Cambodia is progressing toward malaria elimination; there has been a significant reduction in malaria morbidity and mortality over the last 10 years. The overall malaria mortality rate has decreased from 0.98 per 100,000 in 2010 to 0.12 per 100,000 in 2014. No malaria deaths have been reported since 2017. Malaria cases in Cambodia are caused by Plasmodium falciparum, Plasmodium vivax, or a mix of both species and of the reported total malaria cases in last five years from 2016 to 2020, majority were Plasmodium (P.) vivax (62%). In 2020, there were 9,237 malaria cases (936 Plasmodium (P.) falciparum) detected by public health facilities and Village Malaria Workers (VMWs), a 71% decline from 2019, when 31,791 malaria cases (4,990 P. falciparum) were reported. The national malaria incidence in 2020 was 0.56 (0.05 for P. falciparum) among 1,000 population. In 2020, only 10% (936) of cases were P. falciparum or mixed infections compared to 16% in 2019 and 56% in 2017 (National Center for Parasitology, Entomology and Malaria Control 2020).

The National Strategic Plan for Elimination of Malaria in the Kingdom of Cambodia targets malaria elimination by 2025. The Malaria Elimination Action Framework for 2021-2025 describes new strategic updates based on recent changes in the country’s epidemiological and programmatic context. Foci investigations are identified as one of three key objectives of the surveillance program, which aims to determine the drivers of malaria transmission and trigger a targeted response. An intensified approach is required in endemic locations with highest risks, where mobile migrant populations and forest goers may be key to transmission.

Anopheles dirus, An. minimus s.l., and An. maculatus s.l. are the main malaria vectors in Cambodia. An. dirus is found in forested mountains and foothills, cultivated forests, and rubber plantations, whereas An. minimus s.l. is found outside the forests or in areas that have been cleared of forest. An. maculatus s.l. is found in hilly or mountainous areas and breeds in or near permanent or semi-permanent bodies of clean water such as streams or rivers (Sinka et al. 2011).

In year four  (September 2021 – August 2022), the project’s primary objective is to support, in consultation with the National Center for Parasitology, Entomology, and Malaria Control (CNM), entomological surveillance in geographical areas with a high malaria burden. Emphasis is on helping Cambodia achieve its malaria elimination goals by strengthening foci investigations through entomological monitoring. Additionally, insecticide resistance monitoring in coordination with routine vector surveillance, vector incrimination through molecular assays, and identification of members of primary malaria vector species existing as species complexes will be conducted. The project will develop local capacity to implement entomological surveillance, insecticide resistance monitoring, and molecular analysis of mosquito collections. It will also introduce the entomological monitoring data management module into the existing malaria information system.

Field Activities:

  • Continue longitudinal monitoring in Mondulkiri and Stung Treng provinces for vector surveillance through training and provision of equipment to the PHD, OD and health center staff, and close supervision by the CNM central-level technicians and VectorLink Cambodia technicians.
  • VectorLink will conduct an initial assessment on the capacity of provincial staff to determine capacity strengthening needs. Capacity strengthening will entail, for example, training and provision of equipment to the PHD, OD and health center staff, and close supervision by the CNM central-level technicians and VectorLink Cambodia technicians..
  • Conduct pyrethroid insecticide resistance testing in two sentinel sites (one forest and one village) in each of the target provinces.
  • Train and support PHD and OD health staff in case-based entomological investigations as a component of foci investigations, particularly for mosquito trapping methods, and handling and processing mosquito samples in the field. Specific training on Anopheles species identification will begin as classroom training but will be reinforced by on-the-job training on a monthly basis, supported by CNM and VectorLink Cambodia technicians.
  • Train and support the CNM technicians in mosquito trapping methods, handling and processing of mosquito samples in the field, morphological identification, and insecticide resistance testing data recording, entry and management, and reporting.
  • Convene and support CNM to hold national Vector Control Working Group meetings by promoting the triangulation of existing entomological data, case prevalence data from the management information system (MIS), and insecticide resistance monitoring data, for an optimal response.
  • Facilitate CNM to modify data collection, collation, and visualization regarding case-based entomological monitoring in foci investigations by integrating into the existing case-based surveillance platform.
  • Facilitate review of entomological monitoring data by relevant parties to inform and improve integrated vector control decision making at the VectorLink Annual Dissemination and Planning Meeting as well as CNM-convened meetings (e.g., CNM Annual Conference and Technical Workshop) and other malaria stakeholder meetings.
  • Provide technical support to CNM leadership on reporting and using vector control data for decision making at the national level. Support CNM leadership to prepare and present mosquito surveillance data at technical working group meetings.
  • Support CNM laboratory capacity in molecular entomology work through international course, training, etc.

Insectary and Laboratory Activities:

  • Rear F1 generation mosquitoes from forced oviposition of wild-collected malaria vectors at the CNM insectary for insecticide susceptibility tests.
  • Maintain and expand the existing pinned reference collection of Anopheles Develop a pictorial Anopheles species identification guide in Khmer and English for Mondulkiri and Stung Treng provinces.
  • Work with CNM to label mosquito samples for storage and recording prior to in-country ELISA. A barcoding system for samples will be piloted with VectorLink home office guidance during this work plan period.
  • Conduct circum- sporozoite enzyme-linked immunosorbent assay (ELISA) in the National Institute of Health (NIH), National Institute of Allergy and Infectious Diseases (NIAID) laboratory at CNM, molecular species identification of samples tested for CSP- ELISA and a subset of samples from each species by polymerase chain reaction (PCR) in the genetics laboratory at RUPP, data recording, entry and management, and reporting.