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Last Updated: Thursday, 26 August, 2004, 15:14 GMT 16:14 UK
Kenya targets tsetse fly with radiation
Tsetse fly
The male tsetse fly undergoes the radiation treatment
Kenya is set to begin a major new effort to eradicate sleeping sickness-carrying tsetse flies, using the controversial Sterile Insect Technique (SIT).

Two years of ongoing negotiations recently ended with Kenya's Trypanosomiasis Research Institute winning the contract to import irradiating equipment from the International Atomic Energy Agency.

SIT involves blasting male flies with radiation to render them sterile. Although it is both expensive and potentially hazardous, Trypanosomiasis Research Institute director Joseph Ndongu told BBC World Service's One Planet programme that it had the potential to be highly beneficial.

"The risk is worth taking, especially when you consider that this is a scourge that for centuries has put so many people at risk, has caused such loss of life, so much loss of productivity," he said.

"Then it is a worthy risk to take."

Silent killer

SIT has already worked in Zanzibar on tsetse flies, and was also used to successfully eradicate the New World screwworm in Libya, brought into the country in the early 1990s in a batch of sheep.

Kenya is keen to begin using it because the sleeping sickness that the tsetse flies carry can be devastating to both people and livestock.

The flies - endemic to 36 African countries - carry tiny single-celled parasites called trypanosomes. When it bites, the trypanosomes invade the blood of mammals.

In humans, this can cause debilitating anaemia. More than 500,000 Africans are estimated to be infected.

It is called the silent killer because its victims are mostly from rural populations where medical screening is rare and cause of death often goes unrecorded.

Sleeping sickness graves
Sleeping sickness is known as Africa's silent killer
Meanwhile, 10 million square km of sub-Saharan Africa's best pasture and agricultural land is infected by the fly.

"Wherever the tsetse fly is, you get livestock disease," Mr Ndongu said.

SIT works by blasting male flies with rays from radioactive material.

Because the only cells continually dividing in an adult male fly are its sperm, the fly is unharmed - but the radiation breaks the chromosomes in the sperm, making it genetically sterile and unable to reproduce.

However, once a female fly has mated, she assumes she is fertile and will not mate again for the rest of her lifespan. As a result, the population of flies can potentially fall dramatically.

But there are serious doubts growing over whether the technique is effective enough to justify the time and expense.

It requires massive resources, both in terms of cost and co-ordination. And these fears are added to by the risk of having the radioactive sources needed to sterilise the flies in countries where the money to maintain the equipment may not be readily available.

Furthermore, in Kenya's case, there are problems securing a supply of uncontaminated blood to feed the flies before they are released.

As a result, far too few tsetse flies are surviving to have much of an impact when released.

"It's not an easy task," admitted the Insectaries manager at the Trypanosomiasis Research Institute, George Terenketti.

"You cannot do this today and get results tomorrow. The process is long. If you feed the flies blood which has got bacteria or a fungus in it, you will not see any of them tomorrow."

However, Mr Ndongu stressed that these fears had been taken into account, and the Trypanosomiasis Research Institute would not have won the contract if it did not believe these problems could be overcome.

"We had to convince all the stakeholders that we were worthy of acquiring, and taking responsibility for, the equipment," he said.

Gene science targets sleeping sickness
03 Jun 03  |  Science/Nature
New drive to root out deadly fly
18 Feb 02  |  Africa


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