Etiology of Diarrhea in Bangladeshi Infants in the First Year of Life Analyzed Using Molecular Methods

(See the editorial commentary by Ryan on pages 1732–3.) Diarrhea accounts for 26.1% of childhood deaths in South Asia [1], with a peak incidence in the first year of life [2–4]. Beyond this immediate mortality burden, diarrheal episodes contribute to intestinal barrier dysfunction and malnutrition, which underlie additional mortality [5] and disability-adjusted life-years lost [6]. This large burden of disease continues despite improvements from measures such as oral rehydration solution, antibiotics, cleaner water, sanitation, breast-feeding, and rotavirus vaccination [7–10]. The etiology of diarrhea must be understood to accelerate additional preventive measures. Unfortunately, diarrhea is a nonspecific syndrome defined as ≥3 loose stools in a day and can be caused by a diversity of viruses, bacteria, protozoa, helminths, fungi, as well as non infectious triggers [11]. Rotavirus is widely accepted as the major diarrheal pathogen in the first year of life [12–14], but the relative importance of enteropathogens thereafter is less clear. Several methods are needed to detect these enteropathogens including culture, immunoassay, microscopy, and polymerase chain reaction (PCR), yet these are generally applied selectively and vary in their sensitivity [9, 10, 15, 16]. Certain bacteria, such as Campylobacter and Shigella, are difficult to grow, particularly in the global context of widespread antibiotic use. Mixed infections are common but difficult to interpret. For these reasons we developed a series of quantitative multiplex PCR assays for 32 of the main enteropathogen targets, encompassing the major viruses, bacteria, protozoa, helminths, and fungi [17–21]. In this work we applied these assays to infants in Dhaka, Bangladesh, starting from birth, testing all assays with both monthly surveillance and diarrheal specimens . This detection strategy and knowledge of pathogen history preceding diarrhea allowed for a temporal examination of the etiology of diarrhea not possible with most study designs.