Posts Tagged: dengue
It's Halloween tomorrow (Wednesday) but what's really frightening is Aedes aegypti, a mosquito that transmits the deadly dengue. According to the World Health Organization (WHO), dengue is the world's most rapidly spreading mosquito-transmitted disease.
Some 2.5 billion people, or about 40 percent of the global population, are at risk from dengue, WHO says. The disease infects between 50 to 100 million people a year. The most severe form afflicts some 500,000 a year, killing an estimated 2.5 percent or 22,000.
Enter Sarjeet Gill, professor of cell biology and entomology at UC Riverside. He'll speak on on "Bacterial Toxins in Disease Mosquito Vector Control" at a seminar from 12:10 to 1 p.m., Wednesday, Oct. 31 in Room 1022 of the Life Sciences Building, UC Davis.
His longtime colleague and good friend, Bruce Hammock, distinguished professor of entomology at UC Davis, will host him as part of the UC Davis Department of Entomology's fall seminar series.
"Aedes aegypti is an important vector of human diseases, such as dengue fever and yellow fever," Professor Gill says. "Its control has been attempted by eliminating breeding sites, using predators and with chemical insecticides. However, such control is still difficult because of operational limitations and the development of insect resistance. Therefore, Bacillus thuringiensis has been used for decades instead of physical and chemical control methods. B. thuringiensis israelensis is highly active against Aedes aegypti."
"The high insecticidal activity and the low toxicity to other organisms," Gill says, "have resulted in the rapid use of B. thuringiensis as an alternative for the control of mosquito populations. B. thuringiensis israelensis produces a variety of toxins that act synergistically to cause toxicity to larval populations."
Gill says his seminar "will discuss our current understanding of the mode of action of these toxins and provide evidence on how resistance to these toxins has not occurred in Aedes mosquitoes in the field even though B. thuringiensis israelensis has been used for more than three decades."
Gill’s laboratory focuses on two principal research activities. "The first area attempts to elucidate the mode of action of insecticidal toxins from the Gram positive bacteria Bacillus thuringiensis and Clostridium bifermantans," he says. "This research aims to identify novel toxins, and to gain a molecular understanding of how these toxins interact with cellular targets and thereby causing toxicity. The second area focuses on understanding mosquito midgut and Malpighian tubules function, in particular ion and nutrient transport, and changes that occur following a blood meal."
Gill, who received his doctorate from UC Berkeley, joined the UC Riverside Department of Entomology faculty in 1983. He helped establish the Department of Cell Biology and Neuroscience and also served as chair. Currently he is the co-editor of the journal Insect Biochemistry and Molecular Biology.
A noted scientist and a fellow of the American Association for the Advancement of Science, Gill received his doctorate in insecticide toxicology in 1973 from UC Berkeley. See his website.
If you miss his seminar, not to worry. It's scheduled to be recorded and then posted at a later date on UCTV. (See the index of previous Department of Entomology seminars posted on UCTV.)/span>
Aedes aegypti transmits the deadly dengue. (Photo by James Gathany, Centers for Disease Control and Prevention)
Professor Sarjeet Gill at a malaria conference at UC Davis. (Photo by Kathy Keatley Garvey)
So are researchers from the Thomas Scott lab at UC Davis.
Scott, a medical entomologist who directs the state-funded UC Mosquito Research Laboratory, and his field director Amy Morrison, based in Iquitos, Peru, know their foe well.
Their goal: to save lives through research, surveillance and implementation of disease prevention strategies.
Morrison talked about the research efforts today on National Public Radio (NPR).
Morrison told Charles: ""What's fascinating to me about aegypti is it's probably the mosquito that's most closely associated with human beings, and the most adapted to human beings."
The tiger-striped mosquito, is a daybiting mosquito that prefers human blood. Some 2.5 to 3 billion people, primarily in tropical and sub-tropical countries around the world, are at risk for dengue, which Scott describes as "the world's worst insect-transmitted disease." See feature on him on the UC Davis Department of Entomology website, with links to significant research work.
Aedes aegypti is out for blood. And so are the UC Davis-based researchers tracking it.
Aedes aegypti transmits dengue. (Photo courtesy of James Gathany, Centers for Disease Control and Prevention).
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.)
UC Davis medical entomologist Thomas Scott is mentioned in "The War on Dengue Fever," a news article published Nov. 3, 2008 in the New York Times.
Scott is a leading expert on dengue fever, a mosquito-borne disease transmitted by Aeges egypti.
Reporter Thomas Fuller began his story:
BANGKOK — There was little that doctors could do for a 3-year-old boy brought to Bangkok’s main children’s hospital two weeks ago with dengue fever. Like thousands before him, he had reached the most dangerous phase of the disease, dengue shock syndrome, and he died of internal bleeding and organ failure three days after being admitted.
The U.S. Army maintains a medical research laboratory in Bangkok, where military scientists study tropical diseases. One of their goals: to develop a vaccine for dengue.
Here's where Scott comes in:
"The mosquito can breed in something as small as a soda bottle, but its ideal breeding conditions are large containers common in many parts of Southeast Asia to store drinking water," Fuller wrote. "(Unlike other mosquitoes, Aedes aegypti prefers clean water, according to Thomas W. Scott, a professor at the University of California, Davis, who is a leading expert on the species.)"
We wrote about researcher Scott's work in July: On the Trail of Dengue: A Disease with No Vaccine, No Cure.
Scott's goal is to save lives through research, surveillance and implementation of disease prevention strategies. He maintains field stations in Peru, Mexico and Thailand.
He's studying "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."
Basically, Scott assesses risks, develops computer models and implements disease prevention strategies.
The culprit: Aedes egypti, 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.
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 (CDC). An estimated 5 percent with DHF die.
The CDC says dengue outbreaks occur in most tropical urban areas of the world where the Aedes egypti lives.
In the United States, dengue is rare. Occasionally travelers to infected areas return with the disease.
Now the Armed Forces Research Institute of Medical Sciences, Bangkok, is attempting to develop a vaccine for dengue. As New York Times reporter Thomas Fuller wrote, quoting Col. James Boles, the laboratory commander: "There's no dengue in Kansas. No malaria, either. That's why we are here."
And that's why medical entomologists like Thomas Scott are here, too.
Medical entomologist Thomas Scott
In the lab