- TIJUANA -- Epidemiologists
have found the first evidence of West Nile virus in Baja California, tracing
antibodies for the disease to 16 horses across the state and six birds
in the Mexicali area.
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- Although six human cases of the potentially deadly disease
have been confirmed in Mexico, none has been in Baja California. The virus,
carried by migratory birds, is transmitted to humans and horses by infected
culex mosquitoes.
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- Because mosquito populations are down for the winter,
the danger to humans at this time is "greatly reduced," said
Dr. Jorge AcuÒa, an epidemiologist with the federal social security
hospital in Mexicali.
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- But that scenario could change dramatically as spring
approaches.
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- Some researchers are predicting a West Nile virus epidemic
in Mexico because warm weather and tropical climates make many regions
ideal breeding grounds for the mosquito.
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- But others say it is unclear how the disease will play
out. They suggest that the presence in Mexico of another mosquito-borne
disease, dengue fever, may have helped Mexicans build antibodies that will
protect them from West Nile virus.
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- So far, the effects of the disease have been relatively
benign in Mexico.
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- Since it was first identified in November 2002 in horses
in the northern border states of Coahuila and Tamaulipas, federal health
officials say just two horses and 10 birds have died from the disease.
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- In California, the first evidence of the virus was confirmed
in mosquitoes near the Salton Sea in Imperial County in August. The state
has since confirmed three human cases of the disease. The first was in
Riverside County, the second in Imperial County and the third, confirmed
Dec. 24, a 61- year-old man in Los Angeles County.
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- The discovery of animals carrying the disease antibodies
in Baja California is "not surprising at all," said Dr. Steve
Waterman, a medical epidemiologist with the U.S. Centers for Disease Control.
"It confirms what people expected."
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- Dr. Alma Rosa M·rquez of the Baja California Health
Secretariat said the six birds that tested positive for the virus were
migratory, so it is unclear whether they became exposed to the virus in
Baja California or elsewhere.
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- More details are expected later this month. The secretariat
is awaiting the test results on native birds, although sentinel chickens
placed around the state to detect the disease have shown no signs of being
exposed, M·rquez said. Tests on mosquitoes also have been negative,
she said.
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- With a statewide horse population estimated at 12,000,
Baja California agriculture officials are closely following the virus.
Eleven of the horses that tested positive for West Nile are in the Mexicali
area, said Dr. Marco Antonio Vargas, head of animal health for the Baja
California office of Mexico's federal agriculture secretariat. The remaining
five are in Tijuana and Ensenada.
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- "The situation is as we had been expecting,"
Vargas said. "We have the same mosquitoes in Baja California as in
California."
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- The agriculture secretariat has been urging horse owners
to vaccinate their animals against the disease. Some of the horses could
have tested positive because they had already received the vaccine, even
though health officials have been trying to limit their tests to unvaccinated
animals, Vargas said.
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- Baja California state health officials say they share
information with California's Office of Binational Health. But Paula Kriner,
an Imperial County epidemiologist, said local officials communicate only
informally on the topic of West Nile virus.
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- "I'm hoping we can develop an exchange system,"
she said.
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- With the discovery of the Baja California cases, all
six states on Mexico's northern border now show evidence of the virus,
according to Mexico's National Center for Epidemiological Surveillance.
Across the border from Texas, there were four human cases in Chihuahua
and one in Nuevo Leon as of Dec. 25. A sixth case has been identified in
the state of Sonora, but in a location far from the border.
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- In southern Mexico, 564 horses in the state of Chiapas
had tested positive for antibodies to West Nile virus as of Dec. 25, more
than in any other state in Mexico. But none had died as a result of the
disease.
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- http://www.signonsandiego.com/news/mexico/20040102-9999_7m2nile.html
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