Malaria fight hurt by flimsy anti-DDT research

Jasson Urbach & Donald Roberts | 09 May 2023
Business Day (South Africa)
Next year, SA will probably meet its Millennium Development Goal of halting and reversing the incidence of malaria, thanks to the careful, targeted spraying of insecticides, including DDT, in houses. The insecticides protect residents for an entire malaria transmission season, saving countless lives. This method of malaria control is safe for residents and the environment, and is approved by the World Health Organisation (WHO) and the world's leading malaria scientists. Despite the overwhelming public health benefits of spraying with DDT, some, who should know better, campaign against it.

Last year, Prof Henk Bouwman of North-West University and co-authors published a paper in a respectable journal, Environmental Research, claiming that DDT spraying led to thinning of bird eggshells. Bouwman collected just 15 cattle egret eggs, five in an area of Limpopo where DDT is sprayed indoors for malaria control, and 10 where no malaria control is conducted. After measuring eggshell thickness and levels of DDT and its metabolite DDE, Bouwman performed a regression analysis and concluded that DDT thinned eggshells.

The idea that DDT thins eggshells is not new, but Bouwman used his research to advocate against DDT for malaria control. Let us accept for a moment that Bouwman's evidence was solid — one would still have to weigh potential harm to bird populations with the enormous life-saving benefits of using DDT. But, in fact, we cannot even make that supposition, because Bouwman's analysis was false.

In analysing his data, Bouwman, in what we assume was a blunder, transposed the data from the DDT-sprayed areas and unsprayed areas. An accurate analysis of his data actually reveals that the eggshells in the sprayed areas were marginally thicker than in the unsprayed areas. Yet based on his false analysis, Bouwman argued that "there is good cause for concern about the reproductive performance of the cattle egrets in the study area and also in other DDT-sprayed areas in Africa".

We, with seven other malaria experts, published a response to Bouwman's paper in Environmental Research, exposing his falsehoods and incorrect conclusions. Bouwman was alerted to his mistake when our response was accepted for publication in January. To date, no erratum or response from Bouwman or his co-authors has been published. This episode is of great concern to the malaria-control community in Southern Africa. Bouwman and a small clique of scientists have long campaigned against DDT using the flimsiest of data, and in the case of Bouwman's latest efforts, falsehoods. In 2009, Bouwman went so far as to claim on TV that Caster Semenya's intersex condition was somehow linked to DDT, causing alarm in malarial areas, to the detriment of disease-control efforts. Pressed to provide evidence for his scaremongering, he refused. 

This affair raises some important questions. How is it that the peer review process failed so dramatically and the journal went ahead and published such falsehoods? Could it be that the reviewers so clung to previously held beliefs about DDT that they did not check his work? How should SA's taxpayers respond, when they learn that the Water Research Commission, which they fund, sponsored Bouwman's research? And why should taxpayers support faulty research that is then used to campaign against another taxpayer-funded programme that saves lives from deadly malarial mosquitoes?

Anyone can make mistakes, but why does North-West University's governing council permit one of its faculty to behave in an unprofessional manner, making outlandish statements and refusing to communicate with peers, thereby frustrating efforts to correct his mistakes? Since the early 1960s, environmental campaigners have lobbied against DDT, though it has, according to the WHO, saved many millions of lives. This fact has not stopped the campaigns against DDT, though science clearly supports its use in disease-control programmes, where the benefits far outweigh any potential cost.

We fully expect the search for some environmental and/or human health harm from DDT to continue, though thousands of studies over decades have uncovered precious little. Yet we hope that the unfortunate Bouwman affair gives other scientists, journal editors, and the public in general a wake-up call.

Urbach is director of Africa Fighting Malaria, SA. Roberts is professor emeritus at the Uniformed Services University of the Health Sciences, US.