West Nile Virus Threat Reduced By Diversity Among Bird Populations In Surrounding Area

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Main Category: Bird Flu / Avian Flu
Also Included In: Infectious Diseases / Bacteria / Viruses
Article Date: 26 Jun 2008 - 0:00 PDT

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A more diverse bird population can help lower the incidence of West Nile virus in the surrounding human population, in a process called the "dilution effect," according to an article released in the open access journal PLoS ONE on June 25, 2008.

West Nile Virus, usually infecting birds but also affecting humans, is often passed through mosquitoes. Part of the Japanese encephalitis family of viruses, it's symptoms have three phases, but include fever, chills, and diaphoresis.

In the dilution effect, an increased level of biodiversity in wildlife results in a lower risk for humans to be infected by animal diseases. This was first reported in Lyme disease, but this new study, it has been demonstrated in a vector with an avian host. This effect, relating biodiversity of birds to West Nile Virus, is the largest application thusfar of the dilution effect, and may also apply to other infectious diseases such as avian flu or bubonic plague, according to the authors.

John P. Swaddle and Stavros E. Calos worked with the National Center for Ecological Analysis and Synthesis (NCEAS) at the Univeristy of California, Santa Barbara, synthesizing existing data to make inferences for management and policy applications. "We don't yet know the precise mechanism that drives this pattern, but it's likely to be due to diverse areas having relatively few of the bird species that are particularly competent hosts and reservoirs for the virus," Swaddle said.A set of qualities that makes a species best able to contract a particular disease is known as host competence. The highest levels of host competence for West Nile Virus are found in rows, jays, thrushes and sparrows, which also happen to thrive when avian biodiversity is lowest.

This research has many implications, according to Swaddlepoints: by attracting more land species, land management policies could increase biodiversity and thus decrease the number of human infection rates in an outbreak of West Nile Virus. "Biodiversity is giving us a public health service that people have rarely considered and the value of this service should be considered when developing land and managing bird populations in the future," Swaddle said.

About the National Center for Ecological Analysis and Synthesis:

The National Center for Ecological Analysis and Synthesis (NCEAS) was established in 1995. The organization has hosted more than 3,500 scientists from
over 50 countries, and supported more than 430 collaborative projects in ecology and related fields. NCEAS scientists develop new techniques in
informatics, and apply general knowledge of ecological systems to specific issues such as the loss of biotic diversity, global change, and
sustainability of marine ecosystems. NCEAS is among the top 1 % of 38,000 institutions evaluated for scientific impact in environmental research.
NCEAS is funded by the National Science Foundation, the State of California, the University of California, and numerous other donors.

About PLoS ONE

All works published in PLoS ONE are open-access. Everything is immediately available - to read, download, redistribute, include in databases and otherwise use - without cost to anyone, anywhere, subject only to the condition that the original authorship and source are properly attributed. Copyright is retained by the authors. The Public Library of Science uses the Creative Commons Attribution License.

PLoS ONE is the first journal of primary research from all areas of science to employ both pre- and post-publication peer review to maximize the impact of every report it publishes. PLoS ONE is published by the Public Library of Science (PLoS), the Open-access publisher whose goal is to make the world's scientific and medical literature a public resource.

Increased Avian Diversity Is Associated with Lower Incidence of Human West Nile Infection: Observation of the Dilution Effect.
Swaddle JP, Calos SE
PLoS ONE 3(6): e2488.
doi:10.1371/journal.pone.0002488
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Written by Anna Sophia McKenney
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