Our research group is primarily interested the evolutionary biology and ecology of hosts, vectors, and infectious pathogens. We strive to understand the proximate and ultimate drivers of infectious disease transmission across various ecological scales, from dynamics within host individuals, to those that manifest within and between ecological communities across heterogeneous landscapes. A central theme of our work is to combine field, laboratory, mathematical, and statistical techniques to answer questions on the complexity of infectious disease transmission that could not be achieved through one technique alone. By elucidating these mechanisms that modulate infectious disease dynamics, we aim to inform strategies that limit opportunities for infectious disease emergence and develop evidence-based approaches that mitigate transmission risks. The central foci of our program are detailed below.
Cosymbiosis, pathogen infection, and disease transmission
Pathogens often occur in a community of other symbionts within their host. Cosymbionts may interact antagonistically or synergistically through both direct and indirect mechanisms. For instance, coinfecting pathogens may compete over resources in the host, up-regulate the host immune system increasing resistance to other pathogens, or facilitate future infection through host immune suppression. This produces heterogeneity in host quality and variation in the course and outcome of infections. Importantly, these with-in host dynamics scale to influence pathogen transmission between hosts at the population, community, and ecosystem levels. Our work investigates the role of cosymbionts in modulating infectious disease transmission among wildlife and humans. We are looking at the role of cosymbiosis in modulating with-in host disease progression and between-host transmission dynamics across diverse systems. Current active projects include 1) the investigation of factors that structure the mosquito microbiome, 2) the development of paratransgenic platforms for Hawaiian Aedes and Culex mosquitoes, 3) cosymbiosis of pathogens in rats and rat-borne disease transmission, and 4) the avian microbiome and avian infectious disease.
Ecological and environmental determinants of pathogen transmission
Hawai‘i offers a superb system to study the ecological and environmental drivers of pathogen transmission. Hawai‘i has many simple pathogen transmission systems characterized by a low diversity of host, vector, and parasite species. These simple networks offer a greater potential to tease apart transmission dynamics from field-collected samples and facilitates comparisons between data generated in the lab with those generated in the field. Moreover, Hawai‘i supports large environmental gradients in precipitation and temperature over relatively short geographic distances, greatly facilitating natural experiments to understand pathogen transmission. Our lab uses a combination of carefully controlled experimentation and field sampling across natural gradients to investigate the transmission dynamics of 1) Leptospirosis (with Dr. Amber Wright), 2) rat lung worm (with Dr. Robert Cowie and Dr. Amber Wright), and 3) avian malaria and pox.
Heterogeneity in the vectorial capacity of wild mosquitoes
Numerous intrinsic and extrinsic factors modulate the capacity of mosquito populations to vector infectious pathogens between hosts. For instance, gradients in temperature, resource abundance, and competition during the mosquito larval stage have been demonstrated to influence vector competence and life-history traits of adults that affect vectorial capacity. To date, these studies have occurred mostly under controlled laboratory conditions and it remains unclear how natural gradients in temperature, resource abundance, and competition influence the vectorial capacity of wild mosquitoes. Our work investigates the role of environmental and biotic gradients in contributing to spatial heterogeneity in mosquito-borne disease transmission.