The Deputy Director of the Research Tsetse Control Division, Andrew Chamisa, said SIT been used to great effect in Tanzania.
“At the moment we are setting up a structure to do the SIT study and we are doing it with the assistance of International Atomic Energy Agency,” he said.
SIT explained
SIT is the method of reproducing tsetse flies on a large scale in laboratories.
“The male tsetse is exposed to nuclear chemicals to sterilise them so that when they are disposed into the bush they outnumber those mating with wild female flies. The females only mate once, so if we introduce more sterilised males, there will be no reproduction,” he said.
Chamisa said the banning of Dichloro-Diphenyl-Trichloroethane as a pesticide to control tsetse flies had no negative impact in Zimbabwe.
“We last used it in the late 1980s and since then we have been using Delta-methrin, a synthetic pyrethroid insecticide which is very effective and environmentally friendly,” he said.
The use of DDT as a pesticide increased worldwide after World War II, primarily because of its effectiveness against mosquitoes, lice that carry typhus and tsetse flies.
25 million saved
The World Health Organisation estimates that during the period of its use approximately 25 million lives were saved.
DDT was first banned in America in 1973 after it was discovered to have a high toxicity towards fish, birds, humans and the environment. Some American scientists classified DDT as a probable human carcinogen. This classification is based on animal studies in which some animals developed liver tumors.
During the late 1990s United Nations Environment Programme, countries negotiated a treaty, the Stockholm Convention, to enact global bans or restrictions on persistent organic pollutants like DDT.
Argument for DDT
However, a University of Zimbabwe researcher, Chris Magadza, is on record saying that DDT is cheap and the most effective pesticide to eradicate tsetse flies in Zimbabwe.
He said the reproduction cycle of the tsetse fly is slow, compared to many insects, as the females only lay one egg that is incubated for about nine days.
Approximately one month later it emerges as an adult fly.
“The most effective way of eradicating the tsetse flies is ground spraying with DDT, which is now unacceptable world-wide,” he said. “The other pesticide control method is the use of odour-baited traps in rough terrain. There were many traps, approximately 1km apart, set over a vast area in the Zambezi Valley but these have not been maintained,” added Magadza.
SIT expense
Magadza said the use of sterile insect technique was very expensive.
“The use of sterilising the male fly has been tested but is expensive and labour intensive,” he said.
Chamisa said Delta-methrin was environmentally friendly and effective. He added that as well as odour traps they use it when dipping cattle.
“We also spray delta-methrin directly on the ground and surfaces like tree leaves where the tsetse flies like to rest after feeding,” he said.
In September 2006, WHO declared its support for the indoor residual spraying of DDT in African countries where malaria remains a major problem, citing that benefits of the pesticide outweighed the health and environmental risks.
WHO says it is up to countries to decide whether or not to use DDT.
The National Malaria Control Programme Manager, Joseph Mberikunashe, said Zimbabwe would continue using DDT for indoor residual spraying to eradicate malaria.
Post published in: News