Abstract
Background Plasmodium ovale and Plasmodium malariae have long been reported to be widely distributed in tropical Africa and in other major malaria-endemic areas of the world. However, little is known about the burden caused by these two malaria species.Methods and FindingsWe did a longitudinal study of the inhabitants of Dielmo village, Senegal, between June, 1990, and December, 2010. We monitored the inhabitants for fever during this period and performed quarterly measurements of parasitemia. We analyzed parasitological and clinical data in a random-effect logistic regression model to investigate the relationship between the level of parasitemia and the risk of fever and to establish diagnostic criteria for P. ovale and P. malariae clinical attacks. The prevalence of P. ovale and P. malariae infections in asymptomatic individuals were high during the first years of the project but decreased after 2004 and almost disappeared in 2010 in relation to changes in malaria control policies. The average incidence densities of P. ovale and P. malariae clinical attacks were 0.053 and 0.093 attacks per person per year in children <15 years and 0.024 and 0.009 attacks per person per year in adults ≥15 years, respectively. These two malaria species represented together 5.9% of the malaria burden.Conclusions P. ovale and P. malariae were a common cause of morbidity in Dielmo villagers until the recent dramatic decrease of malaria that followed the introduction of new malaria control policies. P. ovale and P. malariae may constitute an important cause of morbidity in many areas of tropical Africa.
Highlights
Plasmodium ovale and Plasmodium malariae have long been reported to be widely distributed in tropical Africa and in other major malaria-endemic areas of the world [1,2,3,4,5]
P. ovale and P. malariae may constitute an important cause of morbidity in many areas of tropical Africa
In malaria endemic areas of tropical Africa, almost all malaria attacks are attributed to P. falciparum, possibly due either to underdiagnosis of P. ovale and P. malariae clinical attacks, to partial cross-immunity between malaria species, or to rapidly acquired species-specific protective immunity against P. ovale and P. malariae
Summary
Plasmodium ovale and Plasmodium malariae have long been reported to be widely distributed in tropical Africa and in other major malaria-endemic areas of the world [1,2,3,4,5]. In forest and wet savannahs areas of West and Central Africa, high prevalence of the two species is common in children, often reaching 15–40% for P. malariae and 4–10% for P. ovale in studies where thick blood films were carefully examined by trained microscopists since parasitemia is usually low [6,7,8,9,10,11] In these areas with a long rainy season and/or perennial or semi-perennial Anopheles breeding sites, P. falciparum is always highly endemic, and most P. ovale and P. malariae infections are associated with P. falciparum infections [8,12]. Little is known about the burden caused by these two malaria species
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