Expanding the roles of community health workers to sustain programmes during malaria elimination: a meeting report on operational research in Southeast Asia

In Southeast Asia malaria elimination is targeted by 2030. Cambodia aims to achieve this by 2025, driven in large part by the urgent need to control the spread of artemisinin-resistant falciparum malaria infections. Rapid elimination depends on sustaining early access to diagnosis and effective treatment. In much of Cambodia, rapid elimination will rely on a village malaria worker (VMW) network. Yet as malaria declines and is no longer a common cause of febrile illness, VMWs may become less popular with febrile patients, as VMWs do not diagnose or treat other conditions at present. There is a risk that VMWs become inactive and malaria rebounds before the complete interruption of transmission is achieved. During 2021–23 a large-scale operational research study was conducted in western Cambodia to explore how a VMW network could be sustained by including health activities that cover non-malarial illnesses to encourage febrile patients to continue to attend. 105 VMWs received new rapid diagnostic tests (including dengue antigen–antibody and combined malaria/C-reactive protein tests), were trained in electronic data collection, and attended health education packages on hygiene and sanitation, disease surveillance and first aid, management of mild illness, and vaccination and antenatal care. In August 2023 the National Malaria Control Programme of Cambodia convened a stakeholder meeting in Battambang, Cambodia. Findings from the study were reviewed in the context of current malaria elimination strategies. The discussions informed policy options to sustain the relevance of the VMW network in Cambodia, and the potential for its integration with other health worker networks. This expansion could ensure VMWs remain active and relevant until malaria elimination is accomplished

The influence of temperature and age-dependent survival on Anopheles gambiae s.s. life-history and population dynamics

Malaria transmission depends on the life-history parameters, and population dynamics, of its vectors, and particularly on the survival of adult Anopheles mosquitoes, the main vector of malaria in Africa. These dynamics are sensitive to climatic and environmental factors, and temperature is a particularly important driver, though the exact extent of this sensitivity is not well established. Some data currently exist on the influence of constant and fluctuating environmental temperature on Anopheles gambiae s.s. survival but very few exist examining other life-history traits, and none exist on the influence of larval temperature on adult life-history. This thesis conducts a detailed investigation into the effect of temperature on life-history parameters of Anopeheles gambiae s.s., and uses experimental results to inform the structure and parameterisation of a suite of mathematical models of mosquito population dynamics. Increasing environmental temperature during the larval stages is shown to decrease larval survival, and significantly increase adult mortality. Higher environmental temperature during the adult stages also significantly lowers adult survival. The data also highlight that mosquitoes senesce, and that age-dependent survival models fit experimental data best. Environmental temperature during the larval and adult stages is also shown to have an effect on a number of other life-history parameters. The set of novel mathematical models of climate-driven mosquito population dynamics developed here are motivated by the experimental data suggesting that in An. gambiae, mortality is temperature and age dependent, and show that age-dependent models consistently fit the data better than the reference model.Open Acces

Additional file 1: of Larval and adult environmental temperatures influence the adult reproductive traits of Anopheles gambiae s.s.

Description of mosquito larvae and adult wing size measurements and additional data tables. (DOC 329 kb

Intermittent preventive treatment for forest goers by forest malaria workers: an observational study on a key intervention for malaria elimination in Cambodia

International audienceBackground Cambodia targets P. falciparum malaria elimination by 2023 and all human malaria species by 2025, aligning with WHO’s Mekong Malaria Elimination program. The Intermittent Preventive Treatment for Forest Goers (IPTf) project aimed at forest-specific malaria elimination. The study aims to pinpoint the main factors driving malaria transmission in Cambodian forests and evaluate the initial implementation and effectiveness of IPTf in accelerating the elimination of malaria by treating and preventing infections among at-risk populations in these areas.Methods From March 11, 2019, to January 30, 2021, a malaria intervention program took place in isolated forests in Northeast Cambodia. The first phase focused on observing forest goers (FGs) within the forests, documenting their malaria risk. In the second phase, a monthly artesunate-mefloquine IPTf was implemented by trained forest malaria workers who were former FGs conducting interviews, blood collection, and IPTf administration.Findings Throughout the two-year period, 2198 FGs were involved in 3579 interviews, with 284 in both the observation and intervention phases. Following IPTf implementation, PCR-confirmed malaria prevalence significantly decreased from 2.9% to 0.5% for P. falciparum and from 21.0% to 4.7% for P. vivax. Among the 284 participants tracked through both phases, malaria prevalence fell from 2.5% to 0.3% for P. falciparum and from 22.5% to 3.7% for P. vivax. The intervention phase demonstrated a rapid decline in P. falciparum prevalence among mobile and previously inaccessible populations, while also revealing a higher P. falciparum infection risk associated with activities inaccurately labelled as farming, underscoring the need for customized interventions.Interpretation The successful implementation of IPTf in Cambodia’s remote forests has markedly decreased malaria prevalence among high-risk groups. Cambodia’s National Malaria Program has acknowledged this strategy as essential for malaria elimination intervention, endorsing forest-specific approaches to meet the 2025 goal of eradicating all human malaria species in Cambodia

Inhibitory receptor expression by Melan-A specific CD8 T-cells depending on vaccination.

<p>(A) Co-expression of KLRG-1, TIM-3, PD-1 and CD160, and of LAG-3, BTLA, 2B4 and CTLA-4 by Melan-A specific CD8 T-cells. Blood samples from healthy donors (HD) or from patients before immunotherapy (before vacc.) or after peptide+IFA vaccination with or without CpG-ODN 7909 were enriched for CD8 T-cells using magnetic beads. Melan-A-specific CD8 T-cells were identified by staining with CD8-specific antibody and tetramer. Positivity for inhibitory receptors was defined respective to isotype controls. n = 4 for HD; n = 3 for before vacc.; n = 9 for after vaccination without CpG-ODN and n = 11 for after vaccination with CpG-ODN. Colors of the pie arcs depict the expression of individual inhibitory receptors, while the color in the pie depicts the number of co-expressed inhibitory receptors. Co-expression was analyzed with SPICE 5.2. p-values of the permutation test are shown in tables next to the corresponding pie charts. (B) Hierarchical clustering based on co-expression data of the eight inhibitory receptors shown in A, including the four differentiation subsets (N, CM, EM, EMRA) of total CD8 T-cells. (C) Mean expression and SD of four inhibitory receptors upregulated on Melan-A-specific T-cells with vaccination. Data from HD and from patients before vaccination were pooled for the group without vaccination (no vacc.). n = 7 for no vacc.; n = 9 for vaccination with CpG-ODN.</p