Streamlined durability monitoring of insecticide-treated nets (ITNs) distributed during the 2021 mass campaign in Malawi, Version 1.0
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Date
2022-08-17
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Kamuzu University of Health Sciences
Abstract
Type of study: This is a prospective longitudinal study. Three types of new long-lasting
insecticidal nets, Olyset Plus, Interceptor G2 and Royal Guard will be monitored for their
physical integrity and biological efficacy under field conditions.
Problem statement: Malaria vector control relies heavily on distribution and use of longlasting
insecticidal nets (LLINs). However, in Malawi, little is known about the performance
of the new types of nets that will be distributed during the 2021 nationwide campaign.
Objectives: To monitor the physical integrity and bio-efficacy of three new types of nets
(Olyset Plus, Interceptor G2 and Royal Guard) that will be distributed for malaria control in
2021-2022. Specifically, this study will 1) assess the insecticidal efficacy of three ITN brands
[Olyset Plus, Royal Guard, and Interceptor G2] in three districts of Kasungu, Salima and
Chikwawa, as measured by cone bioassays, tunnel tests and chemical testing, over a threeyear
period of field use, 2) compare the insecticide effectiveness across these three districts
and ITN brands and identify major determinants of field performance, 3) monitor the physical
integrity of the nets as measured by a net hole assessment and short questionnaire, and 4)
estimate indirectly the level of attrition of the nets at each round.
Methods: In a prospective longitudinal study, three LLINs, Olyset Plus, Interceptor G2 and
Royal Guard nets will be followed up to measure physical integrity and biological efficacy
over a three-year study period. At month zero (pre-distribution) 20 nets from each net type
will be sampled and pieces sent to CDC lab for chemical residue analysis. At 12-month
time point a representative sample of approximately 258 campaign nets from the three
study districts (Chikwawa, Salima and Kasungu), will be identified through a cluster
household survey with all campaign nets from consenting households forming the
sampling frame. These nets will be labelled with a unique identifier. A random sample of
30 campaign nets will be selected from the sampling frame and withdrawn for physical
integrity assessment, bioassays, and chemical residue testing. At each subsequent survey
time point (24- and 36-months) a random sample of 30 campaign nets will be selected
from the sampling frame and withdrawn for bioassays, chemical residue testing and,
physical integrity assessment. The 30 ITNs will be sampled as 2 ITNs from households in
each of 15 clusters. For consistency with the sampling approach used for standard durability monitoring, the
study will work with 15 clusters in each location. The required number of households per
cluster will depend on the mean household size, assuming the standard distribution
strategy of 1 ITN for every 1.8 people was followed during distribution planning.
For biological efficacy, test that require susceptible strain of Anopheles gambiae Kisumu
will be performed at the Malaria Alert Center (MAC) while tests with resistant strain will be
conducted at Kilimanjaro Medical Center in Tanzania. Updated and standard protocols as
per the guidance from PMI/ VectorLink will be used.
Expected findings: Physical integrity may vary by LLIN type and by region. In addition,
efficacy may also vary by LLIN type considering that they are treated with different
insecticides and different technologies.
Dissemination: The findings of this study will inform the program (NMCP), donors, WHO
and the manufacturers on performance of the new types of nets under field conditions.
Annually progress reports will be submitted to COMREC for study continuation approval,
the NMCP, PMI and the three participating districts.
Description
This is a prospective longitudinal study.