Across the countryside: How ecology predicts the movement of parasites and disease
You turn on your local news or open up your local paper looking for the forecast - not for the day's weather, but for an "infection" report. Sometime in the future, finding out about an encroaching illness may be this simple. From measles to rabies to deadly fungus on corals, scientists are conducting research investigating the movement of diseases. Knowing where, how, and how quickly diseases spread, whether transmitted through parasites or from animal to animal, could help society manage these diseases in both humans and ecosystems. On Tuesday, August 7, 2001, some researchers of the Ecological Society of America will examine how diseases and parasites spread in a symposium entitled The Role of Parasites and Infectious Diseases in Ecology. The session, which will be held during the Society's Annual Meeting in Madison, Wisconsin, will examine specific ways of tracking the spread of disease and parasites within an ecosystem, and how this knowledge may be used in the future.
Richard Ostfeld of the Institute for Ecosystem Studies (IES) along with fellow IES colleagues Felicia Keesing, Kathleen LoGiudice, and Kenneth Smith will open the session with a presentation entitled, The dilution effect in disease ecology: the search for host X. Examining rodent hosts such as eastern chipmunks and the white-footed mouse, the researchers will describe how the spread of ailments such as Lyme disease are influenced by the diversity of species in an area, a concept known as "The Dilution Effect." They will report their findings on the importance of animal diversity in regards to the spread, not only of the tick population, but also the chances of the transmission of Lyme disease. While researchers do not know exactly which animals the ticks favor, they will discuss possible alternative hosts such as opossums and certain shrews. The team will focus on the impact of community diversity on the transmission of infectious disease.
The second speakers for the session, Kiho Kim of American University and Drew Harvell from Cornell University, will focus on how diseases affect ocean ecosystems in their presentation Escalating impacts of marine epizootics and the role of a changing environment: insights from a coral fungus pathosystem. Coral reefs have been dying-out rapidly over the past decade, with the exact culprits behind this epidemic unknown. Some of the known suspects are fungi, which infect and kill coral. Kiho and Harvell will explore the manners and rates of transmission of fungal disease (Aspergillus sydowii) on sea fan corals (Gorgonia ventalina) in the Florida Keys. They will discuss the effects of temperature on both the fungus and the coral, and the implications of these findings on the entire Caribbean reef system.
Some types of bacteria also maintain the ability to travel and spread through water. Cholera, for example, frequently inhabits water. The bacteria is known to cause diarrhea, vomiting, leg cramps, and even death in people if left untreated. The topic of the third presentation, Synchronicity, temporal scales, and the role of an environmental reservoir in cholera dynamics, will examine past outbreaks of cholera in an attempt to predict its spread through the waterways. Presenting the paper will be Mercedes Pascual and Manojit Roy, both from the University of Michigan, Andrew Dobson (Princeton University), Xavier Rodo (University of Barcelona) and Menno Bouma (London School of Hygiene and Tropical Medicine). Seasonal and yearly cycles are known to affect the presence of cholera. The team suspects the temperature of the surface of the sea may drive the presence of this type of bacteria in water. The hope is to use this information to predict the spread of cholera along coastlines and other bodies of water. Investigating the coastal environment as well as the climate, the study examines historical records of the disease's birthplace, the Indian sub-continent, in an attempt to discover how seasons and time affect the outbreak of the bacteria. These findings will be discussed in relation to geography and the aquatic environment where cholera lives.
Kevin Lafferty of the University of California Santa Barbara and Leah Gerber of the National Center for Ecological Analysis and Synthesis study the role of infectious diseases on Southern sea otters (Enhydra lutris nereis). In their presentation, Good medicine for conservation biology: the intersection of epidemiology and conservation theory, Lafferty and Gerber will discuss the role disease plays in the health and size of the otters' overall population. Their study will propose that contaminants in the sea may have led to the suppression of the otters' immune systems, affecting the animals' overall ability to survive. They will also discuss how an increased knowledge of infectious diseases may influence how scientists determine when species are in trouble - knowledge that could ultimately lead to methods to protect them.
The fifth presentation examines a prominent new disease affecting house finches which has led to a 60% decline in their abundance in the eastern US. Entitled Spatial and temporal dynamics of an emerging pathogen in an introduced host: mycoplasmal conjunctivitis in house finches, the presenters include Sonia Altizer of Cornell University and her colleagues Barry Hartup (University of Wisconsin-Madison), Wesley Hochachka (Cornell University), Andy Dobson (Princeton University), and Andre Dohndt (Cornell University). By focusing on climate, migratory and social behavior, and the abundance of the finches, the researchers will discuss a model they created to explain the most important factors in the spread of this disease.
Predicting the spatial dynamics of infectious diseases: raccoon rabies as a model system will be the sixth presentation in this session. Since the mid-1970's rabies has been spreading across the eastern US, and cases of the disease have been reported throughout the country. Using information on rabies cases compiled by the state of Connecticut, Leslie Real of Emory University, and her associates David Smith (University of Maryland), Brendan Lucy (Emory University), Lance Waller (Emory University), and James Childs (The Centers for Disease Control and Prevention) will examine factors such as location and habitat in an effort to determine how the disease may spread across the state. By focusing on river barriers, human population areas, and distance the team created a model to simulate the spread of rabies which could be used to predict the future spread of the disease. They will describe the accuracy and implications of this model for present-day scenarios.
Returning to the spread of human disease within an ecosystem is the final presentation, Epidemic waves in the dynamics of measles: wavelets and spatial hierarchies. Bryan Grenfell from the University of Cambridge and Ottar Bjornstad of Penn State University-College Park, will discuss how distance and time affect the spread of measles in cities and villages in England and Wales. Both predator-prey and parasite-host interactions can be described as traveling in waves, through time or across the countryside. Grenfell and Bjornstad will discuss how they determined that waves of measles infection spread regionally from large cities to small towns at a speed of around five kilometers per week. Describing their findings using a "forest fire" analogy, they will explain how "infective sparks" randomly spread the disease from large population centers to smaller villages.
For more information about this session, and all ESA Annual Meeting activities, visit the ESA website: http://esa.sdsc.edu/madison. Held in scenic Madison, Wisconsin the theme of the meeting is "Keeping all the Parts." Over 3,000 scientists are expected to attend.
The Ecological Society of America (ESA) is a scientific, non-profit, 7,800-member organization founded in 1915. Through ESA reports, journals, membership research, and expert testimony to Congress, ESA seeks to promote the responsible application of ecological data and principles to the solution of environmental problems. ESA publishes three scientific, peer-reviewed journals: Ecology, Ecological Applications, and Ecological Monographs. Information about the Society and its activities is published in the Society's quarterly newsletter, ESA NewSource, and in the quarterly Bulletin. More information can be found on the ESA website: http://esa.sdsc.edu.
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