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Posted on 11/14/2005 9:16:10 AM PST by GreenFreeper
An extensive study of malaria-carrying mosquito or "vector" populations in different ecological zones of Cameroon has documented widespread and varied resistance to insecticides, part of an alarming trend across Africa that might ultimately jeopardize efforts to control malaria with treated bed nets and indoor spraying.
The study, which will be presented at a special session on insecticide resistance at the Fourth Multilateral Initiative on Malaria (MIM) Pan-African Malaria Conference, is illustrative of a growing body of research in Africa that is finding increasing mosquito resistance to pyrethroid insecticides, which are used for insecticide-treated bed nets (ITNs), and DDT, which has been used successfully in household spraying programs. (Wednesday, 11:25 a.m., Mahogany Hall, Parallel Session 16, Presentation 102)
Scientists from the Institute of Medical Research and Study of Medicinal Plants (IMPM) and the Organization for Endemic Disease Control in Central Africa (OCEAC) in Cameroon believe their findings are likely applicable to the other malaria endemic regions of Africa because they emerged from analyzing mosquito populations at 32 different sites located across the country. Cameroon is often viewed as "Africa in miniature" due to its diversity of climatic and ecological conditions.
The IMPM/OCEAC study illuminates how mosquitoes in different areas of Africa employ a variety of biological weapons to fight off insecticides. For example, in the northern cotton and rice fields of Cameroon, malaria vectors rapidly detoxify or "metabolize" pyrethroids, effectively neutralizing their killing capability. Meanwhile, in the country's western tropical gardens, mosquitoes survived pyrethroids and DDT through what is known as a "knock-down" or KDR mutation, which is a genetic modification of the target site. This mutation desensitizes the main target of DDT and pyrethroid insecticides-the mosquito's nervous system. In coastal and inland equatorial areas of Cameroon, mosquitoes sometimes have both resistance mechanisms.
"The range of mechanisms involved in resistance is likely having an impact on the effectiveness of treated bed nets," said Josiane Etang, the study's lead author. "Overall, we need to rethink management strategies, especially in areas where the KDR mutation and detoxification are coupled."
She said further research is needed to understand which type of KDR mutation is most prevalent in Cameroon, as there are two varieties that have been identified in African mosquito populations. One is more common in the West, the other in the East, but both may be present in Cameroon. Understanding precisely how mosquitoes in a particular area are resisting insecticides may allow for the selective use of formulations that can overcome these defenses.
"The potential for insecticide resistance to interfere with promising malaria interventions requires urgent attention," said Andreas Heddini, the MIM Secretariat coordinator. "But if we have scientists in the field throughout Africa regularly monitoring mosquito populations then we will have the up to date evidence we need to guide an effective response."
Several other presentations at MIM will discuss the emergence of insecticide resistance and its implications for malaria control. For example:
- Samson Awolola of the Nigerian Institute for Medical Research will present a study analyzing the dynamics of insecticide resistance in a suburb of Lagos, Nigeria where, in 1999, mosquitoes were fully susceptible to both pemethrin and DDT, but since 2001, populations in the area have developed resistance to both. (Wednesday, 12:35 p.m., Mahogany Hall, Parallel Session 16, Presentation 106)
- Rising levels of insecticide resistance in Africa have generated interest in the potential of controlling malaria-carrying mosquitoes in Africa through the introduction of transgenic mosquitoes. But technical challenges and safety concerns abound. The MIM conference will feature a special debate on transgenic mosquitoes in which Andrea Crisanti, an expert on the malaria parasite at London's Imperial College of Science, Technology and Medicine, argues that transgenic mosquitoes will become a viable weapon and Bart Knols, an entomologist at the International Atomic Energy Agency, takes the opposite position. (Moved to Thursday, 5:00 p.m., Bubinga Hall, Current Controversies 3)
Nothing all that new but is worth repeating.
FReepmail me to be added or removed to the ECO-PING list!
I was looking for the first person to say this. Try reading the article.
I was going to say that but thought I'd start the week off being nice, lol.
some more on DDT
http://www.freerepublic.com/focus/f-news/1518764/posts
It's near to impossible to do yardwork here in FL in the summer. I now use Deep Woods Off, which didn't work a few years back. It's the only product they sell which keeps me from being bitten to death outside. I don't think our public works sprays enough to keep these new daytime tiger mosquitos from swarming bigtime.
I think the world's mosquito problem is just one of complacency. Third world countries don't spray, don't seem to be as good at trying to keep the spread down. Of course malaria, dengue and other mosquito-spread diseases are on the upswing.
I was just thinking I could have been more diplomatic.
Forgot to mention: it is frightening that these bugs are becoming stronger and resisting a lot of the insecticides. I guess we are in for super-bugs very soon.
Obviously some mosquitoes have always had a resistance to insecticides, or there would be no mosquitoes. If you keep killing the mosquitoes that have no resistance, and let the resistant mosquitoes keep breeding, than eventually you will have all resistant mosquitoes. This is a very basic form of genetic manipulation (the law of unintended consequences?) that should have been recognized a long time ago and dealt with. Using one pesticide as a one-size-fits-all solution just because it is cheap will produce predictable results.
The transgenic approach might work but what will all the single females do, become lesbians?
bbbbbut, I thought DDT was the solution to all of our problems? /sarcasm
thanks for ping. Was hopeing this DDT issue could have a happier ending. Petrochemical companies, bring it on! We need new generations of really cleverly designed insecticides. Whatever that really means.
LOL. Transgenic crops are one thing but transgenic tinkering with animals seems pretty dangerous to me, especially with a vector species.
The mortality rate for human beings is @ 100%
This cannot be increased
The article says that scientists have discovered that mosquitoes in Cameroon have developed resistance to DDT. Since they have even determined the particular mutation that causes this resitance, I would tend to believe them and not you.
The wikipedia article on DDT also discusses resistance.
Or are you saying that DDT is being used in this location?
Yes
Use of DDT would have caused the loss of any aid or support to that country.
Apparently not. The wikipedia article also discusses the "ban" on DDT and apparently there is not a total ban on international use. It quotes the USAID website as saying " Contrary to popular belief, USAID does not “ban” the use of DDT in its malaria control programs."
I have read recently that African countries are experimenting with indoor spraying of DDT for malaria as they think that this will be easier to implement and have fewer environmental effects than widespread outdoor spraying.
BTW I once worked in a lab where a breakdown product of DDT was applied to rats. It definitely had negative health effects on them.
but I thought DDT was the greatest breakthrough since penicillin? /sarcasm
Interesting! I don't like to wear anything that might weight me down though...! It's too hot here in FL in the spring/summer/fall but the skeeters are murder. So far, the OFF seems to work effectively.
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