10.1371_journal.pntd.0002912.PDF - Viewpoints Blood...

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Viewpoints Blood Drain:Soil-Transmitted Helminths and Anemia in Pregnant Women Theresa W. Gyorkos 1,2 *, Nicolas L. Gilbert 1 1 Parasite Epidemiology Research Group, Division of Clinical Epidemiology, Research Institute of the McGill University Health Centre, Montreal,Canada,2 Department of Epidemiology, Biostatistics and Occupational Health,McGillUniversity,Montreal,Canada Anemia and Maternal Health The main causeof anemiais iron deficiency, which, in turn, can result from a wide range of factors. Iron intake may be insufficient because of a low dietary iron content, less bioavailable (i.e., non-heme) iron, or because of poor absorption of iron due to concurrent ingestion of inhibitors such as cereals and grain [1]. In addition, iron may be lost because of infection by parasites that destroy red blood cells, such asmalaria-causing Plasmodium species, or by blood-feeding parasites, such asthe soil-transmitted helminths (STHs) [1]. Normalhemoglobin distributions vary by age and sex and so do anemia thresholds (i.e., hemoglobin (Hb) concen- trations below which individuals are con- sidered anemic). Among women of repro- ductive age, this threshold is 11 g/dL for pregnantwomen and 12 g/dL fornon- pregnant women [2]. Anemia in pregnant women is of particular concern because of its association with maternal mortality. This association has been known for years [3,4]and hasbeen confirmed by recent evidence from cohort studies [5,6].The World Health Organization estimates that the worldwideprevalence of anemia is 30% in pregnantwomen and 20% in nonpregnant women, with higher levels in women living in developing countries [7]. The estimated prevalence of anemia in pregnantwomenis highestin Africa (55.8%)and Asia (41.6%) and lowest in North America (6.1%) and Europe (18.7%) [7]. The Evidence Linking Soil- Transmitted Helminths and Anemia The associationbetweenhookworm infectionand anemiais well known. Hookworm infection is recognized as a risk factor for anemia, both in pregnant women [8]and in nonpregnant women [9].In pregnantwomen,a meta-analysis published in 2008 showed that even light intensity (1–1,999 eggs per gram [epg]) hookworm infection is associated with a significant decrease in blood Hb, and that the magnitudeof the Hb decrement increases with infection intensity [8]. Since then,new studies have provided further evidencedocumenting the detrimental effect of hookworm infection on Hb levels [10,11]. The evidence linking thewhipworm, Trichuris trichiura, with anemia is less clear. Moststudiesof Hb/anemia in pregnant women compared Trichuris-infected and non-Trichuris-infected women, and found no statistically significant associations [11– 15].However,none ofthese studies had differentiated between Trichuris infection intensity categories. Of the single study which had examined Trichuris infection intensitycategories, resultsshowed that pregnant women with moderate or heavy Trichuris infection in their second trimester of pregnancy had statistically significantly lower Hb levels compared to those with no or light Trichuris infection, despite all of the
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  • Fall '17
  • Major
  • Hookworm, Parasitic worm, Trop Med Hyg, Soc Trop Med, hookworm infection

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