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LLINs: The mosquito nets that both protect & destroy

Kainantu child (Hetzel)MANUEL HETZEL

IN 1899, the famous German microbiologist Robert Koch led a malaria expedition to what was then Kaiser-Wilhelm’s-Land, what we now know as New Guinea.

Koch wanted to investigate the tropical scourge that cost the lives of many foreign labourers and weakened the locals. Near present-day Madang, he had no trouble identifying people who carried malaria parasites in their blood.

In the perfectly warm and humid climate, Anopheles mosquitoes were found in abundance. At night, the female Anopheles would look for blood meals and transmit the malaria parasites to anyone exposing too much skin.

In the Sepik, there were so many mosquitoes that people hid at night in woven mosquito baskets or bags. This was not to prevent the transmission of malaria, but to protect themselves against the nuisance of biting mosquitoes.

Distributors Kainantu (Hetzel)Today, there are still myriads of mosquitoes flying around PNG and amongst them the female Anopheles long for a blood-meal. Mosquito baskets are largely out of fashion; but mosquito nets are not.

In 2004, after more than 20 years of little investment in malaria control, the Global Fund to Fight AIDS, Tuberculosis and Malaria started supporting PNG’s malaria control program.

The money obtained was used for repeated free distribution of long-lasting insecticidal mosquito nets (LLIN) to households across PNG.

Between 2004 and 2014, the Health Department and Rotarians Against Malaria distributed over seven million LLINs to households across PNG.

A recent country-wide survey conducted by the PNG Institute of Medical Research found that, as a result of these campaigns, more than 80% of all households now own LLINs.

LLINs are one of the most effective tools in the fight against malaria. The nets physically protect those who sleep under them and also kill mosquitoes that come in contact with them.

This way, they reduce the number of mosquitoes and provide some degree of protection, even to household members not using a net. LLIN technology is sophisticated: the insecticide permethrin is integrated or permanently coated onto the fibres, making the net resistant to multiple washes.  It can last for several years.

The idea of treating mosquito nets with an insecticide was an important step in the fight against malaria.

Researchers from the PNG Institute of Medical Research in Madang were amongst the first worldwide to demonstrate in a scientific study the protective effect of this measure. Their study was published in 1987 in the Bulletin of the World Health Organisation.

Together with other studies conducted mainly in Africa, this contributed to the overwhelming evidence of the effect that insecticide treated mosquito nets can have on reducing illness and deaths from malaria.

The Institute is one of the few institutions in the developing world with the capacity to conduct scientific research to international standards.

Even so, it took almost 20 years to translate locally generated evidence into policy and implementation.

With hardly any domestic resources allocated to malaria control after about 1980, it required the external support from the Global Fund to provide LLINs to households.

In the Sepik villages, where at one time people hid in mosquito baskets and malaria killed many young children, LLINs are now hanging under traditional thatched roofs.

The nets are very much used; a recent Institute study showed that 90% of people who have access to an LLIN sleep under it.

Robert Koch has long passed on, but similar studies conducted these days provide evidence that LLINs work. Fewer people are infected with malaria parasites and the number of people sick with malaria gradually decreases, particularly in areas with high mosquito net coverage.

At the end of last month, the grant from the Global Fund expired. While negotiations for a renewal are promising, the resources available to support the PNG program will certainly be fewer than before.

It will then be up to the PNG government to find the funds to complement a program which has already shown substantial reductions in malaria around the country.

Permanet (Hetzel)In the meantime, the PNG Institute of Medical Research and its international collaborators will continue to seek international research grants to investigate effective tools and approaches that can complement the effect of the LLINs.

With the success of the current program and the global interest to move beyond malaria control to malaria elimination, there is some hope that research support might be forthcoming and that any promising finding might be translated into practice within less than 20 years.

Dr Manuel Hetzel is a public health epidemiologist and scientific project leader at the Swiss Tropical and Public Health Institute in Basel, Switzerland


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