Submission ID 118426
| Issue/Objective | It is now understood that the large reservoir of asymptomatic Plasmodium falciparum infections in all ages sustains malaria transmission in sub-Saharan Africa. If we are to achieve malaria elimination, the impact of current interventions to reduce this reservoir must be investigated. |
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| Methodology/Approach | Here we present one of few contemporary studies to assess the efficacy of short-term indoor residual spraying (IRS) with non-pyrethroid insecticides and seasonal malaria chemoprevention (SMC) to reduce the reservoir of infection in all ages. Using data collected from an interrupted time series study in northern Ghana (2012-2022), involving five surveys each of ~2,000 participants, we examined the impact of two sequential interventions, IRS and SMC in combination with long-lasting insecticide-treated nets (LLINs), on the P. falciparum reservoir. |
| Results | We showed that the addition of IRS to LLINs reduced the size of the P. falciparum reservoir as measured using PCR, with participants of all ages being significantly less likely to be infected post-IRS in 2015 (41.6%) compared to baseline in 2012 (73.8%). Despite this reduction, in 2017, 32-months after IRS was discontinued, there was a rebound in prevalence to 64.2%. This rebound in the size of the P. falciparum reservoir was found in all age groups, except for the younger children (< 5 years) directly targeted by SMC. In 2020 and 2022, over five to seven years after IRS was stopped, but during the continued implementation of SMC and LLINs, P. falciparum prevalence remained high (~50%) with younger children still being significantly less likely to have an infection compared to the older age groups. This rebound was also associated with higher median P. falciparum densities, suggesting a loss of immunity in all ages due to reduced exposure to infection during IRS. |
| Discussion/Conclusion | These results show that if high-burden countries, like Ghana, are to achieve a 90% reduction in the burden of malaria by 2030, they must implement intervention strategies that can both reduce clinical disease and target the P. falciparum reservoir in all ages. |
| Presenters and affiliations | Kathryn Tiedje The University of Melbourne Oscar Bangre Navrongo Health Research Centre Cecilia Rios Teran The University of Melbourne Samantha Deed The University of Melbourne Mun Hua Tan The University of Melbourne Dionne Argyropoulos The University of Melbourne Kwadwo Koram Noguchi Memorial Institute for Medical Research, University of Ghana Mercedes Pascual New York University Abraham Oduro Navrongo Health Research Centre Patrick Ansah Navrongo Health Research Centre Karen Day The University of Melbourne |
