Amidst concerns over the safety of DEET, scientists are on the lookout for a new mosquito repellent. Now they may have found a way to keep biting insects at bay–by blocking their olfactory sense, according to a paper published in Nature.
Mosquitoes sense the presence of humans and animals by detecting the carbon dioxide we exhale with each breath. Researchers have found two compounds, 2,3-butanedione and 1-hexanol, that could keep the biters at bay by blocking the insects’ ability to detect this gas. Using these compounds could be advantageous because the amount of chemical required is relatively small…. Further, the chemicals themselves are not complicated to manufacture and are available through conventional sources. “From both perspectives, this adds up to a viable tool in tackling the problems like that of malaria in Africa” [Scientific American], says study coauthor Anandasankar Ray. Considering the number of diseases spread by insects such as mosquitoes–for example, 250 million people contract malaria each year–there’s a lot more at stake here than a few itchy bug bites.
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Powerful bug repellant DEET may do more than keep mosquitoes and other biting critters at bay–it might cause neurological damage in mammals, according to a study published in BioMed Central Biology.
Developed in 1946 by the U.S. Army, DEET has been used by the public for more than half a century to repel bugs like mosquitoes, along with the diseases they can carry. The new study, however, shows that DEET—aka N,N-diethyl-meta-toluamide—may be harmful for a variety of animal cells. In lab tests, it caused damage to mosquitoes, cockroach nerves, mouse muscles, and enzymes purified from fruit flies and humans. Applications of DEET slowed or halted the actions of the enzyme acetylcholinesterase. This enzyme hangs out between nerve and muscle cells, breaking down a messenger molecule after it has passed information from one cell to another. If this messenger isn’t properly recycled, it can build up and lead to paralysis [Science News].
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Researchers have determined how malaria first came to afflict humanity, and have laid the blame on our closest relative, the chimpanzee. Researchers have long known that chimps get infected with a malaria parasite of their own, called Plasmodium reichenowi, which is closely related to the human malaria parasite, Plasmodium falciparum, but they believed that the two parasites evolved from a common ancestor many millions of years ago and then developed on parallel tracks. Now a new genetic comparison indicates that the human version more likely developed from the chimpanzee type [AP].
“Current wisdom that P. falciparum has been in humans for millions and millions of years is wrong,” said study co-author Nathan Wolfe, director of the Global Viral Forecasting Initiative…. “We now know that there was a point in time when this was primarily a disease in chimpanzees that jumped and took hold in humans” [National Geographic News]. Malaria probably came to our species when mosquitoes that had previously fed on infected chimpanzees bit humans, Wolfe says, and the transmission may have happened as recently as 10,000 years ago.
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Malaria in Cambodia is becoming increasingly resistant to one of strongest anti-malarial treatment available, according to a study published in the New England Journal of Medicine. That could cause literally millions of deaths as malaria, already the world’s third-deadliest infectious disease, becomes unresponsive to remedies that once proved effective against the disease.
The drugs examined were derived from artemisinin, the basis of the most effective treatment for the bloodborne parasite that causes malaria. To study the treatment’s effectiveness, researchers compared the effects of artemisinin drugs in 40 malaria patients in western Cambodia and 40 patients in northwestern Thailand. On average, the patients in Thailand were clear of malaria parasites within 48 hours, compared to 84 hours for the Cambodian patients [HealthDay News]. That means the remedies were significantly less effective against the mosquito-transmitted parasite in Cambodia. Furthermore, in the time since the study concluded, healthcare workers have observed lengthened clearance times among malaria patients in southern Cambodia, indicating the resistant strain has already begun to spread.
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Developing nations may be where infectious diseases like malaria and tuberculosis flourish, but ironically, these regions often have the fewest resources for equipment to diagnose the maladies.
A new fluorescence microscope, however, could offer an affordable solution: One that attaches to an ordinary mobile phone. Once snapped on to any mobile phone that has a basic camera function, the microscope can illuminate pathogens, allowing the viewer to identify them and even send the image to a health care facility, according to an article published in the journal PLoS ONE.
