Belyhun et al. BMC Public Health 2010, 10:21 http://www.biomedcentral.com/1471-2458/10/21 children living in endemic areas are infected continu- ously from soon after birth and often experience chronic ill health [1,9]. Infections with STHs may have impor- tant health consequences during this developmental stage, affecting child health and development, slowing down growth and reducing adults productivity and work capacity [1,6,7,9]. These helminth infections may also elicit potent immune responses through effects on the immune system [1,10]. Intervention against STH infection is based on regular anti-helminthic treatment, improved water supply, sani- tation and health education [11]. Low-cost, high-cover- age delivery of anti-helminthic treatment has been achieved in some settings [12], but improving sanitation is more complex. In Ethiopia, for example, levels of access to improved sanitation in rural areas are very low (5.4%) [13], making evaluation of other components of intervention important. In this study, we present data from an area in which intermittent mass de-worming has been carried out [14], but where levels of sanitation are still rudimentary. We present data on prevalence of STH infection among mothers and one-year old chil- dren in a rural area of Ethiopia using a population- based birth cohort to define the prevalence of STH infection and identify factors amenable to intervention. Methods Study area and population The study site was the Butajira area, which is located in Gurage zone, Southern Ethiopia. The capital Butajira lies at a distance of 130 Km from the capital, Addis Ababa. The area is predominately rural and most resi- dents live in villages as agriculturists growing coffee, maize, teff (Eragrostos tef), pepper, the stimulant khat (Catha edulis forskal) and enset (false banana) [14]. The total population of the study area is approximately 250,000, with a diverse multi-ethnic group; the Gurages (Meskan, Mareko and Silti) form the majority [14]. Deworming started in the study area in 2006 as part of the Enhanced Outreach Strategy (EOS) [15]. Antihel- minthics have been given regularly in ten successive rounds in under five children, covering 41 administra- tive units of Butajira district and its surroundings [15]. Study design and procedures The Butajira Rural Health Project (BRHP), a Demo- graphic Surveillance Site (DSS) covering nine rural and one urban administrative area, was established in 1987 [14]. The DSS population currently is around 60,000 with more than 13,000 women of reproductive age. Between July 2005 and February 2006 all pregnant women in their third trimester and aged 15-49 years were identified from the BRHP and a birth cohort estab- lished, details of which have been reported elsewhere Page 2 of 7 [16]. Of the 1234 eligible women identified, 1065 were recruited and these women gave birth to 1006 live sin- gleton babies (Fig 1). Those mother-child pairs still liv- ing in the area and alive (n = 932) were followed up and data were collected between July 2006 and June 2007, at the time of the child’s first birthday. Data collection After written consent was obtained from the mothers of participating children, stool samples were collected from both the mother and child. Samples were collected by data collectors known to the mothers and children since the initiation of the birth cohort. The stool samples were placed in labeled plastic tubes containing 10% formalin and transported for analysis to the Aklilu Lemma Institute of Pathobiology, Addis Ababa Univer- sity. Samples were then examined qualitatively using the formol-ether concentration method [17]. Information on demographic and lifestyle factors was collected by inter- viewer-administered questionnaire during initial recruit- ment of the mother during pregnancy and at the first year follow up. Data management and analysis Data on parasites were entered into Excel and manu- ally checked for error against the hard copies. Ques- tionnaire data were double-entered into EpiData Figure 1 Study cohort.