Impact of Insecticide Resistance on Vector Control

Impact of Insecticide Resistance in Anopheles Arabiensis on the Effectiveness of Malaria Vector Control in Sudan

The purpose of the study is to determine whether long lasting insecticidal nets and indoor residual insecticide spraying, alone or in combination, are effective for controlling insecticide resistant anopheles mosquitoes for malaria prevention.

The study will assess the impact that insecticide resistance has on the effectiveness of malaria vector control tools LLIN and IRS. This is done by a cluster randomised trials of universal coverage LLINs versus universal coverage LLINs in combination with IRS, with levels of baseline insecticide resistance in the main vector balanced between the two study arms. In each cluster resistance to the insecticide used on LLINs is monitored, and malaria incidence is estimated from cluster specific cohorts of children followed up over the duration of the study. Resistance impact will be assessed from the ratio of incidence rates in clusters with high compared to those with low resistance and from a continuous measure of resistance expressed as percentage loss of mosquito mortality when exposed to insecticide in standardised WHO tests. Resistance mechanisms will be studied in subsets of study clusters.

Distribution of long lasting insecticidal nets to all community members in the study arm allowing for at least one net per 2 persons

Distribution of long lasting insecticidal nets to all community members in the study arm allowing for at least one net per 2 persons plus indoor residual spraying with insecticide of interior walls of all houses twice yearly.

Application of insecticide to interior walls of domiciliary structures to kill malaria vector mosquitoes which rest on walls after taking human blood meal

Provision of LLIN to all community members in the clusters allocated to the study arm. LLIN protect individuals from bites by malaria vector mosquitoes by providing a physical barrier and insecticidal and repellent effect.

Infection with malarial parasites determined by rapid diagnostic tests/microscopy in cohort members who report or have fever (>37.5C)

Infection with plasmodial parasites (falciparum and/or vivax) in randomly selected members of the study cohort in each study cluster during the peak of the malaria transmission season by rapid diagnostic test

Anopheles arabiensis mosquitoes collected in sentinel clusters by light trap, window trap, clay pot and pyrethrum sheet collection and determination of sporozoite, human blood index, feeding and resting behaviour.

Inclusion Criteria: Children older than 6 months and younger than 10 years in approximately 100 randomly selected households in all 140 study clusters selected in the four study areas Exclusion Criteria: Children living in households within 1 km from the edge of a neighbouring cluster (the buffer zone)

Kafy HT, Ismail BA, Mnzava AP, Lines J, Abdin MSE, Eltaher JS, Banaga AO, West P, Bradley J, Cook J, Thomas B, Subramaniam K, Hemingway J, Knox TB, Malik EM, Yukich JO, Donnelly MJ, Kleinschmidt I. Impact of insecticide resistance in Anopheles arabiensis on malaria incidence and prevalence in Sudan and the costs of mitigation. Proc Natl Acad Sci U S A. 2017 Dec 26;114(52):E11267-E11275. doi: 10.1073/pnas.1713814114. Epub 2017 Dec 11.