Monday, August 2, 2010

Mosquito-borne Dengue Spreads from Mexican Tropics

Frontera NorteSur

Troubling trends in dengue fever outbreaks are worrying health authorities and elected officials in Mexico. In 2010; deaths from the illness are running ahead of last year's fatalities. Dengue-transmitting mosquitoes are turning up in unexpected areas, and the pests are showing resistance to previously-applied insecticides. The federal Secretariat of Health has called on officials to "undertake the greatest efforts at safeguarding the health of the citizenry."

Until recently, dengue had been a problem in low-lying tropical areas along Mexico's coasts. Recently, however, the National Center for Epidemiological Monitoring and Disease Control (Cenavece) has detected Aedes aegypti, the mosquito which transmits the virus causing dengue, in unusual places including the Mexico City metropolitan area, Cuernavaca, Aguascalientes and Queretaro.

According to Health Secretary Jose Angel Cordova, transmitting mosquitoes are now found in zones higher than 5,000 feet — far above elevations where the bugs were previously found.

In Sonora, health authorities reported 65 cases of dengue through the third week of July, mainly in the state capital of Hermosillo and municipalities in the southern part of the state. In Guerrero, meanwhile, state health officials reported a 40 percent increase in dengue cases over last year's numbers. Most of the sicknesses were in the resort city of Acapulco. By the third week of July, the Guerrero State Health Department registered 2,491 cases, including six deaths. Nationwide, 8,850 dengue cases — including 16 fatalities — were tallied in the same time period.

Last year, Mexico recorded 44,000 cases of dengue, which typically surges in the summer and early fall rainy season. Notably, many of this year's cases have been of the hemorrhagic form of dengue, which is potentially more fatal than the classic variety. Of this year's 8,850 dengue cases, 1,750 have been hemorrhagic ones.

Although the U.S. Center for Disease Control (CDC) has a map of dengue-risk areas in Mexico and other nations on its website, the information has not been updated since August 2009. According to a report submitted to the CDC, incidences of dengue fever soared more than 10 times in the Mexican state of Tamaulipas, bordering Texas, from 2000 to 2006.

Five years ago, 25 people in and around the Texas border city of Brownsville came down with dengue. Local exposure was blamed in three of the cases, while travel to Mexico was considered the source of illness for the remainder.

Mexican Health Secretary Cordova revealed last week that Aedes aegypti has developed resistance to commonly used pesticides. In Guerrero, fumigators were forced to switch to clorpirifos, a controversial chemical commonly sold as Dursban, after the previously-applied permethrin fell short of killing its targets. A synthetic pyrethroid, permethrin is classified by the U.S. Environmental Protection Agency as a carcinogen.

At an Acapulco press conference, Guerrero Governor Zeferino Torreblanca Galindo said the development of mosquito resistance warranted a new suppression strategy spearheaded by the Calderon administration and supported by state and local governments.

Increasingly, climate change is considered the cause for the evolution of dengue in Mexico. Hotter temperatures and intense rainstorms are creating favorable conditions for the spread of mosquitoes.

In coordination with state and local authorities, the federal government plans to fumigate more than 90,000 acres in the northern part of the country affected by Hurricane Alex. And in a gesture of support, the state government of Guanajuato announced this week it has dispatched 10 eradication units to Tamaulipas, which suffered severe flooding from the storm.

Gustavo Ampugnani, climate and energy campaign coordinator for Greenpeace Mexico, warned that heavy storms will become more "recurrent." Calling Mexico "vulnerable" to dengue outbreaks because of climate change, Ampugnani urged greater short-term and long-term attention to the problem.

Concerned by the spread of dengue, the health commission of the lower house of the Mexican Congress has requested a report from the Secretariat of Health. Separately, Cenavece Director Miguel Angel Lezana said the federal government has set aside more than $50 million to combat dengue this year. Among other measures, health authorities have urged people to keep their patios clean, avoid leaving accumulations of water that attract mosquitoes, and to remove aquatic plants from the interiors of homes.

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Sources: Milenio.com, July 25, 2010. Boletinplus.net, July 23, 2010. Article by Adriana Covarrubias. El Universal, July 21, 22, 24, 26, 2010. Articles by Ruth Rodriguez, Miguel Angel Sosa, Andrea Merlos and Xochitl Alvarez. La Jornada, July 21 and 23, 2010. Articles by Rene Ramon and Notimex. CDC.gov

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Frontera NorteSur (FNS)
Center for Latin American and Border Studies
New Mexico State University
Las Cruces, New Mexico

 

Reprinted with authorization from Frontera NorteSur, a free, on-line, U.S.-Mexico border news source; translation FNS