LARGEST TRIALS EVER SHOW MOSQUITO NETS COULD SAVE

      500,000 AFRICAN CHILDREN A YEAR - AT VERY LOW COST

Two of the largest trials of mosquito nets ever carried out show that
the lives of some 500,000 African children might be saved each year
from malaria if the nets, treated with biodegradable pyrethroid
insecticide, were widely and properly used.

In the new trials, impregnated bednets and nets, covering windows and
doorways, protected sleeping children from malaria transmitted by
mosquitos, resulting in a dramatic reduction in child (under five)
deaths -- by one third in Kenya and by one sixth in Ghana.

"These are very exciting results," said Ebrahim Samba, M.D., Director
of the WHO Regional Office for Africa in Brazzaville, Congo -- where
an international meeting recently reviewed the trials and called for a
"phased and continuously monitored introduction of impregnated nets"
against malaria.

Malaria is easily the biggest public health problem in Africa. The
disease is caused by a parasite transmitted by the bite of mosquitos
-- generally Anopheles gambiae in Africa -- which bite during the cool
hours of darkness. 

Some 90 percent of the world's more than 1 million deaths a year from
malaria occur in Africa, but until the 1990s, control efforts were
very weak, even though malaria has been getting worse and spreading.

In the Kenya trial, the nets not only saved lives but also led to a 40
percent fall in hospital admissions for severe malaria -- indicating
that nets could reduce the burden on health services. Bob Snow, Ph.D.,
of the Kenya Medical Research Institute in Kilifi, said:

"Malaria is the single largest cause of hospital attendance in
children in Kenya, and any substantial reduction in incidence would
make a tremendous difference to the health services because health
resources are so limited.

Although public health experts foresee substantial social, logistic
and economic problems in distribution and regular six-monthly or
annual re-impregnation of the nets, the new results are being widely
welcomed. 

African ministers of health have already endorsed the use of the nets.
Kazem Behbehani, Ph.D., Director of WHO's Division of Control of
Tropical Diseases, says "the nets should find a very important place
in 38 African countries which have established and begun to implement
national malaria control plans."

The two studies are to be published in the European journal Tropical
Medicine & International Health on April 5. A third large-scale trial
in Gambia showed a life-saving potential of bednets at a quarter. The
fourth study in a very malarious area of Burkina Faso is currently
being analysed with results due in the summer of 1996. 

"These four trials have involved half a million people and 20 research
institutes and donors, and have tested the use of these nets in
different areas with different malaria risks," said Jacqueline
Cattani, Ph.D. of the United Nations Development Programme/World Bank/
World Health Organization Programme Special Programme for Research and
Training in Tropical Diseases (TDR) -- which launched and funded the
studies. "These have been the most demanding field studies ever
undertaken by TDR -- and at nearly $5 million, the most expensive."

Villages were picked at random to receive or not to receive the nets,
and followed for malaria cases for two years. Scientists studying the
effects covered almost all relevant disciplines -- and included
epidemiologists, demographers, parasitologists, clinicians,
entomologists, social scientists, economists, health educators and
health policy specialists.

"The goal was to test widely the results from a small study in Gambia
in 1990," Dr Cattani said. "And indeed, with these wider results,
public health officials can now see that impregnated nets are a very
cost-effective malaria-fighting tool."

Initial TDR economic analysis estimates that investment in nets would
be comparable with global immunization programs for tuberculosis,
measles and polio. Governments may nevertheless ask users to pay. Nets
can be bought for $5-$10, and insecticide for a year would cost
between $.50 and $1.

Africans do spend on protecting themselves from mosquitos. Out of
annual incomes of $300-$400 in some regions, Africans have been
estimated to spend up to $65 -- a fifth of their income -- on items to
combat mosquito bites and on mosquito coils to keep insects out of
their homes. This would be like an American on $30,000-a-year income
spending $6,000 a year on insect repellent.

However, in Gambia an attempt at "cost recovery" -- asking people to
make contributions to pay for the insecticide -- reduced
re-impregnation rates of the bednets from 70 percent to 18 percent.

