Variable effects of non-falciparum species infections on malaria disease severity in high transmission regions in Senegal

In malaria endemic countries, non-falciparum species are often mixed with Plasmodium falciparum in patients with uncomplicated malaria, and their contribution to malaria severity and death is poorly studied. This study assesses the contribution of non-falciparum species to malaria severity in three regions of Senegal with the highest malaria incidence.We analysed 617 blood samples obtained between 2015 and 2021 from confirmed malaria patients at health facilities in Kedougou, Kolda and Tambacounda in Senegal. Plasmodium species composition was determined by PCR and their distribution were analysed according to age and disease severity, and the relative risk of developing severe malaria.Overall, 94.8% of samples contained P. falciparum either as single or mixed with other species. Non-falciparum P. ovale, P. vivax and P. malariae species were detected in 60.12, 13.61 and 1.62% of samples, respectively. Severe malaria was primarily due to P. falciparum, but co-infection with P. vivax led to a 1.63-fold significant (p = 0.05) increased risk of developing severe malaria, contrasting with the non-significant reduced risk (OR = 0.78; CI 95: 0.55-1.11; p = 0.16) associated with P. ovale infections. Children aged < 15 years old significantly suffered of SM than adults patients, whereas no significant association was found in relation to patient' sex.This study reports the first association of non-falciparum species infections with clinical malaria phenotypes in patients from the three most malaria-affected regions in Senegal. Non-falciparum P. ovale and P. vivax species in combination with P. falciparum had a protective and worsening effect, respectively. The findings suggest that interventions targeting only P. falciparum might not be sufficient to eliminate the overall malaria burden, and should take into account the neglected non-falciparum species.