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Monday, Aug 19, 2019

Keeping a step ahead of parasites

If infection-causing organisms were even half as dumb as the dodo, the world would have been free on infection several decades ago. It was not to be.

columns Updated: Jul 14, 2012 23:37 IST

If infection-causing organisms were even half as dumb as the dodo, the world would have been free on infection several decades ago. It was not to be. These superbugs continue to cock a snook at scientific breakthroughs by evading destruction with an ease that makes scientists lose sleep and the world lose billions in drug discovery research.

Worldwide, attempts have been made so far to eradicate eight infectious diseases, of which only two - smallpox and rinderpest, a viral cattle disease — have been successful. Attempts to stamp out malaria, hookworm, yaws and yellow fever were aborted after spectacular failures, but the world is still struggling to beat back polio and guinea worm disease (dracunculiasis), a disabling parasitic disease that spreads through unsafe drinking water.

After several ups and downs, India has been free of polio for 18 months. Yet the killer infection continues to thrive in Afghanistan, Nigeria and Pakistan and this year, new localized infection was found in three countries that were previously polio-free (Angola, Chad and Democratic Republic of the Congo). Eleven countries had outbreaks due to importations of poliovirus from other countries, which makes it vital to stop infection all across the world. This year, 91 cases have been reported, down from 267 n the same period in 2011. In all, there were 650 polio cases last year.

Five more infectious diseases have been identified as potentially eradicable with current technology by the Carter Center International Task Force for Disease Eradication-measles, mumps, rubella, lymphatic filariasis and cysticercosis.

Among the infections most familiar to us is malaria, which arrives in India with the monsoons and kills 15,000 people annually and makes thousands more ill. More than two-thirds of India’s population lives in a malaria-affected district, of which 117 districts are resistant to chloroquine, the standard first-line treatment for the disease. The states worst hit are Odisha, Jharkhand, West Bengal, Chhattisgarh, Madhya Pradesh and the north-eastern states.

It spreads through the bite of an infected female Anopheles mosquito. There are four types of malarial parasites, of which Plasmodium falciparum and Plasmodium vivax are the most common. Plasmodium falciparum is the more deadly of them all and accounts for 90% of all malarial deaths.

Globally, malaria kills over one million, mostly in children, largely because it can strike the same person several times.

What makes malaria particularly lethal is that the body does not develop protective immunity against re-infection, which allows the parasite to strike repeatedly, reports a study from the University of Yale in this week’s Proceedings of the National Academy of Sciences. Inadequate formation and maintenance of infection-fighting memory T-cells is at the cause of this immune malfunction, which also frustrates efforts to develop effective malaria vaccines.

Malaria causes a highly inflammatory response in infected people that leads to the deadly clinical complications of anaemia and cerebral disease, which causes killer headaches. The Yale research team learned that the parasites produce their own version of a human cytokine, or immune hormone, which directs the inflammatory response when a person is infected. They also discovered that this cytokine, called PMIF, incapacitates the anti-malaria immune response by enusing long-lived memory T-cells are not produced in adequate numbers to combat the infection or to protect from re-infection. Developing specific therapies to protect anti-malarial T-cells from death and improve a person’s immune response to infection and to vaccination is the way forward to eradication.

Till that happens, keeping mosquito-breeding in check is the only doable option. You can do your bit by preventing water from stagnating in your home and surroundings.

First Published: Jul 14, 2012 23:34 IST

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