Posts Tagged: Aedes aegypti
It's not just high temperatures that play a significant role in the transmission of dengue, a deadly mosquito-borne disease that strikes millions of people in tropical and subtropical countries.
The size and pattern of fluctuations in daily temperature have a large effect on pathogens transmitted by mosquitoes, according to groundbreaking research published today in the Proceedings of the National Academy of Sciences.
The research, led by French, Thailand and U.S. scientists and conceived by medical entomologist Thomas Scott (right) of the UC Davis Department of Entomology, targets the transmission of spread of dengue.
Lead author Louis Lambrechts (left) of the Institut Pasteur, France, who did postdoctoral research in the Scott lab, points out that the influence of average temperatures on dengue virus transmission has long been known–the higher the temperature, the more efficient the virus transmission—but this is the first study linking temperature fluctuations to the transmission of the disease.
Dengue, transmitted by the daybiting Aedes aegypti mosquito, globally infects 50 to 100 million people yearly. At risk are some 2.5 to 3 billion people, primarily in tropical and sub-tropical countries. The most severe form of the disease, dengue haemorrhagic fever (DHF), strikes half a million a year and kills an estimated 5 percent, according to the Centers for Disease Control and Prevention.
Scott said the study helps to explain a long-standing enigma: “What are the underlying causes of seasonal fluctuations in dengue incidence?” Experiments showed that mosquitoes die faster and are less susceptible to virus infection under large temperature swings, which is typical of the low dengue season, than under moderate temperature variation, which is typical of the high dengue season.
Scott, a noted dengue expert whose goal is to save lives through research, surveillance and implementation of disease prevention strategies, has a longstanding interest in the factors that drive seasonal and annual fluctuations in diseases caused by mosquito-transmitted pathogens. “Traditional explanations for the seasonal increase in dengue are not consistent with my experience in Thailand, Peru, and Puerto Rico,” Scott said.
The dengue mosquito, Aedes aegypti. (Photo courtesy of James Gathany, Centers for Disease Control and Prevention).
Thomas Scott (right), professor of entomology at the University of California, Davis, and a newly elected fellow of the Entomological Society of America, knows his foe well.
His foe? The day-biting, tiger-striped mosquito, Aedes aegypti. It transmits a virus that causes dengue, sometimes called "break-bone fever."
It's the world’s worst insect-transmitted virus.
And it's on the rise.
"Spread by mosquitoes, it can make you feel as if your bones are broken and leave you exhausted for months," writes Zimmer, who teaches Yale University students how to write about science and the environment. "In more serious cases, people suffer uncontrollable bleeding and sometimes die. Dengue is expanding its range, and is even making incursions into the United States. Scott and I talk about what scientists know and don't know yet about dengue, and what the best strategy will be to drive the virus down."
When Scott leaves his mosquito research laboratory at UC Davis, he’s likely heading for his field stations in Peru, Thailand or Mexico to try to stop that killer mosquito from transmitting dengue.
Scott’s goal: to save lives through research, surveillance and implementation of disease prevention strategies.
“I study the patterns of human infection with dengue virus, doing detailed studies of mosquito populations and disease in humans in order to predict which prevention strategies work the best,” said Scott, who assesses risks, develops computer models and implements disease prevention strategies.
The culprit: Aedes aegypti, or the yellow-fever mosquito, that transmits dengue virus to people.
The disease: Dengue, caused by any one of four serotypes or closely related viruses known as DEN-1, DEN-2, DEN-3, or DEN-4. Nicknamed “break-bone fever,” classic dengue is characterized by high fever, headaches, muscle and joint pain, nausea, vomiting and a rash.
At risk: Some 2.5 to 3 billion people, primarily in tropical and sub-tropical countries around the world.
The prevalence: Some 50 to 100 million annual cases of debilitating dengue fever. The most severe form of the disease, dengue haemorrhagic fever (DHF), strikes half a million a year, according to the Centers for Disease Control and Prevention. An estimated 5 percent with DHF die.
There’s no vaccine. There’s no cure. The only way to prevent this disease is to kill the mosquito vector.
Scott directs the state-funded UC Mosquito Research Laboratory, based in Briggs Hall on the UC Davis campus. His team includes UC Davis associate professor and medical entomologist Anthony “Anton” Cornel, based at the Kearney Agricultural Center, Parlier; researcher Amy Morrison who lives in Iquitos, Peru and has directed their research there since 1999; program manager Leslie Sandburg; postdoctoral and graduate students; and a long list of collaborators at his field sites in Mexico, Peru and Thailand.
Listen to the podcast and learn how Thomas Scott (who at 6-foot, 6 inches tall, towers over his tiny foe) is battling this killer.
(Editor's note: Professor Scott will be teaching a winter course on medical entomology at UC Davis, discussing such diseases as malaria, dengue, West Nile virus, lyme disease, yellow fever, and river blindness.)