Robinson Lab

Plasmodium vivax has the ability to cause relapsing infections from long-lasting liver stages called hypnozoites. By studying the effect of removing long lasting liver-stages with primaquine treatment on the subsequent risk of P. vivax infection and illness, we have demonstrated that relapses cause around 80 per cent of P. vivax infections in PNG children and are important in sustaining transmission.

Data from these cohort studies is also being used to develop mathematical models of P. vivax relapses to predict the effectiveness of various intervention strategies against P. vivax and study within host, clonal dynamics.

The intensification of the PNG malaria control program over the past 10 years is significantly reducing the burden of malaria and changing the complex relationships between parasites, human hosts and mosquito vectors.

Through a series of repeated community cross-sectional surveys, longitudinal child cohort studies, entomological surveys and hospital-based surveillance in two endemic areas of the country, we are using sensitive molecular diagnostics to monitor the impact of these changes on the age-specific burden of malaria, the natural acquisition of immunity, behavior of vectors and risk factors for infection and transmission, so as to be able to inform ongoing and future control efforts.

This study aims to determine the risk factors for Plasmodium spp. gametocyte carriage and study the temporal associations between the presence and complexity of asexual and sexual Plasmodium spp. infections. In parallel, the study will investigate the relationship between the presence and density of gametocyte in a blood samples and its infectivity to local vectors by conducting a series of standard mosquito membrane feeding assays.

Knowledge of the gametocyte carriers in a population, when gametocytes are most prevalent, and what are the determinants of infectivity to the mosquito vector, is essential for improving the implementation of current control tools and informing the development of novel interventions aimed at the interruption of local transmission.

Our understanding of antibody and cellular immune responses that underpin the development of natural immunity to malaria is still evolving. Utilising samples collected during longitudinal cohort studies of pregnant women, infants and children in Madang and Maprik areas of PNG, we are investigating the dynamics of antibody and cellular immune responses, their acquisition, suppression, boosting and maintenance.

In addition, we are investigating trans-placental transfer of antibodies to infectious diseases and the role of pre-natal malaria exposure on immune responses and all-cause morbidity during infancy.