STUDIES OF THE EPIDEMIOLOGY OF PEDIATRIC SHIGELLOSIS IN BANGLADESH

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The purpose of this field project is to evaluate the epidemiological patterns and determinants of pediatric shigellosis occurring among residents in a research field site in rural Bangladesh who have had a documented recent exposure to a neighborhood resident having Shigella dysentery. The project entailed assembly of 1934 children under 5 years of age, from 1335 families residing in 240 neighborhoods having a resident who presented for treatment of documented Shigella dysentery within 1 week of the initiation of active neighborhood surveillance. Following assembly of these children, each was followed with intensive active surveillance for one month. This surveillance included, at baseline, sociodemographic characterization, ascertainment of dietary and anthropometric status, and measurement of serum vitamin A. Subjects were visited according to a systematic schedule to ascertain symptomatic histories related to diarrhea, and to collect fecal specimens for microbiological characterization. Analyses of the data thus far have demonstrated that the occurrence of Shigella diarrhea was related to age (being highest in the third year of life), nutritional status (being higher in stunted children), season (being lowest during the monsoon season in the summer months), and breast-feeding status (being lower among breast-fed children, even up to 36 months of age). The presence of a latrine was not related to the risk, due to the fact that the presence of an unsanitary hanging latrine elevated the risk, while the presence of a sanitary slightly depressed the risk. Interestingly, the protective effect of breast feeding was almost entirely attributable to the increase in risk of shigellosis which occurred during the initial 3 months following cessation of breast feeding. Analyses are now in progress to determine the frequency and determinants of the progression of Shigella diarrhea from acute to chronic form and to assess the role of vitamin A deficiency as a risk factor for acute and persistent shigellosis.