Resending: Malaria in the world

[Deborah Harrell]

Hmm, I've waited 5 minutes and no post, so I'm trying
again-

Here are a few article abstracts from PubMed on
mosquito nets and indoor spraying; I have edited for
length, indicated by "..." and commented or elaborated
in []:

>From Eritrea, 2006:
http://www.ncbi.nlm.nih.gov/pubmed/16635265?ordinalpos=35&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum

A steep decline of malaria morbidity and mortality
trends in Eritrea between 2000 and 2004: the effect of
combination of control methods...This study employed
cross-sectional survey to collect data from
households, community and health facilities on
coverage and usage of Insecticide-Treated Nets (ITNs),
Indoor Residual Spraying (IRS), larvicidal activities
and malaria case management. Comparative data was
obtained from a similar survey carried out in
2001...In the period 2000-2004, approximately 874,000
ITNs were distributed and 13,109 health workers and
community health agents were trained on malaria case
management. In 2004, approximately 81% households
owned at least one net, of which 73% were ITNs and
58.6% of children 0-5 years slept under a net...IRS
coverage increased with the combined amount of DDT and
Malathion used rising from 6,444 kg, in 2000 to 43,491
kg, in 2004, increasing the population protected from
117,017 to 259,420. Drug resistance necessitated
regimen change to chloroquine plus
sulfadoxine-pyrimethamine. During the period, there
was a steep decline in malaria morbidity and case
fatality by 84% and 40% respectively. Malaria
morbidity was strongly correlated to the numbers of
ITNs distributed...and the amount (kg) of DDT and
Malathion used for IRS... 


>From the Solomon Islands, 2004 [full article avail.]:
http://www.ncbi.nlm.nih.gov/pubmed/15331840?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum

The incidence of malaria in Solomon Islands has been
decreasing since 1992. The control program used a
combination of methods including DDT residual house
spraying and insecticide-treated mosquito nets. To
determine how much each method contributed to malaria
control, data were analyzed on monthly incidence and
on control activities for 41 of 110 malaria zones over
the same time period (January 1993 to August 1999).
After correction for endogeneity, then spraying,
insecticide treatment of nets, and education about
malaria are all independently associated with
reduction in incident cases of malaria or fever, while
larviciding with temephos is not. The evidence
suggests that although impregnated bed nets cannot
entirely replace DDT spraying without substantial
increase in incidence, their use permits reduced DDT
spraying. The paper shows that non-experimental data
can be used to infer causal links in epidemiology,
provided that instrumental variables are available to
correct for endogeneity.


>From a trial of bifenthrin treated mosquito nets in
India (2005, full article avail.):
http://www.ncbi.nlm.nih.gov/pubmed/15713980?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVAbstractPlusDrugs1

The main rural malaria vector Anopheles culicifacies
has developed resistance to dichloro diphenyl
trichloroethane (DDT), hexachloro cyclo hexane (HCH)
and malathion in the state of Haryana in northern
India. An alternative synthetic pyrethroid insecticide
bifenthrin was therefore evaluated on mosquito nets
against anopheline and culicine mosquitoes, in two
villages...Two formulations of bifenthrin, suspension
concentrate (SC) and micro-emulsion (ME) were compared
with micro-capsule suspension (CS) of
lambdacyhalothrin. The impact of three doses of
bifenthrin (10, 25 and 50 mg/m(2)) [also untreated
controls]...Efficacy of treated nets on mosquito
density was assessed by calculating mosquito entry
rate, immediate mortality, delayed mortality and
excito-repellency to the insecticides...Bioassays on
treated nets against A. culicifacies recorded 100 per
cent mortality up to tenth fortnight for all the doses
of impregnation with bifenthrin (SC and ME) and
lambdacyhalothrin (CS). Ring-net bioassays against An.
culicifacies showed median knock-down time between 3.1
to 11.4 min. Behavioural indices...reduction in entry
rates of anopheline and culicine mosquitoes into the
rooms with treated nets compared to control indicated
good efficacy...Indoor (immediate) mortality of
mosquitoes with bifenthrin ME formulation was
relatively lower compared to SC fomulation of
bifenthrin and based on delayed mortility and
continued susceptibility in bioassays, bifenthrin ME
at the rate of 10 mg/m(2) dose was found suitable for
the impregnation of mosquito nets for phase III trial.


