Mosquito nets or coil: Which is better?
Fri, 4 May, 2012
Mosquitoes feed on humans primarily at night, especially when people are indoor. The proportion of human exposure that occurs indoor, when people are asleep, is therefore, very high. Experts, in a comparison of all methods used in prevention of mosquito bites, say insecticide-treated net (ITN) is the most cost-effective, reports Sade Oguntola.
The rain is here and with it comes mosquitoes in great numbers. Apart from the annoyance a bite can cause, it can also lead to malaria, one of the most serious illnesses in children and pregnant women, which comes from the germ that mosquitoes carry.UNICEF indicated that Malaria kills a child somewhere in the world every 30 seconds. It infects between 350 and 500 million people each year, killing one million, mostly children in Africa. Ninety per cent of malaria deaths occur in Africa, where malaria accounts for about one in five of all childhood deaths. The disease also contributes greatly to anaemia among children — a major cause of poor growth and development.
Malaria infection during pregnancy is associated with severe anaemia and other illness in the mother and contributes to low birth weight among newborn infants — one of the leading risk factors for infant mortality and sub-optimal growth and development.
Malaria is both preventable and treatable. In fact, many people had resorted to the use of mosquito coils, insecticide sprays, local herbs and insecticide treated mosquito nets to prevent mosquito bites.How effective are these protection tools for malaria, which act mainly by preventing the contact between humans and mosquito vectors, with the exception of the insecticide vaporizers which also aim to kill mosquitoes entering dwellings?
Are they safe in terms of their adverse effects on human users? Which is better? No doubt, the effects of these household products are similar. They either kill or repel mosquitoes.
Smoke and mosquito coils were the first methods used by man for protection against mosquito bites. They are widely used all over the world, predominantly in Asia, Africa and the Western Pacific.
Scientists in a systematic review of trials which looked on the effectiveness and safety of insecticide-containing mosquito coils in the 2004 issue of the Journal of Travel Medicine found no evidence that burning these coils prevents malaria acquisition. According to the researcher, “there is consistent evidence that burning coils inhibits nuisance biting by various mosquito species. Thepotential harmful effects of coil smoke on human users should be investigated.”
The review included 38 studies, which tested the efficacy of coils in achieving mosquito bite reduction (reported in 14 studies), mosquito repellence (seven), deterrence (five), “knockdown” effect (five), and percentage mosquito mortality (seven).
Although some insecticide classes and strengths were associated with better antimosquito outcomes than others, one trial identified possible adverse effects (irritation of the eyes and nose) in human users of this technology.
Mosquito biting rates can be reduced by up to 80 per cent in the presence of a burning coil, depending on the size of the room in which it is used and the active ingredient in the coil. Scientists in a 2003 study reported in the Journal of Tropical Medicine and Parasitology that with increase in burning time and distance from the insecticide containing coil, the percentage of mosquitoes that land reduces.
But many consumers complain that after the use of anti-mosquito products such as insecticide treated mosquito coils and aerosol insecticide, there were mosquitoes still in their homes. In addition, although the price of insecticide treated mosquito coils is far less than aerosol insecticides, once the effects of insectide wanes, the mosquitoes come trouping back. This is aside the fact that its smoke causes adverse effects on some individuals.The smoke emitted from the burning mosquito coil consists of submicron particles coated with a considerable amount of heavy metals and a wide range of organic vapours, such as phenol and o-cresol. Therefore, a lengthy exposure to this smoke will cause adverse effects on the consumer.
In most areas, malaria is transmitted by mosquitoes that bite predominantly at night. So, sleeping under a mosquito net treated with an insecticide that repels mosquitoes and kills those that land on the netting can greatly reduce the risk of infection. Insecticide-treated mosquito nets (ITNs) have been shown to reduce deaths in children under five years of age by about 20 per cent and malarial illnesses among children under five and pregnant women by up to 50 per cent. The insecticides used to treat the nets have been approved for safety and efficacy by the World Health Organisation.
Long-lasting ITNs have the insecticide bound to or incorporated within the netting material during production, enabling the nets to maintain their full protective effect through about 20 washes or approximately three years of regular use. However, Dr Chioma Amajoh, Deputy Director, Roll Back Malaria, Federal Ministry of Health, in a cost analysis of mosquito coil usage, aerosol insecticide and insecticide-treated mosquito nets, disclosed that on the long run, the use of an insecticide-treated mosquito net was the cheapest.
Dr Amajoh, who stated that insecticide-treated mosquito nets was the most effective of all these mosquito prevention interventions, pointed out that when there were at least, two insecticide-treated mosquito nets hung in a home, mosquitoes would find it unbearable staying, and as such, move away.
According to her, “mosquito coils do not kill but knock them down. They are resuscitated late to come back to bite because they still need blood.”She also pointed out the need for removing breeding sites of mosquitoes both within and outside the home in a bid to prevent mosquito bites.
Also, Dr Sam Awolola, a malaria expert at Nigerian Institute of Medical Research, Lagos, declaring that mosquito coils and aerosol were not too cost effective methods, stated: “How many days will a can of aerosol insecticide be used? It is not like the insecticide-treated mosquito nets that are used for years. If you come to analyse the cost, you will see that insecticide-treated mosquito nets are cost-effective.”
However, Dr Dipo Ogundare, Co-ordinator, Health Shield Incorporated, Ibadan, a non-governmental organisation which is involved in malaria, immunisation and nutrition advocacy in the community, expressed concern on the availability of insecticide-treated mosquito nets.
He stated: “Non-availability of insecticide-treated mosquito nets is a major problem. It is presently inaccessible to the common man because of its cost. Considering the economic status of most people in the community, not many people buy it. If the government can make it freely available, it would be better.”
According to Dr Ogundare, “Nigeria need not wait on donors to supply insecticide-treated mosquito nets. Corporate organisations and other individuals can make these nets available.”