Such nets have been widely used throughout the world, particularly in
Asia, but are rare in Africa. According to the WHO Regional Office for
Africa in Brazzaville, some 22 of the region's 46 countries have
introduced impregnated nets in recent years, but only on a small
scale.

"Most people in Africa have heard of mosquito nets, but only one in 20
use them, except near swamps and irrigation dams or channels, where
their bites are really irritating," says Christian Lengeler, Ph.D., a
Swiss Tropical Institute scientist who coordinated the present studies
for TDR.

People's attitudes about the nets are already changing. According to
Fred Binka, M.D., coordinator of the Ghana trials: "In Northern Ghana
where we held the trials, the communities are still very traditional
and when we began bednets were very rare. But now they have become a
feature of every household. Proper drug treatment is not easily
available to them, and they recognize that here is a way to save their
children's lives." Dr. Binka estimated that when the bednets were
used, between two and three children slept under each net.

Malaria scientists familiar with the net tests pointed out, however,
that the nets may influence the rate and timing of the acquirement of
natural immunity to malaria, and the effect of the nets on older age
groups must be carefully monitored during their introduction.

Evidence is now available for most stable malaria settings in Africa,
but more information is needed on areas with epidemic malaria and the
highest levels of perennial transmission, these scientists say. 

The effects measured by the trails are considered "realistic", as they
were achieved despite the fact that, for example, in Ghana only 72
percent of the people actually used the nets in the wet season and
only 50 percent in the dry season -- even though the nets and
insecticide were provided free of charge.

A few concerns have already been voiced. For example, could the nets
simply delay the onset of malaria immunity, so that the children saved
under the age of five will simply die when they get malaria later?
Some experts consider that possible, but others point to experience
with protecting young children with chemoprophylaxis -- regular
antimalarial drugs -- which shows that even though such children do
get more malaria when they stop the drugs, their age and strength then
makes them more able to survive it. 

Moreover, the nets may be working not by stopping malaria in the
children altogether, but by reducing the frequency of severe and fatal
infections -- thus allowing immunity to develop. These situations will
need to be watched, particularly in areas where transmission is low
and immunity slow to develop.

Another question will be whether the mosquitoes will develop
significant resistance to the pyrethroid insecticides, as they did to
DDT in the 1950s and 1960s. Eventually they will, the experts say.
Resistance is already reported among certain "nuisance" mosquitoes,
the Culex species, and in isolated instances among Anopheles.
Moreover, pyrethroids are also used in agriculture, causing further
exposure and potential selection of resistant varieties. Presently,
resistance is not considered an operational issue.

What's now needed, according to trial coordinator Christian Lengeler,
is more active interest, attention and marketing of the nets by the
public sector -- for example, by providing information through
schools, and to women when they visit primary health care centres
during pregnancy. Indeed, since pregnant women are excluded from many
treatments for fear of affecting the foetus, if nets could be provided
to them at such visits they could become one of the few disease
interventions actually targeted for pregnant women -- who are also at
risk of increased malaria as pregnancy reduces immunity -- as well as
to their children.

                                    * * *

Organizations contributing to the trials included the International
Development Research Center (IDRC) in Canada, the Overseas Development
Administration (United Kingdom), the Medical Research Council (UK),
and the Wellcome Trust (UK), along with agencies and health ministries
from Denmark, Gambia, Ghana, Italy, and Kenya, and international
bodies such as UNICEF and WHO. The trials were coordinated and funded
by the UNDP/World Bank/WHO Special Programme for Research & Training
in Tropical Disease (TDR). A fifth trial, begun later with the support
of the United States Agency for International Development (USAID), is
under way in a highly malarious region of West Kenya.



For further information, please contact Igor Rozov, Health
Communications and Public Relations, WHO, Geneva. Tel. (41 22) 791
2532, Fax (41 22) 791 4858 or Dr Carol Vlassoff, Special Programme for
Research & Training in Tropical Disease (TDR), WHO, Geneva, Telephone
(41 22) 791 3766, Fax (41 22) 791 4854.

All WHO Press Releases, Fact Sheets and Features can be obtained on
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