ASIA!

According to the World Health Organisation (WHO), malaria is responsible for nearly 3 million deaths worldwide each year. It remains the most important and widespread tropical disease, and its treatment and control have become more difficult with the spread of drug-resistant strains of parasites and insecticide-resistant strains of mosquito vectors.

So when Mauro Marrelli and Chaoyang Li of Johns Hopkins University claimed they could potentially eliminate all risk of contracting malaria by the creation of a genetically modified (GM) mosquito, it made the front page of almost every reputable journal and newspaper in the world.

Gizela Dasilva lives in East Timor with her three children. Just weeks ago, her son and daughter contracted malaria and during the interview they were still regaining their appetite.

"Their fever began in the middle of the night," Dasilva recalls. "I panicked. I had to rush the kids to a private hospital for a blood test."

Blood tests at private hospitals cost about US$1 each. "That is too expensive for most people here," says Dasilva. For those who can’t afford going to a private hospital, public hospitals offer free tests but have a longer wait.

When I tell her the potential of a new malaria-resistant mosquito being introduced into the wild, she laughs delightedly. "If scientists have made a way to stop malaria that would be great! It would be very good for the people here."

Over 40% of the world's children live in malaria-endemic countries. Each year, approximately 300 to 500 million malaria infections lead to over 1 million deaths, of which over 25% occur in Asian children.

It has been estimated that the population at risk of malaria in Southeast Asia alone is about 1.35 billion out of a total population of 1.6 billion. Myanmar accounts for 60% of the total deaths in the region, followed by India with some 2 million affected every year.

Since Dasilva contracted malaria two years ago, she has taken measures to ensure mosquitoes do not bite her family again.

"The biggest fear of the people here is malaria. After that it’s dengue." Dasilva keeps her family safe under mosquito nets at night and applies mosquito repellents liberally. "Just walking from home to work you can get malaria. Everyone here has had malaria, and some will get infected every year."

I ask if she’s considered taking vaccines but she says, "It is better to use mosquito nets, repellents and clear out stagnant water. It’s not too good to take vaccines all the time because the mosquitoes will just develop a resistance."

Malaria is understood to be both a disease and a cause of poverty. It has significant measurable direct and indirect costs, and has recently been shown to be a major constraint to economic development.

The direct costs of malaria include a combination of private and public expenditures on both prevention and treatment of the disease. In some countries with a heavy malaria burden, the disease may account for as much as 40% of public health expenditure, 30-50% of inpatient admissions, and up to 50% of outpatient visits.

Malaria also hampers children's schooling and social development through both absenteeism and permanent neurological and other damage associated with severe episodes of the disease.

Christopher Curtis is a Professor of Medical Entomology at the London School of Hygiene and Tropical Medicine. Thirty-nine years ago, Dr Curtis published a report that suggested linking a gene with the specific plasmodium that causes the malaria disease. The idea was to stop malaria from infecting the mosquito, which in turn would prevent it from spreading the disease to humans.

There are more than 2,500 known species of mosquitoes worldwide. Out of that, four of the protozoan parasite of the plasmodium genus—P. falciparum, P. vivax, P. ovale, and P. malariae—cause malaria in humans.

The recent findings by Marrelli and Li, however, are of P. berghei, a form of rodent malaria. Their plan was to use this parasite to model the lethal P. falciparum in the laboratory.

I ask Dr Curtis what prevented him from developing a mosquito resistant to the human forms of malaria in 1968. "It was technical problems really," he says. Before a mosquito can be made immune to the plasmodium in question, the gene that can prevent the mosquito from getting infected has to be identified. "We are a long way from saying we can do it with humans because they are experimenting with a malaria that is a different plasmodium, and it certainly is a long way from being practised in the field."

Between 1950 and 1969, the world thought it would see the end of malaria when WHO implemented its control and eradication strategy. The number of malaria cases fell from an estimated 100-115 million to a stable 3.5 million, but bounced back to 7.2 million in the late 70s. The good news is that some countries such as the Maldives managed to eradicate malaria altogether, but North Korea, which had malaria-free status, reported an outbreak in its states bordering South Korea.

In the idea put forward by Marrelli and Li, a mosquito is made immune to malaria by tweaking the genes that stimulate its immune system. That works but imposes a burden on the animal’s immune system as materials and energy have to be diverted to the boosted immune system. In practice, such insects are worse off than they would be without the modified gene.

Rohit Naniwadekar is a wildlife biologist and postgraduate student studying in Mysore, Karnataka, India. He was working with the Nature Conservation Foundation in monitoring hornbill populations in Pakke Tiger Reservein western Arunachal Pradesh, North East India, when he contracted malaria for the first time.

Two months later, his malaria relapsed and again seven months later. After the third lapse he began taking an anti-malaria drug called Mefloquine, a single pill of which costs Rs 55 (US$1.27), a price most rural Indians are unable to afford.

Naniwadekar is sceptical about the implementation and success of a project to introduce GM mosquitoes into the wild.

"I think more effort from the government would be enough. Introducing another breed of mosquito into a system could be really dangerous. For all you know the breed might just become a vector for another pathogen."

Dr Curtis agrees: "Better than rendering a mosquito harmless, it’s better to get rid of them altogether."

Naniwadekar also believes introductions of GM mosquitoes in natural systems can have undesirable side effects. "You cannot eliminate them without eliminating lots of other native insect fauna, which is another area of concern."

Dr Curtis doubts there would be any ecological impact of eradicating mosquitoes. "It's pretty unlikely and most high densities are created by human activity so I see it more as cleaning up our own mess."

In the two areas where Naniwadekar carried out his work, Pakke and Namdapha, the incidence of malaria is high and often fatal. "I have seen lots of people die because of malaria. Partly owing to insufficient facilities at the health centre in the village, and also because of lack of awareness by the people."

While there have been some initiatives carried out by the state in these regions to combat malaria incidences, Naniwadekar feels these efforts are not sustained to effect long-term changes.

"The hospital at Pakke is in bad shape, and private doctors can charge as much as Rs 150 (US$3.47)." As a result, villagers consult traditional healers that are known to cure diseases like malaria and jaundice though a customary procedure. "I have seen kids dying," he says. "It’s a sad sight."

The late author and entomologist Andrew Spielman described the mosquito as "our most persistent and deadly foe." As hopeful as the news seemed when it broke in March, the reality of eliminating mosquitoes is going to be far more complex. While some like Dasilva look forward to embracing a new type of mosquito that will create an environment safe for her children to play in, other more informed individuals such as Naniwadekar question the long-term effects of such experimental techniques that have only been tested in laboratories in temperate countries.

The UN believes that private sectors can also play a fundamental role in trying to eradicate the incidence of malaria. Local and international businesses operating in malarious areas are learning that support for malaria control not only reduces levels of absenteeism and lost productivity, but also boosts labour, community and government relations.

It believes that in the long term, the improved productivity from private-sector support for malaria control will encourage market expansion, boost household spending, and change consumption patterns, benefiting of many companies, especially those producing consumer goods or developing local tourist industries.

"They have been saying a vaccine will be developed in five years for the past 25 years," quips Dr Curtis.

Hopefully that will give governments some time to bite back.

 

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