The clinical burden of microscopically patent and sub-microscopic P. falciparum and P. vivax malaria in pregnancy in Indonesia

Abstract

Background Malaria in pregnancy poses a major public health problem in Indonesia with an estimated 6 million pregnancies at risk of P. falciparum or P. vivax malaria annually. The association between microscopically patent and PCR positive sub-microscopic malaria with maternal anaemia and low birth weight babies was assessed in Southwest Sumba and Jayapura district, Papua, Indonesia. Materials and methods Cross sectional surveys were conducted between June 2008-May 2009 in antenatal women and at delivery including home deliveries in SW Sumba (low-moderate transmission) and Jayapura (high transmission). Maternal and placental blood samples were obtained at antenatal attendance and at delivery for haemoglobin measurement, smear microscopy and PCR. Results A total of 4230 women (2598 attending antenatal care and 1632 at delivery) were enrolled. The prevalence of maternal parasitaemia detected by microscopy was 7.0% [(180/2598) (mono-infection with P. falciparum: 58.3%, with P. vivax: 20.6% and 0.5% P. ovale and 5.6% mixed infections (P. falciparum + P. vivax), and this was 12.3% by PCR (P. falciparum 58.4%, P. vivax 31.5%, mixed (P. falciparum + P. vivax): 10.1%) and 10.7% in Sumba and 14.2% in Jayapura, respectively. Submicroscopic parasitaemia (microscopy negative, PCR positive) was detected in 8.3% women. With patent infections only P. falciparum was associated with moderate-severe anaemia (Hb <9 g/dL); [RR 2.2 (95% CI 1.7-2.9) P. vivax RR 0.5 (0.3-0.9)] whereas with sub-microscopic infections both species were associated with increased risk of moderate to severe anaemia [P. falciparum: RR 2.1 (95% CI 1.6-2.8) and P. vivax: RR 1.9 (95% CI 1.3-2.7)]. The prevalence of placental malaria was 4.8% (72/1632) by PCR and 3.3% sub-microscopically; this was 2.4% in primigravidae, 3.1% in secundi and 1.7% in multigravidae (>3 pregnancies). The mean difference in birth weight in women with patent placental P. falciparum infection compared with uninfected women was 101 g (95% CI 70-273 g) with RR 2.1 (95% CI 1.2-3.0) for low birth weight. The reduction in birth weight with sub-microscopic infection was 70 g (63-204 g) with low birth weight RR 1.7 (95% CI 1.0-2.5). Corresponding figures for P. vivax were: patent placental infections: 252 g (57-560 g), low birth weight RR 4.7 (95% CI 2.2-67); and for sub-microscopic infections the mean difference in birth weight was 146 (70-364 g); low birth weight RR 2.9 (95% CI 1.6-3.4). Conclusions Sub-microscopic infections are common in eastern Indonesia and are associated with maternal anaemia and marked reductions in birth weight. Strategies that prevent sub-microscopic infections such as intermittent preventing therapy or that which results in their early detection and treatment, such as intermittent screening strategies should now be explored in South-east Asia.