Profiles of Plasmodium falciparum infections detected by microscopy through the first year of life in Kintampo a high transmission area of Ghana

Abstract

Although malaria mortality among children under five years of age is high, the characteristics of their infection patterns are not well described. The aim of this study was to examine the longitudinal sequence pattern of Plasmodium falciparum infections in the first year of life within a birth cohort in Kintampo, Ghana (N = 1855). Infants were monitored at home with monthly sampling and also at the clinic for any febrile illness between 2008 and 2011. Light microscopy was performed on monthly scheduled visits and febrile ill visits over twelve months of follow-ups (n = 19231). Microscopy-positive visits accompanied with or without symptoms were rare during the first five months of life but were common from six to twelve months of age. Among 1264 infants with microscopy data over a minimum of eight monthly visits and also throughout in sick visits, some were microscopy negative (36%), and others positive: only-symptomatic (35%), alternating (22%) and only-asymptomatic (7%). The median age of microscopic infection was seven months for the alternating group and eight months for both the only-symptomatic and only-asymptomatic groups. The alternating group had the highest cumulative incidence of microscopic infections, the lowest age at first infection and 87 different infection patterns. Parasite densities detected by microscopy were significantly higher for symptomatic versus asymptomatic infection. We conclude that infants in malaria endemic areas experience diverse infection profiles throughout their first year of life. Further investigations should include submicroscopic reservoir and may shed more light on the factors that determine susceptibility to malaria during infancy.

Determinants of the varied profiles of Plasmodium falciparum infections among infants living in Kintampo, Ghana

“…The dynamics of infections, and parasite densities have been previously described in more detail for the cohort [ 26 ]. Briefly, among the 1264 infants, 459 (36%) were repeatedly “parasite negative”, 87 (7%) were “only-asymptomatic”, 444 (35%) were “only-symptomatic” and 274 (22%) had both asymptomatic and symptomatic infections intermittently and referred to as the “alternating” group (Fig.…”

“…A birth cohort study involving pregnant women and their infants was conducted between November 2008 and January 2011 in KNM and KSD [ 25 ]. The cohort consisted of 1854 infants who were followed up in monthly scheduled home visits and unscheduled clinic visits for blood and clinical assessments [ 26 ]. The follow up ended at 12 months of age, or when the infant exited the study due to migration, death, voluntary withdrawal, or ending of the study [ 26 ].…”

“…The longitudinal profiles of asymptomatic infections and symptomatic malaria in the first year of life have been recently reported [ 26 ]. Briefly, symptomatic malaria was adapted from the WHO and defined as a microscopy positive reading together with a history of reported fever or elevated temperature (determined as ≥ 37.5 °C) and illnesses/symptoms (such as vomiting, chills, fever, diarrhoea, cough, difficulty breathing, blood in urine or inability to suckle, drink or eat) within the past 48 h or subsequent seven days after parasite detection during either the scheduled home or unscheduled clinical visit [ 1 , 32 ].…”

“…Thus, the risk of developing malaria, diagnosed by light microscopy, among infants born to mothers in a high transmission area of Ghana was assessed, and it was observed that the incidence of all episodes of parasitaemia and clinical malaria were lowest among infants born to primigravida mothers who were negative for placental malaria [ 25 ]. Following analyses of the malaria infection profiles during the entire first year of life, a large proportion of infants were consistently parasite negative [ 26 ]. Of the infants with detectable parasitaemia, by light microscopy, a small proportion developed only asymptomatic infections which spontaneously cleared without treatment (designated “only-asymptomatic”).…”

“…Of the infants with detectable parasitaemia, by light microscopy, a small proportion developed only asymptomatic infections which spontaneously cleared without treatment (designated “only-asymptomatic”). Significantly larger proportions developed either symptomatic malaria (designated “only-symptomatic”) or a mixture of both asymptomatic and symptomatic infections (designated “alternating”) [ 26 ]. An extension of these studies with a detailed comparison of the risk factors influencing susceptibility to symptomatic malaria using these four groups is presented here.…”