Biting the fly
Eradicating one of Africa's most pernicious insect pests
by Peter Rickwood, IAEA Division of Public Information
ARBA MINCH - Africa’s Great Rift Valley, green and lush as it sweeps majestically through southwestern Ethiopia, is eerily devoid of settlement across its fertile plain.
In the hills, above an unseen boundary, gojos, circular thatched houses, smoke drifting from cooking fires, bloom in profusion.
Herds of cattle, fields of maize, and other crops, in some places extending almost to the hilltops, surround them.
In ten years, or less, experts reckon, much of this land will be irreparably damaged from over-grazing and cultivation.
It is academic to the farmers who’ve retreated to these packed hills: they are trying to escape the advance of a small dun colored biting insect -- the tsetse fly, and nagana the mostly lethal disease it is spreading among their livestock.
Once considered under control, the tsetse fly and trypanosomes - single cell parasites of the blood and nervous system for which it is host - are on a runaway course.
To the south and west of Ethiopia the bite of the fly is spreading one of nature’s cruelest diseases, sleeping sickness. It puts 60 million people at risk and is more widespread than severe epidemics of the 1930’s.
And across nearly 9 million sq. km. of sub-Saharan Africa, an area almost as big as the United States, nagana keeps a door locked that prevents the peoples of 32 of the world’s 42 poorest countries escaping poverty. In all, 37 African countries are infested by the tsetse fly.
Tsetse infested areas in Africa (red area); Approximate cattle distribution (white area)
"It is no accident that the concentration of much of the world's most acute poverty is in regions of sub-Saharan Africa infested with the tsetse fly," says Quian Jihui, Deputy Director General of the International Atomic Energy Agency (IAEA.)
The Vienna based UN organization is providing most of the technical support in a bid to eradicate the tsetse fly, the only vector for nagana and sleeping sickness, whose removal would extinguish the disease.
Until now, experts say, the issue has received little attention largely because it is a rural problem and a disease of the poor.
But in this region of Ethiopia, scientists from the national government, local government officials, farmers and school children are marshaling their resources to stamp out the tsetse forever.
It will be the first major step in a campaign, launched in Ouagadougou, Burkina Fasso, in October 2001, by the Organization of African Unity (OAU), to free Africa from the bite of the tsetse.
|Eradicating Flies - Ending Poverty
The Burkina Fasso launch of the Pan African Tsetse and Trypanosomosis Eradication Campaign (PATTEC) begins fulfilling the declaration by African heads of state, meeting in Lome, in 2000, that tsetse eradication is not only a viable means of controlling nagana and sleeping sicknes, but a key to Africa’s recovery.
"Africa's most viable contribution to her expanding population and to the rest of the world in the new millennium is increased agricultural production. The first step towards the development and realization of this option is the removal of the trypanosomosis constraint," the leaders agreed at the Lome OAU summit.
Africa has the ability to free itself of the tsetse fly, says the IAEA’s Deputy Director General Quian "The only thing lacking is financial support."
"There is a false perception Africa has unique burdens that cannot be overcome -- the tsetse is an example," said Mr Qian. "African politicians now see that it can be eradicated and Africa is showing the world it can solve its own problems."
"The world is committed to halving the number of undernourished people by 2015", said Mr Qian, "but without addressing the root causes for low agricultural productivity all other efforts will fail."
In fact in Sub-Saharan Africa the average amount of food production per person has declined in the last 40 years, says a report delivered to UN Secretary General Kofi Anan, at a meeting of the UN Economic and Social Council, in Geneva, in 2001.
Allowing more African farmers to own livestock, would have a profound impact on hunger and poverty in the continent, says Mr Qian. "But that cannot be achieved without elimination of the tsetse fly."
"This is a priority issue. the first logical step to seriously address poverty reduction. In order to combat poverty at its primary stage, we have to eradicate hunger through helping the poorest to achieve increased agricultural productivity. We have to be realistic and maintain a sharp focus".
At the centre of the muddy meeting place in the village of Chalba, beneath the spreading branches of a Warka tree, the farmers of this rich cropland on the banks of Lake Abaya, gathered today, make a plea.
