[Note: this posting comments on item [4] in the Aug 26 WNV Activity
Update]
A minor correction to article on Arizona as epicenter of WNV --
Minnesota is the land of 10,000 (actually closer to 15,000) lakes and
at least twice as many marshes and lowlands. Those low-lying wet areas
are filled with uncountable numbers of frogs, salamanders, and dragon
fly larvae that gobble mosquitos and their larva. I live on 20 acres
of wetland (outside the reach of the metro mosquito control district)
and have very few mosquitoes, which I believe is related to the frog
population. On a warm June night, you have to speak loudly outside to
another person to overcome the din from the mating frogs -- and that's
just the males.
Patrick T. Redig
University of Minnesota
At 01:20 PM 8/26/2004 -0400, you wrote:
> [1] United States: CDC MMWR: WNV Activity, Aug 18-24, 2004 +
> Cumulative
> [2] Canada: Health Canada Surveillance Data
> [3] Canada: Details from
> [4] Arizona, US Epicenter of 2004 WNV Outbreak -- Why?
>
> ...
> [4]
> ARIZONA: US EPICENTER of 2004 WNV OUTBREAK -- WHY?
>
> Excerpted from ProMED-Mail ID 20040820.2312, submitted by Dan Moynihan
> <moynihan@lpl.arizona.edu>
> Source: Tucson Citizen, AP report, Aug 17, 2004
> <http://www.tucsoncitizen.com/breaking/081704_westnile.html>
>
> With triple-digit heat and nearly nonexistent rainfall, Phoenix seems
> an unlikely spot for this year's WNV epicenter. Yet, federal
> health officials say Arizona is the only state where the mosquitoborne
> virus is an epidemic. "Minnesota may be the land of a thousand lakes,
> but we're the land of thousands of abandoned swimming pools," says
> Will Humble, head of disease control for the Arizona Department of
> Health Services. Those swimming pools, plus irrigation canals that
> slice through parts of the city, patio misters and lush lawns designed
> to
> remind transplants of gardens they left behind have inadvertently
> turned neighborhoods into oases for mosquitoes.
>
> This year, at least 290 of the nation's more than 500 West Nile cases
> and 3 of the 14 deaths have been in Arizona. Nearly all the cases have
> been in the state's most populous county, Maricopa, which includes the
> Phoenix metro area. State health officials estimate at least 30 000
> Arizonans may have the virus without knowing it. Some people never have
> symptoms at all. Only about 1 per cent of West Nile victims develop the
> potentially dangerous inflammation of the brain or spinal cord --
> meningitis or encephalitis.
>
> 2003 was the 1st year the virus appeared in areas west of the
> Continental Divide. It hit Colorado hard and drifted slowly into
> Arizona's northeastern tip, then down south. It's now spreading in
> California, where at least 116 cases have been reported and at least 5
> people have died. Several factors have contributed to Arizona's
> outbreak. "It's like the planets, everything has to align" for an
> outbreak to occur, said John Roehrig, chief of the Centers for Disease
> Control and Prevention's Arboviral Diseases Branch in Fort Collins,
> Colorado. While more humid climates have more mosquitoes and are also
> more prepared to deal with "nuisance mosquitoes," Arizona isn't. And
> while Arizona doesn't have a lot of mosquitoes because of long
> stretches of 100-plus degree days, one type of mosquito thrives here:
> _Culex tarsalis_. The species is one of the best carriers of West Nile
> virus.
>
> _Culex tarsalis_ does well in suburban settings and likes to feed on
> humans. The species can breed in small pools of standing water, such as
> in
> wheelbarrows, kiddie pools and plant saucers. Because the species is so
> dominant here, it doesn't have to compete with other types of
> mosquitoes for breeding spots. The water that people surround
> themselves with to combat the heat can be another major factor. From
> the air, pools form a checkerboard pattern across the desert landscape.
> Of the approximate 600,000 residential swimming pools in the state,
> state health officials estimate about 10 000 are capable of breeding
> mosquitoes. "What we've done is create miniature swamps in our back
> yard," said David Ludwig, who oversees Maricopa County health
> inspectors treating "green" pools with larvicides. Backyard pools are
> to Arizonans what ice scrapers are to Alaskans. Pools are everywhere
> and considered a necessity by some. But sometimes they are neglected --
> by cash-strapped owners who may have a broken pump or who have moved
> before the house has sold. The pools can turn to stagnant pond green in
> no time. Also, many of the city's older neighborhoods still use
> irrigation flooding for lawns, sometimes leaving standing water for
> days. They also have tall, mature trees. Besides mosquitoes, birds love
> these spots, and they can carry West Nile, too. The primary weapon has
> been to spray pesticide at night with fogging trucks that roam the
> neighborhoods. Maricopa County officials recently voted to spend more
> money to increase the spraying. But they also opted against the aerial
> spraying recommended by the CDC. Federal officials are watching to see
> whether the county is able to slow the virus's spread.
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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>
Patrick T. Redig DVM, PhD
Professor and Director
The Raptor Center - SACS
College of Veterinary Medicine
1920 Fitch Avenue
St. Paul, MN 55108
Phone: 612-624-4969
Fax: 612-624-8740
"Pressures resulting from unrestrained population growth put demands on
the natural world that can overwhelm any efforts to achieve a
sustainable future. If we are to halt the destruction of our
environment, we must accept limits to that growth."
World Scientists' Warning to Humanity, signed by 1600 senior scientists
from 70 countries, including 102 Nobel Prize laureates.
Received on Thu Aug 26 14:40:48 2004
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