West Nile Virus is Back — Deal With It

=====================================
Penn State Ag Sciences News 6.21.2007
=====================================

(EDITORS: A printable info graphic to illustrate this story is available
for downloading at http://aginfo.psu.edu/news/may03/mosquito.pdf.)

WEST NILE VIRUS IS BACK; ALTHOUGH IT HASN’T
BEEN SO BAD, MOSQUITO CONTROL STILL NEEDED

UNIVERSITY PARK, Pa. — Although West Nile virus made headlines in
mid-June by showing up in mosquito samples taken in Blair County — the
earliest it has shown up Pennsylvania in any of the last five summers –
the disease has not been nearly as bad here as health officials feared,
according to an entomologist in Penn State’s College of Agricultural
Sciences.

West Nile virus, which can cause a potentially fatal form of
encephalitis — is an invasive species that found its way to North
America from Africa. The disease, which first showed up in the United
States in 1999 in New York, is carried by birds and spread by
mosquitoes. It now has been found in nearly every county in
Pennsylvania.

The 2002 West Nile virus outbreak in North America was the largest
encephalitic disease epidemic ever documented in the Western Hemisphere,
and it was the largest West Nile virus outbreak ever documented,
according to the U.S. Centers for Disease Control. But outbreaks since
have not been so severe.

“Although scientists have been surprised at how rapidly it has
disbursed here, the outbreaks have not been nearly as disastrous as some
predicted,” says extension entomologist Steve Jacobs. “In Pennsylvania,
the first cases of West Nile encephalitis were detected in 2001 (there
were three cases). In 2003 the number of new human cases had risen to
237, but by 2006 the numbers had dropped to just nine human cases.”

It’s a good thing that the disease has not been worse in the United
States because there isn’t much that can be done to isolate it, Jacobs
laments. “There is very little we can do to stop something like this,”
he says. “All we can do — once the virus is spread throughout the state
or the country — is to educate the public to wear insect repellents and
recognize the disease so they can seek treatment. But in terms of
general health risks to the public, West Nile is well down the list. I
think many people believe the risks of dying from West Nile are much
higher than they are.”

Ordinarily, mosquitoes are little more than a mild irritant, Jacobs
notes. But because they can transmit diseases to humans and pets — such
as West Nile encephalitis, eastern equine encephalitis and canine
heartworm — people should take steps to avoid being bitten and to
eliminate mosquito-breeding areas.

Mosquitoes breed in standing water. Only female mosquitoes bite,
according to Jacobs. “In most cases, the female must have a blood meal
before laying eggs,” he says. “The females’ persistent search for blood
brings them into houses and yards, where they may become annoying
pests.”

Many mosquito problems can be traced to containers of water around
the yard, such as children’s toys, pots and cans, tire swings, animal
tracks and clogged rain gutters. Neighborhood breeding areas can include
construction sites, trash dumps and cemetery urns or planters. Most
mosquitoes remain within a half-mile of where they hatch, but some can
fly miles.

During warm weather, mosquitoes can breed in any puddle that stands
for more than four days. “The most effective way to control mosquitoes
is to eliminate standing water,” says Jacobs. He advises homeowners to:

–Remove old tires, tin cans, buckets, glass jars, toys and other
water-catching objects.

–Tightly cover rain barrels to prevent egg-laying.

–Change water in bird baths by flushing with a hose at least once
a week.

–Fill tree holes with sand or cement or drill holes to allow
drainage.

–Keep rain gutters clean and free of obstructions.

–Drain excess water from flower pots.

–Keep swimming pools covered when not in use.

–Turn over wading pools and wheelbarrows when not in use.

–Empty accumulated water from boats and cargo trailers.

–Clear aquatic vegetation from around the edges of ponds to allow
fish to feed on mosquito larvae and pupae.

When going outdoors for an extended period of time, insect
repellents can provide protection from mosquito bites. “Repellents can
protect for up to five hours,” says Jacobs. “But because people vary in
their attractiveness to mosquitoes, the effectiveness of the repellent
may depend on the individual.”

Before using a repellent or insecticide, be sure you thoroughly
read and understand all directions and cautions on the product label,
Jacobs warns.

For a free fact sheet on mosquitoes, contact the nearest county
office of Penn State Cooperative Extension, or visit the Web at
http://www.ento.psu.edu/extension/factsheets/mosquitoes.htm.

###

EDITORS: Contact Steve Jacobs at (814) 863-3963 or by e-mail at
sbj2@psu.edu.

Jeff Mulhollem
Writer/Editor
(814) 863-2719
jjm29@psu.edu