April 25, 2011
World Malaria Day 2011 is a time to reflect on the global effort to control and eliminate malaria, a disease that affects 108 countries around the world, infects more than 250 million people, and kills an average of 850,000 annually. Ninety percent of these deaths occur in sub-Saharan Africa among children younger than five years of age.
Those fortunate enough to not have to seek the shelter of mosquito nets or sprays to ward off this killer may only know of its devastating effects thanks to awareness campaigns like World Malaria Day and the Roll Back Malaria partnership. It is the hope of these and similar campaigns that the general public learn how they can be a part of the solution to bring malaria to zero by 2015. In honor of World Malaria Day, this post will examine a few of the less traditional, and perhaps more surprising, approaches to achieving malaria eradication.
Franken-insects and disease control
Scientific advancements are being made to control and reduce malaria s mortality rate. One example of this progress is genetic modification (GM), in which researchers genetically engineer the DNA or biology of a mosquito to help limit the vector s spread of the malaria parasite.
Oxitec, an English company, has developed a new DNA technology called RIDL, or Release of Insects carrying a Dominant Lethal, which kills an insect s offspring. Essentially, it is a morning-after pill carried by a genetically modified male mosquito.
From a lab to the wild, a GM male mosquito is released to mate with native female mosquitos. Given the male s genetic modification, the female will produce progeny, but her female offspring will quickly die as they lack the muscular development necessary for flight.
The first test of these GM mosquitos occurred on Grand Cayman, and with promising results: the island saw an 80% reduction of the Aedes aegypti, the yellow-fever mosquito, population in 4 months. Although this particular approach was designed to target mosquito s that spread dengue virus, researches behind the study say it could be adapted to control mosquitos that transmit malaria and West Nile fever.
Another GM development on the horizon is the malaria-immune mosquito. Entomologist Michael Riehle at the University of Arizona led a team of researchers to insert a gene that increases mosquito signaling of the Akt enzyme, which controls the insect s growth rate and immunity and disrupts parasitic growth.
The same study found that [t]he increase in Akt signaling also led to an 18-20% reduction in the average mosquito lifespan. In fact, according to field observations, only the oldest mosquitos transmit malaria. That said, given the slightest lifespan reduction could significantly impact parasite tramission. However, to be effective, researchers must find a way to ensure the GM mosquitos are able to dominate native mosquitos, which, according to Dr Riehle, is the hardest task.
Not all GM efforts focus on manipulating the mosquito genome. Scientists at the University of Maryland have engineered a transgenic fungus as yet another method to attack malaria without the use of harmful pesticides to which many mosquitos have grown resistant. According to the Science Daily report, [t]he research team found that compared to the other treatments, spraying mosquitoes with the transgenic fungus significantly reduced parasite development. P. falciparum, a malaria-causing parasite transmitted by female mosquitos, was found in salivary glands of only 25% of the mosquitos sprayed, whereas 94% of unsprayed mosquitos carried the parasite.
Studies such as these go a long way to help scientists further understand the biology of mosquitos and how malaria spreads, but researchers and public health workers may also find ways to translate these new developments into more effective means of disease control.
Grapefruit joins battle against malaria
Grapefruit has begun to gain favor among public health and malaria researchers since the CDC released evidence that nootkatone, which is found in citrus fruit and the Alaska yellow cedar, can serve as an effective insect repellent.
NPR s Morning Edition recently interviewed Marc Dolan of the CDC s vector-borne infectious diseases laboratory on nootkatone. Dolan is leading a research team to develop the natural repellent.
DEET and other synthetic repellents often deter consumers rather than mosquitos because of their foul odor and oily residue. According to Dolan, nootkatone “is nongreasy, dries very quickly, and it has a very pleasant, citrus-y grapefruit odor to it.”
Dolan demonstrates nootkatone s effectiveness by rubbing the repellant on his hand and placing it in a cage containing 50 bloodthirsty mosquitos, all of which fly away in the opposite direction. Five minutes, Dolan s hand is still in the cage unscathed.
Apart from nootkatone s apparent ability to repel hungry mosquitos, it also kills them and quickly. Not only that, but it is environmentally safe and effective against other insects, including ticks. Dolan explains how a single application of a 2 percent solution of nootkatone will control ticks for up to 42 days at greater than 97 percent efficacy, and it breaks down faster in the environment, limiting soil contamination.
Currently, nootkatone does not come cheap. The highly purified material runs as much as $4,000 per kilogram. There is an effort to find cheaper sources, such as from citrus waste products or forestry industries, or to develop more cost-effective forms of the compound.
In line with World Malaria Day s theme of achieving progress and impact to control and eliminate malaria, learn more about CDDEP s >innovative projects to prevent and treat malaria worldwide. You can also learn more about World Malaria Day by visiting rollbackmalaria.org, or by clicking the image below.
Image credit: Roll Back Malaria
