Tsetse fly 'on verge of elimination' on Guinea islands
[CAPE TOWN] Scientists are hopeful that they have for the first time eliminated tsetse flies, which carry sleeping sickness, following an innovative control campaign on a group of islands off West Africa.
The researchers, from France, Guinea and the United Kingdom, have reduced the tsetse fly population to non-detectable levels on the Loos Islands, which are part of Guinea.
The team found that the reduction rate was faster where a combination of control methods was used. These included poison-impregnated traps and targets, selective ground-spraying, smearing pigs with insecticide, and erecting impregnated fences around pig pens.
There have been very few tsetse fly control programmes in the fight against human sleeping sickness in West Africa, said lead researcher Moise Kagbadouno, a senior official in Guinea's ministry of health who also runs the country's national control programme against human African trypanosomiasis (HAT).
"If we succeed, this will be the first time we show [that] eliminating these flies is really possible — and [that it] has an immediate impact because it stops transmission," he told SciDev.Net.
Kagbadouno said that an integrated control campaign is necessary because there is no one method that could be singled out as working best. Such a campaign could be replicated in the rest of Guinea and other countries, he said, adding that control operations on Guinea's main sleeping sickness areas — close to the shore — will start in the next few months.
Chris Schofield, an expert in infectious and tropical diseases at the London School of Hygiene & Tropical Medicine, United Kingdom, cautioned that surveillance must continue for quite a long time to ensure the tsetse population have been eliminated — or it could return to previous levels.
Schofield, who is also a committee member of the African Union Pan African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC), said a joint large-scale project to eliminate tsetse from the KwaZulu-Natal region, southern Mozambique and Swaziland, modelled on the Guinea study, is likely to be launched this year.
"The problem is that sleeping sickness is a neglected disease, and as such, does not benefit from big funding," said Philippe Solano, a researcher withthe French Institute of Development Research.
Sleeping sickness is treated with two drugs that have multiple problems. One drug, melarsoprol, is an arsenic-based treatment that kills around 5 per cent of patients, and another one require a lengthy hospital stay and does not work against all forms of the disease. There are no vaccines or prophylactic drugs for the disease. The WHO estimates that the disease kills around 30,000 Africans a year.
The research was published in Parasites & Vectors last month (10 February).
Parasites & Vectors doi: 10.1186/1756-3305-4-18 (2011)