Research in our lab examines the ecology of infectious diseases in animal systems. Our work integrates field studies, manipulative experiments, comparative approaches and epidemiological modeling. Recent studies have examined how changes in host behavior and reproduction affect local and larger-scale patterns of disease. Other projects explore the ecological and genetic determinants of host immunity and processes that affect the evolution of parasite virulence. We utilize several biologically distinct host-pathogen systems including parasites affecting monarch butterflies, wild songbirds and global-scale comparisons of mammals. |
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Throughout their breeding range, monarch butterflies (Danaus plexippus) are infected with a protozoan parasite, Ophryocystis elektroscirrha. Monarchs are best known for a spectacular long-distance migration that they undertake yearly in both eastern and western North America. Non-migratory populations also occur in Florida, Hawaii, and other tropical locations. Parasite prevalence differs dramatically among populations, with fewer than 8% of monarchs infected in the eastern US, and over 80% infected in S. Florida. Through long-term studies of monarchs and their parasites, we are investigating the effects of parasitism on monarch fitness, the effect of monarch migration on the dynamics of this host-parasite interaction, the evolution of virulence of the parasite, and environmental and genetic determinants of host resistance. |
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We have examined geographic variation in phenotypic traits of monarch butterflies from different populations in North America and Hawaii. Monarch butterflies populate islands and continents worldwide, including North America, South and Central America, Caribbean and Pacific Islands, and Australia. Monarchs in these populations are exposed to different climates, host plant species, and natural enemies, and experience different levels of geographic isolation and migratory strategies. Divergent selective forces may have affected traits associated with monarch flight ability, including wing size and shape, and monarch responses to different host plant species and performance in different thermal regimes. |
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In collaboration with Charlie Nunn (Max Planck Institute for Evolutionary Anthropology), Vanessa Ezenwa, and researchers at 8 other institutions, we contructed large-scale databases of parasites reported from free-living primates, carnivores, and artiodactyls (hoofed mammals) to explore broad patterns of host-parasite ecology and evolution. Collectively, our databases include tens of thousands of lines of data, reflecting published reports of viruses, bacteria, fungi, protozoa, helminths and arthropods recorded in free-living mammal populations. We use these data to examine behavioral and ecological correlations of disease risk and parasite species richness, latitudinal gradients and in parasite biodiversity, and the role of parasites in mammalian extinction risk. |
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| Parasite dynamics in wild songbirds | |
| Doctoral student Catherine Bradley is monitoring several infectious diseases, including West Nile virus and malarial blood parasites, in cardinals and other songbirds along an urban-rural gradient in metro-Atlanta. The overarching goal of this research is to relate processes and patterns in urban landscapes to disease risk in wildlife hosts. With a large-scale field observation study, Cat is evaluating the condition of individual hosts at local sites along the urban gradient and examining hosts for evidence of exposure to infectious agents. |
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With collaborators at the Cornell Lab of Ornithology, we investigated factors associated with outbreaks of a recently emerged eye disease in wild House Finches around metro Atlanta. This disease is caused by the bacterium Mycoplasma gallisepticum (MG). House Finches infected with MG develop mild to severe clinical signs that include swelling, redness, and discharge of conjunctival tissue around their eyes. In extreme cases, the birds are blinded when their eyes swell shut, although birds in both captive and wild populations can recover from infections. Between 2001-05, members of our lab regularly monitored the prevalence and spread of this disease by systematically trapping House Finches each month around Atlanta, GA. We measured characteristics of infected and non-infected birds, including age, sex, body condition, and co-infection with other parasites. |
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Posters from other recent projects in the lab - click here |
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