A recent article in the New York Times describes people using insecticide treated bed nets for fishing instead of sleeping under the nets to protect themselves from malaria-carrying mosquitoes. The article warns that fishing with insecticide treated nets may deplete fish stocks, because the mosquito nets trap more fish than traditional fishing nets and because the insecticide contaminates the water and kills fish (“the risks to people are minimal, because the dosages are relatively low and humans metabolize permethrin [the insecticide] quickly”). We recommend donating to the Against Malaria Foundation (AMF), an organization that funds distributions of long-lasting insecticide treated bed nets, so we’d like to address the concerns raised in the article.

Net distributions funded by the Against Malaria Foundation

We have reasonably high confidence that most people properly use the nets funded by AMF, because AMF requires distribution partners to conduct follow-up surveys on net use. These surveys show that 80% to 90% of households have nets hung up 6 months after distributions (for more detail, see our charity report on AMF). The survey methodology also dictates that interviewers observe whether survey respondents have hung their nets by entering their houses rather than simply asking them if they’ve hung their nets. We believe that the concerns raised in the article largely don’t apply to net distributions funded by AMF.

The prevalence of unintended use of nets

For net distributions more generally, the best data available indicates that usage rates range from 60% to 80%. Surveys asking respondents if they use their nets generally show usage rates of around 90%, but respondents may not want to report that they use nets in ways unintended by donors. One small-scale study found a usage rate of around 70% based on spot visits to homes compared to a usage rate of around 85% based on asking people, so our best guess comes from adjusting the survey rates downwards to correct for overreporting (for more detail, see our intervention report on long-lasting insecticide treated nets). Even taking into account the fact that some people won’t sleep under their nets, the program remains one of the most cost-effective ways to save lives. Given the very large numbers of bed nets distributed, we do not find stories of unintended use in a few areas particularly surprising. We view the anecdotes related in the article as unlikely to be representative of a problem that would change our assessment of the program.

The evidence on possible harm to fish stocks

Besides the harm caused by some people contracting malaria because they don’t sleep under their nets, which we already account for in our cost-effectiveness analysis, the article warns that fishing with insecticide treated nets may deplete fish stocks. In making this case, the article cites only one study, which reports that about 90% of households in villages along Lake Tanganyika used bed nets to fish. It doesn’t cite any studies examining the connection between bed nets and depleted fish stocks more directly. The article states that “Recent hydroacoustic surveys show that Zambia’s fish populations are dwindling” and “recent surveys show that Madagascar’s industrial shrimp catch plummeted to 3,143 tons in 2010 from 8,652 tons in 2002,” but declines in fish populations and shrimp catch may have causes other than mosquito net-fishing.

It’s worth comparing the evidence presented by this article to the evidence available on the benefits of bed nets. Randomized control trials consistently show large declines in child mortality from distributing nets and trends in malaria mortality and net coverage rates also suggest that mass distribution of mosquito nets has contributed to major declines in the burden of the disease. This evidence comprises one of the most robust cases for impact we’ve seen. The article makes the case for a possible harm to fish stocks relying on highly limited evidence.

Malaria control in waterside, food-insecure communities

The article does highlight a potential need to experiment with alternative approaches to malaria control in waterside, food-insecure communities that have very low net usage rates. In these areas, people shouldn’t have to choose between malaria and hunger. But again, we see this as a likely isolated problem, and a much smaller one than the problem of insufficient nets for preventing malaria.

Conclusion

We generally like to see reporting on both the successes and failures of foreign aid. However, we felt the reporting in this case presented an unbalanced view of the magnitudes of the benefits and harms of distributing bed nets.