In Liberia, PMI implemented the Africa Indoor Residual Spraying (AIRS) project to control malaria from 2009 to 2013. Insecticide resistance monitoring during this time indicated that Anopheles gambiae s.l., the major vector of malaria in Liberia, is resistant to the pyrethroid class of insecticides. In 2013, after presenting empirical evidence on vector resistance to pyrethroids and evidence of susceptibility to pirimiphos-methyl, the National Malaria Control Program (NMCP) and IRS Task Force switched from using pyrethroids to pirimiphos-methyl for IRS in 2013. This was the final year in which IRS was implemented in Liberia.
After the withdrawal of IRS in 2014, PMI and NMCP continued entomological monitoring to generate data on vector bionomics including species composition, distribution, and behavior. In addition, a container insectary was established on the NMCP compound for rearing Anopheles gambiae for insecticide susceptibility tests and to perform morphological species identification of field-collected mosquitoes.
Following the end of the PMI AIRS project, entomological monitoring activities transitioned to the PMI VectorLink Project in 2017 with routine monitoring being conducted in three sites – Frank Town (Montserrado County), a peri-urban area; Tomato Camp (Bong County), a rural highland area; and Jeneta (Margibi County), a rural zone. To better understand the dynamics of malaria vectors in areas outside the sentinel sites, VectorLink also began sampling mosquitoes in 10 sites along a transect from Yekepa, Nimba County in the North to Careysburg, Montserrado County, in the South. Mosquitoes were collected in May 2017, October 2017, and May 2018. The final collection planned initially for October 2018 will not be implemented following the decision to expand the number of fixed sentinel sites.
PMI VectorLink has worked in close collaboration with the NMCP and Liberian Institute of Biomedical Research (LIBR) to build local capacity for laboratory analysis of mosquito samples. Currently, laboratory analyses are being conducted by NMCP and LIBR staff at LIBR facilities. Following training in 2018, staff began conducting enzyme-linked immunosorbent assays (ELISAs) to determine sporozoite infection rates among mosquitoes collected in 2015 and beyond.
The PMI VectorLink Liberia Project Year 4 Work Plan covers activities for the period October 1, 2020 through September 30, 2021. In collaboration with NMCP/MOH, LIBR, University of Liberia, as well as county and district staff, routine monthly vector bionomics monitoring and insecticide resistance surveillance will be implemented in Liberia. As usual, the project’s primary objective is to provide technical assistance to support these entities to conduct data collection on malaria vectors and on insecticide resistance surveillance to guide further malaria vector control interventions.
Insectary and Laboratory Activities
- Support the NMCP to manage the established insectary, maintain the mosquito colony, and ensure that all activities in the insectary follow standard protocols;
- Establish a new insectary at LIBR for rearing resistance colony to support monitoring the Interceptor® G2 nets as well as housing the current mosquito colony being maintained at NMCP;
- Build the LIBR staff capacity in laboratory analyses of mosquito samples through virtual and on-site training and supervision;
- Enable in-country molecular analyses of entomological samples at LIBR to include analyses for mosquito species identification, Plasmodium falciparum sporozoite rate, and identification of molecular markers for insecticide resistance and analysis of blood-meal source.
- Conduct insecticide susceptibility testing in 11 sites across eight counties, prioritizing those insecticides that are used to treat ITNs. This will include pyrethroids (deltamethrin, permethrin, alpha-cypermethrin) with and without pre-exposure to the synergist PBO and chlorfenapyr. The Interceptor® G2 net will be in country around March-April 2021, and will be distributed during the national mass campaign in mid-2021.
- Conduct monthly vector bionomics monitoring in eight routine sites. These sites are selected to monitor the spatial and temporal distributions and densities of Anopheles vector species, and characterize their biting and resting behavior.
- Provide practical training to local staff in routine entomological monitoring sites in the field and at the insectary.
- Support standard ITN durability monitoring data collection for the 36-month time point.
- Plan for Interceptor® G2 ITN “durability monitoring-lite” (bio-efficacy and chemical content monitoring only) in Year 5. Year 4 activities will include establishing an insectary at LIBR and final selection of monitoring sites.
- Implement the ITN campaign monitoring plan to include: 1) accessing, processing, and analyzing baseline (pre-campaign) data; 2) designing the ITN monitoring dashboards; 3) populating dashboards with baseline data; 4) conducting a data review meeting with stakeholders and obtaining feedback on the dashboards; and 5) finalizing the ITN monitoring dashboards based on stakeholder feedback.
- Continue with the entomological and epidemiological baseline data collection for monitoring of Interceptor® G2 nets until the start of distribution in 2021 and start post-distribution data collection to monitor impact of Interceptor® G2 ITN mass distribution, including collection of entomological data and insecticide resistance data in four sites.
- Train and supervise the NMCP technicians and University of Liberia staff in entomological techniques of malaria vectors and provide on-the-job training and coaching of these staff at sentinel sites;
- Support development of NMCP, UL, LIBR and county staff skills on data management and analysis, managing the insectaries and entomological monitoring;
- Support the ITN durability monitoring activities planning and implementation in coordination with NMCP, PSI and PATH.
Success stories from PMI VectorLink Liberia