• English
  • العربية
  • 中文
  • Français
  • Русский
  • Español

You are here

Suppressing Tsetse Flies to Improve Lives

Dagim Dagne ploughs his father's field in Ethiopia's Southern Rift Valley. (Photo: P. Pavlicek/IAEA)

In the foothills of Ethiopia's Addo Malla Mountain, a young man guides a wooden plough pulled by two oxen over a rough field. He is preparing the land to grow maize.

This form of ploughing has been practised for centuries in many parts of the world, but in the Southern Rift Valley it is something fairly new.

"Four years ago this was just forest," says 19-year-old Dagim Dagne, who is working on his father's farm during a break from college. "Now we can use this land for agriculture."

When asked why it was not possible to farm here in the past, he replies: "The flies were killing the cows, but now the flies have gone."

The flies he is referring to are Glossina pallidipes, more commonly known as tsetse flies.

They are the carriers of the parasites that cause nagana, a wasting disease similar to human sleeping sickness which is transmitted when they bite animals to feed on their blood.

Many cattle die of the disease, while many more have spontaneous abortions or their production of milk suffers. The disease also makes them too weak to be used for ploughing or transport.

Several years ago, tsetse flies were present at very high levels in this part of Ethiopia. The impact was severe.

Farmers had to buy costly medicine to prevent the infected animals from dying. Arable land was being wasted, farmers were losing money, and there was less work available for labourers.

In addition, there was a chronic lack of dairy and meat products to eat and sell.

All this began to change in 2009, when the Government-run Southern Tsetse Eradication Project (STEP), with the support of the IAEA, started to carry out intensive activities to suppress the tsetse fly population.

These include the spraying of pesticides, treating the backs of cattle with insecticides and erecting targets that attract and then kill the wild flies.

The fly population is now down by more than 90 per cent.

In Kanchama, Awoke Woyese is busy tending to his animals and fields.

"In the past my cows were very weak and were dying, so I couldn't farm. Even the medicine I had to buy privately wasn't working, and the cows would die anyway," he says.

"Since the Government started spraying the pesticides, the cows are not tired and not dying from the tsetse flies. The cows are fine, the calves are fine and we're happy."

In addition to having healthy livestock, he has kilos of maize to eat and sell, enough milk for his family and a surplus to take to the market.

Not only is he able to support his family financially, he now has five employees working on his farm.

The benefits of tsetse suppression can be seen all over the region. Dairy products are now widely available at markets.

Farmers can even sell their milk at a newly opened distribution centre operated by a local Villagers' Association.

Healthy livestock can be seen everywhere, including donkeys which are an important form of transport.

However, in order to maintain these benefits, suppression alone is not sufficient or sustainable.

Therefore the ultimate goal of the STEP project is to eradicate the flies over a 25 000 km2 area in the Southern Rift Valley, using a method known as the Sterile Insect Technique, or SIT.

This is a form of pest control that uses radiation to sterilise male flies which are mass-produced in special rearing facilities.

The sterile males are released by air into tsetse-infested areas, where they mate with wild females. These do not produce offspring and, as a result, this technique can eventually eradicate populations of wild flies.

Before the SIT can be used, the wild fly population needs to be reduced to very low levels using other control methods.

The IAEA, through its Joint Division with the UN's Food and Agriculture Organization and its Technical Cooperation programme supports the implementation of over 25 SIT projects worldwide, for the control of a variety of plant and animal insect pests including the tsetse fly.

In Ethiopia, the Agency has been providing technical and financial assistance to the STEP project since it was launched in 1997.

IAEA entomologist Andrew Parker travels frequently to Ethiopia to monitor the project: "Suppression takes time, money and effort. When you succeed, the problem seems to disappear because the disease decreases," he says.

"Then people lose interest and motivation to continue the suppression, and the problem comes back."

According to the tsetse expert, the reason for using the SIT after successful suppression is to "go the final step," to completely remove the flies.

"This means there's no possibility for the flies to come back, and there's no need for continual control of the flies in the future."

A further advantage of the Sterile Insect Technique is the fact that - after an initial phase of insecticide-based suppression - it does not require the use of pesticides and reduces environmental contamination.

In the Kality suburb of Addis Ababa, the STEP project operates a rearing facility, where tsetse flies are produced in large numbers and irradiated. This process damages their DNA and renders them sterile, but does not affect their flying or mating ability.

Dr. Thomas Cherenet, Director General of the STEP project, says: "Livestock form the backbone of Ethiopian society. The country is totally dependent on agricultural products and we don't use mechanised farming methods. So we don't just need livestock for milk and meat, but draught power too."

He added: "Nagana has caused a lot of losses in production in my country. We spend up to US$ 240 million a year on medicines alone to treat it, since there's no vaccination."

Under the STEP project, aerial releases of sterile males are currently taking place over the Deme Basin region.

The releases started in April 2012, after area-wide suppression activities, and between 30 000 and 60 000 sterile male flies are being distributed in this area weekly.

Before release, the flies are fed blood containing a drug that will prevent them from picking up the parasites that cause nagana.

During tsetse SIT operations, weekly assessments of the impact of the released sterile male flies on the wild target population need to be made.

The STEP team based in Soddo maintains traps in the Deme area where the sterile males are being released.

According to Dr. Cherenet an increasing number of sterile males in their traps, compared to the number of wild males, is an indication that the project is working.

The STEP team uses an ultra-violet light to identify the fluorescent dye which is put on the sterile males at the facility in Addis Ababa to distinguish captured sterile files from wild flies.

A further method to test if the SIT is working is the dissection of the reproductive system of captured female flies to see if they have mated with a sterile or a wild male.

Once the area-wide tsetse suppression activities have been completed in the Arba Minch region and enough male tsetse flies are available at the Kality facility, aerial releases of sterile flies will also begin in this part of the project area.

"In this area, we have the Nechisar national park, which is a major source of flies and the Sterile Insect Technique will be a very important component in eliminating the flies here without damaging the environment," says Andrew Parker.

The park is an area of particular concern for the livestock owners in this region.

With its dense vegetation and large number of animals, it is the perfect habitat for the flies and an area that is not easily accessible for insecticide-based control methods.

"We need to prevent the park from being a source of re-infestation of flies into the rest of the project area," says Andrew Parker.

Ethiopia is just one of around 37 African countries that are affected by tsetse flies. It is estimated that nagana kills around three million livestock a year. In some areas up to 25 per cent of animals are affected by the disease.

The IAEA is supporting 14 African countries in their efforts to combat the pest using the Sterile Insect Technique.

Last update: 27 Jul 2017

Stay in touch