The Epidemiology of Sapovirus in the Etiology, Risk Factors, and Interactions of Enteric Infection and Malnutrition and the Consequences for Child Health and Development Study: Evidence of Protection Following Natural Infection.

Background: Sapovirus is one of the principal agents of acute viral enteritis in children. Because it has not been routinely included in diagnostic evaluations, the epidemiology and natural history remain poorly described.

Methods: A birth cohort of 1715 children from 8 countries contributed surveillance samples (n = 35 620) and diarrheal specimens (n = 6868) from 0 to 24 months of age.

Determinants of Campylobacter infection and association with growth and enteric inflammation in children under 2 years of age in low-resource settings.

Campylobacter species infections have been associated with malnutrition and intestinal inflammation among children in low-resource settings. However, it remains unclear whether that association is specific to Campylobacter jejuni/coli. The aim of this study was to assess the association between both all Campylobacter species infections and Campylobacter jejuni/coli infections on growth and enteric inflammation in children aged 1-24 months.

Use of quantitative molecular diagnostic methods to assess the aetiology, burden, and clinical characteristics of diarrhoea in children in low-resource settings: a reanalysis of the MAL-ED cohort study.

Background: Optimum management of childhood diarrhoea in low-resource settings has been hampered by insufficient data on aetiology, burden, and associated clinical characteristics. We used quantitative diagnostic methods to reassess and refine estimates of diarrhoea aetiology from the Etiology, Risk Factors, and Interactions of Enteric Infections and Malnutrition and the Consequences for Child Health and Development (MAL-ED) cohort study.

Methods: We re-analysed stool specimens from the multisite MAL-ED cohort study of children aged 0-2 years done at eight locations (Dhaka, Bangladesh; Vellore, India; Bhaktapur, Nepal; Naushero Feroze, Pakistan; Venda, South Africa; Haydom, Tanzania; Fortaleza, Brazil; and Loreto, Peru), which included active surveillance for diarrhoea and routine non-diarrhoeal stool collection.

Use of quantitative molecular diagnostic methods to investigate the effect of enteropathogen infections on linear growth in children in low-resource settings: longitudinal analysis of results from the MAL-ED cohort study.

Background: Enteropathogen infections in early childhood not only cause diarrhoea but contribute to poor growth. We used molecular diagnostics to assess whether particular enteropathogens were associated with linear growth across seven low-resource settings.

Methods: We used quantitative PCR to detect 29 enteropathogens in diarrhoeal and non-diarrhoeal stools collected from children in the first 2 years of life obtained during the Etiology, Risk Factors, and Interactions of Enteric Infections and Malnutrition and the Consequences for Child Health and Development (MAL-ED) multisite cohort study.

Enteroaggregative Escherichia coli Subclinical Infection and Coinfections and Impaired Child Growth in the MAL-ED Cohort Study.

Objective: We evaluated the impact of subclinical enteroaggregative Escherichia coli (EAEC) infection alone and in combination with other pathogens in the first 6 months of life on child growth.

Methods: Nondiarrheal samples from 1684 children across 8 Multisite Birth Cohort Study, Malnutrition and Enteric Diseases (MAL-ED) sites in Asia, Africa, and Latin America were tested monthly; more than 90% of children were followed-up twice weekly for the first 6 months of life.

Results: Children with subclinical EAEC infection did not show altered growth between enrollment and 6 months.

Astrovirus Infection and Diarrhea in 8 Countries.

Background And Objectives: Astroviruses are important drivers of viral gastroenteritis but remain understudied in community settings and low- and middle-income countries. We present data from 8 countries with high prevalence of diarrhea and undernutrition to describe astrovirus epidemiology and assess evidence for protective immunity among children 0 to 2 years of age.

Methods: We used 25 898 surveillance stools and 7077 diarrheal stools contributed by 2082 children for enteropathogen testing, and longitudinal statistical analysis to describe incidence, risk factors, and protective immunity.

Epidemiology of enteroaggregative Escherichia coli infections and associated outcomes in the MAL-ED birth cohort.

Background: Enteroaggregative E. coli (EAEC) have been associated with mildly inflammatory diarrhea in outbreaks and in travelers and have been increasingly recognized as enteric pathogens in young children with and without overt diarrhea. We examined the risk factors for EAEC infections and their associations with environmental enteropathy biomarkers and growth outcomes over the first two years of life in eight low-resource settings of the MAL-ED study.

