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Long lasting Insecticidal Nets (LLINs) are the cornerstone of malaria vector control in
Sub-Sahara Africa. Together with early diagnostic and treatment they have helped to
reduce malaria incidence by 42% and mortality by 66% in Africa, in the past 15 years
(World Health Organization 2015) .
LLINs at high coverage rates provide both community protection by reducing vector
density and personal protection through the physical barrier of the net and irritancy of the
pyrethroids. In areas of pyrethroid resistance studies, looking at entomological outcomes
suggest a loss of personal protection when the nets have holes (Asidi et al. 2012;Ochomo
et al. 2013). Nevertheles, s despite a reduction in personal protection (indicated by an
increased rate of blood feeding in the mosquitoes) the remaining toxicity could prevent
transmission even among resistant mosquitoes (Randriamaherijaona et al. 2015).
Similarly, a multi country analysis of semi-field condition hut trials indicates that despite
a small impact of resistance on entomological indicators, LLINs continue to provide
personal protection regardless of resistance in the vectors (Strode et al. 2014). One
possibility of alleviating the impact of resistance has been to develop nets that
incorporate a synergist, piperonyl butoxide (PBO) which acts by inhibiting enzymes
involved in the natural defense mechanism of the insect and enhance penetration of the
insecticide. An important advantage of Olyset Plus which is a combination of
pyrethroid and PBO nets over Olyset net incorporating pyrethroid nets is that once these
nets become worn or holed, they will normally restore protection(Irish et al. 2008).
The present study will examine the impact of holes on the effectiveness of two different
LLIN, the standard Olyset net incorporating pyrethroid and Olyset Plus a combination or
pyrethroid and PBO that have been deployed in area of high pyrethroid resistance in
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North West Tanzania. The torn nets will the holes measured in size using WHO
guideline 2013 and the results will be recorded under the following objective: (i) Blood
feed success of An.gambiae and An.funestus between Olyset versus Olyset Plus
according holes index and number of year used. (ii) Knockdown Mortality of
An.gambiae and An.funestus exposed to newly used and 2 years Olyset and Olyset Plus
(iii) Composition and sporozoite rate of Anopheles found inside the Olyset and Olyset
Plus nets.
Mosquitoes will be collected using CDC light trap placed in 40 HH and mouth
aspirator/procopac will be used to collect Freshly blood-fed and unfed female Anopheles
mosquitoes from their resting sites inside LLIN. The wild collected mosquitoes will be
given fresh 10% glucose solution and transported to the field centre for susceptibility
testing using piece of net in cylinder test to compare resistance level (knockdown and
mortality) between Olyset and Olyset Plus. Laboratory reared Anopheles gambiae
Kisumu-strain will be exposed to pieces of LLIN as a reference susceptible population.
Species composition will be done using real time PCR to estimate different species found
in both LLIN. Sporozoite rate for wild mosquitoes will be done using ELISA technique
to quantify entomological inoculation rate.
The information obtained from this study will help in the refining of net replacement
strategies set by WHO for LLIN and also encourage wide coverage of treated net with
additional of synergy (PBO) to reduce resistance level especially in sub-Saharan Africa |
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