Sero-epidemiological studies of malaria in pregnant women and newborns from western Kenya

Abstract

A sero-epidemiological longitudinal study of the impact of plasmodial infections on pregnancy was undertaken in a holoendemic area of western Kenya. The study involved a cohort of 393 pregnant women followed prospectively for peripheral parasitaemia and clinical complaints from time of enrollment until delivery. Plasma was tested for seroreactivity to synthetic malarial peptides representing the three major B-cell immunodominant epitopes of Plasmodium falciparum ring-infected erythrocyte surface antigen (Pfl55/RESA) i.e., RESA4, RESA8 and RESA11 and the circumsporozoite (CS) repeat peptide (NANP-5) using FAST-ELISA. At delivery, the outcome of pregnancy was recorded. Peripheral parasitaemia was detected in 33.3% of the women at some point during pregnancy, with P. falciparum accounting for 95.3% of the infections. Infection rates were higher among the primigravidae group irrespective of the duration of pregnancy. Parasite densities were higher in the same group early in pregnancy, and decreased with progression of pregnancy to levels similar to those of multigravidae at delivery. The prevalence of placental parasitaemia was 34.7% (n=248) with high infection rates and parasite densities being observed among the primigravidae. Umbilical cord parasitaemia was 2.7% (n=224), with a congenital parasitaemia infection rate of 4.8% (n = 124). The mean birth weight of babies whose mothers were parasitaemic was significantly lower than the mean birth weight of babies born to uninfected mothers (p<0.05). The outcome of pregnancy showed a maternal death rate of 0.3% and a miscarriage rate of 3.6%. Stillbirth and neonatal death rates were 2.1% and 2.6% respectively. Seroreactivity to the malarial peptides among pregnant women ranged from 82-95%. The proportion of responders was generally similar in all parity groups; however, the mean antibody levels as reflected by OD values were higher among the multigravidae than primigravidae or secundigravidae. Aparasitaemic pregnant women had significantly higher antibody levels to RESA4 peptide when compared to parasitaemic women (p<0.01) and; no such differences were observed for other peptides. This suggests that naturally acquired antibodies against RESA4 may contribute to the control of parasitemia. Seroreactivity by cord plasma ranged from 28-79%. Minimum reactivity by both maternal and cord plasma was observed on RESA11. There was a positive correlation between mean maternal and cord plasma antibody levels, with mean cord OD values being generally lower than maternal OD values. The significance of these results has been discussed.