A few of our recent lab projects:
Characterizing the distribution and population genetics of the Lyme disease pathogen Borrelia burgdorferi and its reservoir hosts
Lyme disease is caused by the bacterium Borrelia burgdorferi, which is transmitted to people and other vertebrates by blacklegged ticks (Ixodes scapularis; also known as "deer ticks") in the northeastern and upper midwestern United States. It is the most common vector-transmitted infectious disease in the United States, likely infecting nearly half a million people every year. Ticks become infected by biting an infected "reservoir host", often a small mammal or bird; once infected, ticks can transmit the bacterium to humans.
We use molecular genetic approaches to identify B. burgdorferi infections and to sequence the genomes of B. burgdorferi, blacklegged ticks, and reservoir hosts in the wild. We are using these data to understand 1) how human Lyme disease risk varies over time and space, 2) how B. burgdorferi spreads, and 3) how the genetics of the bacterium, tick, and reservoir hosts interact to create the infection patterns we observe in nature.
Evaluating a rodent-targeted vaccine for Lyme disease
As part of the CDC-funded VectorED network we are evaluating the effectiveness of a Lyme vaccine for white-footed mice (Peromyscus leucopus). White-footed mice are common reservoir hosts of the Lyme disease pathogen B. burgdorferi. If white-footed mice are immune to infection, ticks would not become infected as frequently and, therefore, neither would humans. Lots of research has been done on developing a Lyme vaccine for white-footed mice, delivered orally via mouse food pellets. We are will determine the extent to which such a vaccine can lower the rate at which blacklegged ticks become infected in the wild. If shown to be effective, a rodent-targeted vaccine for Lyme disease could become an essential tool for Pest Management Professionals and state health agencies.
Borrelia burgdorferi and the host microbiome
The microbiome is the full diversity of bacteria and other microbes found in any place; many of these bacteria are not pathogenic. Gut microbiomes have been shown to be involved in infectious disease dynamics through the interactions of pathogens with non-pathogenic bacteria in the gut.
We are exploring whether bacteria in the gut microbiome of small mammals can interact with B. burgdorferi and influence infection outcomes. We collect fecal samples from small mammals in the field, extract DNA, and use a genetic sequencing to identify the bacteria present. We also investigate the microbiomes of ticks. We are using these data to identify bacteria that promote resistance to or tolerance of B. burgdorferi infection.
Delaware's mosquitoes
Over 50 species of mosquitoes have been identified in Delaware and a substantial number of them bite humans and may transmit viruses like West Nile Virus. We are conducting genetic sequencing of these mosquitoes to 1) identify novel viruses that they transmit, 2) develop new methods to differentiate among mosquito species that look very similar, 3) determine how they disperse across Delaware, 4) determine their host species feeding preferences, and 5) understand their evolution and how they may develop resistance to insecticides. We are also evaluating a novel West Nile Virus surveillance method.
This work is becoming more pressing as climate change allows mosquitoes to shift their geographic distributions. For example, the yellow fever mosquito (Aedes aegypti) has recently been found in Baltimore and may eventually reach Delaware.
Avian malaria
Malaria is often thought about as a disease of humans only. But in fact, it is a disease of wildlife and the parasites that causes malaria jumped to humans from other host species via mosquitos. Malaria parasites are most diverse in birds - there are around 10,000 species of birds in the world and perhaps as many avian malaria parasites. The avian malaria system provides incredible opportunities to observe and test hypotheses regarding the evolution and host-switching of pathogens and may provide general insights into pathogen evolution. We are working on genome sequencing of avian malaria parasites in birds across the world and documenting how they have coevolved with birds.
Evolution and ecology of host specificity
Host specificity refers to the diversity of host species a parasite infects. Parasites vary from generalists that infect many host species to specialists that infect one or a few closely related host species. Generalists are thought to more frequently disperse long distances and become emerging infectious diseases relative to specialists, which may have more difficulty adapting to new host species or populations.
While host specificity is a fundamental parasite trait, understanding its evolution and ecological consequences can be challenging and requires investigations of many related parasites that vary in host specificity. We investigate questions related to host specificity across all of the systems we study.
