Overall, with one year of follow-up, no effect of deworming on growth could be detected in this population of preschool-age children. Low baseline STH prevalence and intensity and/or access to deworming drugs outside of the trial may have diluted the potential effect of the intervention. Additional research is required to overcome these challenges and to contribute to strengthening the evidence base on deworming.

A randomized, double-blind, placebo-controlled trial was conducted to determine the effect of deworming (500 mg single-dose crushed mebendazole tablet) on growth in one-year-old children in Iquitos, Peru. Children were enrolled during their routine 12-month growth and development clinic visit and followed up at their 18 and 24-month visits. Children were randomly allocated to: Group 1: deworming at 12 months and placebo at 18 months; Group 2: placebo at 12 months and deworming at 18 months; Group 3: deworming at both 12 and 18 months; or Group 4: placebo at both 12 and 18 months (i.e. control group). The primary outcome was weight gain at the 24-month visit. An intention-to-treat approach was used. A total of 1760 children were enrolled between September 2011 and June 2012. Follow-up of 1563 children (88.8%) was completed by July 2013. STH infection was of low prevalence and predominantly light intensity in the study population. All groups gained between 1.93 and 2.05 kg on average over 12 months; the average difference in weight gain (kg) compared to placebo was: 0.05 (95% CI: -0.05, 0.17) in Group 1; -0.07 (95%CI: -0.17, 0.04) in Group 2; and 0.04 (95%CI: -0.06, 0.14) in Group 3. There was no statistically significant difference in weight gain in any of the deworming intervention groups compared to the control group.

Appropriate health and nutrition interventions to prevent long-term adverse effects in children are necessary before two years of age. One such intervention may include population-based deworming, recommended as of 12 months of age by the World Health Organization in soil-transmitted helminth (STH)-endemic areas; however, the benefit of deworming has been understudied in early preschool-age children.

The World Health Organization recommends starting population-based deworming interventions as of 12 months of age where intestinal worm infection is common; however, little is known about the benefits in early preschool-age children. We conducted a clinical trial to determine the effect of deworming on growth in one-year-old children in Peru. Participating children were randomly assigned to: 1) deworming at 12 months of age; 2) deworming at 18 months of age; 3) deworming at 12 and 18 months of age; or 4) no deworming (i.e. control group). A total of 1760 children were enrolled between September 2011 and June 2012, and followed up for one year. Overall, with one year of follow-up, no effect of deworming on growth could be detected in this population of preschool-age children. The potential benefit of the intervention may have been affected by low baseline infection prevalence and/or low compliance to the randomly assigned intervention. Additional research is required to overcome these challenges and to contribute to strengthening the evidence base on deworming.

Funding: This study was supported by grants from the Thrasher Research Fund ( https://www.thrasherresearch.org ) and the Canadian Institutes of Health Research ( http://www.cihr-irsc.gc.ca/ ) (MOP-110969) (Principal Investigator: TWG; Co-investigators: SAJ, AM, MC, BJW, GSM, ER). SAJ also received personal and project support from the Canadian Institutes of Health Research (Vanier Canada Graduate Scholarship; Michael Smith Foreign Study Supplement; Planning and Dissemination Grant), the Research Institute of the McGill University Health Centre ( http://muhc.ca/research ) and the Fonds de Recherche du Québec– Santé ( www.frsq.gouv.qc.ca ). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Copyright: © 2015 Joseph et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Considering the unique nutritional demands and growth patterns of younger children, aggregated results from older children do not provide a clear indication of the potential benefit of deworming on growth and nutrition in younger age groups. To fill this research gap, we therefore conducted a randomized controlled trial on the effect, and optimal timing and frequency, of a deworming intervention incorporated into routine child health services at one year of age. Our objective was to determine whether deworming would improve growth by two years of age.

