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Genetically-modified mosquitoes that are resistant to the malarial parasite may be the first step in the eradication of the deadly disease from the planet. These mosquitoes have the ability to thrive in the wild and outgrow normal mosquitoes, which are the carriers of malaria, researchers at the Malaria Research Institute at Johns Hopkins University said.
The genetically-engineered mosquitoes are equipped with an additional gene that halts the plasmodium parasite, which causes malaria. Lead researcher Marcelo Jacobs-Lorena and colleagues released 1,200 genetically modified mosquitoes into a cage containing malaria-infested mice.
The cage also held an equal number of wild malaria-causing mosquitoes. The researchers observed subsequent generations of mosquitoes and noted the pre-dominance of transgenic mosquitoes. Additionally 70 percent of the mosquitoes were malaria-resistant nine generations after the experiment began.
“To our knowledge, no-one has previously reported a demonstration that transgenic mosquitoes can exhibit a fitness advantage over non-transgenics. This fitness advantage has important implications for devising malaria control strategies,” the researchers wrote in the journal Proceedings of the National Academy of Sciences.
Malaria is a deadly disease caused by a parasite that can infect humans. There are four types of malarial parasite, which can cause serious illness to man. These include Plasmodium falciparum, P. vivax, P. ovale, and P. malariae. Among them infection with P. falciparum has the potential to be fatal if prompt treatment is not given.
The World Health Organization estimates that each year 300-500 million cases of malaria occur worldwide and more than 1 million people die of malaria. It has become an endemic condition in sub-Saharan Africa where, a child dies from malaria every 30 seconds. The disease presents as fever, sweats, chills, headaches, malaise, muscles aches, nausea and vomiting.
An eradication campaign to uproot malaria was launched in the 1950s, but failed because the malaria parasites developed resistance to drugs used to treat them and also because the mosquitoes became resistant to insecticides used to kill them.
A strategy that was advocated was to develop genetically altered insects, which would resist infection with the malarial parasite. Ever since scientists at the National Institute of Allergy and Infectious Diseases (NIAID) mapped out a high-resolution genetic map of Plasmodium falciparum in 1999, scientists have thought about genetically modifying mosquitoes to bar entry of the malarial parasite.
Marcelo Jacobs-Lorena and colleagues have realized that strategy. "What we have shown in this work that will be published is that the mosquito that carries the gene has an advantage if it bites an infected individual," he said. Researchers are hopeful of conducting trials in sub-Saharan Africa in the next five years.
However the next step is to prove that these genetically altered mosquitoes do not trigger a more aggressive form of malaria, or spread to other insects.
"We have to be absolutely sure that any genetically modified mosquito does not cause any harm in the environment or cause unpredictable harm to people that they bite," Jacobs-Lorena agreed. "But I think we are on the way."
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