Claim: Several people believe that sleeping under a mosquito bed net treated with insecticide (or not treated) is ineffective and harmful to human health.
Verdict: The claim that sleeping under bed net is harmful to human health and ineffective is misleading. Medical experts and scientists have affirmed that sleeping under a bed net reduces the risk of man-vector contact as mosquitoes bite at night and it is, thus, an effective preventive measure without any harm when the ‘user’s guide’ is promptly adhered to.
Commenting on an article on ‘Treatment and use of Insecticide-treated Mosquito Nets’ by the National Vector Borne Disease Control Programme, some people shared their experiences on the use of treated nets.
On September 30, 2019, one of them, Ajith, raised a question on the website, saying: “I want to know how the itching of the net can be removed??? For reuse”.
Also on April 26, 2020, another person, Pradip, reacted to the article with the comment: “when I sleep under it during night, I feel irritation in my face and eyes, what to do.?”
Likewise on May 26, 2020, W. Maynard, another contributor, claimed that sleeping under a treated net caused a burning sensation around the eyes and face and would like to know why?
Another person who joined the conversation on the website, Monica, also reacted on May 27, 2020, noting that: “I have the same problem tingling and burning sensation on the face especially around the eyes.” These are few among many claims about health hazards of Insecticide treated bed nets.
A screenshot of the claims. But is this true or there are some misconceptions somewhere?
Brief on Malaria and Mosquito bed nets:
Malaria and certain other diseases are transmitted by bites from Anopheles mosquitoes. To prevent this, experts counsel that sleeping under mosquito preventive bed nets reduces both mosquito bite and malaria. However, using ordinary mosquito nets, those not treated, provide limited protection because mosquitoes may still bite through the net after perching on the untreated net, depending on how close the person inside the net is to the net.
According to an article written by Brian Mcneill from Virginia Commonwealth University, the nets, which serve as a protective barrier for the people sleeping under them, have been proven to help prevent the spread of malaria, a disease that saw 219 million cases and 435,000 deaths in 2017, according to the World Health Organization.
As the name implies, Insecticide Treated Bednets (ITNs) or Long Lasting Insecticide-Treated Nets (LLINs) are treated with insecticide to provide better and effective protection by keeping away mosquitoes, as well as killing them. ITNs and LLINs also kill or keep away other nuisance insects like cockroaches, bedbugs, houseflies, fleas, etc. But there have been reports or claims that the insecticide treated bednet does not work and are harmful to human health. Are these claims true? Or, are there other things we are ignorant of that we really need to know about ITN or LLIN?
Mosquitoes and mosquito nets
Mosquito nets, also called bednets, are hung over beds. Some tents are made of mosquito-net fabric to help campers avoid the pesky insects. Light and air can easily penetrate mosquito nets, but mosquitoes cannot; nevertheless, the sharp proboscis of the mosquito, that is, the long, narrow mouthpart the mosquito uses to pierce the skin and suck the blood of its victim can penetrate the net if draped directly on the human body.
The word insecticide is used to describe any chemical that is applied against undesired insects that cause harm to animals, humans, and plants; but all pesticides are toxic in nature. The risk of adverse effects from a pesticide depends on the toxicity of the chemical and the degree to which an organism is exposed to it.
The insecticide used in Insecticide-Treated Nets, ITNs, is deadly to mosquitoes, but generally harmless to people and pets. It slowly breaks down when the material is washed or constantly exposed to sunlight. Some ITNs need to be replaced every six months, while newer versions last up to three years. ITNs that last three years are called Long-Lasting Insecticide-Treated Nets (LLINs).
ITNs are one of the most effective methods of preventing mosquito-borne diseases in the developing world, reducing the number of malaria cases by 20%, most of which involve children not yet five years old. ITNs are crucial in the developing world, where lack of money, lack of available medications, and lack of distribution networks can prevent communities from accessing antimalarial drugs.
Although, new research indicated that mosquitoes may develop behavioural resistance to insecticide-treated nets (ITNs), ITNs are the most effective tool against malaria in the developing world. According to NOVA Next, “the reductions in transmission are nothing short of astonishing — 25%, 50%, even 80% fewer cases in some places.”
LLINs are mosquito nets which have the insecticide embedded in their fibre, so that it is not removed by as many as 20 washes. Because these nets have an even and quality controlled insecticide application, they are generally more effective than conventional ITNs. Also, the LLIN is more cost-effective (as it can be used for three to five years) than conventional bed nets that are treated with insecticide once or twice a year. Conventional ITNs are therefore only a rational option in areas, where the population already has so many nets.
