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[afro-nets] Mosquito and Malaria Control (43)

Mosquito and Malaria Control (43)

Dear Colleagues

Sorry this is rather long ... but it is a big subject.

I would like to follow up on a message that Chris White sent last September 
about Mosquito/Malaria Control. Chris made the point that interventions that 
are used in the United States are wrong for Africa ... but in all honesty, I 
don't think he made a strong case for this.

The discussion had talked about the use of aerial spraying in the USA in the 
aftermath of the Katrina hurricane ... and he correctly pointed out that this 
was not spraying against malaria, but against various other mosquito borne 
diseases (yellow fever, dengue and west nile virus). Since malaria has not been 
a problem in the area since around 1950, spraying against malaria is not done 
... which seems to make sense! My conclusion is that aerial spraying is a very 
appropriate and cost effective way of delivering anti-mosquito pesticide, 
especially with modern understanding of pesticide and the use of ultra low 
volume (ULV) technology. I have made some cost estimates for aerial treatment 
and it is very low cost per acre ... and depending on population density can be 
very low cost per capita of human population.

Chris talks about the mosquito (specifically anopheles gambiae s.s.) breeding 
in all sorts of small, transient rain-fed pools ... and how it is unrealistic 
and uneconomic to expect that larvaciding can be effective. I am not at all 
sure that Chris is right. From a practical scientific point of view, 
larvaciding works ... though it is difficult to organize over a big area. I 
don't think this problem is insurmountable, though it must not be ignored. 
Arguably cleaning up the environment and larvaciding is the best way to break 
the cycle of mosquito population rebuilding. Building the Panama Canal 100 
years ago was done in the face of virulent malaria, in large part by cleaning 
up the environment where the work was going on and where workers were living. 
Spatial information seems to suggest that not all water has the same breeding 

I have not been able to find much cost and result information that convinces me 
that insecticide treated bednets is the best way to go for effective mosquito 
malaria control interventions. While an individual seems to get less malaria 
when they use a bednet ... the cumulative experience in the community does not 
seem to change very much. This may not be the right conclusion, because the 
information available is not very clear. Rather than having a focus on costs 
and results (as measured by reduction in the prevalence of malaria in the 
community), much of the cost performance information relates to merely the cost 
and the scale of distribution of bednets into the community ... an interesting 
metric, but not a metric that helps determine the effectiveness of bednets as 
an anti-malaria intervention. I think it is fair to conclude that bednets on 
their own do not make much of a difference, even when they are widely 
distributed. I would love to know more about costs and reduction in malaria 
parasite prevalence using the bednet approach.

There seems to be a lot of information that shows that interior residual 
spraying (IRS) does have a significant impact on the prevalence of malaria in 
the community ... and especially when DDT is used as the pesticide. The cost of 
a large scale IRS program is substantial, but the results seem to justify the 
expenditure, especially if DDT is permitted. Sadly use of DDT in a country has 
the possibility of creating trade issues with Europe, not so much because of 
prevailing legislation but because of corporate environmental sensitivities and 
concern that there might be adverse consumer impact.

The role of medical interventions is not insignificant. Remove the parasite 
from the human host and malaria transmission will be reduced ... though it is 
not easy to get the reduction in malaria transmission low enough so that the 
parasite population gets reduced. It can be done ... but it is not the norm for 
Africa at the moment.

Clearly resistance is an issue in any chemical intervention ... whether against 
the mosquito or the malaria parasite. A modern management information system 
for any intervention should take this into consideration and collect 
appropriate data and use it to manage the interventions.

Lastly ... the information I have been able to collect seems to suggest that a 
variety of interventions going on together and coordinated gives the best 
results at least cost. A data driven program, including spatial information 
about all the interventions and all the results can be used to keep costs down 
and to deliver better than "average" results. But in order for data to be 
useful, they must be organized as "management information" for decision making 
and not merely to satisfy academic criteria.

I would love to get more information that will help move me along in the design 
of an integrated mosquito malaria control model ... and a program that can be 
helpful in Africa to optimise mosquito and malaria control interventions.


Peter Burgess
Transparency and Accountability Network
Tr-Ac-Net Inc.
New York

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