Magazine article Geographical

Swatting Flies from Space

Magazine article Geographical

Swatting Flies from Space

Article excerpt

Each year, across Africa, sleeping sickness kills tens of thousands of people and billions of pounds worth of lifestock. Geordie Torr reports on an ambitious attempt to use satellite technology to control the flies that spread the disease

It all starts with a bite from a fly--a pretty big fly, up to a centimetre and a half in length, inserts its proboscis and starts sucking up blood. The bite itself is, unsurprisingly, rather painful, but if the bitee is unlucky, things are about to get a lot worse.

Because this particular fly is carrying a parasite, a protozoan known as a trypanosome, which heads down the fly's proboscis and into its new host. There it begins to reproduce, its offspring quickly spreading around the host's bloodstream.

The symptoms, when they start, are relatively benign at first--fever, headaches, joint pain, itching--but then, as the parasites enter the lymphatic system, the lymph nodes swell, often to tremendous size. The symptoms begin to escalate--anaemia, endocrine, cardiac and kidney dysfunction--and eventually, possibly months or even years later, the parasites cross the blood-brain barrier and all hell breaks loose.

As they invade the central nervous system, the host becomes confused and loses co-ordination. Sleep cycles are disrupted, alternating between manic periods and bouts of fatigue. Without treatment, mental deterioration eventually leads to coma and death.

This is 'sleeping sickness', human African trypanosomiasis (HAT), the scourge of sub-Saharan Africa. The fly in question--the tsetse--has an extensive range that brings it into contact with large numbers of people. About 8.5 million square kilometres in 37 sub-Saharan Africa countries are infested with tsetse, resulting in 70 million people with exposure risk,' says Joseph Messina, a professor of geography at Michigan State University (MSU), who's leading an ambitious new project using satellites to track the flies and direct control efforts to areas where they'll be most effective.


Attempts to control the flies and hence reduce the prevalence of sleeping sickness began in the early 20th century--first by removing the fly's preferred habitat, then by spraying DDT and finally by the use of traps and targets. And for a while, they seemed to be working. 'By the mid-1960s, HAT appeared to be under control,' Messina says. 'However, during the mid-1970s, it re-emerged due to a breakdown in surveillance and control programmes, compounded by drug resistance, genetic changes in the parasite, civil conflict, changes in land use and cover, and climatic changes. And during the mid-1990s, it was estimated that at least 300,000 cases were underreported due to a lack of surveillance capabilities, diagnostic expertise and access to health care.' Today, it's thought that fatalities caused by sleeping sickness each year number in the tens of thousands.

To make things worse, the disease isn't restricted to humans; the parasites also infect wildlife and livestock. Animal African trypanosomiasis is considered to be one of the most damaging diseases, economically, in sub-Saharan Africa, reducing livestock productivity by 20-40 per cent in tsetse areas,' Messina explains. The value of the lost livestock is estimated to amount to some US$4.5billion a year.

The key to controlling the disease lies in controlling the flies, but no-one has yet figured out how to do that effectively. They've been trying to control the tsetse for more than 100 years,' Messina says, 'but nothing has worked on a large-scale basis.'

Messina's project emerged from a series of MSU-sponsored meetings in Michigan and Kenya to explore seemingly intractable problems in health and the environment through the lens of interdisciplinary sciences. 'It was during the Nairobi meeting in February 2006 that the tsetse "problem" was defined.' Messina explains. 'Dr Joseph Maitima, a Kenyan, and I largely worked out the core of what has become our existing project. …

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