Cholera in its present day scenario

Area of Science:

• Microbiology
• Epidemiology
• Environmental Science

Background:

• Cholera has a long history, with the Gangetic delta recognized as its origin.
• Vibrio cholerae non-O1 strains are taxonomically distinct from O1 strains, yet both can cause cholera-like illnesses.
• While humans are a reservoir for V. cholerae O1, the bacterium also has a free-living environmental cycle, particularly in brackish water.

Purpose of the Study:

• To explore the ecological and epidemiological aspects of cholera, focusing on Vibrio cholerae.
• To understand the environmental survival and behavior of Vibrio cholerae, including its non-culturable states.
• To investigate the factors contributing to cholera outbreaks, such as seasonality and plankton blooms.

Main Methods:

• Taxonomic separation of Vibrio cholerae strains (O1 and non-O1).
• Investigation of Vibrio cholerae survival in different water types (brackish vs. fresh).
• Observation of Vibrio cholerae conversion to a viable but non-culturable state.
• Analysis of Vibrio cholerae growth on chitin-containing media.
• Correlation of outbreaks with environmental factors like sea-surface temperature and plankton blooms.

Main Results:

• Vibrio cholerae exhibits a free-living cycle, thriving in brackish water.
• The bacterium can enter a viable but non-culturable state, reducing in size and ceasing growth on standard media.
• Chitin serves as a sole carbon source for all Vibrio cholerae biotypes.
• Cholera outbreaks are linked to plankton blooms and warmer sea-surface temperatures.
• Vibrio cholerae O1 biotype El Tor remains globally prevalent, with V. cholerae O139 Bengal emerging in Asia.

Conclusions:

• The seasonality, starvation response, and dormancy of Vibrio cholerae suggest an origin as an estuarine dweller.
• Environmental factors significantly influence the ecology and epidemiology of cholera.
• Understanding the environmental dynamics of Vibrio cholerae is crucial for predicting and controlling outbreaks.