New Man-Biting, Disease-Carrying Mosquito Spreading Into Northern States
WASHINGTON (AP) _ A new disease-carrying mosquito with a taste for human blood can survive harsh winters in the Midwestern United States, a finding scientists say could mean the pest will make itself at home in northern states as it has in the South.
The aggressive Asian tiger mosquito, a species first spotted in this country in 1985, is spreading from the South up through the Midwest and eastern United States, and cold weather is not a barrier to the invader, scientists said Thursday.
Researchers at the University of Notre Dame and the federal Centers for Disease Control said the tiger mosquito, called Aedes albopictus, lays eggs that can withstand winters as cold as those in northern Indiana and Ohio.
The North American strains of the mosquito, which apparently came to the United States in imported used tires, appear to be the types found in the more temperate parts of Asia rather than tropical areas, they said.
Cold kills adults and larvae, but the insects sustain themselves in an area by leaving eggs that hatch in the spring, scientists said.
Known to endure the harsh winters of northern Japan and China, these strains therefore could reach as far north as Minnesota and Michigan, the researchers said.
Health officials are concerned about the insects because they are potential carriers of viral diseases. In Asia, they carry dengue fever, a sometimes fatal disease that causes painful joint inflammation, and other maladies.
Dengue occurs in the United States, such as an outbreak in south Texas last year, and could become more common if it has a good insect carrier, one of the researchers, Dr. William Hawley of the University of Notre Dame, said.
Laboratory tests also indicate the tiger mosquito might be a good carrier of different types of encephalitis, including the California and LaCross varieties, he said. Encephalitis causes inflammation of the brain, which can result in retardation or death.
The tiger mosquitos, which prefer humans to other hosts as sources of blood, are so named because of the distinct black and white stripes on their legs and a white stripe down the top of their middle sections.
In a report published in the May 29 issue of the journal Science, scientists said tiger mosquito eggs survived to hatch after wintering in controlled locations as far north as South Bend, Ind., where temperatures reached as low as minus 7 degrees Fahrenheit some days.
Hawley and a Notre Dame colleague, Dr. George Craig Jr., said all of the eggs from tropical strains of Aedes mosquitos died during the winter tests. However, of the five North American and two Japanese strains tested, in no case was the mortality due to subfreezing temperatures greater than 22 percent.
″Our results imply that this northward expansion is not a transient phenomenon, but the beginning of the permanent establishment of Aedes albopictus at these latitudes,″ wrote the researchers, including Paul Reiter of the CDC and Notre Dame graduate students Robert Copeland and Charles Pumpuni.
Hawley said in a telephone interview Thursday the mosquito has been found in at least 12 states, so far: Texas, Louisiana, Florida, Illinois, Indiana, Tennessee, Georgia, Alabama, Mississippi, Missouri, Kentucky and Ohio.
″There is a good possibility they are up through the mid-Atlantic states as far as Virginia and the District of Columbia, but we don’t know because no one has looked for them there yet,″ Hawley said.
None of the insects has yet been seen in the Southwest or on the West Coast, he noted, perhaps because the amount of rainfall is insufficient there during the summer mosquito season.
Researchers believe the tiger mosquito, first identified in Houston in 1985, arrived in some of the millions of used car tires imported from the Orient for recapping each year. Moisture in the tires makes them ideal breeding grounds for mosquitos to lay eggs.