Infant Nutritional Status, Feeding Practices, Enteropathogen Exposure, Socioeconomic Status, and Illness Are Associated with Gut Barrier Function As Assessed by the Lactulose Mannitol Test in the MAL-ED Birth Cohort.

The lactulose mannitol (LM) dual sugar permeability test is the most commonly used test of environmental enteropathy in developing countries. However, there is a large but conflicting literature on its association with enteric infection and host nutritional status. We conducted a longitudinal cohort using a single field protocol and comparable laboratory procedures to examine intestinal permeability in multiple, geographically diverse pediatric populations.

Age and Sex Normalization of Intestinal Permeability Measures for the Improved Assessment of Enteropathy in Infancy and Early Childhood: Results From the MAL-ED Study.

Objectives: The aim of the study was to describe changes in intestinal permeability in early childhood in diverse epidemiologic settings.

Methods: In a birth cohort study, the lactulose:mannitol (L:M) test was administered to 1980 children at 4 time points in the first 24 months of life in 8 countries. Data from the Brazil site with an incidence of diarrhea similar to that seen in the United States and no growth faltering was used as an internal study reference to derive age- and sex-specific z scores for mannitol and lactulose recoveries and the L:M ratio.

Early Antibiotic Exposure in Low-resource Settings Is Associated With Increased Weight in the First Two Years of Life.

Objectives: The potential growth-promoting effects of antibiotics are not well understood among undernourished children in environments with high pathogen exposure. We aimed to assess whether early antibiotic exposure duration and class were associated with growth to 2 years of age across 8 low-resource sites in the MAL-ED birth cohort study.

Methods: We followed 1954 children twice per week from birth to 2 years to record maternally reported antibiotic exposures and measure anthropometry monthly.

Rotavirus Infection and Disease in a Multisite Birth Cohort: Results From the MAL-ED Study.

Background: In a multicountry birth cohort study, we describe rotavirus infection in the first 2 years of life in sites with and without rotavirus vaccination programs.

Methods: Children were recruited by 17 days of age and followed to 24 months with collection of monthly surveillance and diarrheal stools. Data on sociodemographics, feeding, and illness were collected at defined intervals.

Determinants and Impact of Giardia Infection in the First 2 Years of Life in the MAL-ED Birth Cohort.

Background.: Giardia are among the most common enteropathogens detected in children in low-resource settings. We describe here the epidemiology of infection with Giardia in the first 2 years of life in the Etiology, Risk Factors, and Interactions of Enteric Infections and Malnutrition and the Consequences for Child Health and Development Project (MAL-ED), a multisite birth-cohort study.

Use of antibiotics in children younger than two years in eight countries: a prospective cohort study.

Objective: To describe the frequency and factors associated with antibiotic use in early childhood, and estimate the proportion of diarrhoea and respiratory illnesses episodes treated with antibiotics.

Methods: Between 2009 and 2014, we followed 2134 children from eight sites in Bangladesh, Brazil, India, Nepal, Pakistan, Peru, South Africa and the United Republic of Tanzania, enrolled in the MAL-ED birth cohort study. We documented all antibiotic use from mothers' reports at twice-weekly visits over the children's first two years of life.

Dynamics and Trends in Fecal Biomarkers of Gut Function in Children from 1-24 Months in the MAL-ED Study.

Growth and development shortfalls that are disproportionately prevalent in children living in poor environmental conditions are postulated to result, at least in part, from abnormal gut function. Using data from The Etiology, Risk Factors, and Interactions of Enteric Infections and Malnutrition and the Consequences for Child Health and Development (MAL-ED) longitudinal cohort study, we examine biomarkers of gut inflammation and permeability in relation to environmental exposures and feeding practices. Trends in the concentrations of three biomarkers, myeloperoxidase (MPO), neopterin (NEO), and α-1-antitrypsin (AAT), are described from fecal samples collected during the first 2 years of each child's life.

How multiple episodes of exclusive breastfeeding impact estimates of exclusive breastfeeding duration: report from the eight-site MAL-ED birth cohort study.

The duration of exclusive breastfeeding (EBF) is often defined as the time from birth to the first non-breast milk food/liquid fed (EBFLONG), or it is estimated by calculating the proportion of women at a given infant age who EBF in the previous 24 h (EBFDHS). Others have measured the total days or personal prevalence of EBF (EBFPREV), recognizing that although non-EBF days may occur, EBF can be re-initiated for extended periods. We compared breastfeeding metrics in the MAL-ED study; infants' breastfeeding trajectories were characterized from enrollment (median 7 days, IQR: 4, 12) to 180 days at eight sites.

