West Nile Virus More Prevalent in Orchards And Vineyards

West Nile virus is more prevalent among mosquitoes in orchards and vineyards from where it spreads to birds, horses and people, finds a research.

The finding, reported in the latest issue of the journal PLOS ONE, is the most finely scaled look at the interplay between land use and with the virus's activity in key hosts. By giving a more detailed description of how the disease moves across the landscape, it opens the door to management efforts that might bring the disease under control, says David Crowder, a WSU entomologist and the paper's lead author.

About Mosquito Diseases
Mosquito-borne diseases, like malaria, filaria, dengue, etc are common in places conducive of mosquito breeding. Swamps, ponds and stagnated drainage provide optimal breeding ground for mosquitoes.

Since it was first seen in New York in 1999, West Nile virus has reached across the country and shown few signs of abating. Last year, the Centers for Disease Control had the highest number of reported cases—5,387, including 243 deaths—since 2003.

Roughly one in five infected people experience a fever, headache, body aches and, in some cases, a skin rash and swollen lymph glands. One in 150 people can get a high fever, headache, neck stiffness, disorientation and neurological problems.

Most efforts to suss out the ecological workings of the virus have focused on reports of infected people, "a crude indicator at best," says Crowder. Almost all victims have no symptoms or are misdiagnosed, while others can be infected far from where they file a report, he says.

Rise in West Nile Virus Deaths
According to health authorities, the number of West Nile virus deaths and infections continued to rise in the United States last week, but at a slower pace.

Agricultural areas have also seen higher percentages of infected people, but that still does not get at the underlying mechanism. "Is that because there are more birds there?" says Crowder.

"Is that because there are more mosquitoes there? That hasn't really been linked together." Crowder, working with fellow entomologist Jeb Owen, other WSU colleagues and the state Department of Health, merged data from a variety of sources, including West Nile infections in humans, horses and birds, surveys of virus-bearing mosquitoes, breeding bird surveys, and detailed land use maps and climate data from around the Northwest.

Public Must Take Precautions Against West Nile Virus, Says Annals of Internal Medicine Commentary
Official data indicates that West Nile virus (WNV) has become endemic in North America, with cases in 2012 exceeding that of any other year.

The researchers found that habitats with high instances of the disease in horses and birds also have significantly more mosquitoes, as well as American robins and house sparrows, the two bird species implicated the most in the disease's transmission.

"These same habitats are also resulting in much higher rates of infection within mosquitoes themselves," said Crowder.

US Reports Largest West Nile Virus Outbreak Ever
The United States has seen at least 1,118 cases of West Nile virus this year, the most since the mosquito-borne disease was first detected in 1999, with 41 deaths, authorities said Wednesday.

"We find that all three of these things—abundances of house sparrows and American robins, abundance of mosquitoes, and the actual prevalence of West Nile in mosquitoes—are all increasing in landscapes with a higher proportion of land in orchard habitats." These habitats, says Crowder, include both orchards and vineyards.

It's still unclear why the habitats would create such a perfect storm for the virus. The researchers speculate that mosquitoes are drawn to orchards for plant nectar during flowering, while robins and house sparrows use them for nesting and feeding. Together, the insects and birds become focal points for the disease.

Source-Eurekalert