Dubious studies poison war on malaria

Richard Tren | 29 Oct 2009
Business Day (South Africa)
For years, fear and uncertainty, fuelled by politically driven and misleading information, undermined the fight against HIV/AIDS in SA. The result was the avoidable deaths of more than 300000 people. Now fear and uncertainty are being peddled again, this time against DDT use in malaria control. Without strict adherence to evidence and good science, the consequences for malaria control and human lives in Africa will be dire.

A recent paper published in the British Journal of Urology International by University of Pretoria researchers measures the incidence of urogenital birth defects in about 3300 boys in Limpopo, some born in houses sprayed with DDT and some not. The study purports to find evidence that if a house is sprayed with DDT, the chances of a boy born with a urogenital defect will increase by one third.

This finding sounds alarming and would have serious implications for control of insect-borne disease if the evidence was solid. In reality, the evidence is weak and should have no bearing on policies to use DDT. Problems with the study abound. There is a weak definition of DDT exposure and poor control for other pollutants and important factors like consanguinity and the mother's age.

In trying to find a statistically significant relationship between exposure to DDT and urogenital birth defects, the researchers did not use the standard 95% threshold for statistical significance, increasing the likelihood of a chance result being seen as statistically valid. If the investigators had used conventional standards of statistical significance, they would have identified no relationships at all between DDT and urogenital birth defects.

A critical review of their research will show that the incidence of urogenital birth defects is actually remarkably similar between the DDT-sprayed areas and the nonsprayed areas. In fact, for two of the birth defects studied, the incidence was higher in areas never sprayed than in sprayed areas.

DDT has been used in vast quantities for decades. The US used DDT since the mid-1940s for agriculture, pest control and malaria control, and it was sprayed almost everywhere with gleeful abandon. Millions of mothers would have ingested and been exposed to high levels of DDT. With the advanced health systems in developed countries, any increase in birth defects of this nature would have been picked up rapidly. Yet there is no record of any such increase in the US or in any country that used DDT. Any rational evaluation of the cost and benefits of DDT would argue for its use.

As pressure mounts against DDT, public health professionals battling malaria face stark choices. The range of insecticides that can be used is limited and insecticide resistance menaces their efforts. There is no replacement for DDT and environmentalist campaigns have increased the cost of developing and using insecticides to such a degree that the research pipeline is worryingly empty.

Environmentalist groups such as Pesticide Action Network campaign against insecticides and suggest the use of mosquito larvae-eating fish and other flaky, unproven notions as alternatives. These ideas would be laughable if the implications for some of the poorest and most vulnerable people on earth weren't so deadly.

In the face of lies that antiretrovirals were poisons and would kill AIDS patients and that beetroot was a viable alternative, activists, scientists and the public pushed back. They defended the science and stood up for common sense. The malaria community needs that same courage and support. Without it, a vital public health tool will be demagogued out of use, and lives in SA will be put at risk.