Diarrheal disease and enteric infections in LMIC communities: how big is the problem?

Studies of enteric diseases have historically focused on observations of clinical diarrhea as a cause of mortality and morbidity. Emerging evidence suggests that diarrhea dramatically underestimates both exposure to enteropathogens and the long-term consequences arising from infection. High burden of pathogens in the gut, even in the absence of diarrhea, is common in infants in low and middle income countries.

Early-life enteric infections: relation between chronic systemic inflammation and poor cognition in children.

The intestinal microbiota undergoes active remodeling in the first 6 to 18 months of life, during which time the characteristics of the adult microbiota are developed. This process is strongly influenced by the early diet and enteric pathogens. Enteric infections and malnutrition early in life may favor microbiota dysbiosis and small intestinal bacterial overgrowth, resulting in intestinal barrier dysfunction and translocation of intestinal bacterial products, ultimately leading to low-grade, chronic, subclinical systemic inflammation.

Norovirus Infection and Acquired Immunity in 8 Countries: Results From the MAL-ED Study.

Background: Norovirus is an important cause of childhood diarrhea. We present data from a longitudinal, multicountry study describing norovirus epidemiology during the first 2 years of life.

Methods: A birth cohort of 1457 children across 8 countries contributed 7077 diarrheal stools for norovirus testing.

Pathogen-specific burdens of community diarrhoea in developing countries: a multisite birth cohort study (MAL-ED).

Background: Most studies of the causes of diarrhoea in low-income and middle-income countries have looked at severe disease in people presenting for care, and there are few estimates of pathogen-specific diarrhoea burdens in the community.

Methods: We undertook a birth cohort study with not only intensive community surveillance for diarrhoea but also routine collection of non-diarrhoeal stools from eight sites in South America, Africa, and Asia. We enrolled children within 17 days of birth, and diarrhoeal episodes (defined as maternal report of three or more loose stools in 24 h, or one loose stool with visible blood) were identified through twice-weekly home visits by fieldworkers over a follow-up period of 24 months.

Opportunities to assess factors contributing to the development of the intestinal microbiota in infants living in developing countries.

Recent evidence suggests that establishment of a healthy gut microbiota shortly after birth is important to achieve optimal growth and development of children. Being born into a resource-poor environment presents challenges to the establishment of a healthy gut microbial flora in the newborn. Among these challenges are births that occur at home, traditional pre-lacteal feeding of newborns leading to failure to initiate lactation, poor sanitation and water quality, early environmental exposure to, and infection with, enteric or other pathogens, suboptimal breast feeding duration and intensity, deficiencies in weaning and childhood diets contributing to micro- and macro-nutrient deficiencies, and the frequent use of antibiotics.

The MAL-ED cohort study: methods and lessons learned when assessing early child development and caregiving mediators in infants and young children in 8 low- and middle-income countries.

More epidemiological data are needed on risk and protective factors for child development. In The Etiology, Risk Factors and Interactions of Enteric Infections and Malnutrition and the Consequences for Child Health and Development (MAL-ED) cohort study, we assessed child development in a harmonious manner across 8 sites in Bangladesh, Brazil, India, Nepal, Pakistan, Peru, South Africa, and Tanzania. From birth to 24 months, development and language acquisition were assessed via the Bayley Scales of Infant and Toddler Development and a modified MacArthur Communicative Development Inventory.

Assessment of environmental enteropathy in the MAL-ED cohort study: theoretical and analytic framework.

Individuals in the developing world live in conditions of intense exposure to enteric pathogens due to suboptimal water and sanitation. These environmental conditions lead to alterations in intestinal structure, function, and local and systemic immune activation that are collectively referred to as environmental enteropathy (EE). This condition, although poorly defined, is likely to be exacerbated by undernutrition as well as being responsible for permanent growth deficits acquired in early childhood, vaccine failure, and loss of human potential.

Microbiologic methods utilized in the MAL-ED cohort study.

A central hypothesis of The Etiology, Risk Factors and Interactions of Enteric Infections and Malnutrition and the Consequences for Child Health and Development (MAL-ED) study is that enteropathogens contribute to growth faltering. To examine this question, the MAL-ED network of investigators set out to achieve 3 goals: (1) develop harmonized protocols to test for a diverse range of enteropathogens, (2) provide quality-assured and comparable results from 8 global sites, and (3) achieve maximum laboratory throughput and minimum cost. This paper describes the rationale for the microbiologic assays chosen and methodologies used to accomplish the 3 goals.