Prospective study of diarrhoeal disease in a cohort of rural Mexican children: incidence and isolated pathogens during the first two years of life

Abstract

Colonization of the intestine by putative pathogens was followed longitudinally in a cohort of 56 infants born during one calendar year in a rural Mexican village with faecal cultures taken every fortnight and every time a child had diarrhoea. The frequency of isolation of pathogens during episodes of diarrhoea was compared with that of matched controls from the same cohort. Incidence of diarrhoea during the first year of life was 98%, diminishing to 93% during the second year. The incidence curves for each year were not significantly different (P greater than 0.1). Isolation of enteropathogenic Escherichia coli, enterotoxigenic Escherichia coli producing heat-stable (ST) and/or heat-labile (LT) enterotoxins and rotaviruses was significantly higher in infants with diarrhoea during the first 2 years of life. In the case of shigella, although no significant differences were found by semester of life, 13 of 16 children in which these strains were found had diarrhoea. Isolation of Salmonella spp., Campylobacter spp. and protozoa were not significantly different in the two groups during the period studied. Strains showing localized adherence to HEp-2 cells or the presence of colonization factor antigens I or E8775 were found with significantly higher frequency in children with diarrhoea. Eighty-two percent of ST+ or LT+ ETEC strains isolated produced one of the three known colonization factors.

PIP: The incidence of diarrhea in the 1st 2 years of life and the pathogens isolated during these episodes were investigated in a longitudinal cohort study of the 56 infants born in March 1982-March 1983 in the rural Mexican Village of Stone Houses. Fecal cultures were taken every fortnight and at each episode of diarrhea. Overall, the incidence of diarrhea was 98% during the 1st year of life and 93% during the 2nd year. The average number of episodes of diarrhea per child was 3 during both years analyzed. Enteropathogenic Escherichia coli (EPEC) and enterotoxigenic E coli (ETEC) strains, along with rotaviruses and possibly shigella, were associated with 75% of cases of diarrhea in these children. With the exception of ETEC strains producing both heat-stable (HT) and heat-labile (LT) enterotoxins and rotaviruses, the frequency of isolation of other pathogens differed significantly by age group. While LT-producing ETEC strains were found throughout the 1st 2 years of life in both cases and controls, EPEC strains were only found in children under 18 months of age and always more frequently in those with diarrhea. Strains showing localized adherence to HEp-2 cells or the presence of colonization factor antigens I or E8775 were found with significantly higher frequency in children with diarrhea. 82% of ST+ or LT+ ETEC strains isolated produced 1 of the 3 known colonization factors. The results of this investigation can be used to develop a more appropriate biological approach to the prevention of childhood diarrheal disease. While vaccines against EPEC and ETEC should be administered during the 1st months of life or perhaps through the breast milk of immunized mothers, a rotavirus vaccine could be given at a later age.