Operation Cat Drop: history or hoax?

Many accounts of Operation Cat Drop were accompanied by comics, so this seemed appropriate.(Sketch by HT)

Many accounts of Operation Cat Drop were accompanied by comics, so this seemed appropriate.(Sketch by HT)

Once upon a time in Borneo, everybody was dying of malaria, so they sprayed a lot of the insecticide DDT (dichlorodiphenyltrichloroethane), which killed the mosquitoes that transmitted the disease. Cases dropped, but inexplicably, peoples’ roofs started caving in. DDT had also killed wasps that kept the caterpillar population in check, so the caterpillars ate the roof thatch. Geckos ate the wasps, and cats ate the geckos. Cats started dropping dead, and the rat population flourished, which lead to an outbreak of the plague. So, to solve the problem, health officials parachuted cats into Borneo.

Or, at least that’s how the story goes.

I first heard of this ecological fable — nicknamed “Operation Cat Drop” — from a friend who liked to break it out at dinner parties. Frankly, it sounded a bit ridiculous. So, ridiculous in fact, that somebody could very well have made it up, and some have argued that the tale is just that: fiction. The cat story started popping up in print in the 1960s, making appearances in The New York Times, Time, and Natural History magazine. In the late 1960s and early 70s, biomagnification and the ecological impacts on avian species took center stage in the public debate over the safety of DDT. But, I’ve always wondered whether there was any truth to the cat story, which did come up in congressional hearings on DDT use. Turns out, there’s more than you’d think. Patrick O’Shaughnessy, an environmental engineer at the University of Iowa, did some digging and found kernels of truth from which the cat drop myth probably grew. His work was published in the American Journal of Public Health. Here’s what we know…

In the 1950s, the World Health Organization (WHO) launched a global effort to eradicate malaria, following successful campaigns in the United States, Europe, and Venezuela. Resistance to the insecticide had popped up in some mosquitoes, but they were very optimistic. Perhaps a little too optimistic. From 1952-55, in the Sarawak region of Borneo, malaria control teams sprayed DDT, benzene hexachloride, and briefly dieldrin twice a year inside local long houses with thatch roofs. At first, the program enjoyed some success. From 1953 to 1955, the fraction of local mosquitoes carrying the disease fell from 35.6% to 1.6%.

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