Abstract
The origin, spread and molecular epidemiology of altered El Tor Vibrio cholerae O1 strains isolated from cholera outbreaks/surveillance studies between 1995 and 2019 from different district of Odisha were analyzed. The stock cultures of V. cholerae O1 strains from 1995 to 2019 were analyzed through molecular analysis using different PCR assays and pulse field gel electrophoresis (PFGE) analysis. The spread map (month, year and place) was constructed to locate the dissemination of altered El Tor variants of V. cholerae O1 in this region. A total of 13 cholera outbreaks were caused by V. cholerae O1 Ogawa biotype El Tor carrying ctxB1 and ctxB7 genotypes. The ctxB1 alleles of V. cholerae O1 mostly confined to the coastal areas, whereas the ctxB7 genotypes, though originating in the coastal region of Odisha, concentrated more in the tribal areas. The positive correlation between virulence-associated genes (VAGs) was found through Pearson’s correlation model, indicative of a stronger association between the VAGs. The clonal relationship through PFGE between ctxB1 and ctxB7 genotypes of V. cholerae O1 strains exhibited 80% similarity indicating single- or multi-clonal evolution. It is evident from this study that the spread of multidrug-resistant V. cholerae O1-altered El Tor was dominant over the prototype El Tor strains in this region. The origin of altered El Tor variants of V. cholerae O1 occurred in the East Coast of Odisha established that the origin of cholera happened in the Gangetic belts of Bay of Bengal where all new variants of V. cholerae O1 might have originated from the Asian countries.
Highlights
Cholera is a severe form of watery diarrheal disease, dates back to antiquity, and is caused by the ingestion of food or water contaminated with the pathogenic strains of Vibrio cholerae of serogroup O1 or O139 (Pollitzer, 1954)
We have undertaken a retrospective analysis on V. cholerae O1 strains which were isolated during the cholera outbreaks and surveillance studies reported from 1995 to 2019 from different districts of Odisha to illustrate the chronology of the appearance and spread of V. cholerae O1 El Tor variant strains to different parts of the state
Odisha being a coastal state of India has faced recurrent cholera outbreaks/epidemics followed by cyclone/flood almost every year causing significant morbidity and mortality since 1995–2019 (Nayak et al, 2021)
Summary
Cholera is a severe form of watery diarrheal disease, dates back to antiquity, and is caused by the ingestion of food or water contaminated with the pathogenic strains of Vibrio cholerae of serogroup O1 or O139 (Pollitzer, 1954). The cholera epidemics after the disastrous super cyclone in 1999 affected more than 10 million of the population. This might be due to coastal saline-rich aquatic environmental water along the side of Bay of Bengal favoring V. cholerae to spread its territory. No detailed molecular epidemiological report is available on the origin and dissemination of the altered El Tor V. cholerae O1 strains to different parts of Odisha. We have undertaken a retrospective analysis on V. cholerae O1 strains which were isolated during the cholera outbreaks and surveillance studies reported from 1995 to 2019 from different districts of Odisha to illustrate the chronology of the appearance and spread of V. cholerae O1 El Tor variant strains to different parts of the state
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