"In the name of God don’t stop this program," says an elder, translating from the local language Gamunia, into Amharic, the official language of Ethiopia, for the sake of visitors.
Around Chalba, where child herders drive invading troops of baboons out of the fields, and a lion ambles through the bush, black and blue tent shaped fabric traps dot the landscape.
Hundreds of the insecticide impregnated traps have been set by village associations of farmers, baited with fermented cow urine, to lure the tsetse flies. Drugs - and insecticide, applied to the backs of cattle also offer protection.
"We don't intend to do this forever," says Assefa Mebrate, of the Ethiopian Science and Technology Commission, who heads the national program.
Once the present tsetse population is reduced, waves of male tsetse flies, factory reared and sterilized by x-ray strength gamma rays, will be released.
Although they cannot reproduce, their ardour is not dampened, and the result of their couplings is fruitless.
One plus one equals zero, says a home-made sign in a regional control office in Ethiopia. It best expresses the method known as the sterile insect technique. Its promise is that will push the tsetse into extinction.
In the last century the mass slaughter of game, destruction of bush, and spraying of DDT, were strategies in an unsuccessful war against the fly. Piecemeal measures that followed have been ineffective and not economical, says Assefa.
Ethiopia has chosen a 25,000 sq. km. region around Arba Minch, confined by mountains and lakes, as a proving ground to develop its ability to use the sterile insect technique. It builds on the historic success of the method in eradicating the tsetse fly from the East African island of Zanzibar.
In September 1996, the last fertile tsetse fly was caught on the island after a joint program between the government of Tanzania and the United Nations International Atomic Energy Agency (IAEA), supported by the UN Food and Agriculture Organization program (FAO). The International Fund for Agricultural Development (IFAD), Belgium Canada, China, Sweden, the UK and the USA, also lent support.
IAEA experts, supporting the Ethiopia program, say that the sterile insect technique, unlike insecticide programs that aren’t selective, is environmentally friendly.
It’s a standard tool in the successful control of the Mediterranean fruit fly in Chile, Mexico and California, the melon fly in Japan, and it eliminated the New World Screw worm in the United States, Mexico, Central America, and Libya.
In the hills behind Arbor Minch, near the town of Sodo, which straggles down an elevated flank of the Rift valley, Mt. Damot has been ploughed to a hair's breadth of its summit.
"Five years ago there was no cultivation on it," says Berisha Kapitano, a government veterinarian, gazing at the tonsured hillside from the main road below.
"The farmers on Mt. Damot don’t practise any soil conservation. In a few years time it will no longer support them. Then where will they go?"
As if a portent, heavy trucks loaded with maize, rumble along the road on their way to relieve drought stricken areas where crops have failed.
In a country of nearly 65 million people, about 85 per cent of Ethiopians are farmers.
The simple explanation for the cultivation of Mt. Damot, and the pressure on the highlands here, is the farmers’ dependency on cattle.
Cattle support a trinity of survival in Africa, that is about 10,000 years old, providing food, traction and fertilizer.
Without their draught power, farmers till by hand, carry produce to market on their backs, and forego milk, meat, and manure. Nearly 90 per cent of crops grown in Sub-Saharan Africa are produced without animal power. The lost potential costs Africa nearly $4.5 billion every year, the FAO says.
|Cattle - Africa's Lifeblood
The most profound expression of Africa’s dependency on cattle is illustrated by the people of the Surma tribe, in Ethiopia’s lower Omo valley, near the Kenya-Sudan border, whose diet is mostly milk and blood taken from living cattle.
Wealth and cattle are interdependent: 19th century European explorers reported bounteous regions of east Africa with large herds of cattle, grazing side by side with wild animals.
In the village of Makela , on the eastern slopes of the Rift Valley, the living arrangements for the family of Maseret Kenen are normal: his family occupy one side of their large gojo, on the other side of a flimsy wall, live their cattle.
