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My research evaluates the health and disease ecology of the American Crow (Corvus brachyrhychos) in urban and agricultural settings. I assess environmental and genetic risk factors for disease, examine the fitness and population impacts of these diseases, and evaluate risks that they present to human health. This work will advance scientific knowledge by providing rare information of disease ecology in a free-living wildlife population. The information gathered will be of interest to scientists across a wide breadth of disciplines, including population ecologists interested in the factors driving population dynamics in human-commensal wildlife, evolutionary biologists interested in disease as a selection pressure, and conservation biologists interested in declining species within and on the edges of human-dominated landscapes. This work will advance public welfare by identifying environmental predictors of zoonotic wildlife diseases (e.g., West Nile virus) and by determining the role crows play in the movement of pathogens across human-dominated landscapes. <P>Objectives: 1. To understand the ecology, feeding, and movement patterns of crows in urban and agricultural environments. 2. To characterize infectious diseases and their environmental and genetic risk factors in crows in urban and agricultural environments. 3. To assess habitat-specific fitness and population impacts of crow disease. 4. To examine the movement of pathogens of human health concern (e.g., Campylobacter, E. coli 0157; antibiotic-resistant bacteria) across the urban and agricultural landscapes through crow feces 5. To identify management practices that promote individual health and population stability of urban and agricultural wildlife, as well as human health Duration and outputs: <P>The proposed work will require five years, including data collection and publication. Spring 2012: 100 crow nestlings marked and measured. Characterization of Campylobacter prevalence and pathogenicity underway. Campylobacter manuscript will be prepared and submitted for publication in winter 2012. 2013-2014: An additional 200 nestlings and 100 adults will be marked and measured and used to create a California crow health profile. Manuscripts reporting disease prevalence, disease risk factors, and the effects of urbanization and agricultural practices on crow health will be prepared and submitted for publication. 2015-2017: radio tags will be applied to marked birds to better assess their potential for moving pathogens across the landscape. Manuscript will be prepared and submitted for publication in winter 2017.
Non-Technical Summary:<br/>
Human-commensal American crows are often found in high densities in urban and agricultural landscapes throughout North America. These high densities, combined with the stress, pollution, and low-quality food often encountered by wildlife in human-dominated landscapes, could combine to elevate disease prevalence. Disease in crows could pose a threat to the health and populations of other species of wildlife, as well as to human health and to animals of economic importance. For example, previous studies have shown that West Nile virus (WNV), a zoonotic disease to which crows are particularly susceptible, has a particularly strong impact on crow populations in urban settings. Other studies have shown that feces under rook roosts in Western Europe harbor bacteria of human health concern, including antibiotic resistant E. coli and Salmonella, leading the authors to suggest that corvids could serve as reservoirs and transmitters of antibiotic resistant bacteria across the landscape. Here, we examine the ecology of disease among crows in urban and agricultural landscapes in Yolo County, California. Free-living crows in a focal site spanning the UC Davis campus and adjacent agricultural fields are caught, marked, and tested for disease presence (e.g., WNV, trichomonas, fecal parasites and bacteria, blood parasites, avian flu) and measured for overall condition. Survival and movement of these marked crows are monitored, and crows that die on the study site are submitted for diagnostics at the California Food Health and Safety Lab. Results of this work will advance public welfare, within and beyond California, by identifying environmental predictors of zoonotic wildlife diseases and by determining the role crows play in the movement of pathogens across human-dominated landscapes.
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Approach:<br/>
1. Crow ecology. To investigate the ecology of crows on an urban-agricultural gradient, I established a focal site spanning the UC Davis campus and the agricultural fields to the west of campus. Nestling crows from 40 nests have been marked and monitored for survival and dispersal patterns. I will begin catching, marking, and monitoring adult crows in our study site in the fall of 2012. This work will be repeated annually. In years four and five, I will put radio transmitters on the birds to better document movement patterns.
<br/>2. Infectious disease characterization. At the time of marking, crows are tested for disease presence (e.g., WNV, trichomonas, fecal parasites and bacteria, blood parasites, avian flu) and measured for overall condition (e.g., through blood chemistry, body condition, and hematology). Carcasses of crows that die on the study area are necropsied and tissues submitted for histopathology and diagnostics. Crows are genotyped at 10 microsatellite loci to determine molecularly-based inbreeding coefficients, which previous studies have shown to be predictors of disease mortality in crows (Townsend et al. 2009, Townsend et al. 2010).
<br/>3. Fitness impacts. Survival and disease outcomes will be modeled as a function of environmental and genetic characteristics to assess disease risk factors. Survival analyses are carried out in a mark-recapture modeling framework to account for imperfect detection probability.
<br/>4. Bacterial assays. Bacteria of human health concern (e.g., Campylobacter, E. coli 0157, Salmonella, antibiotic-resistant bacteria) have been cultured from crow feces. PCR-based techniques will be used to assess virulence and diversity of strains encountered. Feces will be collected from focal birds throughout the year to assess the potential for movement of these bacteria across the urban and agricultural landscape.
<br/>5. Management. Risk factors for wildlife and human disease and management strategies will be identified. This information will be disseminated on an international scale through publications in peer-reviewed journals. Information on appropriate management actions will also be disseminated to the agricultural and urban clientele though the Yolo County Cooperative Extension Advisors.