Mosquito/Malaria Control (19)
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Dear AFRO-NETS:
As someone who managed the final year of the unsuccessful USAID-
supported 7-year Zanzibar Malaria Control Project (ZMCP), which
ran from 1981-87 and cost about US$ 1 million per year, I feel
compelled to provide a cautionary note to Bill Nesler and others
who advocate a full-scale assault on malaria in African coun-
tries.
In brief, when the ZMCP began, about 38% of children in Unguja
(the main island of Zanzibar) had malaria parasites in their
blood. Midway through the program, this rate had falled to 3-5%.
By the end of the ZMCP, the rate had risen to about 35%. What
went wrong?
As I recall, the main problems were as follows:
1. A full campaign of indoor house-spraying, larviciding, public
education and prompt treatment requires a military approach to
the problem -- with detailed maps, careful ongoing monitoring of
outbreaks, quick response to outbreaks, extremely high partici-
pation (over 90% of the public). In Zanzibar, after some initial
success, the people running the activity "lost steam" and did
not maintain the level of commitment and effort needed, even
though resources were there.
2. Unless indoor spraying of DDT is done extremely well -- i.e.,
with the correct amounts of DDT applied per square inch, with
greater than 90% of households opening their homes to the spray-
ing, with all walls being covered, with all spraying in an area
done at roughly the same time period -- then high levels of mos-
quito resistance to DDT can develop. Unfortunately, with the
ZMCP, it encountered all of the problems often found in develop-
ing countries: sloppy spraying, community residents refusing to
participate, incomplete coverage during key time periods, etc.
So resistance to DDT rose to extremely high levels. (In 1988,
one member of the ZMCP evaluation team put DDT into a petri dish
and added 100 mosquitoes. A few days later, he found 96 of them
still alive in what he dubbed the "DDT swimming pool").
3. With high levels of resistance to DDT, which is actually a
fairly safe and inexpensive pesticide, it was necessary for the
ZMCP to move to much more toxic, smelly and expensive sub-
stances, such as malathion. Unfortunately, without solving the
previous problems mentioned, the mosquitoes' resistance to
malathion also rose. Another problem was that, upon finishing
the spraying in a certain area, the sprayers occasionally left a
few remaining bags of malathion in the community. These bags
were not left in secure locations and children were found play-
ing in them -- a serious public health hazard.
4. Larviciding did not work much better. First, there were some
people who resisted larviciding of stagnant water. The classic
problem was an enormous swimming pool at one of Zanzibar's big-
gest hotels which was not properly maintained and chlorinated.
It hence was a huge mosquito breeding ground, but the hotel did
not want unsightly larviciding to occur. Second, some stagnant
water remained for a relatively short time. For instance, during
the rains certain football fields became swampy breeding
grounds. But the ZMCP was not vigilant in larviciding these ar-
eas, which only stayed swampy for 1-3 weeks at a time. Lastly,
the evaluation team found that mosquitoes could breed in stag-
nant water sites as small as a cow's hoofprint. This made it ex-
tremely difficult to larvicide effectively.
5. To conduct a full assault on malaria control is very costly.
At the time, the combined islands of Unguja and Pemba had less
than 750,000 residents. The ZMCP was costing about Us$ 1.50 per
person per year. If the government had been paying for it, this
would have represented about one-third of its total health
budget.
6. The ZMCP had numerous logistical problems, which again are
common in developing countries. For instance, some vehicles need
to be designated as spraying vehicles only, and not be used for
other purposes because they can inadvertently contribute to re-
sistance if they enter areas where spraying has not yet oc-
curred. But sometimes high-up officials demanded to use one of
the ZMCP's vehicles, and the staff was powerless to refuse. If
all of the ordinary vehicles were in use, the officials would
grab the vehicles designated for spraying.
I could go on, but I believe that this will give readers a good
sense of the difficulty of mounting this kind of campaign. Be-
cause of failures of this kind, my understanding is that the
ZMCP represented the last major effort of a donor to conduct a
comprehensive malaria control effort of the kind carried out in
Panama, Florida, etc.
With best wishes,
Paula Tavrow, PhD
Visiting Associate Professor
Department of Community Health Sciences
School of Public Health
University of California at Los Angeles
mailto:ptavrow@ucla.edu