At the turn of the century, rinderpest, a distemper-like disease introduced with Europeans, swept across Africa killing millions of cattle. Grazing lands became overgrown with bush, and the tsetse fly, previously not as widespread, found conditions in which to flourish.
Only the poorest breeds of cattle --- maintained by drugs to which nagana has become resistant -- can survive in tsetse infested regions. A strong animal may be able to cope with the disease but cows abort, bulls become infertile and their growth is slowed.
Cross breeds – whose milk production is nine times that of the characteristically hump backed native zebu, cannot survive the tsetse fly.
African farmers explain that a reason for keeping large herds of zebus, a feature of many regions, is insurance against sickness, when they would rather have smaller, and more manageable herds of cross breeds.
Nagana and sleeping sickness are insurmountable obstacles to
farmers working land, no matter how fertile, where they are epidemic: as a consequence millions are condemned to the futility of cultivating poor soils while fertile land lies fallow.
These are key elements in a spiral of poverty and hopelessness that traps much of rural Africa.
A Rising Tide
The tsetse are rising like a tide in Ethiopia -- possibly in response to a warming
climate. Their presence has been a fact of life in the lowlands, but farmers had been relatively safe from the fly by occupying the highlands.
As a result 90 per cent of Ethiopians and 80 per cent of their livestock occupy the highlands, which take up 55 per cent of the land mass.
How fast that refuge is shrinking is made clear on the eastern side of the Rift valley from Arba Minch, where Cheha was the centre of a flourishing agricultural district.of 50,000 just 13 years ago.
Today it is abandoned, says Solomon Mekuria, a government veterinarian based in Awasa, administrative centre for the region Cheha occupies.
Out of 77 rural districts in the region 60 have fallen to the tsetse fly, says Solomon, the son of a farmer. "This was a good production area growing different fruits, coffee, and cereal crops. Nowadays only 10 per cent of it is cultivated."
Tractors? Farmers, who can barely afford shoes can’t afford tractors, said Solomon, and even if they could, steep hillsides make their use impractical.
"Having all these problems we can’t go anywhere,"
In the Rift valley and elsewhere in Africa, the expansion of the fly's range and the exodus of farmers from their land offers no choice but to finally break the cycle.
Any step towards trying to live with the tsetse is a backward move, a group of experts meeting in Vienna, early in 2001 concluded.
Nearly 45,000 cases of sleeping sickness were reported in 1999.
However, only three to four million of the over 60 million people at risk are being screened and the number of cases may be as high as 500,000, the World Health Organization (WHO) reports.
In the absence of effective screening “most people with sleeping sickness die before they can ever be diagnosed,” WHO says. Early diagnosis offers a relatively high chance of cure.
There are two distinct forms of sleeping sickness: in central and West Africa, the tsetse fly carries the gambiense strain, and in southern and east Africa it transmits the rhodesiense trypanosome.
Rhodesiense causes an acute infection that emerges after a few weeks and is easier to detect . Gambiense can infect a person for months, or years, without symptoms while parasites multiply in the bloodstream and lymphatic system.
When they cross the blood-brain barrier and invade the central nervous system, there are neurological changes that are often irreversible.
Treatment at this stage must follow the same path and is radical: Melarsoprol, an arsenic and glycol compound may cause up to ten per cent fatalities; Eflornithine, a modern alternative, requires a strict and complex regimen of treatment.
The current sleeping sickness epidemic in Africa began in the mid-1970s, WHO says. Systematic screening between 1940 and 1960 resulted in the number of cases of sleeping sickness declining to almost zero.
In some provinces in the Democratic Republic of Congo, gambiense is the leading cause of death, taking more lives than HIV/AIDS, WHO says.
In the region of conflict between southern Sudan and northern Angola, that includes the Democratic Republic of Congo, it is estimated that half the population is infected.
Human trypanasomes can be carried by animals.
Many insects invest their security in numbers, producing huge amounts of offspring, some of which will survive. The tsetse fly, however, carries its young to their full larval development before giving birth. The larvae rapidly pupate and adults emerge in about a month.
The female mates in the first days of life, seldom more than once, and stores sperm in pockets in her abdomen that she releases each time she ovulates. In a life span of three months she produces on average three to six offspring.
