We may have to kill off the deadly mosquito

LUGNANO is a municipality in Italy’s Umbrian region. Archaeologists, working in La Necropoli dei Bambini (the Cemetery of the Babies) there this summer, found the skull of a child with a stone in its mouth, writes Richard Collins.

According to David Soren, who oversaw the excavation, this is a most unusual find. The Roman burial site, which dates to the 5th century AD, was used only for the interment of children; over 50 remains have been found there to date. The child with the stone, aged about 10 when it died, was older than the others found there. But why was the body treated in this strange way?

The youngster suffered from a tooth abscess, a side-effect of malaria, after an epidemic of this deadly disease. A stone in the mouth, according to the mindset of the time, would prevent the child from rising from the dead and trap the evil spirit within the body. The hands and feet of a three-year-old girl had been weighed down with stones. Birds’ talons and toads’ bones, found in other graves, probably had a similar purpose.

Witchcraft couldn’t conquer malaria, nor has modern medicine succeeded in doing so. This Horseman of the Apocalypse infects over 400m people annually, killing half a million children.

But, now there’s a glimmer of hope, thanks to ground-breaking research carried out in London.

People fear sharks, big cats, and poisonous snakes, but these are far from being the most dangerous wild creatures. That distinction goes to a humble insect, the anopheles mosquito.

About 40 of the 460 species in the anopheles genus play host to the malaria parasite, which multiplies within their bodies. A female mosquito needs blood to form eggs. She picks up the parasite through biting an infected person and passes it on to her next blood victim. When the proportion of malaria-carrying people in a community reaches a certain threshold, the disease becomes established.

We have anopheles mosquitoes in Ireland. Soldiers, infected during the Crimean War, sparked a malaria outbreak, when they returned to Cork between 1854 and 1860.

The disease petered out, because, presumably, the parasite failed to create a sufficiently large pool of infected people to sustain it.

Now gene technology has come to the rescue.

A team, led by Dr Andrea Crisanti, at Imperial College London, has engineered a piece of genetic material capable of rendering a female mosquito unable to lay eggs. Using gene-editing cut-and-paste techniques, they inserted the patch into the DNA of mosquitoes in the laboratory. The females continued to mate normally, but the modified gene prevented them from forming eggs.

Playing God is dangerous, but, if deemed safe to do so, such generically-altered mosquitoes could be released into the wild. Then, normal females, mated by modified males, would no longer produce fertile daughters. Their sons and grandsons, however, would inherit the disabling gene. With their segment of the population increasing exponentially, they would continue infecting females in the wild, until the mosquito population collapsed.

Taking such a step is daunting. The long-term ecological consequences of rendering an insect species virtually extinct are unknown. However, malaria is such a terrible killer, that scientists have no choice but to act, even with the risk of releasing evil spirits.

- ‘Vampire burial reveals efforts to prevent child’s return from the grave’, University of Arizona report, October, 2018.