authored by Ddembe on 21. March 2007 at 10:34
Start spraying DDT for those willing to have it
By Prof. George Kirya
It is sad that some Ugandans don’t regret looking at the graves of 300-400 fellow citizens, mostly children and pregnant women, who die of malaria daily.
There is no scientist or medical personnel of any specialisation, any where in the world, who has proved or shown that the use of DDT causes liver cancer, infertility, blindness, brain disorder, genetic defects and so on, as some Ugandans claim. Those opposed to the use of DDT should produce evidence to support their claims.
There is written evidence that from 1955 to 1969, DDT was used under the WHO Malaria Eradication Programme covering Europe, Asia, parts of the former USSR, several countries in the Middle East, the Caribbean, large areas of North and South America, including the whole of USA, Australia, Singapore and Korea. At the end of the campaign, malaria had virtually been eradicated from all developed countries where the disease had been endemic and from large areas of tropical Asia and Latin America. Ironically, the meeting for the Global Malaria Eradication Campaign was held in Kampala in 1950.
Use of DDT for mosquito control in these areas was also found to contribute significantly to the prevention of other vector-borne diseases like leistimaniasis or Kala azar and Plague.
It was also widely applied on people’s hairy body parts to rid them of lice and flee infestation. As a food preservative, it was used on beans, groundnuts and maize against weevils and other pests, and the foods were later eaten.
During that period a malaria epidemic in northern Kigezi (now Kanungu District) was contained by the use of DDT. The migrants, originally from southern Kigezi (now Kisoro and part of Kabale Districts) had no previous experience with malaria. Indoor Residual Spray (IRS) was done in their houses and malaria was controlled.
In 2005, top Ugandan scientists carried out a comprehensive analysis of the impact of DDT on the environment and the population in Kanungu. They interacted with men and women in their 70s and 80s who were recipients of IRS in their houses. None of them was found suffering from any of the conditions alleged to be caused by exposure to DDT, although some still had traces of DDT in their blood.
There are a number of elements found in people’s bodies which include iron, calcium, potassium, lead, among others, which if in reasonable quantities are vital for one’s survival, though they can be dangerous if in large quantities. Since no harm has been established in any human being that was a result of DDT persisting in one’s body, it might be playing a positive role yet to be discovered by scientists.
Countries which found some problems with DDT are those which misused it by applying it massively on their farms as a pesticide.
In the USA, up to 80,000 tons of DDT were being used per year by the time it was banned. It was widely sprayed into the environment for agricultural use, with the largest quantities applied to cotton and the rest for public health. This quantity was bound to have an ecological impact. But there is no record of anybody being affected by DDT, yet big quantities were used.
Uganda does not intend to use DDT as an agricultural pesticide. It is going to use it only for indoor residual spraying under careful control and supervision.
In the past, DDT was being dissolved in highly toxic substances such as fuel oil, petroleum distillate, benzene hexachloxide or mentholated naphthalene, which will not be used this time.
At a WHO meeting of Ministers of Health held in Johannesburg, South Africa, in 2002, it was agreed that use of DDT starts in accordance with WHO recommendations if alternative and cheaper insecticides were not available.
DDT is being used in Ethiopia, Malawi, Mauritius, Magdascar, Namibia, South Africa, Zambia and Zimbabwe, among others. To say that there will be extensive environmental pollution arising from indoor residual spraying, is far fetched and unjustified.
The advent of DDT use in 1930s-40s presented an opportunity for a new method of interrupting malaria transmission, by killing the mosquito at its epidemidogically most important stage, the adult, when it feeds on human beings in their dwellings and transmits malaria. When the WHO recognised that malaria was not only killing more people than any other disease but also interfered with the development plans, particularly in the Third World, it began to seriously consider fighting the disease. It is, therefore, a great shame to see that malaria in Africa, and Uganda in particular, has remained a major cause of mortality and morbidity among our nationals despite the fact that it is entirely preventable (and curable).
Several malaria control programs that have environmental management as the central feature are available, but have a slow impact. These are bush clearing, modification of river boundaries, application of oil to stagnant water and use of mosquito screens to house windows. Treated insect nets are already widely used and publicised in Uganda, as a personal protection against mosquito bites, but 80% national coverage is a pre-requisite for effectiveness. Use of alternative chemicals for the dual purpose of indoor residual spraying and treatment of mosquito nets has been negated by the cost-benefit analysis in favour of DDT.
Every technology used in life has some negative aspect. Examples are drugs commonly used by many people like aspirin, penicillin, anti-cancer drugs, chloroquine, various vaccines and even eating meat or groundnuts. So, what is always done is to weigh all the dangers and risks of any technology against all the benefits of using it, constantly. As a result, innovations and technologies are adopted after a cost benefit analysis has been made. This is what has been observed worldwide as far as using DDT for malaria control is concerned.
Scientific studies have shown that DDT has been found best suited for the Anopheles gambiae mosquito because of its high mortality effect on the mosquito. It is also found that 50% of mosquitoes entering a house sprayed with DDT will be repelled from the house or get so excited that biting becomes completely inhibited. No other residual insecticide has this effect.
DDT is classified as a Persistent Organic Pollutant (POP), under the Stockholm Convention, which Uganda ratified in July 2004. The Convention declared that DDT could be produced and used only for disease vector control and according to the recommendations and guidelines of the World Health Organisation. They also said that DDT would continue to be used as long as safe, effective and affordable alternatives are not available.
Contrary to rumours that the European Union (EU) would abandon Uganda when it starts using DDT, there is evidence that EU supports use of DDT against malaria in Uganda because the EU supports DDT use in South Africa, Mauritius, Namibia, Zambia and other countries.
The EU recognises that DDT residues may be found in some agricultural commodities and to this end, EU permits low levels of DDT contamination in some crops, provided such levels are safe to consumers and are not due to illegal spraying of DDT as a pesticide.
Indoor residual spraying of DDT should start now in houses of Ugandans who are willing, as the Government and other stakeholders continue to sensitise those who are doubting the usefulness and safety of using DDT.
The writer is the former Vice Chancellor of Makerere University and former Head of the Department of Medical Microbiology, Faculty of Medicine, Makerere University