Evaluating the technical feasibility of serological testing and treatment for Plasmodium vivax in mobile at-risk of malaria Cambodian populations

Background

Cambodia is targeting malaria elimination by 2025, aligning with the WHO's Mekong Malaria Elimination program. While elimination of Plasmodium falciparum is nearly achieved, Plasmodium vivax elimination presents challenges inherent to this species due to the occurrence of dormant parasite stages, known as hypnozoites. A new approach has been proposed to serologically identify individuals likely carrying hypnozoites that should receive appropriate antimalarial treatment: P. vivax serological testing and treatment (PvSeroTAT). This study aims to determine the technical feasibility of a PvSeroTAT approach in malaria endemic communities with highly mobile populations in Eastern Cambodia.

Methods

From October 24th 2021 to February 26th 2023, two successive rounds of PvSeroTAT were conducted in adult and adolescent males in three villages of Mondolkiri, Eastern Cambodia. At each round, capillary blood samples were collected from consenting participants to be used for P. vivax serology and G6PD activity determination. Seropositive participants, who were G6PD normal, were then recontacted to be provided an anti-hypnozoite primaquine regimen following Cambodian treatment guidelines (0.25 mg/kg for 14 days). Cross-sectional surveys to evaluate P. vivax prevalence were conducted before, during and after the PvSeroTAT interventions in the same three villages and in three additional neighboring control villages where interventions were not implemented.

Findings

Participation was high, with 96% (456/477) of eligible individuals enrolled in at least one round of PvSeroTAT. However, only 63% of participants enrolled in the first PvSeroTAT round agreed to participate in the second round. In the first and second round of PvSeroTAT, 31% (101/327) and 30% (98/334) of enrolled participants, respectively, were seropositive and among those, 82% (163/199) were eligible for primaquine treatment. All 163 seropositive eligible individuals could be recontacted and offered a primaquine treatment, this occurred within 10 days for 96% of individuals (157/163). P. vivax prevalence decreased in all villages, including the control ones, after the first round of PvSeroTAT from 7.7% to 2.7% overall.

Interpretation

The participation rates and overall technical feasibility of PvSeroTAT in highly mobile individuals living within communities in malaria endemic areas of Cambodia were very promising. PvSeroTAT with a lab-based assay is feasible in Cambodia even if it is logistically more challenging than using point-of-care assays. Further studies to understand community perspectives about test and treat approaches in the absence of clinical symptoms will be important for the development of tailored community education and awareness material to improve participation in multiple rounds of test and treat interventions.

Funding

The PvSeroTAT interventions received funding from the Global Fund RAI3 initiative. Cross-sectional surveys were funded by the NIH International Centers of Excellence for Malaria Research (ICEMR) Asia–Pacific (U19AI129392).