Complex Interactions between Soil-Transmitted Helminths and Malaria in Pregnant Women on the Thai-Burmese Border

Machteld Boel,Marcus Rijken,Pratap Singhasivanon,Mupawjay Pimanpanarak,Rose Mcgready,Moo Koo Paw,Wendi Bailey,Stephane Proux,François Nosten,Oh Moo,Nicholas J White,Mathieu Nacher,Verena I Carrara,Hser Gay,Simon Brooker

doi:10.1371/journal.pntd.0000887

Abstract

BackgroundDeworming is recommended by the WHO in girls and pregnant and lactating women to reduce anaemia in areas where hookworm and anaemia are common. There is conflicting evidence on the harm and the benefits of intestinal geohelminth infections on the incidence and severity of malaria, and consequently on the risks and benefits of deworming in malaria affected populations. We examined the association between geohelminths and malaria in pregnancy on the Thai-Burmese border.MethodologyRoutine antenatal care (ANC) included active detection of malaria (weekly blood smear) and anaemia (second weekly haematocrit) and systematic reporting of birth outcomes. In 1996 stool samples were collected in cross sectional surveys from women attending the ANCs. This was repeated in 2007 when malaria incidence had reduced considerably. The relationship between geohelminth infection and the progress and outcome of pregnancy was assessed.Principal FindingsStool sample examination (339 in 1996, 490 in 2007) detected a high prevalence of geohelminths 70% (578/829), including hookworm (42.8% (355)), A. lumbricoides (34.4% (285)) and T.trichuria (31.4% (250)) alone or in combination. A lower proportion of women (829) had mild (21.8% (181)) or severe (0.2% (2)) anaemia, or malaria 22.4% (186) (P.vivax monoinfection 53.3% (101/186)). A. lumbricoides infection was associated with a significantly decreased risk of malaria (any species) (AOR: 0.43, 95% CI: 0.23–0.84) and P.vivax malaria (AOR: 0.29, 95% CI: 0.11–0.79) whereas hookworm infection was associated with an increased risk of malaria (any species) (AOR: 1.66, 95% CI: 1.06–2.60) and anaemia (AOR: 2.41, 95% CI: 1.18–4.93). Hookworm was also associated with low birth weight (AOR: 1.81, 95% CI: 1.02–3.23).Conclusion/Significance A. lumbricoides and hookworm appear to have contrary associations with malaria in pregnancy.

Highlights

In 1994 and 2002 the World Health Organization (WHO) recommended anthelminthics be given to girls, pregnant and lactating women to reduce the burden of anaemia in areas where hookworm and anaemia are common [1,2,3]
The WHO recommends deworming in pregnancy in areas where hookworm infections are frequent
Some studies indicate that coinfection with worms and malaria adversely affects pregnancy whereas other studies have shown that coinfection with worms might reduce the severity of malaria

Summary

Introduction

In 1994 and 2002 the World Health Organization (WHO) recommended anthelminthics be given to girls, pregnant and lactating women to reduce the burden of anaemia in areas where hookworm and anaemia are common [1,2,3]. A Cochrane review, including three prospective randomised controlled trials studying the effect of deworming in pregnancy, concluded that the evidence to date is insufficient to recommend use of antihelminthics for pregnant women after the first trimester of pregnancy [16]. Deworming is recommended by the WHO in girls and pregnant and lactating women to reduce anaemia in areas where hookworm and anaemia are common. We examined the association between geohelminths and malaria in pregnancy on the ThaiBurmese border

Methods

Results

Discussion

Conclusion