Precaution and funding of vector control must be based on evidence

Richard Tren & Donald Roberts | 18 May 2023
Malaria Journal
In their paper "Status of pesticide management in the practice of vector control: a global survey in countries at risk of malaria or other major vector-borne diseases," van den Berg et al. make some generally accepted and valid arguments about the need for improved management of public health insecticides (PHIs). Given the importance of vector control, it would be beneficial for malaria control program managers and staff to be trained in proper insecticide use and management, if only to slow the spread of insecticide resistance. However the authors reveal an anti-insecticide bias and an ideological approach to disease control that could potentially undermine disease prevention efforts.

In stating "All chemical pesticides are inherently toxic to humans and precaution is required to minimize exposure and adverse health effects," the authors are creating opportunities for scaremongering. The needs for research and for improved procedures to minimize exposures to both disease-carrying insects and insecticides are self-evident. Yet, invoking "precaution" at the level of warning residents their houses are being sprayed with a harmful chemical to minimize adverse health effects should be based on proof of such adverse effects. Such proof does not exist, as exemplified by the circular logic displayed by the first author in another paper in which he and co-authors argue residents should be warned of possible harm from DDT exposures. In that paper the authors trumpeted "precaution" by justifying a claim of adverse health effects with the statement, "The very fact that there are so many precautions built into the WHO guidelines shows that IRS chemicals are considered hazardous." Such rationalizations reveal clear intent to expand the precautionary principle to restrain PHI use in disease control programs. Reasonable people know existence of safety measures (which often result from mere claims of potential dangers) does not imply IRS chemicals are dangerous. On the other hand, reasonable people accept that prudent safety standards are important. Warning residents that DDT and other PHIs are dangerous is neither prudent nor good public health policy because it would result in spraying refusals, an outcome that would increase risks of malaria transmission.

The authors conclude with the statement that support for vector control by donors and funding agencies should be contingent on them pursuing an IVM approach. We disagree strongly. Support for vector control programs should be based on the evidence of disease control efficacy. If a program that relies heavily on IRS delivers the best results in terms of disease reduction, then that is what should be supported. Though IVM should embrace effective methods of malaria control, such as IRS, we believe that IVM is far too often interpreted as adopting any and every vector control method except the spraying of insecticides. This is proven by the highly biased track record of funding malaria control programs without PHIs by the UN Environment Programme and Global Environment Facility. Making IVM a condition of funding elevates ideology above evidence and has no place in disease control programs.

In summation, the authors reveal intent to invoke the precautionary principle over disease control programs and use power of the purse strings to pressure governments away from critically important uses of PHIs to control malaria and other insect-borne diseases. The disease control community must continue to resist the anti-PHI agenda.