Navigation Links
New strategy developed to combat West Nile Virus

The spread of West Nile Virus appears to be triggered by a complex interaction of mosquitoes, nesting birds and specific weather patterns, scientists say, which leads to "amplification" of the virus within mosquito populations.

Researchers from Oregon State University and the University of Florida have identified how those factors mesh to create heightened risk of the West Nile Virus in southern Florida, and they hope to expand their studies to the rest of the nation.

Results of the research have been published by the Centers for Disease Control.

Many early hydrologic models predicting the transmission of West Nile Virus and other mosquito-borne diseases may have been a bit too simplistic, relying on factors such as total rainfall to estimate disease risk, said Jeffrey Shaman, an assistant professor of atmospheric sciences at Oregon State University. The situation, he adds, is much more complex.

"In some cases, rain can actually help control mosquitoes by flushing away larval habitats," Shaman said. "And simply having more mosquitoes doesn't necessarily mean that we'll experience a greater incidence of West Nile Virus. The mosquitoes themselves must first be infected with the virus. Researchers call the process through which more mosquitoes become infected 'amplification,' and there are a number of factors that lead to that stage.

"By identifying these factors in the wild, it will enhance our ability to create control strategies."

In their studies, Shaman and colleague Jonathan F. Day from the University of Florida found that spring drought followed by continual summer rainfall is critical for the amplification and transmission of West Nile Virus and a similar disease, St. Louis Encephalitis Virus, in southern Florida. When drought occurs early in the year, the limited water resources confine mosquito populations to selected habitats ?specifically isolated, densely vegetated hammocks where conditions remain humid.

These moist hammocks also happen to be the spring nesting and roosting sites of many species of wild birds, which act as hosts and carriers for the diseases. While confined in the hammocks, the mosquitoes feed almost exclusively on the nesting birds and as a result, each bird is bitten by numerous mosquitoes. A single infected bird can thus infect many more mosquitoes than if conditions were wet and the mosquitoes were more broadly dispersed, Shaman said.

"This phenomenon, called 'drought-induced amplification,' is a key to transmission," he said.

When summer rainfall increases, surface humidity levels rise and the mosquitoes are able to disperse and initiate secondary transmission away from the original amplification sites, the researchers pointed out. With this dispersal, the mosquitoes are more likely to come into contact with humans ?elevating the risk of human incidence of the diseases.

"Drought-induced amplification may be somewhat unique to southern Florida, where drought tends to occur in the spring and coincides with the birds' nesting season," Shaman said. "The mosquito situation itself also is somewhat unusual. In most areas of the country, one species of mosquito infects the birds and another species then passes the disease along to humans.

"Florida has one species of mosquito that routinely bites both," he added.

Not all of the world's more than 3,600 species of mosquitoes transmit diseases to humans. The mosquito must be sufficiently competent to act as a carrier, thus some species can act as hosts for certain diseases, while others are more "refractive," ?not carrying enough of the disease to transmit it.

West Nile Virus transmission requires mosquito species that prefer feeding on birds, but like mosquitoes, not all birds are good carriers. Some are ineffective hosts, Shaman said, while others ?like crows ?are very susceptible and may die from the virus. Birds that are effective hosts may carry the v irus and infect biting mosquitoes for 4-5 days before recovering from the illness.

"It is this coming together of factors that leads to the spread of the disease," Shaman said. "But because the amplification is concentrated ?in time and space ?it does make it easier to devise control strategies. Chemical application is the most likely scenario, but because it could be applied in selected areas, it would be more cost-effective and potentially less environmentally threatening."

The spread of West Nile Virus through the U.S. has been sporadic, the researchers say, with hotspots arising one year in Colorado, and other regions during other years. The key to understanding the spread of the disease is to investigate the local conditions that may lead to amplification.

"It is a localized phenomenon," Shaman said. "We have to understand what goes on at the local level, at the appropriate scale, before we can reach the same conclusions that we found in southern Florida. But in almost all cases, the amplification of West Nile Virus will start with mosquitoes that carry the disease mingling with birds that are good carriers.

"How fast and far it spreads from there depends on weather, terrain, vegetation, humidity, the types of birds that live in the region and even the number of housing developments in a given area," he added. "These are the variables that need to be studied across the country."

Shaman and Day hope to expand their studies to analyze different regions of the country and create models similar to that of southern Florida, where certain weather patterns set off the chain of events that leads to amplification.


'"/>

Source:Oregon State University


Related biology news :

1. Gene silencing technique offers new strategy for treating, curing disease
2. AIDS expert says global strategy needed to combat feminization of HIV/AIDS
3. Asleep in the deep: Model helps assess ocean-injection strategy for combating greenhouse effect
4. Melanoma vaccine strategy shows promise in laboratory experiments
5. Study by Einstein researchers could lead to a novel strategy for treating obesity
6. Team discovers possible universal strategy to combat addiction
7. Researchers discover way to transport environmental arsenic to plant leaves in new clean-up strategy
8. Attacking cancers sweet tooth is effective strategy against tumors
9. New strategy rapidly identifies cancer targets
10. Researchers unveil strategy for creating actively-programmed anti-cancer molecules
11. Circumcision: A proven strategy to prevent HIV
Post Your Comments:
*Name:
*Comment:
*Email:


(Date:6/1/2016)... NEW YORK , June 1, 2016 ... Biometric Technology in Election Administration and Criminal Identification to ... According to a recently released TechSci Research report, " ... Sector, By Region, Competition Forecast and Opportunities, 2011 - ... $ 24.8 billion by 2021, on account of growing ...
(Date:5/16/2016)... , May 16, 2016   EyeLock LLC , ... announced the opening of an IoT Center of Excellence ... and expand the development of embedded iris biometric applications. ... level of convenience and security with unmatched biometric accuracy, ... identity aside from DNA. EyeLock,s platform uses video technology ...
(Date:5/3/2016)... , May 3, 2016  Neurotechnology, a ... the MegaMatcher Automated Biometric Identification System (ABIS) ... large-scale multi-biometric projects. MegaMatcher ABIS can process multiple ... using any combination of fingerprint, face or iris ... MegaMatcher SDK and MegaMatcher Accelerator , ...
Breaking Biology News(10 mins):
(Date:6/27/2016)... ... June 27, 2016 , ... Rolf K. Hoffmann, ... faculty of the University of North Carolina Kenan-Flagler Business School effective ... at UNC Kenan-Flagler, with a focus on the school’s international efforts, leading classes ...
(Date:6/24/2016)... 2016 Epic Sciences unveiled a liquid ... to PARP inhibitors by targeting homologous recombination deficiency ... new test has already been incorporated into numerous ... types. Over 230 clinical trials are ... including PARP, ATM, ATR, DNA-PK and WEE-1. Drugs ...
(Date:6/23/2016)... ... June 23, 2016 , ... UAS ... the launch of their brand, UP4™ Probiotics, into Target stores nationwide. The company, ... proud to add Target to its list of well-respected retailers. This list includes ...
(Date:6/23/2016)... , June 23, 2016 Houston ... with the Cy-Fair Sports Association to serve as ... the agreement, Houston Methodist Willowbrook will provide sponsorship ... and connectivity with association coaches, volunteers, athletes and ... with the Cy-Fair Sports Association and to bring ...
Breaking Biology Technology: