Daily News Archive
Resistance in Mosquitoes Being Studied
The southern house mosquito is the primary vector for viruses causing St. Louis encephalitis and West Nile encephalitis in Texas urban areas.
Fragments of mosquito
genes will be cloned and sequenced to determine what mutations, if any,
have occurred, Pietrantonio said.
The project is similar to one she completed in the Houston area in 1998 involving the organophosphate insecticide, malathion. Pietrantonio found in some areas the southern house mosquito was resistant to the insecticide malathion being used. The district switched to pyrethroid pesticides to control the pests. Pyrethroids are chemicals that are linked with endocrine disruption, neurotoxicity, and respiratory irritation. Symptoms of acute toxicity due to inhalation include sneezing, nasal stuffiness, headache, nausea, incoordination, tremors, convulsions, facial flushing and swelling, and burning and itching sensations.
In 2003, the Mosquito Control Division in Harris County sprayed 2 million acres with pyrethroid insecticides in an effort to control disease-bearing mosquitoes, said Ray Parsons, division director.
"History has shown that overuse of pesticides will lead to resistance in insects," said said Dr. Jim Olson, Experiment Station entomologist.
The project was started with a federal U.S. Department of Agriculture Cooperative State Research, Education and Extension Service grant, Olson said.
"This is serving as a model for similar problems that could arise anywhere in the state of Texas or the United States," he said.
"We have like concerns, particularly for the Culex quinquefasiciastus in other areas of the Gulf Coast of Texas all the way into the metropolitan areas of the state such as Dallas where there is extensive spraying for mosquitoes going on."
"We have to develop new methods of controlling mosquitoes," Parsons said. "We know we can control them with insecticides, but it's very expensive and it only works to a certain degree. It's going to take people going out into the field and learning more about the mosquitoes: the biology of the mosquito and how to control it."
The resistance project is part of a larger program investigating the frequency of mosquito-borne diseases and other possible control methods for mosquitoes, he said.
"In many parts of the state, we don't have a clue as to what level of insecticide resistance exists," Olson said. "It's a bad time to find out you've got it in the middle of a disease outbreak. It is better you take care of it well in advance."
The Experiment Station
developed a Mosquito Control Research Initiative that will be submitted
to the next session of the Texas Legislature. The Experiment Station
is asking for $1 million per year, which would allow them to expand
mosquito-related research and educational programs.