1 research outputs found
Permethrin impregnated bednets and DDT residual spraying, multicentre comparative trial in Solomon Islands
A malaria intervention comparative trial
was
carried out
in
Solomon Islands
between 1987 and 1992, involving 7
pairs
14
communities, with
29,182
people.
Seven
communities were given bed nets
impregnated
with
permethrin annually
at
0.5g/m2,
and the others sprayed biannually with
DDT
at
dosage
2g/m2.
Each
pair was
evaluated for about two years,
by
measuring entomological
indices,
prevalence
of
infection, incidence of infection, and
levels
of community
compliance.
An intensive
differential cost analysis of
both interventions
was
done in
one pair
of the
communities and an analysis on
cost and
benefit
of
PCD
mechanism
was
done in
three pairs.
Anopheles farauti, the main vector,
(A.
punctulatus,
an
inland
vector
became
very rare with interventions), maintained the
early
evening
biting
peak
and
high
outdoor biting. The highest transmission
potential
was
indoor
with
high
parity
(54.1%) and sporozoite rate (1.42%). It
avoided
contact
on
DDT
sprayed
surface and
was not killed even though it
was
still
sensitive with a
75.1%
mortality.
There
were neither changes in biting density,
nor
parous
rates
with
DDT
spraying.
Permethrin impregnated bed nets reduced
biting
density
by
an
estimated
53.69%. The
parous rate indoor was reduced
by
11.64%
when
compared
with that
in the
comparison area, and those caught
in the
bed
nets
area
did
not
have
any
sporozoites. Prevalence of
infection, by
quarterly
prevalence surveys revealed
a
21.2% difference between the
intervention
areas
after two
years.
The
most
significant decline was in the
under
10
year
old
group
(p<0.01) in
permethrin
treated bed nets, including in infants
(p<0.05).
The
decline
was
especially
marked
with Plasmodium falciparum. There
were
increases in the
DDT
area,
including P. falciparum in the younger age
groups.
DDT
spraying
did
not
have
any effect
on
the incidence of infection. Permethrin impregnated
bed
nets reduced
malaria
incidence, by an estimated
49%.
This
reduction
was particularly
significant
however
on children under ten years old
(p<0.0001)
and
marked with
P. falciparum.
Compliance with DDT declined
by 30%
but
with
bednets it
remained
high
above 85%. These results confirmed that
permethrin
impregnated bednets
are
more
effective than DDT residual spraying
in
controlling
malaria
in Solomon Islands.
The operational costs for DDT spraying was
3.85
per capita per year. The mean cost of processing
and
examining
a
PCD
slide
is
$0.40.
These cost indices took account of all
materials,
personnel
and
administration
involved. It took a mean of
6.1
days from the time the
smear
was taken to the time
examined (SE = 0.21,95%CI 5.71 to
6.53
days). It
would take twice this time
for
a
result to be received by the
health
workers
managing
patients.
Only
20%
of
blood
slides could contribute to patient
management.
Based
on these
findings,
all that
is necessary is to make blood smears
of
patients
less than
10
years
of age
for
epidemiological evaluation of vector
control
interventions in
malaria
programme.
This will save scarce resources at
primary
health
care
level.
Making
blood
slides
of everyone would not further add significant
information
and
benefit,
at an
extra
cost. The only exceptions are, those
critically
ill
with malaria,
complicated
malaria and a patient suspected to
have
drug
resistant
malaria.
Permethrin
impregnated bednets are a cost effective way to
control malaria
in
primary
health
care and the most cost benefit way to
evaluate vector control
intervention is
careful monitoring of PCD results, especially
with
P. falciparum
malaria of
children under 10 years old