Placental malaria and neonatal anti-tetanus antibody status: Any association?
Background. Neonatal tetanus (NT) has long remained an important cause of neonatal morbidity and mortality in the tropics, where it coexists with a high prevalence of placental malaria. The current strategy for the control of NT involves stimulating the production of a protective level of an anti-tetanus antibody in the mother, through tetanus toxoid immunisation, and transferring it through the placenta to the fetus. Placental malaria is known to alter the morphology and functions of the placenta, but the results of studies on the effect of the transfer of the anti-tetanus antibody, specifically, remain inconclusive.
Objective. To study the influence of placental malaria on the transplacental transfer of anti-tetanus antibodies among mother-infant pairs at the University of Maiduguri Teaching Hospital in north-eastern Nigeria.
Method. Maternal and cord-blood samples were collected from 162 mother-infant pairs, and analysed for anti-tetanus antibody levels using the enzyme-linked immunosorbent assay technique. Placental biopsies were also taken from each mother-infant pair, and placental malaria diagnosed histologically.
Results. A total of 71.6% (n=116) of the 162 mother-infant pairs were positive for placental malaria, out of whom 50.9% (n=59) had chronicactive, 37.9% (n=44) acute and 11.2% (n=13) past placental malaria. In addition, 25.3% (n=41) babies were classified as seronegative for tetanus antibodies, of whom 72.7% (n=32) were delivered to mothers who were positive for placental malaria. A total of 34.5% (n=56) mother-infant pairs had poor placental transfer for tetanus antibodies, as signified by a cord-maternal ratio of <1.0 antibodies; of these, 24.7% (n=40) were positive for placental malaria. There was a statistically significant association between type of placental malaria and serostatus (p=0.0009), and efficiency of placental transfer (p=0.0340). Mothers with chronic-active malaria were 7.4 times more likely to deliver a seronegative infant compared with mothers with acute malaria (p=0.0002; odds ratio (OR) 7.353; 95% confidence interval (CI) 2.327 - 23.234). Similarly, maternal-infant pairs with chronic-active malaria were 2.9 times more likely to have inefficient placental transfer (p=0.0221; OR 2.859; 95% CI 1.200 - 6.859).
Conclusion. Placental malaria has remained a very common medical condition in Maiduguri among pregnant women, and may partly account for the high level of neonatal tetanus prevalent in the area.