Cholera

Abstract

Cholera is a bacterial infection that has sickened and killed millions of individuals since ancient times. It is caused by the Gram-negative bacterium Vibrio cholerae and is transmitted by the fecal-oral route, mainly through contaminated drinking water. Colonization of the human small intestine by Vibrio cholerae requires presence of the toxin-coregulated pilus (TCP) and allows for multiplication of the bacterium. As it multiplies, V. cholerae secretes cholera toxin (CT), which targets heterotrimeric G proteins and induces production of cyclic AMP. Buildup of this molecule leads to secretion of chloride ions into the intestinal lumen, which in turn prompts massive fluid loss in the form of secretory diarrhea. In some cases, patients can lose a liter of fluid every hour and quickly become severely dehydrated, often resulting in death. Over the past several decades, cholera fatality rates have dropped significantly due to the introduction of oral rehydration therapy, an inexpensive and effective method of treatment. Two vaccines, Dukoral and Shanchol, are currently recommended by the World Health Organization (WHO) for prevention of cholera. Both are oral heat-killed whole-cell vaccines that provide >50 % protection when administered correctly. However, cholera is still a grave problem in areas where water sanitation is insufficient, such as developing countries and regions where conflict or natural disasters have damaged infrastructure.