Wet Or Dry, Montana Still under Attack By West Nile Virus
Pastor Dale Morgan
Wet Or Dry, Montana Still under Attack By West Nile Virus*
by Evelyn Boswell
MSU News Service
Bozeman MT (SPX) Jun 13, 2008
West Nile virus is apparently here to stay despite Montana's cool, wet
spring, says Montana State University entomologist Greg Johnson.
Urging Montanans to protect themselves with repellents, Johnson said the
mosquitoes that carry the virus are sure to emerge when temperatures
reach the 70s and 80s. Infection rates and deaths may not always be as
high as they were in 2003 and 2007, but Montanans should be aware of the
threat.
"Regardless of whether it's a wet or dry year, we still need to think
about mosquitoes and West Nile virus," Johnson said.
Elton Mosher, disease surveillance specialist with the Montana
Department of Public Health, said West Nile virus infected 202 Montanans
last year and killed five people. They were from Cascade County,
Chouteau County, Dawson County, Sheridan County and Yellowstone County.
Last summer was Montana's second highest season on record for the number
of people affected by West Nile, Mosher said. First was 2003 when 226
Montanans were infected and four people died.
This summer could be another busy season if the rain continues and
temperatures rise as expected, Mosher said.
Johnson, now in his sixth summer of a statewide study of West Nile
virus, said the Culex tarsalis mosquito is the primary species that
transmits West Nile virus in Montana. The mosquito likes river
drainages, extensive wetlands and areas irrigated for agriculture.
Hot spots in the state are the Medicine Lake National Wildlife Refuge in
northeast Montana, the Yellowstone River and the Milk River. More
infected mosquitoes have been found in eastern Montana than western.
Johnson and his research teams have been studying West Nile virus since
it first appeared in Montana in 2003. This summer, they'll conduct
research in about 20 counties. They have already returned to Medicine
Lake to capture mosquitoes, trap stable flies and monitor pelicans. They
will also trap mosquitoes along the Yellowstone and Milk rivers,
locations in western Montana and in some state parks.
Mosquitoes play a major part in the transmission of West Nile virus, but
stable flies may play a role, too, Johnson said. He already believes
that birds and not mosquitoes are responsible for bringing West Nile
virus into the state. Those could be a variety of birds -- ranging from
sparrows and robins to shore birds -- coming from various locations.
It appears that West Nile virus is transmitted between birds as well as
between mosquitoes and other species, Johnson said. At Medicine Lake,
for example, pelicans shed West Nile through their mouths and feces.
Since the Medicine Lake pelicans live in colonies and nest on the
ground, they may pass the virus to each other.
Johnson suggested that Montanans protect themselves against West Nile by
using mosquito repellents. He recommended Picaradin (trade name: Cutters
Advanced) or repellents that list DEET as an active ingredient. Some
people prefer Picaradin, he said, because they like its scent more than
DEET's. It's also less oily than DEET and doesn't dissolve nylon
watchbands or clothes.
The Culex tarsalis mosquito is most active an hour before sunset to
midnight, Johnson said. It stops flying when temperatures fall below 50
degrees.