High prevalence of asymptomatic malaria infections in adults, Ashanti Region, Ghana, 2018

Background Ghana is among the high-burden countries for malaria infections and recently reported a notable increase in malaria cases. While asymptomatic parasitaemia is increasingly recognized as a hurdle for malaria elimination, studies on asymptomatic malaria are scarce, and usually focus on children and on non-falciparum species. The present study aims to assess the prevalence of asymptomaticPlasmodium falciparumand non-falciparum infections in Ghanaian adults in the Ashanti region during the high transmission season. Methods Asymptomatic adult residents from five villages in the Ashanti Region, Ghana, were screened forPlasmodiumspecies by rapid diagnostic test (RDT) and polymerase chain reaction (PCR) during the rainy season. Samples tested positive were subtyped using species-specific real-time PCR. For allPlasmodium ovaleinfections additional sub-species identification was performed. Results Molecular prevalence of asymptomaticPlasmodiuminfection was 284/391 (73%); only 126 (32%) infections were detected by RDT. While 266 (68%) participants were infected withPlasmodium falciparum,33 (8%) were infected withPlasmodium malariaeand 34 (9%) withP. ovale.The sub-speciesP. ovale curtisiandP. ovale wallikeriwere identified to similar proportions. Non-falciparum infections usually presented as mixed infections withP. falciparum. Conclusions Most adult residents in the Ghanaian forest zone are asymptomaticPlasmodiumcarriers. The highPlasmodiumprevalence not detected by RDT in adults highlights that malaria eradication efforts must target all members of the population. BeneathPlasmodium falciparum,screening and treatment must also include infections withP. malariae,P. o. curtisiandP. o. wallikeri.