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Super Mozzies
Modern technology has dealt with many of natures dangerous diseases. But mosquitoes have survived some of the most powerful insecticides. And these 'super mozzies' have the experts buzzing with desperation.
Sally Burdette, "In Touch" presenter, explores the frightening ramifications of Super Mosquitoes.
Don Ferreira suffers recurring bouts of malaria and Sally talks to him to find out just how bad it is: "It's like having the flu, but ten times over and fever and shaking; you have about six blankets on you and you are still shaking," says Don. Which is why we now have a drink called gin and tonic," says Sally. "Tonic water is actually just plain old soda water with quinine added. Quinine is simply the best thing to take when you're being treated for malaria, which is why the Brits drank the stuff by the gallon in India in the 1800's, mixed of course with a modicum of gin to make the experience more palatable and of course more convivial." In the sixties they found something that really killed insects - it was called DDT, and soon, planes were spraying the African bush with clouds of DDT. The only problem was, DDT killed a lot more than insects.
Soon scientists found it was cheaper and easier to manufacture a synthetic version of pyrethrum, which they called pyrethroids. "So we didn't have to squash up hundreds of Chrysanthemums and we could still kill insects safely," says Sally. "Great. Problem solved. Humans, one, Mozzies, nil." Except, there was a small problem, and it started in West Africa. Sally speaks to Prof Maureen Coetzee at the SAIMR about the strain of mozzies which built up a resistance to pyrethroids. "One of the main interventions against malaria mosquitoes these days is the use of pyrethroid treated bed nets. Pyrethroids are also widely used in agriculture and is probably this that has resulted in mosquitoes becoming resistant to pyrethroid insecticides. In West Africa, countries such as Cote D'Ivoire and Burkina Faso, have recorded huge increases in resistance in the main malaria vector anopheles gambiae. And obviously everyone is very concerned that this is going to rapidly spread throughout Africa. Work done in West Africa was carried out by a French researcher and we have currently set up the technique here in our lab to test our local mosquitoes. In South Africa you can find the malaria vector mosquitoes in the low lying areas of the Northern Province, Mpumalanga and Northern KwaZulu Natal.
It is all very well spraying in a specific area to kill mosquitoes, but you'll never kill them all. What if one lands on you, bites and gives you malaria? What are the symptoms of malaria and how does one treat malaria? Sally speaks to Lucille Blumberg at the SAIMR about this. "A patient will present in a similar way as flue, with headache, fever, cold shivers, hot sweats," says Lucille. "These symptoms are very non-specific and can occur in many other diseases. A very important question to elicit on history is, where has the patient been? If the malaria has been acquired in Africa and is uncomplicated, one may choose a drug like sulphadoxine pyremethemine, but on the whole quinine is the mainstay treatment of malaria, particularly complicated malaria and it is a very effective drug and there is very little resistance in Africa.
It is not likely that we will visit malaria controlled areas dressed like we are about to enter a hospital room contaminated with a deadly disease, but as you have seen, the problem is a serious one. New technology and advanced research techniques are taking on the super mozzie aggressively. "In the meantime, if you are going to be visiting a malaria area, consult your doctor," advises Sally.
CONTACTS:
Prof Maureen Coetzee
Basil Brooke
Lucille Blumberg |
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There are many places in Africa where that simple little annoyance, the mosquito, can bring a debilitating and often fatal disease - malaria. The anopheles mosquito carries a parasite called plasmodium. "As it bites you, the parasite is released into your blood, where it multiplies and attacks your red blood cells. The result is malaria, and it's not a nice thing to have," says Sally.
DDT doesn't break down very easily. So it accumulates in the food chain: fish eat DDT - infested mosquito larvae, and fish eagles eat the fish. "The DDT in the eagle's system had side effects - one was in the eggs. The shells became very thin and usually broke, resulting in a massive loss of bird and other wildlife", says Sally. "So we moved to a new insecticide. It was a lot less harmful, and came from Chrysanthemums. They have a chemical called pyrethrum in them, and unlike DDT, pyrethrum is safe around humans, but deadly to most insects."
The mosquitoes breed in small standing pools of water, such as rain pools, for instance, and these occur all over the place. If the malaria control program in South Africa was ever to stop, we would find the mosquitoes spreading and a huge increase in the incidence of malaria and probably many people would die."
The South African Medical Research Institute is working hard on the new problem, and Entomologist Basil Brooke and others are working on the resistance of mosquitoes. What they are looking for is an alternative to pyrethroids; something that will work across the whole spectrum of mosquitos. Says Basil Brooke, SAIMR :"What we do, is collect mosquitoes from the area under consideration, and expose them to the insecticide in question. These exposures typically last an hour and if we see any survival after an hour, then we know we have resistance. Insecticide resistance in mosquitoes is already widespread. There is a known insecticide resistance mechanism to every class of insecticide already used to date, and there is good reason to suspect that mosquito populations could develop resistance to any new classes of insecticides that come along in future."
If you take a drug and it is not one hundred percent effective, it may have the effect of prolonging the incubation period, the time from when the malaria was acquired to when the first symptom appears. You may have some difficulty with diagnosis initially, but that, with time and repeated smears, will sort itself out, and definitely the symptoms will be less severe. You have still very effective drugs to treat and prevent malaria, but I am not sure what the future holds."