Prior to 2002, children under two years of age had been excluded from deworming interventions as the burden of STH infection was perceived to be low in this age group and the safety profile of available anthelminthics was not well established. In 2002, WHO convened an informal consultation of experts, and subsequently recommended the inclusion of children between 12 and 24 months of age in deworming activities using single-dose albendazole (in a reduced dose of 200 mg) or mebendazole (in the usual dose of 500 mg) [ 9 ]. These recommendations were based on animal studies, toxicity data and other safety data [ 10 ]. Despite the WHO recommendations and increasing evidence of the occurrence of STH infection in early preschool-age children [ 10 – 15 ], many countries still exclude children under 24 months of age from their national deworming programs. Providing evidence on the potential benefits of deworming in the younger age group between one and two years of age is essential. A study reviewing data from 54 countries confirmed that preventive interventions must occur during the first two years of life to prevent growth deficits, such as stunting and underweight [ 16 ]. Interventions at this time are essential to prevent both short- and longer-term adverse health effects [ 17 ]. The evidence-base on including deworming as one of the essential early childhood interventions in this critical window is, however, limited. Randomized controlled trials conducted exclusively in school-age children or in both preschool-age and school-age children have provided mixed evidence on deworming benefits on growth and development [ 6 , 18 , 19 ]. Few studies have focused exclusively on the preschool-age population [ 12 , 20 – 22 ]. There is some evidence that adverse consequences of even low prevalence and intensity STH infection may be more pronounced in children during this critical time period [ 11 ].

WHO recommends large-scale preventive chemotherapy programs, using anthelminthic treatment (i.e. deworming), for the high-risk groups of women of reproductive age, especially pregnant women, school-age children (i.e. 5 to 14 years of age), and preschool-age children (i.e. 1 to 4 years of age) in STH-endemic areas [ 4 , 5 ]. Adverse effects from deworming are infrequent, and when reported, are mild and transitory, including gastrointestinal upset and diarrhea [ 6 ]. Deworming interventions are often school-based in order to reach school-age children. In preschool-age children, deworming is often piggybacked onto vaccination or supplementation programs, child health days, or programs for the elimination of lymphatic filariasis [ 7 ]. However, preschool-age children lag behind their school-age counterparts as scaling-up of school-based programs continues while that of preschool programs remains a challenge [ 7 ]. The global proportion of at-risk preschool-age children receiving deworming in 2012 was estimated to be on the order of 25% [ 7 ]. This coverage has decreased since previous reports [ 8 ].

The soil-transmitted helminth (STH) disease cluster includes ascariasis, trichuriasis and hookworm disease. It is considered to be one of the most common Neglected Tropical Diseases (NTD), affecting an estimated 1.45 billion people worldwide [ 1 ]. STHs are transmitted in contaminated food, water and the environment in areas of poverty in low- and middle-income countries. These intestinal parasites have a direct and indirect adverse impact on nutritional status by disrupting normal nutrient intake, excretion and utilization in their hosts and by causing blood loss and loss of appetite [ 2 , 3 ].

Methods

Ethics approval and trial monitoring This study received ethics approval in Peru from the Comité Institucional de Ética of the Universidad Peruana Cayetano Heredia and the Instituto Nacional de Salud, in Lima, and the local Ministry of Health office (Dirección Regional de Salud (DIRESA) Loreto) in Iquitos (S1 Text). Ethics approval was obtained in Canada from the Research Ethics Board of the Research Institute of the McGill University Health Centre in Montréal, Québec (S1 Text). An independent Data Safety and Monitoring Committee (DSMC) was established with three members, from Canada, the U.S., and Peru, to review all adverse events and approve continuation of the trial at three time points. At baseline, eligibility was assessed, and an informed consent form was signed by both parents or guardians of the child. In the case of a single parent (e.g. due to death, separation or divorce), only one signature was required. The trial was registered with ClinicalTrials.gov (NCT01314937). The CONSORT checklist is described in S1 Checklist and the trial protocol is described in S2 Text.

Study design and enrollment procedures We conducted a randomized, double-blind, parallel, placebo-controlled trial of a deworming intervention incorporated into routine growth and development (‘Crecimiento y Desarrollo” or CRED) visits in Iquitos, an STH-endemic area of the Peruvian Amazon. Details on baseline enrolment methodology and the study population have been described elsewhere [14]. Briefly, children were enrolled into the trial in their homes or participating health centres. Inclusion criteria were: 1) children attending any one of the 12 participating health centres for their 12-month CRED visit; and 2) children living in Belén, Iquitos, Punchana or San Juan districts. Exclusion criteria were: 1) children attending the health centre for suspected STH infection; 2) children who had received deworming treatment in the six months prior to the trial; 3) children whose families planned to move outside of the study area within the next 12 months; 4) children under 12 months of age or 14 months of age or older; and 5) children with any serious congenital or chronic medical condition. Any child who was excluded for medical reasons, and who was not already receiving regular health care, was referred to the health centre for follow-up by appropriate health personnel. A baseline socio-demographic and epidemiological questionnaire (including family and child health and nutrition information) was administered in the home or health centre to the primary caregiver of the child. Baseline outcome measurements, including weight, length and the provision of a stool specimen, were ascertained in a subsequent visit in the health centre. All procedures were performed by dedicated, trained research assistants.

