The GiveWell Blog

Putting the problem of bed nets used for fishing in perspective

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.


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.


  • Avi Norowitz on February 5, 2015 at 9:56 pm said:

    Thanks for taking the time to address these arguments.

  • Richard Chappell on February 6, 2015 at 2:49 am said:

    Yes, very helpful, thanks!

  • Daniel Gastfriend on February 6, 2015 at 7:59 am said:

    Thanks for this assessment. I agree with this conclusion, but I wonder if there is more we should be doing to investigate and mitigate the potential harms discussed in the NY Times article.

    Even with non-usage rates of just 10%-20%, that still seems to be a sufficiently large number of nets to cause substantial harm, if the arguments in the article are accurate. While the evidence in the article is limited, the argument strikes me as sufficiently plausible that we should be concerned.

    AMF is already in a much better position than other bed net funders to address this issue, given its emphasis on monitoring. Would it be possible to map out high-risk areas in advance (food-insecure waterside communities with low bed net usage), conduct more intensive monitoring there, and adjust implementation protocols accordingly if sufficiently high rates of misuse are found? I’m not sure what the best response would be – perhaps pairing bednet distributions with other interventions (community organizing, education programs, cash transfers, etc.) or substituting bednet distribution with alternative anti-malaria strategies if fishing with bednets is causing substantial harm and can’t be controlled. In any case, it would be worthwhile knowing the extent to which these distributions are causing harm, and I suspect collecting this data would also reveal potential solutions.

  • Rob Mather on February 6, 2015 at 9:52 am said:

    For readers’ interest, we recently wrote a blogpost on this subject:

    Rob Mather, AMF

  • Thanks. I read the NYT article and wasn’t the least bit alarmed. I suspect many GiveWell donors are too rational to let anecdotal news stories affect their giving decisions.

  • tangent on February 8, 2015 at 12:29 am said:

    How about distributing proper fishing nets along with mosquito nets, for lakeside communities? They would reduce the bycatch-to-catch ratio, and not have the insecticides.

    Could still be overfishing, if the food insecurity is severe, but then that’s a situation to address, not to add malaria on top of.

  • Thanks everyone for the comments and questions.

    Daniel and tangent – these sound like reasonable ideas, though the question of whether the benefits would justify the costs seems an open one. If AMF, or another outstanding LLIN distribution organization, wanted to try something like this we’d be supportive. At the same time, we think AMF is best positioned to set its priorities and don’t plan to push ideas like these.

  • Laura Liebstaedter on February 16, 2015 at 3:30 pm said:

    years ago, when mosquito-nets were distributed but not impregnated, I heard they were very much in demand as veils for future brides!

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