Vibrio cholerae growth response to natural factors, and its transmission control

Burden

Cholera, caused by V. cholerae, is a killer disease. In Bangladesh, cholera occurs endemically at defined seasons resulting significant morbidity and mortality each year. V. cholerae is a native flora of the estuarine aquatic environment. The bacterium existing in the environment is found mostly in a dormant, non-cultivable state; and can regain active state and flourish to initiate the seasonal epidemics of cholera. Although seasonal cholera is driven by natural climate factors, the disease takes the turn of epidemic through rapid transmission of infectious V. cholerae via fecal-oral mode as marginal people relies on contaminated surface water for drinking and other domestic purposes.

Knowledge gap

We want to understand V. cholerae growth response, particularly what triggers the bacterium to be active from dormant non-culturable state, and if locally available no-cost items such as ashes could kill the infectious bacterium shed in stool to decontaminate the environment; the aim is to develop a sustainable method to prevent cholera transmission.

Relevance

This study will generate knowledge on V. cholerae growth responses, and no-cost method of stool decontamination, and the aim is prevent cholera transmission.

Hypothesis

• Climatic and human factors contribute to active growth of V. cholerae responsible for seasonal cholera to prevent cholera transmission
• Wood ashes might provide a sustainable method of stool decontamination to prevent V. cholerae transmission

Objectives

• Study the environmental and human factors activating naturally occurring non-cuturable V. cholerae that initiates seasonal cholera
• Test efficacy of wood ashes in decontaminating V. cholerae shed in stools to reduce cholera transmission

Methods

Water samples will be collected from four Mathbaria sites, and temperature, turbidity, pH, salinity, total dissolved solids and conductivity of water monitored bi-weekly during March-May and September-November and monthly for the rest of the year. Toxigenic V. cholerae will be isolated (Alam et al. 2006a) and characterized in terms of virulence adaptive polymorphisms (VAPs) and molecular fingerprinting. Also, laboratory microcosms will be constructed with two toxigenic V. cholerae to test growth response of the bacterium, and the role of cyanobacteria (Islam et al., 1990a; Islam et al., 1990b) and bile will be monitored at different temperatures, pH, salinity, and conductivity. In this study, efficacy of decontamination of discarded diarrheal stools carrying V. cholerae would be monitored and compared with commercially available disinfectant such as bleaching powder.

Outcome measures/variables

Growth response of V. cholerae to different climate factors, and the role of cyanobacteria and bile in microcosms would be an outcome to measure. V. cholerae burden in cholera stool at different concentrations and time of treatment with wood-ashes would also be an outcome measure.

Vibrio cholerae often escapes culturing methods while in a dormant and non-culturable state in the aquatic environment, although they can become actively growing to cause seasonal epidemicsof cholera. We designed this study to unveil the climate and/or natural no-cost substaces that could drive the growth responses of the bacterium to be able to aid diseases prevention in endemic settings.

Vibrio cholerae is an aquatic bacterium which passes the interepidemic period in a dormant and non-culturable state. The well-defined climate or natural factors driving the growth responses of the bacterium could aid in diseases prevention in endemic settings.