Epidemiology of vector-borne diseases
Vector-borne diseases present problems in epidemiology and ecology because systems are inherently multi-trophic, often modulated by community biodiversity, and typically dynamic and variable across space and time. We study vector-borne disease in people, domestic animals, and wildlife in order to provide tools for disease management, understand how biological diversity contributes to disease persistence, and use detailed natural history data to inform theoretical ecology of disease. We continue to study the ecology of granulocytic anaplasmosis, Lyme disease, leptospirosis, rickettsioses, plague, tularemia, and mange. Some target host species and ecosystems include all the diverse chipmunks in California, western gray squirrels, dusky-footed woodrats, coastal redwood ecosystems, the Mojave Desert, Panamanian forests, and disturbed and peri-urban ecosystems across California.
Evolution of antigens in Anaplasma phagocytophilum
As a tick-transmitted, obligate intra-cellular parasite, Anaplasma phagocytophilum experiences a set of evolutionary forces including drift particularly at the low population sizes that occur early after tick inoculation, high rates of mutation (recombination), and strong selection as the host develops immunity. We study the host community in nature and bacterial evolution in animal models, including wild rodent reservoir species, to understand how this pathogen emerged across the Holarctic, persists in diverse host communities, and utilizes a large array of functional pseudogenes to evade immunity.
Associates are engaged in simulation and analytical modeling of infectious disease persistence and emergence in nature. Examples include modeling persistent plague in a highly biodiverse small mammal and flea community, economic and SIRS-coupled modeling of tick-borne disease in high risk Humboldt County, and statistical modeling of nidicolous ticks and their contribution to the persistence of Anaplasma phagocytophilum.
Leptospirosis is a "forgotten" disease. Cases occur frequently in dogs, causing kidney and sometimes liver failure and death. Humans also experience leptospirosis often associated with water-oriented sporting events and exposure to domestic animals and wildlife, especially rats. Yet we don't understand most aspects of Leptospira ecology. Our research focuses on the epidemiology of leptospirosis in dogs, small mammals, and mesocarnivores in California.
Disease and forest change
Anthropogenic habitat change can alter the probability of disease emergence. In the literature, changes often are attributed to global warming but deforestation, reforestation, and fire also can catastrophically alter natural communities and change disease risk. Our work focuses on anthropogenic forest change and its impact on diseases transmitted by ticks including Ixodes ricinus group hard ticks such as Lyme disease and anaplasmosis. New work is underway to study effects of logging on ticks and to monitor re-establishment of a tick-borne disease cycle after a devastating wildfire.
Conservation ecology and disease
We are involved in a variety of projects aimed at discovering the risk infectious agents pose to vulnerable wildlife species and understanding how best to manage these species. These include a survey of infections in western pond turtles; assessment of disease risk due to climate change and overlap with sympatric small mammals in pikas; comprehensive study of natural history, extinction risk, and disease risk in Amargosa voles; studies of emergence of mange in bobcats, western gray squirrels, golden eagles, and San Joaquin kit foxes; and work to protect western burrowing owls near Davis.