Project Details

An evaluation of low-cost specimen preservation for characterization of enteric disease in children

Amanda Debes, PhD

Summary

BACKGROUND: Worldwide, more than 600,000 children under five years of age die annually from diarrheal diseases; nearly one-third of pediatric diarrheal deaths are due to Enterotoxigenic Escherichia coli (ETEC) and Shigellae. GAP: There is a further lack of understanding of the predominant strains and serotypes that are found in endemic areas, information which is crucial to the development of effective vaccines targeting the most vulnerable populations. Standard methods which rely on classical microbiological methods are not practical in remote areas or in resource constraint settings where future vaccine efficacy trials need to be conducted. HYPOTHESIS: This is exploratory analysis, and we hypothesize that ETEC and Shigellae cause a large proportion of moderate-to-severe diarrheal illnesses which may be controlled with vaccines currently being developed. METHODS: We propose to nest a pediatric ETEC and Shigella surveillance cohort into on-going multi-site surveillance efforts in Cameroon. Study subjects were enrolled between 1/1/15 and 12/31/17 and included children and adolescents <18 years of age and were recruited based on having 3 or more loose stools within 24hours with the presence of dehydration (based on established WHO criteria) and/or blood, providing a stool specimen with epidemiological information upon enrollment. A total of 3522 persons were enrolled, for which 2222 meet the enrollment criteria and whose specimens are currently being screened for the analysis. RESULTS: To date, we have screened 198 specimens using the Taqman Array Card (TAC). Through qualitative analysis we have found 34.0% (N=67) are ETEC positive, of which there are 35.8% (N=24) are LT-STh positive, and 10.4% (N=7) are LT-STp positive. 32.8% (N=22) of ETEC positive were in patients >5 years of age. CFs were found present in 41.8% of ETEC positive samples. We found 34.0% (N=67) of persons presenting with diarrhea with MSD and/or bloody and/or mucoid stool are IpaH positive, of which 31.3%(N=21) are in patients over 5 years of age. With use of model-derived quantitative cutoffs to assess individual diarrheal cases, 77 (85.6%) of 90 cases had one diarrhea-associated pathogen detected and 13 (14.4%) had two or more, with Shigellae and rotavirus being the pathogens most strongly associated with diarrhea in children with mixed infections. The five most common attributable pathogens are Shigellae, rotavirus, ST-ETEC, V. cholerae, Norovirus GII which accounted for 85.5% of all attributable diarrhea. By age group the top attributable pathogens are: 0-2 Shigellae, rotavirus, V. cholerae; 3-5 Shigellae, rotavirus, ETEC; and 5-17 Shigellae, rotavirus, V. cholerae. IMPACT: The results of this study will aid in identifying potential field sites for evaluation of the vaccine candidates being developed, and the genetic and phenotypic characterization of strains identified will provide critical information to improve the effectiveness of these vaccines in the most vulnerable populations in Cameroon and other endemic countries. Website Link: www.stopcholera.org

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