According to Sierra Leone’s Malaria Indicator Survey (SLMIS) 2016, malaria is endemic in the country with the stable and perennial transmission. Malaria prevalence is 40% among children age 6-59 months and is the main cause of morbidity and mortality among children under 5 years. Malaria prevalence is two times higher in rural areas (49%) than in urban ones (25%).
Insecticide-treated bednets (ITNs) are distributed to children between 12 and 59 months of age upon successful completion of PENTA3 immunization, and to pregnant women during the first contact for antenatal care. The first mass distribution of ITNs took place in 2006 in Bo and Pujehun districts. The same year, a countrywide mass ITN distribution for children under 1 year of age occurred alongside a measles vaccine campaign. Mass distribution of ITNs was subsequently conducted in 2010, 2014, and 2017. These mass campaigns, together with other distribution channels, helped increase the ownership of ITNs from 37% in 2008 (SLDHS, 2008) to 60% in 2016 (SLMIS, 2016). In 2019, 67.9% of the households owned at least one ITN in Sierra Leone (DHS, 2019). The insecticide resistance monitoring conducted in 2018-2019 indicated strong resistance of the main malaria vector Anopheles gambiae in Sierra Leone to pyrethroids.
After pre-exposure to piperonyl butoxide (PBO), the mortality rate observed for both deltamethrin and permethrin increased in the four sentinel districts but was below the 90% cut-off point for confirmed resistance indicating that a monooxygenase-based resistance mechanism is partially involved, but is not fully responsible for the pyrethroid resistance observed. Based on this finding, the NMCP is planning an ITN mass campaign for May 2020. All ITNs distributed will contain either the pyrethroid deltamethrin or permethrin plus the synergist PBO. This will be the first time in Sierra Leone that a nationwide mass distribution campaign of ITNs with the PBO synergist will be undertaken.
In 2019, VectorLink Sierra Leone supported the NMCP in the maintenance and management of the insectary established in Makeni (Bombali District) which was established in 2018. VectorLink continued to maintain the susceptible Kisumu strain of An. gambiae. VectorLink also supported the monitoring of vector bionomics, providing information on vector density, distribution, and behaviors. The susceptibility of An. gambiae s.l. to the insecticides used in public health was assessed, and these data guided the development of the Insecticide Resistance Monitoring and Management Plan (IRMMP), the Integrated Vector Management Policy (IVMP), and Strategic plans. The information also helped the NMCP select the appropriate ITNs for distribution during the 2020 mass campaign. In 2020, the project will continue to provide technical and financial assistance to the NMCP to conduct malaria vector bionomics monitoring in 15 sentinel sites in five districts and insecticide resistance of An. gambiae s.l. (see Table 1 in Section 3.1). In 2020, VectorLink will continue to support the NMCP in holding quarterly meetings of the VCTWG and semi-annual meetings of the IVM National Steering Committee to review entomological data for decision making on vector control interventions for malaria and other vector-borne diseases
The information collected on vector density, seasonal distribution, behavior, and infectivity will be used to determine the optimal time to do IRS and it will serve as baseline data for assessing IRS impact. In addition, VectorLink will support ITN durability monitoring after the 2020 ITN mass campaign and will start the baseline data collection for the assessment of the impact of the co-deployment of PBO nets and IRS in Sierra-Leone.
PMI VectorLink Sierra Leone has the following objectives for its third year of implementation:
- Maintain a functional insectary in Makeni with An. gambiae Kisumu strain available at all times
- Continue measuring the susceptibility of the main malaria vector, An. gambiae s.l., in order of priority, to deltamethrin, permethrin, alpha-cypermethrin, clothianidin, chlorfenapyr and pirimiphos-methyl from Bo, Bombali, Kono, and Western Area Rural districts and start the monitoring in Port Loko district
- Measure the intensity of resistance to pyrethroids and perform synergist assays, where appropriate
- Subcontract with Centre Suisse de Recherches Scientifiques (CSRS) a regional laboratory based in Cote d’Ivoire to use polymerase chain reaction (PCR) to process mosquitoes samples to identify them to the species level, and use PCR/ Enzyme-linked immunosorbent assay (ELISA) to test sample mosquitoes for infectivity
- Subcontract with CSRS to use PCR to identify the mechanism associated with the resistance observed (kdr and Ace-1 mutations)
- Monitor the density, biting rate, behavior, and parity of malaria vectors in 10 sentinel sites
- Support the NMCP in conducting ITN durability monitoring covering the two types of ITNs to be distributed in 2020
Assessment of Co-deployment of PBO Nets and IRS
- Support the NMCP in the collection of baseline data for the assessment of the co-deployment of IRS and PBO nets
Indoor Residual Spraying:
- Conduct geographical reconnaissance for IRS to assess logistics and procurement needs and identify appropriate IRS operations sites and insecticide storage facilities in Bombali and Bo districts
- Conduct a Supplemental Environment Assessment (SEA) to ensure the environmental compliance of IRS in 2021
- Conduct the enumeration of the eligible structures in Bombali and Bo for the IRS campaign in 2021
- Support the NMCP in conducting master training on IRS
- Develop and start the implementation of a social and behavior change communication (SBCC) plan for IRS based on Sierra Leone context
- Support the NMCP in organizing IRS planning meetings
- Build the capacity of the NMCP and district health staff to use entomological data for decision making
- Support the NMCP to hold quarterly meetings of the VCTWG and semi-annual meetings of the IVM National Steering Committee
- Provide technical support to the NMCP and other stakeholders for data review prior to the selection of ITNs, IRS insecticides, and target IRS districts
- Provide technical support to NMCP to finalize the insecticide selection for IRS