DDT may not be the longterm answer to the problem of malaria in Uganda.


Dear forum,

I have just completed studying  an advanced  module on malaria and I don’t think former MP for Lubaga South,Ken Lukyamuzi, should be crucified for refusing to use DDT. DDT may not be the longterm answer to the problem of malaria.

The focus of control should be directed towards the high risk groups (children under 5 years, pregnant women), prompt diagnosis and adequate treatment of malaria, intermittent presumptive treatment of pregnant women, prophylaxis for non-immune short-term visitors.

Another cheaper reliable method of control would be supplying of free long-term insecticide treated mosquito nets. Because the weather and environmental conditions are very favourable for the growth of malaria parasites and their mosquito vectors, DDT may not be able to eliminate malaria before significant resistance to it by mosquitoes has developed.

Prompt diagnosis and treatment will reduce the number of people carrying parasites, while bed nets will reduce the mosquito density.

The government has not also yet explained whether Ugandan mosquitoes are sensitive to DDT.The problem with the Ugandan government is corruption. When a drug company strikes a deal with a Ugandan policy maker, it goes on to sign a long term contract with the company without any research. For example, they signed a 25 year contract with a company that manufactures COARTEM (first line anti-malarial drug in Uganda) but this drug has started showing signs of resistance before even five years have elapsed.

From epidemiological and economic points of view, I don’t think DDT is the first priority to our malaria problem. Let the government first thoroughly explain the feasibility and safety of using DDT visa vie other modes of control because the harm DDT might cause to living organisms including humans in the long term may be worse than the likely short-term benefits.

What I want to say is that different malaria situations require different control measures and the situation in some parts of Uganda such as Apac, is best handled using a strategy cheaper and more feasible than spraying. In brief, I wanted to say the following:

  • It is impossible to eradicate mosquitoes using DDT, so this goal of control is unrealistic.
  • The benefits of and applicability of using DDT have not been investigated

Although Ken’s argument is about the environmental effect of DDT, my argument is about the feasibility and cost-effectiveness of this strategy. One needs to know the following facts:

  • The type of malaria transmitting mosquitoes (female anopheles gambiese) in Uganda only bite at night (from dusk on wards)
  • Both methods (nets and Indoor residual spraying-IRS) use the same principle of control, i.e reduce the number of mosquitoes by killing them on contact. Every mosquito that enters the house must not leave alive.
  • Mosquitoes adapt different feeding behaviours (either feed on humans or cattle, either bite outside or inside and after feeding they can either rest inside the house on the walls or outside)

Let’s now compare the two methods: The method of using spraying on the walls assumes that the mosquitoes bite indoors and rest indoors on the walls to digest their blood meal. Once mosquitoes realise the toxicity of the walls, they can adapt behaviour of resting outside the house or atleast a proportion of them (if this happens all the investment will be a flop!)

The use of DDT has the potential of selecting for mosquitoes that are resistant to DDT, in other words as the sensitive mosquitoes die, the proportion of resistant mosquitoes will increase and we shall go back to square zero after the heavy investment.

What determines its effectiveness? The type of walls of houses. Although it may be feasible in towns where houses are plastered and painted, it may not be the same in a rural mud house or even a hut. The biggest proportion of Ugandans live in houses where use of IRS is of limited effectiveness

Cost!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

  • The amount of chemical necessary to spray a single two bed roomed house can treat hundreds of bed nets
  • Equipment for spraying (protective gear, sprayers), transport, number of personnel, allowances etc..

BED NETS

Bed nets work on the assumption that a mosquito is attracted to a person inside the net by some chemicals including carbon dioxide. It hits the net and is killed by the chemical on the net. The mosquito has little room for adaptation unlike IRS where a mosquito must rest on the wall after feeding for it to be killed and it can decide to rest outside if the inside is hostile.

Its effect not determined by the type of walls, even if someone is in a grass thatched hat.

Cost of the Chemical is minimal, no equipment, one person can supply and demonstrate use of a net in one central place (how many costs have you eliminated?)

In conclusion I am saying that in Uganda, IRS is not feasible and is not cost-effective given the many hindrances to its effectiveness. I think someone was promised something to push for a method that is not feasible and cost-effective. This is before we think of its long term effect to the environment. But note that my view is a purely scientific, not based on hatred of the corrupt NRM government!!!!

Abu-Baker Ggayi

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Comments

5 Comments so far. Leave a comment below.
  1. billie kadameri,

    Forum,

    I have just finished reading the lead story in Time magazine in which specialists and WHO officially lists Apac district as the malaria capital of the world, with the largest concentration anywhere on earth, of the malaria-carrying mosquitos. This is largely because its marshy terrain and the many swamps, little rivers and the marshy Lake Kwania and Lake Kyoga.

