish this, researchers will examine disease transmission patterns by characterizing trypanosome diversity, prevalence, and host overlap in frog breeding aggregations, and by conducting transmission experiments to determine the major modes of infection. Then, they will investigate the importance of host species composition in shaping transmission dynamics by testing whether mixed-species frog choruses suffer differing rates of infection, and by characterizing how vector attraction at long and short distances is influenced by the species identity of hosts. Finally, field-measured parameters will be used to construct a model of eavesdropping vector-mediated disease transmission in mixed-species assemblages. This research will provide a framework for understanding the importance of vector behavior in disease transmission within mixed-species assemblages and wild communities. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.