Enhanced Health Facility Surveys to Support Malaria Control and Elimination across Different Transmission Settings in the Philippines

Abstract

Following substantial progress in malaria control in the Philippines, new surveillance approaches are needed to identify and target residual malaria transmission. This study evaluated an enhanced surveillance approach using rolling cross-sectional surveys of all health facility attendees augmented with molecular diagnostics and geolocation. Facility surveys were carried out in three sites representing different transmission intensities: Morong, Bataan (pre-elimination), Abra de Ilog, Occidental Mindoro (stable medium risk), and Rizal, Palawan (high risk, control). Only one rapid diagnostic test (RDT)-positive infection and no PCR confirmed infections were found in Bataan and Occidental Mindoro, suggesting the absence of transmission. In Palawan, the inclusion of all health facility attendees, regardless of symptoms, and use of molecular diagnostics identified 313 infected individuals in addition to 300 cases identified by routine screening of febrile patients with the RDT or microscopy. Of these, the majority (313/613) were subpatent infections and only detected using molecular methods. Simultaneous collection of GPS coordinates on tablet-based applications allowed real-time mapping of malaria infections. Risk factor analysis showed higher risks in children and indigenous groups, with bed net use having a protective effect. Subpatent infections were more common in men and older age-groups. Overall, malaria risks were not associated with participants' classification, and some of the non-patient clinic attendees reported febrile illnesses (1.9%, 26/1,369), despite not seeking treatment, highlighting the widespread distribution of infection in communities. Together, these data illustrate the utility of health facility-based surveys to augment surveillance data to increase the probability of detecting infections in the wider community.

Prevalence and temporal changes of mutations linked to antimalarial drug resistance in Plasmodium falciparum and Plasmodium vivax in Palawan, Philippines

“…The design of the original study ( Reyes et al., 2021 ) from which these samples were obtained included all health facility attendees, regardless of symptoms. A preliminary analysis was performed to compare the mutations amongst subclinical (participants who presented without fever) and symptomatic (with fever) infections.…”

“…Samples were collected between June and December 2016 in the Municipality of Rizal in the southwest of Palawan Province in the Philippines, as part of a larger survey ( Reyes et al., 2021 ; Figure 1 ; Supplementary Material Table S1). Palawan is a malaria endemic province, with over 7000 cases reported in 2015 (DOH, 2020b).…”

“…Blood from a finger prick was collected from each participant for microscopy examination of malaria blood film, rapid diagnostic tests, and preparation of dried blood spots for molecular assays. Details of the study design and sampling have been reported previously ( Reyes et al., 2021 ).…”

“…Genus and species-specific Plasmodium DNA in the extracted samples were confirmed using a modified standard nested-PCR assay, which targeted a highly conserved region of the 18s rRNA gene ( Fuehrer et al., 2011 ; Singh and Snounou, 2002 ; Snounou et al., 1993 ). The results of the PCR amplifications have been published elsewhere ( Reyes et al., 2021 ).…”

“…In order to provide recent data for the Philippines, this study presents findings on the prevalence of mutations based on the genetic markers pfmdr1, pfcrt, pfdhfr, pfdhps, pf k13, pvmdr1, pvdhfr , and pvdhps from samples collected in the Philippines as part of a research study to employ enhanced surveillance methodologies in the country ( Reyes et al., 2021 ). Furthermore, modelling outcomes on temporal trends in the prevalence of these mutations after combining results with historical data are also presented.…”