To use the device, called the CellScope, fluorescent molecular “tags” are added to a blood sample, which attach themselves to a certain pathogen, such as tuberclosis-causing bacteria. The pathogens are then illuminated by microscope, which uses cheap commercial light-emitting diodes as the light source – in place of the high-power, gas-filled lamps used in laboratory versions of the device, and cheap optical filters to isolate the light coming from the fluorescent tags [BBC News]. The apparatus allows the viewer to “see” things as small as one-millionth of a meter.
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Unconventional is the theme of the Bill & Melinda Gates Foundation’s latest round of endorsements. The foundation on Monday awarded 81 five-year research grants of $100,000 to scientists pursuing bold ideas that could lead to breakthroughs, focusing on ways to prevent and treat infectious diseases, such as HIV, malaria, tuberculosis, pneumonia and diarrheal diseases [AP].
One grant, for example, will be awarded to Rutgers University’s Eric Lam, who is working to develop tomatoes that can deliver antiviral drugs. Another grant will fund a British research team attempting to compile a library of all possible mutations of HIV with the ultimate goal of a vaccine that can protect against many variant forms of the virus. In the US, [one researcher will receive] a grant to see if shooting a laser at a person’s skin before administering a vaccine can enhance immune response [Telegraph].
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The U.S. Food and Drug Administration has approved human trials of a new malaria vaccine: it is made from a weakened form of the entire malaria-causing parasite, Plasmodium falciparum, extracted from irradiated mosquito spit. Sanaria, the company producing the vaccine, has been working with a particular stage of the P. falciparum parasite called a sporozoite. This is the stage when it leaves the mosquito’s salivary glands to enter the human bloodstream [Reuters].
To produce the vaccine, Sanaria weakens the parasite by feeding human, infected blood to mosquitoes, then [exposes] the mosquitoes to enough irradiation to cripple the parasite [New Scientist]. The mosquitoes are then killed and their saliva is extracted by hand, with each of six laboratory workers averaging a rate of 100 mosquitoes per hour. With every mosquito containing about two doses in its spit, Sanaria founder Stephen Hoffman estimates that about 1,200 doses are produced per hour.
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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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Researchers have invented a microscope that’s about the size of a tiny iPod shuffle, and say the cheap, disposable, and sturdy device could be a boon for doctors in the developing world. The microscope, which researchers say could be mass-produced for about $10, could be used to quickly scan a patient’s blood for the parasites that cause malaria, sleeping sickness, and other tropical diseases, for example.
The new tool could be a useful alternative to the typically bulky optical microscopes, in which lenses and lights normally needed to illuminate, magnify and focus an image take up a lot of space, and are fragile and expensive to boot [New Scientist]. In contrast, researcher Changhuei Yang says his invention could be slipped into a doctor’s pocket, and could be brought to the most isolated village. “The whole thing is truly compact, it could be put in a cell phone, and it can use just sunlight for illumination, which makes it very appealing for Third World applications,” he said [The Independent].
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It’s a mind-boggling piece of medical news: A genetic variant that’s commonly found in people of African descent raises the risk of HIV infection by about 40 percent, but also causes HIV-infected people to live longer. Researchers say the trait is extremely common because it used to have a beneficial effect; it protected people against a form of malaria that is now fairly rare.
The genetic variant may partially account for the high HIV rates in sub-Saharan Africa, where over 24 million people are currently living with the disease. While the differences in HIV prevalence in different parts of the world can be partly explained by different social conditions and sexual behaviour, scientists have long suspected that there may be genetic reasons why the virus is rife in certain communities [BBC News].
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Villagers living deep in the Guyanese rain forest have developed resistance to an antibiotic they’ve never taken, and a malaria drug may be to blame. Researchers say the malaria drug is chemically similar to a type of widely used antibiotic, and they believe that the E. coli bacteria in the villagers’ guts evolved a broad resistance to both medications.
Antibiotic resistance is a major problem in Western countries, where strains of disease-causing bacteria such as Staphylococcus have adapted to beat some of the most commonly-used drugs. However, for a resistant strain to develop, bacteria usually need to be exposed to the drug involved [BBC News]. In this case, researchers say that a cheap malaria medication called chloroquine is similar enough to the antibiotic ciprofloxacin to allow the E. coli to develop defenses to the unknown drug.
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