Intervention groups Following confirmation of eligibility, informed consent and all baseline outcome assessments in the health centres, children were randomized into one of four intervention groups: Group 1 (MBD/PBO): Usual care and deworming at the 12-month CRED visit and usual care and placebo at the 18-month CRED visit. Group 2 (PBO/MBD): Usual care and placebo at the 12-month CRED visit and usual care and deworming at the 18-month CRED visit. Group 3 (MBD/MBD): Usual care and deworming at both the 12 and 18-month CRED visits. Group 4 (PBO/PBO): Usual care and placebo at both the 12 and 18-month CRED visits (i.e. control group). Deworming consisted of a single-dose mebendazole tablet (500 mg) (manufactured by Janssen Pharmaceuticals Inc.; donated by INMED Peru). The placebo was identical to the deworming tablet in terms of size, colour and markings (manufactured and purchased from Laboratorios Hersil, Peru). Tablets were crushed and mixed with juice for ease of administration and safety [23]. The crushed tablet was administered by research assistants at the end of each visit after all outcome assessments had been completed. All children received deworming at the 24-month visit according to Peruvian Ministry of Health guidelines [24]. Children received usual care interventions and services from health centre personnel [24]. This included the administration of measles, mumps and rubella (MMR) vaccination at the 12-month visit, and diphtheria, pertussis and tetanus (DPT) vaccine booster at the 18-month visit.

Sample size Sample size calculations were based on detecting the smallest meaningful difference among intervention groups in mean weight gain over 12 months, and took into account potential effect dilution from treating infected and non-infected children. From previous research in the study area, STH prevalence was expected to be 25% at 12 months of age [13]. To estimate expected growth, longitudinal growth data was collected from health centre registries in the study area in 2011. Mean weight gain ± standard deviation between 12 and 24 months in 100 untreated children was calculated to be 2.0 kg ± 0.8 kg. The sample size was calculated a priori such that comparisons could be made between all four groups to look at the overall effect of deworming, as well as the effect of timing and frequency of deworming. In order to have 80% power to detect a minimum difference of 0.20 kg in mean weight gain among intervention groups, assuming a common standard deviation of 0.8 and a significance level of 0.05, and using a one-way ANOVA which accounts for pair-wise multiple comparisons between all groups (i.e. 6 comparisons) using the Tukey correction, the estimated sample size per group was 366 children. The required sample size was increased to 440 children per group (1760 in total), to take into account potential loss-to-follow-up of 20% after 12 months (based on attrition rates from previous studies in the area by the research team [25,26]) (MC4G Software©, GP Brooks, Ohio University, 2008).

Randomization and masking Computer-generated randomly ordered blocks of eight and twelve were used to randomly assign children to each intervention group in a 1:1:1:1 allocation ratio. Blocking ensured that the number of children assigned to each group would be balanced and reduced the potential for bias and confounding [27]. The random allocation sequence was generated by a biostatistician who was not otherwise involved in the trial. Research personnel not directly involved in the trial prepared small envelopes containing the randomly assigned intervention for each visit. These were numbered from 1 to 1760, with each number corresponding to one of the four intervention groups. Envelopes were stored in a temperature-regulated pharmacy at the research facility, and distributed by the Project Director (SAJ) or the local Study Coordinator (LP) in sequential order to research assistants until the sample size was achieved. Appropriate allocation concealment and randomly ordered block sizes ensured that the randomization sequence would not be predictable [27]. All health centre and research personnel, and parents of participants were blinded to intervention status.