Another 2005 from India; this includes indoor DDT
spraying as one branch:
http://www.ncbi.nlm.nih.gov/pubmed/16134977?ordinalpos=29&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum

A field trial was carried out...on the efficacy of
mosquito nets treated with a tablet formulation of
deltamethrin (K-O TAB) against malaria vectors.
Treated nets were used in one village, and in the two
control villages, one used untreated nets and the
other used indoor spraying with DDT, without
nets...Bioassays repeated on domestically used nets
over 7 months showed persistence of almost 100%
mortality of An. fluviatilis, whereas An. culicifacies
showed a decline from 100% to 71% mortality over this
period...The sum of collections of mosquitoes resting
in village houses and those in exit traps and dead on
floor sheets showed a reduction in the numbers of the
two vector species due to the treated nets, compared
with untreated or no nets, but no reduction in other
anophelines or Culex species...Treated and untreated
nets reduced the proportion of anophelines that had
blood-fed; the treated nets did so more effectively
than the untreated in the case of An. culicifacies and
of Culex mosquitoes... [I don't see figures for the
DDT controls in this abstract.] 

>From 2004, ?Pakistan [Allahabad cantonment area].
http://www.ncbi.nlm.nih.gov/pubmed/16509253?ordinalpos=21&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum

The study was undertaken to evaluate the impact of
deltamethrin impregnated mosquito nets on malaria
incidence, mosquito density, any adverse side effect
among users and collateral effects on bed bugs and
houseflies. A field trial was carried out over a
period of three years in two adjacent military
stations...keeping one as a trial and other as a
control station. During first year, baseline data were
collected and during next two years residual spray was
replaced with use of deltamethrin impregnated mosquito
nets in trial station. The use of deltamethrin-treated
bed nets resulted in a significant decline in malaria
incidence and annual parasite index (API). The average
mosquito density of anopheline mosquitoes decreased by
67.8% and culicine by 49.7%. The insecticide was found
safe for use amongst troops and had favourable
collateral effects against bed bugs and flies. Use of
deltamethrin impregnated bed nets has beneficial
impact on integrated control of malaria. [?Use of
indoor spraying part of "integrated control"?]

>From Boloivia, 2007:
http://www.ncbi.nlm.nih.gov/pubmed/17940319?ordinalpos=39&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum

...A double blind, placebo controlled
cluster-randomised clinical study. SETTING: Rural
villages and peri-urban districts in the Bolivian
Amazon. PARTICIPANTS: 4008 individuals in 860
households. INTERVENTIONS: All individuals slept under
treated nets; one group also used a plant based insect
repellent each evening, a second group used
placebo...We analysed 15,174 person months at risk and
found a highly significant 80% reduction in episodes
of P vivax in the group that used treated nets and
repellent (incidence rate ratio 0.20, 95% confidence
interval 0.11 to 0.38, P<0.001). Numbers of P
falciparum cases during the study were small and,
after adjustment for age, an 82% protective effect was
observed, although this was not significant (0.18,
0.02 to 1.40, P=0.10)...


This 2005 Vietnamese study documents a significant
decline in malarial disease, but "effects of the
interventions could not be discerned with statistical
significance." [?]
http://www.ncbi.nlm.nih.gov/pubmed/15807800?ordinalpos=40&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum

The National Malaria Control Program (NMCP) in Vietnam
is based on application of insecticide-treated bed
nets (ITNs), spraying of insecticides and early
microscopic diagnosis of malaria and treatment (EDTM)
with artemisinin drugs. This study explores the
implementation of the NMCP at provincial level and its
impact on malaria incidence (mi) and prevalence in
Binh Thuan in southern Vietnam... Control activities
focused on the highly endemic zones where ITNs were
distributed free of charge to ethnic minority groups,
including twice yearly re-impregnation, from 1992
onwards. This almost completely replaced insecticide
spraying. Complete ITN coverage of these groups was
achieved in 1995, constituting 40% of the entire
population... Before 1994, mi peaked to over 50/1000,
pi to over 16% in the highly endemic zones. In 1998,
these had decreased to below 9/1000 and 4%
respectively. The effects of the interventions could
not be discerned with statistical significance.
CONCLUSION: Malaria incidence and prevalence declined
significantly in Vietnam, possibly due to the malaria
control efforts, but coinciding with rapid
socioeconomic changes.


My interpretation: Treated nets, properly used, are
highly effective in reducing malarial disease; many
areas require additional control measures such as
indoor spraying.  Education of the population at risk
and coordinated use of healthcare workers region-wide
is essential to success.  Ongoing research for vector
control and new antimicrobials is also essential as
mosquitos become pesticide-resistant (see multiple
cites in others' posts) and Plasmodium also develops
drug resistance (this is well-documented; I can find
cites if you wish).

Debbi
who spent way the heck more time on this than the
ponies' state of muddiness recommended!  :)



      ____________________________________________________________________________________
Looking for last minute shopping deals?  
Find them fast with Yahoo! Search.  http://tools.search.yahoo.com/newsearch/category.php?category=shopping