In order to prevent and control malaria, there was a global partnership in 1998 by the World Health Organization (WHO), the United Nations Development Program (UNDP), the United Nations Children’s Fund (UNICEF), and the World Bank to found Roll Back Malaria (RBM). The goal was to halve the world’s malaria burden by 2010, with the period 2001–2010 tagged as the “United Nations Decade to Roll Back Malaria.” The RBM partnerships include national governments, civil society and nongovernmental organizations, research institutions, international development agencies, and development banks. Also between 2015 and 2017, 624 million insecticide-treated mosquito nets were distributed, mostly for free, to reduce malaria, severe disease and death in regions of the world where malaria is endemic.
According to an Associate Professor at the Faculty of Pharmaceutics, Obafemi Awolowo University, Ile-Ife, Dr Olusola Aremu, the main purpose of the treated bed nets is to protect an individual against the mosquito. He noted that the chemical solution used in treating the ordinary net kills the mosquito once inhaled or serves as a repellent to such mosquito from the odour of the chemical.
Speaking on why the treated net is neither harmful nor ineffective, Dr Aremu noted that the chemicals used in treating the net were meant to kill or repel the mosquito. Human beings, also a living organism, can be affected if the instructions on the manual for net users are not adhered to, he said.
He added that the essence of drying the net for hours before use is to allow for escape of some of the chemicals to reduce toxicity.
Answering to why some are affected by the net even after all instructions are adhered to, Dr Aremu noted that people’s genetic makeup differs and what affects ‘Mr A’ at the first instance may not have impact on ‘Mr B’ at several instances; and the drug ‘Mr A’ can take without any complication can adversely affect ‘Mr B’. He advised that people whose genetic makeup cannot tolerate the chemical left on the net after it has been exposed to coolness for over 12 hours, such as those that get itching, irritation, burning sensation around the eyes and face, etc; should use other methods of preventing mosquitoes.
Dr Aremu further stated that in advanced medical practice, consultation and drug administration is being individualised, that is, the medication given to ‘Mr A’ might not be given to ‘Mr B’ because his body might not tolerate it; hence, the need to know the genetic makeup of a patient before administering medication is highly recommended.
Another expert wade in
In an interview with the Medical Rep, at Vaticanbells Pharmaceutical Ltd, Ibadan, Pharm. Cosmas Ayilola, noted that an untreated bed net only serves as a barrier for any mosquito that wants to penetrate into the net while treated ones, aside serving as a barrier, also has the tendency to kill the mosquito lingering too much on the net.
Pharm. Ayilola said the bed net “is harmful to human health and not harmful, depending on the individual and precautions taken. Exposing it in a cool atmosphere, a good ventilated area free from the sun between 12 to 24 hours reduces the harmfulness drastically and will have little or no effect on humans”. He added that the untreated bed net can be tagged inactive when the net is not well tucked in because mosquitoes can still find their ways in. While the treated bed net can be tagged harmful when the necessary precautions are not diligently adhered to. He also noted that an untreated bed net can effectively serve the function of an urgent and immediate use.
Talking on why and how a treated bed net can be harmful to human health, Pharm. Ayilola said “those who take it from the nylon and use immediately would be exposed to the chemicals that were used in treating the net which may have a negative effect on their respiratory system and eventually may have its way to their lungs and then to their bloodstream. When a person keeps sleeping under this type of net or gets constantly exposed to such net, the chemical will also find its way inside and the effect of this chemical is cumulative….cumulative in the sense that it will be accumulating in the system, so it might get to a threshold whereby the effect will be significant. So precaution is what makes the difference”. He also advised that “treated bed nets should be obtained from reliable sources so that untreated nets or ITNs are not presented to you as LLITNs”.
But how come some are not effective, hazardous and others are effective and not a threat to human health?
Pharm. Ayilola noted that what really differentiates these types of nets are the treatment and level of chemicals used. He added that an untreated net has no chemical at all, so it is not a threat to human life but can be tagged ineffective if it touches the human body because a mosquito can bite through it, as there is no chemical to kill or repel the mosquito.
In his response to this, Dr Aremu also noted that the INTs cannot last as much as the LLITNs, adding that, the lasting of the nets also depends on the area it is used and the number of times it is washed. But opined that the untreated bed net is ineffective because the smallest size of mosquito can penetrate through it and feed on the body of its victim. He
Dr Aremu submitted that whether your net is washed weekly, biweekly, monthly or as you deem fit, the net should be changed at the 20th wash.
Perspectives from researches
Anyanwu, E.C., Ehiri, J.E., Kanu, I., and Merrick, J. in an article titled: “Health effects of long-term exposure to insecticide-treated mosquito nets in the control of malaria in endemic regions” noted that, one key strategy that has emerged as a tool for malarial control under the leadership of RBM and its allies is the use of insecticide-treated mosquito nets ITMNs.
