High prevalence of Plasmodium ovalewallikeri in co-infections with Plasmodium falciparum in symptomatic than asymptomatic Plasmodium parasite infections in Kisumu, Kenya.

Plasmodium falciparum (Pf), Plasmodium ovalewallikeri (Pow), Plasmodium ovalecurtisi (Poc), and Plasmodium malariae (Pm) coexists in Kenya sympatrically. Some infections progress to classical symptoms of malaria prompting hospital visits, while others remain asymptomatic. There is limited information on whether the species composition status of infections in endemic areas influences progression to either asymptomatic or symptomatic infection. This cross-sectional study determined the composition of Plasmodium species among symptomatic versus asymptomatic participants in Kombewa, Kenya. Between 2015 and 2016, samples from 741 individuals, comprising of 437 from symptomatic participants at Kombewa Subcounty hospital and 304 from asymptomatic participants from within Kombewa Subcounty hospital's catchment area were analyzed for Plasmodium species composition using real-time qPCR assay targeting the small subunit ribosomal RNA (ssrRNA) gene. R Studio was used to describe Plasmodium species prevalence, and the odds of occurring within a given infection presentation. Co-infection analysis revealed 741 samples predominantly contained Pf 655/741 (88.3%) followed by Pow 153/741 (20.6%), Pm 70/741 (9.4%) and Poc 64/741 (8.6%); 12/741 (1.62%) samples did not amplify any species. A total of 535/741 (72.2%) samples contained single species, and 194/741 (26.18%) samples contained multiple species. Species distribution differed significantly, with Pf and Pow more prevalent in symptomatic cases, while Pm and Poc were more common in asymptomatic individuals (p = 0.000). Pm and Poc single-species infections occurred among asymptomatic infections only. There were significantly higher odds of multiple species occurrence for infections containing Pf/Pow 92 (95.8%) among symptomatic than asymptomatic infections (OR 1.5, 95% CI [1.36-1.65], p = 0.000). Overall, mixed-species infections involving Pf and Pow were significantly more common in symptomatic individuals, posing a risk of false diagnosis by Pf-Histidine-Rich Protein 2 test. This underscores the need for deployment of interventions that target all Plasmodium species. These findings on the burden across symptomatic vs asymptomatic infections suggest a need for determination of the role of species composition in disease progression.