Blogs / 80beats

To combat the persistent scourge of dengue fever, researchers have infected the virus-carrying mosquitoes with a bacterium that kills them before they’re old enough to transmit the virus to humans. Researchers say this “biopesticide” technique could cheaply and quickly reduce deaths due to dengue fever in the tropics, as the bacterium could rapidly spread through mosquito populations. Traditional [malaria-oriented] methods for controlling the spread of mosquito-borne disease, such as using bed nets and draining wetlands, are ineffective for the Aedes aegytpi mosquitoes that spread dengue fever virus because they bite during the day and thrive in urban areas [Nature News].

While the new process has only been tested in the lab thus far, researchers are very optimistic about the possibility of whittling away at the 20,000 deaths caused each year by the disease, and say it’s conceivable that transmission of the virus could be reduced to nearly zero. “We’re not trying to eliminate the population, but to let a bacterial symbiont in, and then shift the population,” said University of Queensland bacterial geneticist Scott O’Neill. “There will still be mosquitoes around, but only young ones. It’s a biological control” [Wired News].

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Firing new shots in the malaria war, a vaccine still in the testing stage is now a step closer to becoming a public health reality [Science News]. Two field trials in Kenya and Tanzania showed that the experimental drug reduced malaria infections by more than 50 percent in infants and young children; if a final set of trials proves that the vaccine is indeed safe and effective, the vaccine could be ready for use by 2011.

If the phase three trials are successful, it would be “an extraordinary scientific triumph,” said Dr. W. Ripley Ballou, deputy director for vaccines and infectious diseases for the Bill and Melinda Gates Foundation, which helped fund the research. But more importantly,” Ballou added, “it could save millions of children’s lives” [Los Angeles Times]. Malaria kills about 1 million people around the world each year, and most of the victims are children under the age of five.

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Researchers have decoded the genomes of two different malaria parasites that plague people in Southeast Asia and South America, and say the new information will boost efforts to find a vaccine for the mosquito-borne disease. The work builds on the sequencing of the first malaria genome six years ago, when scientists tackled the most deadly malaria parasite, Plasmodium falciparum, which is endemic in Africa. By comparing the genetics of Plasmodium falciparum to that of the newly sequenced species, P. knowlesi and P. vivax, the two teams have begun to identify the different mechanisms by which each species maximizes its chances of evading the host immune system [The Scientist].

P. vivax is the main cause of malaria in Latin America and Southeast Asia, and although it’s rarely deadly researchers say it still causes plenty of misery. It’s also challenging to eradicate because it can lie dormant in the liver for months. “It makes people very sick,” says lead researcher Jane Carlton…. “It can come out of the liver weeks or months after the initial mosquito bite. That makes it a very serious risk to human health.” Vivax malaria is so debilitating that sufferers, most of whom are poor, can’t support themselves or their families. “Vivax is one of the stealth reasons that poor people can’t escape poverty,” says [tropical disease expert] Peter Hotez [USA Today].

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A warmer world will also be a sicklier place for both animals and humans, according to a new report from the Wildlife Conservation Society (WCS). Dubbed the “deadly dozen,” sicknesses such as Lyme disease, yellow fever, plague, and avian influenza, or bird flu, may skyrocket as global shifts in temperature and precipitation transform ecosystems. Babesia, cholera, Ebola, intestinal and external parasites, red tides, Rift Valley fever, sleeping sickness and tuberculosis round out the list [National Geographic News].

The report spells out how global warming is changing the ranges and habitats of animals that carry these infectious diseases, bringing the ticks that transmit Lyme disease and the mosquitoes that carry yellow fever and Rift Valley fever into contact with new human populations. “We’ve seen Lyme disease work its way up from the US into Canada, and West Nile fever as well,” said William Karesh, director of WCS’s global health programmes. “Basically what you have now are fewer frozen nights in this region, and that allows the ticks and mosquitoes that carry these diseases to survive further north” [BBC News].

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Finally, the U.S. Department of Defense is working on a bomb that even peaceniks can get behind — a bug bomb!

Motivated by the need to protect soldiers in the field from biting pests, the Defense Department teamed up with the Department of Agriculture to search for a longer-lasting and more effective insect repellent. “That was the principal motivation, the usability for the military,” says USDA investigator Ulrich Bernier. “You don’t want your soldiers reapplying every 15 to 20 minutes” [Science News].

Researchers have already identified several chemical compounds that seem far more effective than the current standard-bearer, DEET. In one test, a cloth soaked with a particularly promising compound repelled mosquitoes for 73 days, while DEET-soaked cloth lasted only 13 days.

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