Most households in Kenya own insecticide treated bed nets which are meant to keep malaria spreading mosquitoes at bay.
The
nets play a key role in protecting high-risk populations such as
pregnant women and children from the adverse effects of the disease.
But
over the years the efficacy of these nets in keeping mosquitoes away
and the resultant malaria prevention has been waning as the insects
develop resistance to insecticides lacing the nets (known as
pyrethroids) that are meant to kill them.
As a result,
more children have been dying from the disease in high risk areas than
was the case years back when the bed nets were rolled out in Kenya.
Even though the problem has not yet reached critical levels,
malaria experts have been racking their brains with the aim of finding a
sustainable solution to the problem before the nets become completely
ineffective in malaria control.
After many years of research, there seems to be light at the end of the tunnel.
A
new study published in The Lancet journal shows that bed nets treated
with a new chemical known as piperonyl butoxide (PBO) are more effective
in malaria control compared to nets treated with pyrethroids only.
The
two-year research conducted in Tanzania revealed that the new nets
reduced the prevalence of the disease by 44 per cent and 33 per cent in
the first and second year respectively compared to standard nets.
The
study, which involved more than 15,000 children, is the first to offer
clear evidence that nets treated with PBO can significantly improve
personal and community protection from malaria compared to standard
pyrethroid treated nets in areas where there is high pyrethroid
resistance.
Findings of the study also showed
unprecedented malaria control through indoor residual spraying (IRS)
with a novel insecticide known as pirimiphos methyl, which after a
single spraying round reduced malaria infection by 48 per cent for an
entire year.
Aside from mosquitoes developing
resistance towards them, current insecticides for indoor residual
spraying are short-acting and hence need to be re-applied between two
and four times a year depending on the type of chemical used.
Indoor
residual spraying refers to the application of certain insecticides
inside houses, on walls and other surfaces that serve as a resting place
for malaria infected mosquitoes.
The insecticide kills mosquitoes when they come in contact with treated surfaces, thus, preventing malaria transmission.
The
development of these new chemicals is a result of a collaborative
initiative between the World Health Organisation (WHO) and the London
School of Hygiene and Tropical Medicine (LSHTM).
The
two have been working with the chemical industry for over a decade to
develop new types of insecticides for use in bed nets and indoor
residual sprays.
The project was initiated as a
safeguard measure to ensure alternative chemicals for malaria control
are available, should the existing ones begin to lose their efficacy, as
is currently the case.
“It’s imperative that we try
and remain one step ahead of insecticide resistance which threatens to
reverse the great gains made in combating malaria,” said Natacha
Protopopof, lead author of the study from the LSHTM.
“We
must develop an improved strategy based on new classes of long lasting
insecticide treated nets to control malaria transmitted by pyrethroid
resistant mosquitoes,” said Dr Protopopof.
The counties most affected by the resistance problem include Migori, Kisumu, Homa Bay, Busia and Siaya.
Simon
Kariuki, head of the malaria programme at the Kenya Medical Research
Institute (Centre for Global Health Research) noted that the study
offers hope for malaria control in Kenya which has over the years
grappled with mosquitoes’ resistance to insecticides used in bed nets
and IRS.
“It’s good that we now have something that is
working well. This will give scientists time to come up with new
interventions to fight the disease,” said Dr Kariuki.
“We
were worried as we seemed to be dealing with the resistance problem
everywhere. Aside from bed nets and IRS, malaria treatment drugs were
also affected.”
Dr Kariuki said that to delay mosquitoes from developing resistance to insecticides used in malaria control and prevention, scientists were using a combination of two chemicals to develop new insecticides.
Dr Kariuki said that to delay mosquitoes from developing resistance to insecticides used in malaria control and prevention, scientists were using a combination of two chemicals to develop new insecticides.
“If the mosquitoes develop resistance to one, the other will still work.”
For
indoor residual spraying, experts are also recommending the application
of two different types of insecticides - on different sides of the wall
- so as to minimise resistance.
As a direct
consequence of the research trial done in Tanzania, the WHO introduced
an interim policy recommendation allowing the use of the new PBO bed
nets in affected areas.
Jan Kolaczinski, Coordinator
for Entomology and Vector Control in the WHO Global Malaria Programme,
noted that the nets should be deployed for malaria prevention in areas
where mosquitoes are resistant to pyrethroids, provided that full
coverage (of affected populations) is maintained.
Long-lasting insecticidal nets and indoor residual spraying are the cornerstones of malaria control in sub-Saharan Africa.
Together
with effective treatment, these interventions are estimated to have
globally reduced malaria and arising deaths by 41 per cent and 62 per
cent respectively between 2000 and 2015.
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