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An article by a researcher for the WHO in The Bulletin of the World
Health Organization (Cheng 1963, see reference below) confirms the
thatch-eating-caterpillars feature of the story. After insecticide
spraying to eradicate malaria was conducted by teams organized by the
WHO, complaints were made by representatives of areas in Sabah and
Sarawak (see map) during a conference on malaria because the spraying
caused the deterioration of the thatched roofs of the buildings in those
areas. As mentioned in the story, Cheng states that the reason was
because the moth larvae (caterpillars) somehow avoided DDT whereas their
parasite, a small chalcid wasp which injected their larvae into the
caterpillars, was highly susceptible to the DDT causing their decline
and the subsequent increase in caterpillar numbers. What is not stated
in the cat story but related in this report is that a population study
of the caterpillars in villages located in Sabah determined that DDT
spraying caused a 50% increase in caterpillars per roof area over that
of the normal population, but the huts sprayed with a more toxic
insecticide, dieldrin, had almost no caterpillars. Oddly, then, there
would have been no complaints of this sort had the more toxic
insecticide been used everywhere, thus killing both moth caterpillar and
wasp. Also, it is likely that versions of the cat story that contain
North Borneo (Sabah) as the place, and dieldrin as the insecticide, are
linked to this study.
A literature search to determine where DDT and dieldrin were used in
Sarawak and Sabah resulted in several relevant articles. A report was
written by the members of the WHO anti-malarial team working in Sarawak
(de Zulueta and LaChance 1956). Their report describes the first efforts
to spray DDT and another insecticide, BHC, in Sarawak to prevent malaria
between 1952 and 1955. In essence, spraying only occurred inside
dwellings, which for each village, consisted of one structure, or
“longhouse”, a large thatched-roof building that could house as many as
100 families. This living arrangement was advantageous for the
eradication of malaria as it meant that spraying could be localized
unlike areas where people lived a nomadic or semi-nomadic existence. The
report also describes the spraying technique used: DDT was mixed as a
75% solution in water and applied on walls and under beds at the rate of
2 g/m2 twice a year. This application rate was high enough to form white
spots of DDT residue on surfaces (Sandosham 1959). Colbourne et al.
(1960) also add that dieldrin was first used in Sarawak in 1955 because
its higher toxicity required less volume to be transported through the
jungles of Sarawak. According to Colbourne et al., dieldrin was used
throughout “the First Division” of Sarawak, but because of its higher
cost and toxicity, its use was discontinued, presumably at the end of
the spraying effort in 1957. For administrative purposes, Sarawak was
divided into five divisions of unequal area numbered one to five from
west to east across Sarawak (Morrison 1993). Therefore dieldrin was
primarily used in the westernmost part of the state which includes the
capital, Kuching (Figure 1). Detailed reports on the anti-malarial
program in Sabah similar to those provided by de Zulueta and LaChance
(1956) and Colbourne et al. (1960) for Sarawak could not be found.
However, in an analysis of the program in certain parts of Sabah, Cheng
(1967) states that DDT was “the residual insecticide in use in the
programme.”
References:
- Cheng FY. 1963. Deterioration of thatch roofs by moth larvae after
house spraying in the course of a malaria eradication programme in
North Borneo. Bulletin of the World Health Organization. 28:136-7.
- Colbourne MJ, Huehne WH, Lachance F de S. 1960. The Sarawak
anti-malaria project. The Sarawak Museum Journal 9:215-248.
- de Zulueta J, LaChance F. 1956. A malaria-control experiment in
the interior of Borneo. Bulletin of the World Health Organization.
15:673-693.
- Sandosham AA. 1959. Malariology with special reference to Malaya.
Singapore: University of Malaya Press.
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