Enhanced geospatial surveillance for identifying malaria transmission hotspots using antenatal screening in PNG

Plasmodium falciparum malaria is a significant global health problem and its transmission is strongly associated with geographic location. Geospatial surveillance is crucial to identify changes in transmission intensity over time and to allow for precise spatial targeting of interventions. Most surveillance approaches provide only high-resolution snapshots of very limited areas and over short periods of time. These are usually some form of community-based cohort study, which utilises RDT, microscopy or PCR based detection of active parasite infection. Vector surveillance is usually limited to infrequent mosquito trapping activities. These approaches are resource-heavy, and cannot be sustained as long-term surveillance strategies2. The most practical and inexpensive way of obtaining population-level transmission markers is to study antibody levels against combination of different malaria antigens. The appropriate choice of antigens is a question that has received much attention and the solution seems to be the use of combinations of antigens that are informative regarding both more remote and more recent exposure, assessed using statistical techniques that look at antibodies as more than simple dichotomous variables. While antibodies to P. falciparum are good indicators of both exposure and transmission intesity, antibodies to vector antigens have also received attention in the past 10 years and are validated correlates of both vector density and entomologic inoculation rates4. Pregnant women are an important high-risk group. They are often infected with parasite strains that exhibit unique and well-conserved PfEMP1 variants that are clinically relevant, and which can be useful biomarkers of infection during pregnancy. Pregnant women also represent a reliable sentinel population from which to determine local transmission levels in the rest of the community. They can also be a highly efficient surveillance group because they generally selfpresent to antenatal clinics, especially for first visit, thus greatly facilitating the process of surveillance and reducing costs. There are no studies of pregnant women that have combined recent advances in geospatial mapping, integrated approaches into serological markers for parasites and vectors and then modelled these parameters to give high-precision geospatial estimates of malaria transmission. This project will achieve this using existing samples and data, including plasma samples, demographic data (including residence) and Plasmodium spp. infection data (microscopy and qPCR, for P. falciparum from a cohort of 2775 pregnant women attending antenatal clinics between 2009 and 2013 in Madang Province, PNG.

Women in the study were recruited at one of nine antenatal clinics in Madang and Sumkar districts of Madang Province, PNG. Plasma samples were collected at enrolment and women were tested for P. falciparum infection by qPCR and microscopy. Demographic data, including place of residence, were collected by questionnaire. About half of all women were in their first pregnancy. All study sites experience year-round malaria transmission. Plasma samples are currently available and stored in Stephen Rogerson’s laboratory in Melbourne.

Measurement of Transmission
Surveillance

Nov 2018 — Oct 2023

$15,000

Australia

Australian Centre for Research Excellence in Malaria Elimination (ACREME)