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AFRO-NETS> Malaria Protection for Children

  • Subject: AFRO-NETS> Malaria Protection for Children
  • From: "Mercy Wambui" <mwambui@iconnect.co.ke>
  • Date: Tue, 19 Aug 1997 14:43:12 -0400

Malaria Protection for Children may have strange side-effect

By Judith Perera

LONDON, Aug 19 (IPS) - Since the mid-1990s, bednets dipped in insecticide
have been widely used as a defence against malaria-carrying mosquitoes. In
Africa, they are estimated to have cut deaths among children by a third.

However, groups of researchers in Kenya and Britain believe they have
discovered an ironic side effect to the technique that could soon begin a
lively debate about the long-term effects of this simple and cheap
preventive measure.

Scientists working at the Wellcome Trust at the Kenya Medical
Research Institute in Nairobi and at Britain's Oxford University are
suggesting that protecting young children from malaria with bednets may
reduce their immunity to the disease, making them more susceptible to it
later -- when the symptoms may be more severe.

One of the researchers, Bob Snow, admits that no-one knows how
reducing people's exposure to malaria in infancy will affect their long
term survival. There have been no long-term trials comparing houses with
and without bednets because it is considered unethical to deliberately
withhold nets from families.

However, it is generally recognised that the most dangerous forms of
malaria are less common in areas where the children's exposure is very
high, possibly because immunity is higher. Moreover babies under six months
of age are more likely to survive an attack than older children because
they are still protected by the antibodies transmitted to them by their

Snow and his colleagues have looked at severe malaria cases in five
areas of Africa with different exposure rates and have compared the ages
and death rates of those infected.

They looked at the number of children admitted to hospital with
severe malaria and predictably found these were lowest in Bakau in the
Gambia, the area there malaria was mildest. In this area only two percent
of children under the age of nine are infected.

However, the greatest number of admissions was not in the areas where
malaria infections were most intense but in areas of moderate infection --
Sukuta in The Gambia where the infection rate is 37 percent and Kilifi
North in Kenya where it is 49 percent.

In the areas with the highest malaria transmission rates of over 75
percent -- Kilifi South and Siaya in Kenya -- hospital admissions were

The researchers then looked at the pattern of cerebral malaria, the
severe form which causes coma and kills one in five of those infected. They
found most cases were in those areas with the lowest infection rates and
the smallest number of cases in those with the highest infection rates.

Snow says it is possible that in areas of high infection where the
use of bednets for infants is high, it may be that attacks of cerebral
malaria are simply being postponed until the children are over three years
of age and spend more time out of the bednets.

But they would then be more susceptible because they would not have
had the opportunity to build up immunity while still protected by parental

The researchers conclusions have proved unpopular with aid agencies
that have worked hard over the past few years to distribute nets to those
communities most at risk of malaria.

Jacqueline Cattani, head of a special programme on bednets funded by
the World Health Organisation (WHO), the World Bank and the U.N.
Development Programme, says Snow's suggestions are "irresponsible". She
says the nets substantially reduce the chances of children dying before the
age of two years.

However, other scientists feel the issue is worthy of further
investigation. According to Brian Greenwood of the London School of Hygiene
and Tropical Medicine, while nets should not be withdrawn or denied to
those at greatest risk, it is important to recognise that there is a
complex relationship between the malaria parasite and its host "and if you
upset the two you are likely to get surprises".

He adds that other factors may also explain the differences found by
Snow and his colleagues, such as differences in the strains of parasite
between areas and differences in seasonal patterns of transmission.

What Snow's work shows is the real need for more research in this
complex area.

Meanwhile it is unlikely that the use of bednets will be reduced, not
least because research shows that they not only reduce the incidence of
malaria in young children but other diseases as well such as pneumonia.

It seems that protection from malaria generally improves children's
health, explains Louis Molineux, a former head of tropical disease control
at WHO.

He says any rise in cerebral malaria caused by the use of bednets
would probably be more than compensated by the reduction in deaths from
other diseases.

Resolving the issue remains a problems, as it would require a long-
term project comparing households with and without bednets. And
deliberately allowing malaria-bearing mosquitoes to feed of some children
and not others remains an unethical concept.

Alternatively careful and long-term monitoring of death rates in
areas where nets are used and where they are not used may be possible.

But funding for this is not available at present and the issue is
likely to remain controversial for the foreseeable future.

Mercy Wambui

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