Cross-Sectional Study On The Distribution And Epidemiology Of Plasmodium Ovale Species In Asymptomatic And Symptomatic Individuals In Gulu, Uganda

Abstract

Despite global progress in malaria control, Plasmodium ovale remains an under-recognized contributor tothe malaria burden in sub-Saharan Africa. Its ability to form dormant liver-stage hypnozoites enables silent, recurrent transmission that often escapes detection by routine diagnostics. This cross-sectional study investigated the prevalence, species distribution, and clinical profile of P . ovale infections in Gulu, Uganda, comparing asymptomatic individuals from the community to symptomatic patients presenting at Gulu Regional Referral Hospital. Molecular diagnostics, including qPCR, nested PCR, and hemi-nested PCR, were used to detect and differentiate P . ovale curtisi and P . ovale wallikeri. Geographic sampling was conducted across 33 parishes in five districts, utilizing a population-proportional stratified design. A total of 600 community samples and 102 hospital samples were collected. Results revealed that P . ovale mono-infections were more prevalent in the community (8.7%), whereas co-infections with P . falciparum were predominant in the hospital (3.9%). Logistic regression analysis demonstrated that P . falciparum co-infection significantly increased the odds of hospitalization among P . ovale-positive individuals (OR = 3.5, 95% CI: 1.2–5.8, p = 0.01). Spatial clustering was observed in Omoro District, particularly in Lukwir Parish, suggesting localized transmission dynamics. Species differentiation using nested PCR confirmed two P . ovale curtisi and two P . ovale wallikeri infections among hospital cases. Additionally, four qPCR-positive hospital samples exhibited faint bands in hemi-nested PCR, indicating low-density infections that were undetectable by standard nested PCR alone. These ambiguous results emphasize the limitations of traditional methods in low-parasitemia settings and underscore the value of employing red diagnostic strategies. The findings suggest that P . ovale is sustained in the community as a largely asymptomatic reservoir and may be contributing to ongoing transmission despite control efforts targeting P . falciparum. Integrating species-specific molecular diagnostics, liver-stage treatments, and broader surveillance of non-falciparum species is essential for achieving comprehensive malaria elimination in Uganda