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

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 South-west 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. Sub-microscopic 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.