Transmission of Infectious Vibrio cholerae through Drinking Water among the Household Contacts of Cholera Patients (CHoBI7 Trial).

Raisa Rafique,Christine M George,R Bradley Sack,David A Sack,Md Toslim Mahmud,Mohsena B Sharif,Mahamud-Ur Rashid,Md Sazzadul I Bhuyian,Fatema-Tuz Johura,Saiful Islam,K M Saif-Ur-Rahman,Shirajum Monira,Tahmina Parvin,Sabita R Rahman,Munshi Mustafiz,Zillur Rahman,Munirul Alam

doi:10.3389/fmicb.2016.01635

Abstract

Recurrent cholera causes significant morbidity and mortality among the growing population of Dhaka, the capital city of Bangladesh. Previous studies have demonstrated that household contacts of cholera patients are at >100 times higher risk of cholera during the week after the presentation of the index patient. Our prospective study investigated the mode of transmission of Vibrio cholerae, the cause of cholera, in the households of cholera patients in Dhaka city. Out of the total 420 rectal swab samples analyzed from 84 household contacts and 330 water samples collected from 33 households, V. cholerae was isolated from 20%(17/84) of household contacts, 18%(6/33) of stored drinking water, and 27%(9/33) of source water samples. Phenotypic and molecular analyses results confirmed the V. cholerae isolates to be toxigenic and belonging to serogroup O1 biotype El Tor (ET) possessing cholera toxin of classical biotype (altered ET). Phylogenetic analysis by pulsed-field gel electrophoresis (PFGE) showed the V. cholerae isolates to be clonally linked, as >95% similarity was confirmed by sub-clustering patterns in the PFGE (NotI)-based dendrogram. Mapping results showed cholera patients to be widely distributed across 25 police stations. The data suggesting the transmission of infectious V. cholerae within the household contacts of cholera patients through drinking water underscores the need for safe water to prevent spread of cholera and related deaths in Dhaka city.

Highlights

Severe cholera without adequate rehydration can have a case fatality rate of up to 50% (Sack et al, 2004)
Of total 420 rectal swab samples analyzed from 84 household contacts and 330 water samples (165 source water and 165 household stored drinking water samples) collected from 33 households, V. cholerae was isolated from 20%(17/84) of household contacts, 18%(6/33) of stored drinking water, and 27%(9/33) of source water samples
Out of the 33 cholera patient households, we found 15%(5/33) of households with V. cholerae isolated from both household contacts and water samples, 21%(7/33) of households with V. cholerae only isolated from household contacts, 18%(6/33) of households with V. cholerae only isolated from water, and 45%(15/33) of households with no household contact or water samples with detectable V. cholerae (Table 1)

Summary

Introduction

Severe cholera without adequate rehydration can have a case fatality rate of up to 50% (Sack et al, 2004). Worldwide an estimated 3–5 million cholera cases occur annually (WHO, 2015). V. cholerae serogroup O1 strains have two major biotypes, classical and El Tor, which differ in major phenotypic and genetic traits (Safa et al, 2010). V. cholerae O1 strains have three serotypes- Ogawa, Inaba, and Hikojima (Stroeher et al, 1992). V. cholerae O1 classical biotype caused the first six out of seven cholera pandemics before being replaced with the El Tor biotype which has been responsible for the ongoing seventh pandemic since 1961. The El Tor biotype strains have undergone genetic changes such as a new hybrid El Tor carrying the classical biotype CT (Nair et al, 2006)

Methods

Results

Discussion

Conclusion