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The story of the real sting

Far away from hidden TV cameras, mutant monsters are quietly biting into the health of the nation. Sanchita Sharma provides an insight into the mosquito menace.

india Updated: Sep 16, 2007 05:16 IST
Sanchita Sharma

Seven-month-old Benji Lhato’s (name changed) body burns with fever as he lies in a paediatric intensive care unit where his mother Sana rushed him two days ago. The child has been diagnosed with P falciparum malaria, which accounts for 90 per cent of malarial deaths.

Until a decade ago, P falciparum infection accounted for 30 per cent of malaria cases in India and was limited to the Northeast, Orissa, West Bengal and Jharkhand. Today, the brain strain of the disease is reported from across the country and is responsible for 60 per cent of all malaria infections.

P falciparum malaria is more dangerous and often requires hospitalisation,” says Dr Anupam Sibal, director, hospital services, Indraprastha Apollo Hospital. “Until five years ago, most patients came either from endemic areas such as the Northeast and Orissa, or had recently travelled there. Now, people who have not stepped out of town are also getting infected, showing there is localised transmission,” he adds.

Formidable foe
The mosquito remains a bitter enemy. Malaria is still widely prevalent in most of the tropical world, affecting 500 million people and killing one million every year. In humans, infection is caused by four different species of the Plasmodium genus: P falciparum, P malariae, P vivax, and P ovale. Of these, P falciparum is the most dangerous as it affects the brain and is the one most likely to cause death.

The bad news: the pest has become resistant to anti-malarial drugs such as chloroquine, insecticide-treated mosquito nets, DDT and other mosquito vector control measures that are used to reduce the impact of malaria.

The resistance to chloroquine has increased from 30 per cent before 1996 to 91 per cent in 2000-2001, according to studies by the Indian Institute of Science (IISc), Bangalore, and the All India Institute of Medical Sciences (AIIMS), Delhi. “We need to redefine chloroquine therapy in India. A single drug no longer works,” says Govindrajan Padmanabhan, scientist emeritus at IISc.

Scientists at the IISc have identified a genetically mutant malaria parasite that is not affected by chloroquine. Until now, the mutation had not been reported outside South America.

But there is hope. Padmanabhan’s team has found that curcumin, a component of turmeric, can reduce the number of chloroquine-resistant parasites.

Officials working on the National Vector Borne Disease Control Programme (NVBDCP) say the department is already using alternatives to chloroquine, though in limited areas. “The artesunate and sulphadoxinepyre-methamine combination therapy has been introduced,” says an NVBDCP director.

Nuking the pest
Having identified malaria as one of the biggest health threats to humanity, along with tuberculosis and HIV/AIDS, scientists at the UN have decided to nuke mosquitoes.

Their grand plan: to expose the killer mosquito radiation to sterilise it so that the female produces unfertilised eggs. Called Sterile Insect Technique (SIT), this method of mosquito annihilation is being developed by UN’s International Atomic Energy Agency (IAEA).

“In the past, the IAEA has used this biological control technique to wipe out the tsetse fly, which transmits the fatal sleeping sickness, from the island of Zanzibar. El Salvador, too, has successfully used SIT to eradicate the malaria mosquito from parts of the country,” says Dr Alan Robinson, an entomologist with the IAEA.

“The malaria parasite undergoes developmental changes in humans and in the mosquito vector that transmit the parasite,” says Prof Nirbhay Kumar, department of molecular microbiology and immunology, Malaria Research Institute. “This ensures continuous genetic evolution of the parasite and makes it resistant to drugs,” he adds. Prof Kumar, who has worked at the Malaria Research Institute at Johns Hopkins University, US, for over 20 years, is in the final stages of developing a vaccine that makes it impossible for the malaria parasite to infect humans.

Kumar’s colleagues at the Malaria Research Institute are also developing genetically-modified mosquitoes that cannot infect people with malaria. Besides this, scientists at the New Delhi-based International Centre for Genetic Engineering and Biotechnology have developed a vaccine for trials with its partner, the Hyderabad-based Bharat Biotech International.

Caught in a time warp
Since mosquitoes exist in different ecotypes urban, forest, rural and coastal strains the patterns of disease transmission differs with the change in weather and lifestyle. Hence, control programmes also need to differ.

As of now, NVBDCP has adopted a three-pronged strategy that includes detection and treatment, spraying of insecticides in high-risk areas, use of insecticide-treated bed nets, introduction of larvivorous fish such as guppy in ponds, and awareness campaigns.
Scientists blame this one-size-fits-all approach for the recurring outbreaks. “NVBDCP’s generalised approach, which worked in the 1940s and 1950s because of the initial effectiveness of DDT, no longer helps,” says Sibal.

That might be so. But since DDT is cost-effective, its use is likely to continue for a long time to come. The battle against malaria will rage on.