Investigations into the association between soil-transmitted helminth infections, haemoglobin and child development indices in Manufahi District, Timor-Leste

Type Journal Article - Parasites & vectors
Title Investigations into the association between soil-transmitted helminth infections, haemoglobin and child development indices in Manufahi District, Timor-Leste
Volume 10
Issue 1
Publication (Day/Month/Year) 2017
Southeast Asia harbours one-third of the world’s soil-transmitted helminths (STH) [1], and Timor-Leste is one of the poorest countries in the region [2]. Two recent cross-sectional studies identified moderate school-based (29%) [3] and high community-based (69%) [4] STH prevalence in the Manufahi District of Timor-Leste, using different diagnostic techniques. Specifically, in this area, prevalence of Necator americanus was 60%, Ascaris spp. 24%, Ancylostoma spp. 4.7%, and Trichuris trichiura 0.33%, with Giardia duodenalis the most common protozoan identified (13%) [4]. Inadequate water and sanitation infrastructure and hygiene behaviours in this area likely contribute to high STH endemicity [4], which in turn could contribute significantly to morbidity.

STH have previously been associated with anaemia, stunting and wasting [5, 6, 7, 8, 9]. The mechanism whereby hookworms contribute to reduced haemoglobin and more indirectly to poor growth and development outcomes is via blood loss and inflammation, with heavily-infected people at greatest risk of morbidity [10]. Ascaris lumbricoides is not considered a contributor to blood loss (reviewed in [11]) and T. trichiura contributes to blood loss in heavy infection. Whilst STH have been shown to be associated with stunting and wasting [12, 13] the causal relationship is not clear.

Despite inability to establish causality with observational analyses, investigating the relationship between STH infection and haemoglobin concentration, and child anthropometric indices, is of considerable importance in Timor-Leste. Extremely high proportions of Timorese under 5 years of age are reported as stunted (50%) and wasted (11%) [14], yet knowledge of the contribution of STH to this is very limited, with no prior investigations identified. A cross-sectional survey in 2008 found 22% of children aged 24–59 months of age were anaemic [15]. Additionally, a demographic health survey in 2009–2010 found 38% of Timorese children aged 6–59 months, and 21% of Timorese women aged 15–49 years were anaemic [16]. Since this time, risk factors for anaemia in women of reproductive age have been investigated [17]. However, limited data on STH have prevented STH contributions from being assessed.

Using quantitative polymerase chain reaction (qPCR) for STH diagnosis and intensity of infection assessment [18], we aim to (i) determine classes of STH infection intensity from PCR-derived data, and (ii) provide the first analysis of morbidity associated with STH infections in Manufahi District, Timor-Leste. We used an algorithm to correlate quantification cycle (Cq) values from qPCR to eggs per gram of faeces (epg) equivalents, determined by seeding experiments [18]. The association between intensity of N. americanus and Ascaris spp. (as exposures) and mean haemoglobin concentrations and anaemia diagnosis (as outcomes) were then investigated for all community members, and associations with stunting, underweight and low BMI-for-age (as a measure of wasting) as outcomes in children aged one to 18 years were also investigated.

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