Background Malaria remains a public health issue particularly in sub-Saharan Africa with special features of seriousness in young children and pregnant women. Older children and adults reported to have acquired a semi-immune status and therefore show low parasitaemia and less pronounced symptoms if any. We aim to explore parasitaemia and symptoms in adolescents and adults with malaria compared to younger children in the Lambaréné area.

Methods We conducted a cross-sectional study in CERMEL for a month in 2018. Adults and children were screened for malaria at health facilities in Lambaréné and Fougamou and their respective surrounding villages in the central region of Gabon. Malaria infection was determined either by rapid diagnostic test (RDT) or by thick blood smear (TBS). Body temperature, history of fever, age, sex, haemoglobin level, and location were collected.

Results From 09 January to 09 February 2018, a total of 596 patients were screened and 280 (47%) belonged to the adult population. Plasmodium falciparum infection in adults was diagnosed based on the detection of P. falciparum in thick blood films. Prevalence among the adults was 56% (n=141); 34% of adult patients had a parasite count between 1015–116,079 pf/µl. Fever was found in 31% of adults and several symptoms were reported by the same patient. Vomiting, loss of appetite, and fatigue were significantly more present in the adult population than in children.

Conclusion This study shows a high rate of Plasmodium falciparum infection in adults associated to clinical symptoms and high level of parasitaemia. Adults seem to become an at-risk population, suggesting that malaria programmes should consider including adults in the implementation of a malaria prevention programme.