Effects of human land-use and landscape change on tick-borne disease risk in the Midwestern United States.
Urban/Exurban Land-Use: Human land-use has enormous potential to impact wildlife communities in ways that alterhuman risk of exposure to tick-borne diseases. Since 2008, we have been conducting a large-scale investigation of the effects of human land-use in the St. Louis, Missouri region on the prevalence and risk of bacterial pathogens transmitted by the lone star tick (Amblyomma americanum). We have found that invasive bush honeysuckle (Lonicera maackii), an exotic plant that thrives in human-altered habitats, causes an increase in the abundance of lone star ticks, their vertebrate hosts, and tick infection rates with pathogens (Allan et al.2010 – PNAS). Further, we found that the removal of bush honeysuckle significantly reduces the disease risk posed by lone star ticks due to reduced habitat and forage for critical tick hosts (e.g., deer). These findings suggest that management of plant invasions can reduce human disease risk, a possible win-win scenario for conservation and human health.
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Fire Management: The Ozark Ecosystem of southern Missouri and northern Arkansas is often managed by prescribed burns on both state and federal forested lands. To determine the impacts of fire management on lone star ticks, I conducted a study in a heavily fire-managed region of the Ozarks, comparing tick and tick host abundance among sites that varied in recentness of application of fire management. I found that the abundance of lone star ticks increases substantially in the time periods immediately following a prescribed burn, and then drop to pre-burn levels in the later stages of recovery (Allan 2009 – JME). These changes in tick abundance appear to be driven by the positive response of white-tailed deer to fire management. Thus my results run contrary to the prevailing dogma among managers that prescribed burns are an effective means of tick population control.
The ecology of the West Nile virus outbreak in the United States.
We organized a large-scale study of the ecology of West Nile Virus (WNV) in the Saint Louis, Missouri region. Our goal was to elucidate the ecological factors that determine the prevalence of WNV along an urban-to-rural gradient in the St. Louis region. We also utilized several publicly available data sets concerning human incidence of WNV across the United States. Our results indicated that low bird diversity was an important predictor of high WNV incidence in vector mosquitoes locally and in humans nationally (Allan et al. 2009).
We explored the impacts of climate on the prevalence of West Nile Virus (WNV) infection in humans during the United States outbreak from 2001 to 2005. Using data on human prevalence of WNV and precipitation levels, we demonstrated that human cases of WNV were positively correlated with below average rainfall in the western United States, indicating that droughts are a strong predictor of WNV outbreaks in this region (Landesman et al. 2007).