As the WHO asserts, “there is no doubt about the effectiveness of ITMNs; the challenge is to scale up their use”. This recommendation is based on field trials on the effectiveness of ITMNs, which demonstrated significant reductions in mortality following their use. However, few people, mainly because of their high cost and the perception that the chemicals used to treat them have dangerous effects on pregnancy and the fetus, use ITNs.
In another report, Anyanwu et al. noted that health risks arising from the use of ITMNs primarily include exposure during storage and transport, during net treatment, and during use, exposure to vapors, or dermal or oral contact; adding that evidence showed that all organochlorines, organophosphates, carbamates, pyrethroids, and some fumigants used as insecticides are known neurotoxicants.
Feldman, J. in his research noted that people apply pesticides without protective masks and they usually spray or light the insecticide “coils” in their bedrooms before going to sleep; in such a situation, it would be impossible to avoid direct pesticide inhalation and at least residual neurotoxic response to the chemical insecticide. To investigate the extent of the problem, the U.K. Pesticide Action Network undertook case study evaluations of the safe use of ITMNs in a number of African countries. In Gambia, for example, the group selected permethrin, the insecticide used to treat bed nets in the country’s malaria control program and imported into Gambia by the Government and a number of aid agencies. There were 1300 villages involved in the program and studies have shown that the use of permethrin-impregnated bednets has reduced the number of fatalities from cerebral malaria; however, permethrin is a neuropoison and, as well as acting on the nervous system, can cause itching and burning sensations on exposed human skin.
Also, Field studies revealed significant risks of exposure at a number of stages of the chemical life cycle. These included the time when the pesticide is decanted from the large imported drums, when the bed nets are impregnated by village health workers or by individuals in their own homes, when unlabelled containers are brought into the home, and from misuse of the chemical.
A recent study in the U.S. suggests that 80% of most people’s exposure to pesticides occurs indoors and that measurable levels of up to a dozen pesticides have been found in the air inside homes. The amount of insecticides found in homes appears to be greater than can be explained by recent pesticide use in those households., which is certainly a threat to human health.
Kakko et al. reported that when whole communities were provided with treated nets, ovarian age grading showed a reduction in mosquito survival rate and in the number of sporozoite-positive mosquitoes in malarious communities. Thus, a high percentage of coverage of all members of malaria-endemic communities is considered the most effective way of providing protection for highly malaria-vulnerable children and pregnant women. They also stated that there was evidence for reduced antimalaria antibody levels in children in communities where treated nets have long been used. However, overall benefits in reduced anemia and mortality are sustained.
Curtis et al. conducted a randomized controlled trial to assess the long-term effects of bednet protection during early infancy. A total of 3387 neonates from 41 villages in rural Burkina Faso were individually randomized to receive either bednet protection from birth (group A) or from age 6 months (group B). They then concluded that their study provided additional evidence for the efficacy of ITNs in young children living in areas of intense malaria transmission. But both the aim and outcome of the Curtis et al. research seem to support only the efficacy of the temporal use of bednets, but not the use of IIBNs, and do not tell much about the long-term effects of IIBN exposures.
It is important people know that exposure to insecticides without following precautions places them at increased risk of a variety of acute and chronic conditions, including cancer. Also, according to, Anyanwu et al., many of the anticipated behavioural effects caused by insecticide use could be avoided by the use of untreated bed nets, which, according to them, is supported by the evidence from studies on the efficacy of untreated bed nets to which they provided a reasonable degree of protection against malaria.
As you use your net, whether treated or not treated, always remember:
- Insecticides used for mosquito nets are not harmful to people, if used correctly. Direct skin contact with the insecticide on a still wet net may cause a tingling sensation on the skin. This is not harmful, even for small children.
- The treated net should be spread in a cool atmosphere for 12 to 24 hours before use. This will guard against a direct contact or/ and inhalation of the chemical by the user and also allow the reduction of the chemical before use.
- When using the untreated net, make sure it is well tucked into your bed and it is not draped directly on your body. Hence, mosquito nets are hung from frames and not touching your skin because people can still be bitten through most nets; so, your net should be well fixed.
- The treated net touching the human body can also cause itching and other skin discomfort, so it should also be well placed to avoid skin discomfort.
- Use the insecticide-treated net every night, all year round, even if mosquitoes are not seen/heard.
- Preferably, everyone should sleep under a treated mosquito net or, at least pregnant women and children under five years must sleep under a treated net.
- After treatment, the net may smell of insecticide. This will go away in a few days.
- If you cannot treat your net, then, replace it at the twentieth wash.
The researcher produced this fact-check per the Dubawa 2020 Fellowship partnership with the Broadcastings Corporation of Oyo State, to facilitate the ethos of “truth” in Journalism and enhance Media Literacy in the Country.