Transmission and Age Impact the Risk of Developing Febrile Malaria in Children with Asymptomatic Plasmodium falciparum Parasitemia

Abstract

<jats:title>Abstract</jats:title> <jats:sec> <jats:title>Background</jats:title> <jats:p>Plasmodium falciparum infections lead to febrile illness unless the host has sufficient immunity, in which case infection may cause no immediate symptoms (ie, “asymptomatic parasitemia”). Previous studies are conflicting on the role of asymptomatic parasitemia in determining the risk of developing febrile malaria.</jats:p> </jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>We monitored 2513 children (living in Kilifi, Kenyan Coast) by blood smears in 17 cross-sectional surveys to identify asymptomatic parasitemia and used active surveillance over 11325 child-years of follow-up to detect febrile malaria. We evaluated the interaction between transmission intensity, age, and asymptomatic parasitemia in determining the risk of developing febrile malaria.</jats:p> </jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>In the moderate and high transmission intensity settings, asymptomatic parasitemia was associated with a reduced risk of febrile malaria in older children (&amp;gt; 3 years), while in the lower transmission setting, asymptomatic parasitemia was associated with an increased risk of febrile malaria in children of all ages. Additionally, the risk associated with asymptomatic parasitemia was limited to the first 90 days of follow-up.</jats:p> </jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>Asymptomatic parasitemia is modified by transmission intensity and age, altering the risk of developing febrile episodes and suggesting that host immunity plays a prominent role in mediating this process.</jats:p> </jats:sec>

Point prevalence of asymptomatic Plasmodium infection and the comparison of microscopy, rapid diagnostic test and nested PCR for the diagnosis of asymptomatic malaria among children under 5 years in Ghana

“…Based on nested PCR, this study reports a high point prevalence (36.8%) of asymptomatic Plasmodium infection among a paediatric population in the Atwima Nwabiagya North district of Ghana. Asymptomatic malaria in children under 5 years has been reported in some African countries [33][34][35]. In Ghana, Crookston, et al [46] reported an asymptomatic malaria � Anaemia was defined as haemoglobin level <11 g/dL and graded as mild (10-10.9 g/dL), moderate (7-9.9 g/dL), and severe (<7 g/dL).…”

“…Thus, accurate diagnosis of asymptomatic malaria as a potential reservoir of infection, especially in children, is crucial. Although a number of studies on asymptomatic malaria in older children have been conducted across Ghana [ 30 – 32 ] and children under 5 in neighboring African countries [ 33 – 35 ], there remains a dearth of published data on asymptomatic malaria in children under 5 years in Ghana, particular in the northern sectors of the country where adequate health facilities are wanting. This study assessed the point prevalence of asymptomatic malaria infection and evaluated the performance of malaria RDT, light microscopy and nested PCR (nPCR) for the diagnosis of asymptomatic malaria infection in children under 5 years old in Atwima Nwabiagya North district, Ghana.…”

Understanding P. falciparum Asymptomatic Infections: A Proposition for a Transcriptomic Approach

“…This is due to the wide range of definitions that complicates the comparison of results across studies (Table 1). The most basic definition seems to be the presence of parasitemia and the absence of malaria symptoms, mainly fever (axillary temperature <37.5°C) (14, 19, 20). This definition is ambiguous and most studies have modified it by incorporating strict inclusion criteria.…”

“…This allows for the exclusion of those who experienced symptoms in the recent past and then sought treatment. However, there is no consensus on the duration of history and it ranges from 2 weeks to 1 month (5, 14, 20). The longitudinal follow-ups after diagnosis reduces the chances of “false” asymptomatic parasitemia that are defined during P. falciparum incubation toward a clinical outcome.…”

“…A risk-benefit analysis is required to determine the tradeoffs to inform the public health impact of MDA on asymptomatic infections. The possibility of developing febrile malaria among asymptomatic carriers has been shown to vary due to transmission intensity and age (Figure 1) (20, 39). A study in Kenya compared the risk of developing febrile malaria among children (0–15 years) who were uninfected with P. falciparum and those with asymptomatic parasitemia.…”