Follow-up visits Children were followed-up at their 18 and 24-month visit in the health centre, at which time all outcome ascertainments were repeated. At the 18-month visit the second randomly assigned intervention was administered. Each visit was scheduled six months after the previous visit. In the case that a participant did not attend their 18-month visit, children remained eligible for the 24-month visit, which was scheduled 12 months after initial enrolment. If participants were not located prior to the day of their anticipated follow-up visit, or a scheduled date was missed, a minimum of four additional attempts were made to locate them. The original end dates of the 18-month follow-up and 24-month follow-up (i.e. trial completion) were each extended by one month (i.e. seven months and 13 months after the end of enrolment, respectively) to maximize follow-up rates. A monetary reimbursement was provided to cover travel costs for each visit.

Outcome measurements The pre-specified primary outcome measure was weight gain between the 12 and 24-month visit. Pre-specified secondary outcome measures were weight-for-age z-score, length gain, length-for-age z-score, change in STH infection prevalence and intensity, and change in development (i.e. cognitive, language and fine motor skills) between the 12 and 24-month visit. The development outcomes are reported separately. Prior to commencing recruitment, in-depth practical training of the research assistants took place according to WHO guidelines [28,29] to ensure accurate outcome assessment and standardization. Inter and intra-rater reliability of over 95% was achieved for weight and length assessments, which are considered acceptable levels for anthropometric measurements [28,30]. Methods used for outcome measurements are described elsewhere [14]. Briefly, weight was measured using a portable electronic scale, accurate to the nearest 0.01 kg (Seca 334, Seca Corp., Baltimore, MD, USA). Length (i.e. the recommended measurement of height in children less than two years of age) was measured in duplicate as recumbent crown-heel length on a flat surface using a stadiometer (Seca 210, Seca Corp., Baltimore, MD, USA), accurate to the nearest millimetre. One stool specimen per child was collected to assess STH (e.g. Ascaris, Trichuris and hookworm) infection prevalence and intensity. For ethical reasons, only specimens from children receiving deworming treatment were immediately examined by trained laboratory technologists at the local research facility using the Kato-Katz method (single slide) for the presence and intensity (i.e. eggs per gram of feces) of STH infection [31]. At each time point, specimens from those children receiving placebo were stored at room temperature in 10% formalin and analyzed by the direct method for the presence of STH infection upon trial completion (Table 1). PPT PowerPoint slide

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larger image TIFF original image Download: Table 1. Randomly allocated treatment and corresponding analysis (method and timing) of stool specimens by group and visit. https://doi.org/10.1371/journal.pntd.0004020.t001 This approach ensured that children found to be infected were treated. This approach also aimed to minimize effect dilution which would have occurred if treatment had been provided to those found to be STH positive, but randomized to receive placebo. The Kato-Katz method is the recommended technique for assessment of the prevalence and intensity of intestinal parasitic infection in fresh stool [31]. For a one-stool specimen, sensitivity and specificity are over 96% for Ascaris and over 91% for Trichuris [32]. There is lower sensitivity and specificity for hookworm; however, hookworm infection is generally uncommon in very young children in this study area [13]. Additional details on the collection of stool specimens, including the ethical rationale for using two methods of analysis and how blinding was maintained, are published elsewhere [14]. Lower sensitivity to detect STH infection from storage and later analysis of specimens by the direct method was also anticipated [14]. A socio-demographic and epidemiological questionnaire was administered at each visit. At the follow-up visits, this included a question on whether deworming had been received between study visits (i.e. outside of the trial). Information on minor and severe adverse events was obtained through passive reporting at follow-up visits or in between visits. Severe adverse events were based on WHO definitions and included: 1) death; 2) life-threatening conditions; 3) in-patient hospitalization or prolongation of an existing hospitalization; 4) persistent or significant disability/incapacity; 5) cancer; or 6) overdose (accidental or intentional) [5]. All reported illnesses that did not meet the definition of a serious adverse event were considered to be minor adverse events. All adverse events were reported to ethics committees. Summary reports of adverse events were also provided to the DSMC. Data collection activities during fieldwork were regularly supervised by the Project Director (SAJ) and local Project Coordinator (LP). The consistency of egg count assessments was evaluated among the laboratory technologists using standard quality control methods [31]. The laboratory supervisor read 10% of the slides of the laboratory technologists without prior knowledge of the result to ensure quality control.