A ProMED-mail post
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International Society for Infectious Diseases
Date: Tue 17 Aug 2010
Source: Channel 2 News, KTVN.com [edited]
Area chickens test positive for western equine encephalitis, Nevada
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The Washoe County Health District says chickens in Lemmon Valley have
tested positive for western equine encephalitis.
Authorities say chickens are good test subjects because they have
immunity, but will test positive for the virus. "What we do is, every
2 weeks or so, we come out and we take blood samples and that way we
can tell if mosquitoes have bitten the chickens and given them the
viruses," says Tracie Douglas. Health officials say the western
equine encephalitis is a rare disease in humans, but still anyone can get it.
Some people maybe more at risk than others including those living in
or visiting an area that has infected mosquitoes.
Western equine encephalitis inflames the brain and spinal column. The
disease is fatal to about 3 percent of people who develop severe
symptoms. While there is no specific treatment for the disease,
health officials say the best thing to do is to avoid mosquitoes all together.
If you have to be outside, make sure to take precautions. "Use
repellents. It's so easy to do; read the bottle. If you have to
reapply it every couple of hours, do so. You don't have to use
something that has a real high content of repellent. You can use
products with DEET or lemon or eucalyptus oil."
Health officials say the virus affects more horses. "Most people
don't get, that is, it very rarely it attacks humans. But, it does
attack horses a lot," Douglas says.
And it's not just the encephalitis, but West Nile to worry about.
That's why they're urging horse owners to get their equines
vaccinated. "Horses are very sensitive to these viruses and so it can
kill them," she says.
[Byline: Nick Montes]
--
Communicated by:
HealthMap Alerts via ProMED-mail
[Western equine encephalitis virus, a member of the family
_Togaviridae_, genus _Alphavirus_, is closely related to eastern and
Venezuelan equine encephalitis viruses.
Infection can cause a range of illnesses in people, from no symptoms
to fatal disease. People with mild illness often have only a headache
and sometimes fever. People with more severe disease can have sudden
high fever, headache, drowsiness, irritability, nausea, and vomiting,
followed by confusion, weakness, and coma. Young infants often suffer seizures.
Western equine encephalitis is a disease that is spread to horses and
humans by infected mosquitoes. It is one of a group of mosquito-borne
virus diseases that can affect the central nervous system and cause
severe complications and even death. Other similar diseases are
eastern equine encephalitis, St Louis encephalitis, and LaCrosse encephalitis.
The virus that causes western equine encephalitis has a complex life
cycle involving birds and a specific type of mosquito, _Culex
tarsalis_, which is common in farming areas and around irrigated
fields. Humans, horses, and other mammals are not an important part
of the life cycle of the virus.
Western equine encephalitis is found in North, Central, and South
America, but most cases have been reported from the plains regions of
the western and central United States.
Western equine encephalitis was first isolated in the United States
in 1930. In 1941, a US epidemic involved 300 000 horses and 3340
humans. Since then, occasional smaller epidemics have occurred. The
risk of exposure has been increasing in recent years as people move
into previously undeveloped areas where the virus lives. Expansion of
irrigated agriculture in the North Platte River Valley (Colorado,
Wyoming, and Nebraska) during the past several decades has created
habitats and conditions that favor increases in the number of
grain-eating birds and mosquitoes that spread western equine encephalitis.
The western equine encephalomyelitis (WEE) virus group includes the
western equine encephalitis (WEE), Sindbis, Ft Morgan, Aura, and Y
61-33 viruses. The western equine encephalitis virus can cause
disease in humans, horses, and some species of birds. A related
virus, the Highlands J virus, is sometimes isolated in the eastern
United States. The Highlands J virus can cause disease in turkeys. It
has also been linked to a single case of encephalitis in a horse.
Eastern and western equine encephalomyelitis are very similar in
horses. The initial clinical signs are usually fever, anorexia, and
depression. In severe cases, this prodromal stage is followed by
neurologic signs; the symptoms may include involuntary muscle
movements, impaired vision, aimless wandering, head pressing,
circling, an inability to swallow, ataxia, paresis, paralysis, and
convulsions. Periods of excitement or intense pruritus can also be
seen. Laterally recumbent animals may develop a characteristic
"paddling" motion. Both EEE and WEE can also cause asymptomatic
infections or mild disease without neurologic signs. Occasional cases
of encephalitis have been seen in pigs.
Portions of this post have been extracted from
- Mod.TG]
[The state of Nevada can be located on the HealthMap/ProMED-mail
interactive map at
Washoe County can be located on the map at
[see also:
Western equine encephalitis - USA (Arizona): alert 19990907.1569
Western equine encephalitis - USA (Arizona): advisory 19990802.1315]
...................................sb/tg/mj/dk
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