While the female is feeding, digesting, resting and producing larvae, the male is actively trying to mate, a busy pursuit that reduces his life span to about four weeks.
Unlike most insects that break down their food for sugar, the tsetse fly’s metabolism requires protein for nutrition. Proportionate to its body size it has to ingest a massive amount of blood in order to meet its food needs.
As well as having an unusual chemistry it is also a poor flyer enduring only about five minutes on the wing before its energy falls off. It cannot fly long distances.
The origin of the relationship between the tetse fly and trypansome parasites is not clear. The fly becomes the host for the parasite after feeding on the blood of an infected animal, or human.
After it is taken up by the fly, the cycle of the parasite in the tsetse takes 12 to 21 days before it can enter a new host.
Less than 90 per cent of tsetse flies carry the parasite and the percentage can be as low as one to two per cent, yet even small numbers of infected flies are know to be efficient vectors.
Frequently parasites block the mouth parts of the fly, reducing the amount of blood it can take up, forcing it to feed more often, increasing the parasites’ chance of reaching more cattle and humans.
Because of its poor mobility, parasitic infections caused by the tsetse are usually concentrated in small areas.
There are about 30 species of tsetse fly, divided into three major groups, savannah, riverine and rainforest.
The key to their elimination, says Arnold Dyck, a Canadian entomologist, who was director of the succcesful Zanzibar project, is simply exploitation of the male’s natural promiscuity. Males mate with more than one female partner.
Sokoine Village – The calf has just died and rigor mortis is setting in. Its small corpse lies inconspicuously on the dusty ground. Cause of death: probably nagana, perhaps complicated by a tick born disease.
Lembile Roketa, a Masai cattle owner is familiar with this scene. He says he’s lost hundreds of cattle to the tsetse.
The deaths usually occur during the dry season when a sickened cow is unable to cope with increased stress, says Peter Masungwa, municipal livestock officer in nearby Morogoro.
"Nagana is common in this district, especially where there’s bush," he says. The cattle are small and scrawny zebu, in large herds. Milk yields are low and the Masai are poor.
In July 2001 agricultural officials from Tanzania, Uganda, Ethiopia and Kenya, meeting together, agreed that the tsetse problem was so acute shock therapy was needed, says Solomon Haile Mariam.
Solomon, a scientist in the OAU’s Inter African Bureau of Animal Resources (IBAR) project office, says that nagana and sleeping sickness has reached crisis proportions.
"This has been getting worse and worse during the past two decades. What has contributed to the disease is the insecurity and the conflict problems in central and east Africa."
In the north east of Uganda the local hospital that treats sleeping sickness is full with acute cases, he said.
In north western Kenya there has been an invasion of tsetse flies mirroring events in Ethiopia. "There is practically no way of staying in that area with animals, people are absolutely poor."
Refugees from conflict are crossing borders without surveillance, government delivered veterinarian systems have collapsed.
Meanwhile farmers are trying to fend for themselves using sub standard drugs on their cattle against nagana , or reducing the dosage to save cost, Solomon said.
The result is the spread of sleeping sickness and Nagana.
"Of course if you remove the tsetse fly it removes the cause of the disease and poverty alleviation will result," Solomon said.
"But I don’t believe African governments will be able to find adequate resources to meet the budget for the first phase of elimination."
"We are counting on international donors. If debt relief could be met and money switched to tsetse eradication I think most governments would support the idea."
In the successful war against the tsetse fly in Zanzibar, the Jozani Forest, a national park and the only remnant of the island’s original forest, was a critical target. The 25 sq. km forest on the east African island, researchers determined, was a reservoir for tsetse flies.
When tsetse control began in the forest, a refuge for bush babies, among other rare species, Saleh Kombo Khiari, director of the Josani Environmental Conservation Association, became alarmed.
Traps that had been set to reduce the tsetse population prior to the release of sterile males caught so many other insects he feared there would be a long term impact.
But five years after the last tsetse fly was seen, Saleh said that there is no evidence that eradication of the tsetse fly has had a negative impact on the forest.
