Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Global economic pressures trickle down to local landscape change, altering disease risk

21.09.2012
The pressures of global trade may heighten disease incidence by dictating changes in land use. A boom in disease-carrying ticks and chiggers has followed the abandonment of rice cultivation in Taiwanese paddies, say ecologist Chi-Chien Kuo and colleagues, demonstrating the potential for global commodities pricing to drive the spread of infections. Their work appears in the September issue of ESA's journal Ecological Applications.

After Taiwan joined the World Trade Organization in 2001, active cultivation of rice paddies fell from 80 percent to 55 percent in just three years. The government of Taiwan subsidized twice-yearly plowing of abandoned fields to reduce the spread of agricultural pests into adjacent fields still in cultivation. Compliance has been spotty. Kuo found that, while plowing did not suppress rodent populations, it did inadvertently reduce the presence of the ticks and chiggers that use rodents as their primary hosts.

"The government considers only agricultural pests such as insects and rodents. They don't think about the disease factors," said Kuo. But land use policy can have complex and unexpected reverberations in the ecology of the landscape.

Chiggers, the larval stage of trombiculid mites, spread scrub typhus (Orientia tsutsugamushi), a bacterium that gets its name from the scrubby, dense vegetation that often harbors its flesh-loving host. Scrub typhus is a common culprit underlying visits to Southeast Asian hospitals for flu-like symptoms. Without antibiotics, the infection is often fatal. Ticks (Ixodidae) transmit bacteria spotted fever group rickettsiae, causing fever, aches and rash similar to Rocky Mountain spotted fever. Neither pest prefers to live underwater.

Hualien, Kuo's study area, is one of the least populous of Taiwan's counties, yet had nearly the highest incidence of scrub typhus from 1998-2007. The county is a smattering of small villages surrounded by a patchwork of flooded, plowed, and abandoned rice paddies. Flooded paddies are poor habitat for ticks and chiggers, and so cultivation of rice, which locally means carefully managed flooding of fields to drown agricultural pests, likely suppresses ticks and chiggers as well. Even the seemingly unkillable ticks die after a few weeks of submersion, and chiggers are similarly terrestrial. Though studies are few, limited data indicate that most chiggers die after a month under water.

This study did not assess flooded paddies due to the difficulty of finding and collecting rodents, ticks, and chiggers underwater. Instead, Kuo trapped rodents in fallow and plowed fields and examined their tick and chigger passengers, testing the arachnids for presence of disease-causing rickettsial bacteria. He found 6 times as many ticks on the rodents living in fallow fields – and the proportion of infectious ticks in fallow fields was three times higher, compounding the risk. Chiggers rode rodents at a rate 3 times higher in fallow fields than plowed fields.

"This study is a great example of the kinds of indirect effects that trickle down from human policies," said Bob Parmenter, an ecologist unaffiliated with the study. "It tells a nice story about how changes in international trade barriers can have unforeseen consequences." Parmenter is director of the USDA's Scientific Services Division at Valles Caldera National Preserve near Los Alamos, New Mexico, and an expert on the influence of ecology on deadly Hantavirus outbreaks, like the current episode in Yosemite National Park (California, USA) that has infected nine visitors and killed three.

The consequences of economic pressures on land use are also present in the eastern United States, where the small farms of the eighteen and nineteenth centuries have reverted, to a large degree, to forest. With the return of deer and wildlands has come a rise in ticks, and concurrent rise in Lyme disease. Conversely, opening new land to farming or housing can bring its own disease risks.

Many studies have investigated influence of global forces on disease, said Kuo. "Most are focused on how climate change, global travel, or habitat destruction will affect the emergence of vector-borne and zoonotic disease. We show that economic organizations can actually affect human health, by influencing the landscape."

Title:
Cascading effect of economic globalization on human risks to scrub typhus and tick-borne rickettsial diseases. Ecological Applications volume 22 issue 6
Authors:
Chi-Chien Kuo, Geography and Environment, University of Southampton, Southampton, UK
Douglass A Kelt, Department of Wildlife, Fish, & Conservation Biology, University of California, Davis, CA, USA

Jing-Lun Huang, Pei-Yun Shu, Pei-Lung Lee, and His-Chieh Wang, Research and Diagnostic Center, Centers for Disease Control, Department of Health, Taipei, Taiwan, ROC

Contacts:
Chi-Chien Kuo: +44 (0)2380584319, ccckuo@ucdavis.edu
Douglass Kelt: 530-754-9481, dakelt@ucdavis.edu
His-Chieh Wang: +886-2-3393-5054, sjwang@cdc.gov.tw
Robert Parmenter: 505-428-7727, bparmenter@vallescaldera.gov
The Ecological Society of America is the world's largest community of professional ecologists and the trusted source of ecological knowledge. ESA is committed to advancing the understanding of life on Earth. The 10,000 member Society publishes five journals, convenes an annual scientific conference, and broadly shares ecological information through policy and media outreach and education initiatives. Visit the ESA website at http://www.esa.org or find experts in ecological science at http://www.esa.org/pao/rrt/.

Liza Lester | EurekAlert!
Further information:
http://www.esa.org

More articles from Studies and Analyses:

nachricht Drone vs. truck deliveries: Which create less carbon pollution?
31.05.2017 | University of Washington

nachricht New study: How does Europe become a leading player for software and IT services?
03.04.2017 | Fraunhofer-Institut für System- und Innovationsforschung (ISI)

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Touch Displays WAY-AX and WAY-DX by WayCon

27.06.2017 | Power and Electrical Engineering

Drones that drive

27.06.2017 | Information Technology

Ultra-compact phase modulators based on graphene plasmons

27.06.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>