    When the government tried to use DDT to combat malaria in Apac, Ken Lukyamuzi said he would fight to the death if DDT is used and indeed the first trial spraying has been stopped.

    Should the people of Apac and Lango in general therefore consider Ken Lukyamuzi as their worst enemy on earth, wishing them extermination and therefore, reject anyone who tries to deal with Lukyamuzi in anyway?

    Would Lukyamuzi be so much against the use of DDT if Lubaga South was the malaria capital of Uganda, let alone the world?

    Billie

  2. Mike Ssegawa,

    Abu-baker Ggayi,

    As I write this mail, I am feeling symptoms of malaria. From here, I am going to see my doctor – certainly, he will bill me, money that should have gone to other priorities. Like you can understand, an average Ugandan spends less than eight hours in bed…when you talk about mosquito nets (which is a good initiative), it looks like one does not get a mosquito bite outside those bed hours. Therefore, it is important to safeguard our surrounding and environment against the bites.

    And you are already talking about resistance to coartem, and to add, the theft and cost of drugs in this country is so high.

    I don’t blame it on my good friend Ken. He cannot fail government in the spraying of DDT. I am pretty sure about this because this NRM government has always done whatever it wants to do — irrespective of what Ken and others think. It is that someone or some people have failed to stop this thing called mosquito, irrespective of what ecologists say.

    To be sincere with you, the pain, monetary and physical cost of suffering malaria is not higher than the cost of spraying DDT countrywide. You mean elsewhere DDT is sprayed there are no children and pregnant women…any way, I do not really understand the science of DDT, but I am desperate for the eradication of mosquitoes.

    I will be the first volunteer to accept spraying my home.

  3. Ggayi Abu-Baker,

    Dear Segawa,

    Thank you for the appreciation.
    The next question I would have asked is whether the episodes of malaria you are talking about are confirmed in professional labaratories. Sometimes healthworkers treat people for malaria without any justification. If the nets have failed to protect you from malaria, then IRS is unlikely to do better because they target the mosquito using similar means. Actually IRS kills a mosquito that has already fed (and possibly transmitted malarai) while a net is likely to kill a mosquito that hasn’t yet fed on a human. So in terms of individual protection, nets should be better, while at communal level the effect is likely to be similar.
    Over protecting your selves from mosquito bites might still be a problem in an endemic area like Uganda.In absence of an effective vaccine, we need to rely on the protection we get when we receive a certain number of infective mosquito bites as we grow up.
    That is why government must concentrate on averting the adverse consequences of malaria in high risk non-immune people (children and pregnant women) instead of resorting to unreliable methods before exhausting basic ones.
    At individual level, those of you who can afford both nets and IRS can do so, but at policy level, the government will not even cover a quarter of the population.

    Kind regards,

    Abu-Baker Ggayi

  4. Sheme Chemangey Masaba,

    The controversy whether or not we should use DDT to control malaria in Uganda has been raging for sometime now and it is not about to the end. Ken Lukyamuzi, the leader of the Conservative Party, has earned himself the title of an environmentalist through his opposition to the use of DDT.
    There is no denying that DDT is harmful to the ecosystem, and indeed, to life. The same is the case with so many other chemical we daily use to control animal insects and crop pests. If used in small amounts and judiciously, the harm DDT can cause is negligible.
    DDT had its heyday in large scale malaria eradication and control programs of the 1940s to 1960s until its harmful effects became better understood and a number of countries stopped using it.
    We now know that DDT can accumulate in plants and be passed to animals that eat plants and then to carnivores along the food chain. Its harmful effects have clearly been seen in bird eggshells where it prevents calcium from being deposited so that the eggs have very thin shells that can easily break. And if this condition continues then the bird population decreases and may eventually become extinct.
    There is very little about DDT’s effect on humans. So, if I were faced with a serious malaria situation, I wouldn’t hesitate to use DDT.
    In 1984, I spent two months in India on a WHO fellowship on malaria. By then Indians were still busy using DDT while we had already stopped using it here in Uganda.
    We are wasting time debating whether or not to use DDT because malaria must be tackled from all sides. To deal with malaria, you need to consider the environment, the vector and the human host. Mosquitoes breed in a dirty environment and the one we have today is ideal with mosquito breeding. Discarded polythene bags (buvera), clogged drainages and rotting rubbish are everywhere and provide mosquito vectors the right conditions in which to breed and spread.
    The use of insect impregnated nets and treatment with antimalarial drugs will not make much impact on the level of transmission without cleaning up the environment. .
    (Visit my blog: http://aparasiteworld.blogspot.com.

  5. Gale,

    Thanks $author! You share some great %keyword advice. Thanks for sharing this and making it clear enough for everyone to understand. I’ve subscribed to your RSS feed and I’m looking forward to your new advice I also share some information on Heart Vector ideas.

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