An atomic-powered plan to end sleeping sickness
By Fred Pearce, Globe Correspondent, 11/12/2002
Many biologists think the idea is ill-advised. The only successful trial of the project cost an estimated $500 per dead fly. But the United Nations is backing it, along with many African governments.
For 12-year-old Joseph Taneba, the blitz is too late. He lay silent and confused in a tiny hut in the grounds of a sleeping sickness clinic in Uganda. Bitten by a tsetse fly while looking after his family's cattle in the bush about a month before, Joseph was now close to death - the victim of an epidemic that will claim 300,000 people in Africa this year.
Sleeping sickness is the disease that modern medicine forgot. It is caused by the trypanosome parasite, which also causes Nagana, a cattle disease that makes livestock farming all but impossible across much of the continent. In Uganda, where millions died of sleeping sickness in an epidemic a century ago, cases of sleeping sickness have doubled in the past two years. Amid the continent's civil wars and economic decline, conventional efforts to contain the disease with pesticides and insect traps are failing.
Enter Arnold Dyck. The booming voice of the former Mennonite lay preacher from Canada rang out across the bush. ''We realize you have a big problem with the tsetse fly here,'' he told hundreds of farmers assembled in the village of Lante, deep in Ethiopia's Rift Valley. ''But there is a solution coming soon. Scientists from your government and the world are going to help you. Very soon you will have healthy cattle and children, and good crops and a happy life.''
Dyck gave up religious preaching to take up science, and now works for the UN's International Atomic Energy Agency in Vienna. He is helping develop a plan to spray the bush in 40 countries with tens of billions of specially reared male tsetse flies made sterile by a quick blast of radiation. The aim is to systematically crowd out the wild, fertile males and cause tsetse populations to crash.
The atomic energy agency, looking for new roles with the end of the Cold War, has adopted this project as part of an expanding mission.
Freeing Africa of the tsetse will, Dyck admits, cost tens of billions of dollars and take several decades. But the plan is backed by most African nations and has received support from several other UN agencies, including the World Health Organization. The trouble is, most independent specialists think it will never work.
Hans Herren, director of the International Centre for Insect Physiology and Ecology in Nairobi, a body backed by the World Bank, said: ''We think it is a crazy idea. There are so many tsetse that you are bound to miss a few. The populations will regenerate and you are back to square one.'' David Rogers, zoology professor at Oxford University, calls it ''a deeply cynical manipulation of the hopes of many Africans.'' The IAEA, he says, is supposed to be on a mission to find uses for nuclear energy, not to save Africa from disease.
Ugandan scientist John Kabayo, who heads the Pan-African Tsetse and Trypanosomosis Eradication Programme, an agency set up by African governments to coordinate strategy, dismisses this: ''The solution to tsetse is within our reach.'' The project may be ambitious, but ''it is not acceptable that we Africans suffer from a disease which can be stopped. If it takes a hundred years, we are going to do it.''
The stakes are high. While sleeping sickness takes its dreadful human toll, the cattle variety of the disease saps the continent's economy. Nagana kills 3 million cattle and costs farmers an estimated $4.5 billion a year. In Lante, Berza Bassa said he has lost 40 cattle, almost his entire herd, to the disease. ''I have no milk for sale and no oxen to plough my fields. I can no longer afford to send my children to school.''
Ethiopia wants to become the first country out of the 40 targeted in the IAEA's plan to eradicate the tsetse fly using sterile insects. Construction began this summer on the continent's largest insect-rearing center, south of Addis Ababa. Ten million captive females flies here will soon be producing two million flies a week. The plan is to sterilize their male offspring by irradiation, and then spray the males from aircraft across the bush. Weekly flights across Ethiopia's Rift Valley, a hotbed of the disease, could begin as early as this winter and continue for at least two years.
Sterile-insect technology has been used before in the Americas to fight the Mediterranean fruit fly and the screwworm. But the tsetse is a much tougher target. There are 22 species across Africa. Each must be targeted individually. And the work must be coordinated, since several species often occupy the same area and each species is ready to move into the ecological niche vacated by another.
Can it succeed? There is one success story. Dyck spent the mid-1990s using sterile insects to eliminate every last tsetse on the Tanzanian island of Zanzibar. It worked, and cattle herds are booming as a result. But critics say it is an unlikely model for success on the mainland of Africa.
The island was chosen, Dyck agrees, because it was an easy target. The flies were all of one species and money was no object. Dyck sprayed around 8 million sterile male flies over the island to eradicate a population of around 10,000 host flies. With a final bill of more than $5 million, that works out at $500 per fly.
That was certainly overkill, designed to be absolutely sure of success. And Dyck admits few records were kept, so it is hard to be sure how much of an overkill. Continuing questions about the ecology of the affected areas and the lifestyle of the tsetse add to the uncertainty. Female tsetse flies appear to mate only once, so mating with a sterilized fly will effectively prevent her from having offspring. But little research has been done into critical issues such as the minimum viable population of tsetse flies or the rate at which they can re-invade an area.
Zanzibar was protected from re-invasion by ocean, and so far the flies have not returned. But mainland Africa has few such natural barriers. So the plan is to protect the areas of bush cleared of tsetse with dense thickets of traps and regular chemical spraying. But critics say no such barrier can be 100 percent effective.
Even Dyck admits: ''There isn't an example of artificial barriers being used successfully.'' He pins his hopes on ''a moving front,'' in which active zones of eradication themselves form the barrier. That, he says, requires ''continuous long-term funding. If you stop, it will go back. You'll be no better off.''
Even if Africa can find the funds for such an operation, critics say too much can go wrong. Hundreds of millions of dollars could be spent clearing a country, only to have the tsetse reinfest and return it to its present state, only much poorer. Tsetse flies respect no borders. Uganda can't eradicate the tsetse until neighboring Congo clears its rebellious borders. Likewise Ethiopia most likely can't succeed while civil war continues in southern Sudan.
Dyck accuses skeptics of being ''fatalistic, resigned to the inevitability of hunger and poverty.'' Africa shouldn't be denied this technology, he says. But Rogers insists it will all end in tears.
''If the IAEA scheme succeeds, there is no doubt the benefits would be enormous,'' he said. ''But there can be no partial success. It either succeeds or fails, with no benefits at all. And the chances of success are vanishingly small.''
This story ran on page C1 of the
Boston Globe on 11/12/2002.
© Copyright 2002 Globe Newspaper Company.