Its community of Red Colobus monkeys has grown to 700 from 500 in the five year period and concern that farmers who previously shunned the forest would start to graze their cattle in it have proven unfounded.
There is no evidence that tstse are "key-species", whose disappearance from an ecosystem would threaten its identity, or function, says Udo Feldmann, an IAEA entomologist, who is a world authority on tsetse and their control.
However, it is a fact that tsetse and trypanosomes affect land use and its cover by crowding livestock and people into tsetse free and environmentally vulnerable areas, he said.
Elimination of the tsetse, however, requires knowledge of land use patterns, thorough planning and strict monitoring of how best to make use of resources that are available.
To Market to Market
Abdullah Khalfan is talking on his mobile telephone, under the shining zinc sheet roof he has erected over the freshly painted white dairy produce stall in the bustling market in Zanzibar’s historic Stone Town.
He's just finished serving Rahma Riyamy, who is buying milk for her family. It's not pasteurized and she'll scald it when she gets home. "I buy milk every day, sometimes we use it for the children. I like to make desserts from it."
"No it wasn't so easy to get milk before, but the market is improving, it has a good selection."
From goat to local beef, milk and yoghurt, the results of ridding Zanzibar of the tsetse fly are plain to see in the market stalls.
Abdullah sells on average 200 litres of milk every day, most of it for consumption by children, he says. Some of the milk is from his own herd of 18 mixed breed cows that he keeps on his small farm at the edge of town.
Mixed breeds produce more milk, are bigger and stronger than the native zebu. But they couldn’t survive nagana. Zebus produce one to three litres of milk a day compared to seven to 10 litres for mixed breeds.
"Of course getting rid of the tsetse fly made a difference," says Abdullah, who bought his first cow, while there was still tsetse, in 1994 after working as a merchant seaman. "There weren’t so many cows before. I’d like to add maybe 40, or 50. When there was tsetse it didn’t make any sense."
If one of his cows gives birth to a bull calf Abdullah says that he always gives it away, but he jealously hordes the manure, that his cows produce.
Post tsetse dairy farming practice in Zanzibar, is to bring feed to cows instead of grazing them on pasture. And there’s nothing that this new generation of healthy cows produces that isn’t of value.
Behind the cow pen and paddock shaded by spreading mango and rain trees Abdulla grows a variety of grasses to feed his cows.
"I have a good life, I like this business. We are all living better, I would even advise my daughter (four years old) to go into dairy farming."
September 2001 was the fifth anniversary of the elimination of the tsetse on Zanzibar.
"We broke the yoke of the tsetse fly on Zanzibar," says Kassim Juma, commissioner for livestock on the island.
"The Zanzibar example is seen as a model for most sub-Saharan countries. It is not true that you are exposing land to degradation when you eradicate the tsetse."
"We also realise that livestock can play a very important role in reducing poverty."
In Mungoni village, two year old Mohamed Mohamed is crying over the milk he's just spilled. It’s goat's milk and his mother and other women in this community close to the Indian ocean are the owners of large Saanen and Tonnerburg goats that they’ve just milked.
This was a no goat zone while the tsetse fly proliferated. The women’s goats have been donated by a non governmental organization under a scheme which requires them to give the offspring of their goats to other recipients.
Their children benefit from a new protein source. The government operates a similar and successful cattle artificial insemination program that is distributing cross breed cattle throughout the island. Each first born heifer is given to another farmer.
The value of livestock production to the Zanzibar economy has almost tripled, since the eradication of the tsetse says a report commissioned by the IAEA undertaken by the department of agricultural economics, at Sokoine University, in Morogoro, Tanzania.
There is a mood of optimism entering agriculture in Zanzibar. Young men are becoming ploughmen, cattle manure is a valuable commodity, the demand for cows exceeds their supply.
As well as Ethiopia, Mali, Botswana and Kenya are developing tsetse eradication programs.
"The dream is to do this for all of Africa," says the IAEA’s Arnold Dyck. "But if we hadn’t had success in Zanzibar the dream would have died."