Featured Research

from universities, journals, and other organizations

Geneticists Trace The Evolution Of St. Louis Encephalitis

Date:
May 18, 2008
Source:
American Museum of Natural History
Summary:
Researchers have sequenced the entire genetic code of 23 strains of Flavivirus, the virus that causes St. Louis encephalitis, to understand its evolutionary history. This study, published in Molecular Phylogenetics and Evolution, found that a single mutation made the virus pathogenic to humans and that the North and South American strains divided about 116 years ago.

Before West Nile virus arrived in this country, we had (and still have) a home-grown relative of this pathogen. An epidemic of unknown origin exploded around St. Louis, Missouri in the autumn of 1933, a disease that is now known to be transmitted by mosquitoes from birds to people. Now, a new analysis of the genome of St. Louis encephalitis completed at the Sackler Institute for Comparative Genomics at the American Museum of Natural History (AMNH) is shedding light on the evolution of this virus.

Under the direction of Susan Perkins, Assistant Curator of Microbial Genomics, postdoctoral fellows Gregory Baillie, Sergios-Orestis Kolokotronis, and Eric Waltari sequenced the entire genetic code of 23 strains of the virus that cause St. Louis encephalitis, all from the genus Flavivirus. Previous research had found that recombination (the cutting and pasting of strands of genetic material, in this case RNA) explained the evolution of this virus, but these studies sequenced just a single gene of the virus.

Because the whole-genome approach turned a microscope on the entire set of instructions for St. Louis encephalitis, the AMNH researchers were able to determine that a single mutation in the coding for an envelope protein rather than recombination most likely caused changes that made the virus pathogenic to humans. "Recombination is important for disease; it makes novel proteins or genes that the immune system has never seen before," explains Perkins. "But in this case, it was population dynamics combined with slight changes in the form of point mutations that have been important in the evolution of this virus."

Genetic analysis also allowed Perkins and colleagues to trace the evolutionary path of the Flavivirus virus. They determined that the older, less derived strains, or more ancestral strains, are from South America. The North American and Haitian strains were passed from common bird hosts such as finches, robins, blue jays, and doves into humans by the Culex mosquito after the virus exploded into a new continent. To time this event, researchers again turned to the genomic code: by determining the rate of mutation in the virus, Perkins found that the division between the South and North American strains happened about 116 years ago. "St. Louis encephalitis is a perfect storm between infected bird hosts coming into a new area and the mosquito vectors transferring the virus to humans," says Perkins. "It is the North American version of West Nile."

St. Louis encephalitis is currently found throughout the United States, and, according to the Centers for Disease Control, there were 4,651 cases between 1964 and 2005. Symptoms range from a mild headache to high fever and tremors. Mortality is between 5 and 30% and is higher among the elderly.

This research was published in the May issue of the journal Molecular Phylogenetics and Evolution. Additional coauthors are Joseph Maffei and Laura Kramer from Arbovirus Laboratories of the New York State Department of Health. The research was made possible by the U.S. Army Research Laboratory, the U.S. Army Research Office, the Wadsworth Center Media and Tissue Culture facility, and the World Reference Center for Emerging Viruses and Arboviruses through the University of Texas Medical Branch in Galveston, the Computational Biology Service Unit from Cornell University, and CamGrid at the University of Cambridge.


Story Source:

The above story is based on materials provided by American Museum of Natural History. Note: Materials may be edited for content and length.


Cite This Page:

American Museum of Natural History. "Geneticists Trace The Evolution Of St. Louis Encephalitis." ScienceDaily. ScienceDaily, 18 May 2008. <www.sciencedaily.com/releases/2008/05/080515113308.htm>.
American Museum of Natural History. (2008, May 18). Geneticists Trace The Evolution Of St. Louis Encephalitis. ScienceDaily. Retrieved April 20, 2014 from www.sciencedaily.com/releases/2008/05/080515113308.htm
American Museum of Natural History. "Geneticists Trace The Evolution Of St. Louis Encephalitis." ScienceDaily. www.sciencedaily.com/releases/2008/05/080515113308.htm (accessed April 20, 2014).

Share This



More Plants & Animals News

Sunday, April 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Mich. Boy Unearths 10,000-Year-Old Mastodon Tooth

Mich. Boy Unearths 10,000-Year-Old Mastodon Tooth

Newsy (Apr. 20, 2014) A 9-year-old Michigan boy was exploring a creek when he came across a 10,000-year-old tooth from a prehistoric mastodon. Video provided by Newsy
Powered by NewsLook.com
Vermont Goat Meat Gives Refugees Taste of Home

Vermont Goat Meat Gives Refugees Taste of Home

AP (Apr. 18, 2014) Dairy farmers and ethnic groups in Vermont are both benefiting from a unique collaborative effort that's feeding a growing need for fresh and affordable goat meat. (April 18) Video provided by AP
Powered by NewsLook.com
Man Claims He Found Loch Ness Monster With... Apple Maps?

Man Claims He Found Loch Ness Monster With... Apple Maps?

Newsy (Apr. 18, 2014) Andy Dixon showed the Daily Mail a screenshot of what he believes to be the mythical beast swimming just below the lake's surface. Video provided by Newsy
Powered by NewsLook.com
First Ever 'Female Penis' Discovered In Animal Kingdom

First Ever 'Female Penis' Discovered In Animal Kingdom

Newsy (Apr. 18, 2014) Not only are these newly discovered bugs' sex organs reversed, but they also mate for up to 70 hours. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins