Long-lasting insecticidal nets and indoor residual spraying may not be sufficient to eliminate malaria in a low malaria incidence area: results from a cluster randomized controlled trial in Ethiopia

Abstract

Background Conflicting results exist on the added benefit of combining long-lasting insecticidal nets (LLINs) with indoor residual spraying (IRS) to control malaria infection. The main study objective was to evaluate whether the combined use of LLINs and IRS with propoxur provides additional protection against Plasmodium falciparum and/or Plasmodium vivax among all age groups compared to LLINs or IRS alone. Methods This cluster-randomized, controlled trial was conducted in the Rift Valley area of Ethiopia from September 2014 to January 2017 (121 weeks); 44 villages were allocated to each of four study arms: LLIN + IRS, IRS, LLIN, and control. Each week, 6071 households with 34,548 persons were surveyed by active and passive case detection for clinical malaria. Primary endpoints were the incidence of clinical malaria and anaemia prevalence. Results During the study, 1183 malaria episodes were identified, of which 55.1% were P. falciparum and 25.3% were P. vivax , and 19.6% were mixed infections of P. falciparum and P. vivax . The overall malaria incidence was 16.5 per 1000 person-years of observation time (PYO), and similar in the four arms with 17.2 per 1000 PYO in the LLIN + IRS arm, 16.1 in LLIN, 17.0 in IRS, and 15.6 in the control arm. There was no significant difference in risk of anaemia among the trial arms. Conclusions The clinical malaria incidence and anaemia prevalence were similar in the four study groups. In areas with low malaria incidence, using LLINs and IRS in combination or alone may not eliminate malaria. Complementary interventions that reduce residual malaria transmission should be explored in addition to LLINs and IRS to further reduce malaria transmission in such settings. Trial registration PACTR201411000882128 (08 September 2014) Electronic supplementary material The online version of this article (10.1186/s12936-019-2775-1) contains supplementary material, which is available to authorized users.

Evaluating the impact of larviciding with Bti and community education and mobilization as supplementary integrated vector management interventions for malaria control in Kenya and Ethiopia

“…In the case of Tolay study site in Ethiopia, it should be noted that vector control also often involves the use of IRS in addition to LLINs, and this could generally have also contributed to low indoor anopheline vector densities observed in the study site [ 4 , 51 ]. However, combining LLINs with IRS has been shown not to further reduce malaria incidence beyond what is achieved with LLINs in Ethiopia in spite of its having an impact on indoor vector density [ 52 ]. Finally, low indoor anopheline densities in Tolay could also have been due to local houses not having open eaves.…”

Impact of combining indoor residual spraying and long-lasting insecticidal nets on Anopheles arabiensis in Ethiopia: results from a cluster randomized controlled trial

“…The main hypothesis of this study is that the combined use of IRS and LLINs will significantly reduce vector density and HBR as compared to either their separate use or the control group. The epidemiological results of the trial were published in a separate paper [11]. In this paper, the effect of the interventions on the vector densities and HBR is reported.…”

Spatiotemporal clustering of malaria in southern-central Ethiopia: A community-based cohort study

“…To fill this gap in the literature, we assessed the spatiotemporal patterns of malaria transmission in the presence of different malaria controls in a low-transmission area of southern-central Ethiopia. This study was a part of the cluster- randomized controlled trial utilizing the data collected for primary analysis published in elsewhere [27]. We followed a large cohort of 34,548 people from October 2014 to January 2017 (121 weeks) in 13 kebeles (the lowest government administrative unit) that were targeted for the trial [27, 28].…”

“…This study was a part of the cluster- randomized controlled trial utilizing the data collected for primary analysis published in elsewhere [27]. We followed a large cohort of 34,548 people from October 2014 to January 2017 (121 weeks) in 13 kebeles (the lowest government administrative unit) that were targeted for the trial [27, 28]. The objectives of this study were to assess whether malaria infection were clustered in areas with LLINs alone, IRS alone, a combination of LLINs and IRS interventions, and to determine the risk factors for the observed clustering.…”