This week’s physiology class blog, reposted here. This really is a great reason why we should support organizations out there digging wells to get people clean water. Cholera likes to break out in a clean water supply, causing an epidemic and killing lots of people. No special drug is needed to heal them, they simply need fluids and electrolytes! This is another health problem that we really could make major headway at eliminating.
The gastrointestinal disease Cholera is caused by the bacteria Vibrio cholera, which produces a potent toxin that causes acute onset of severe diarrhea and subsequent dehydration. Without immediate rehydration, it can be fatal within hours. The World Health Organization estimates that there are 3-5 million cases per year, with approximately 100,000-120,000 deaths annually. It is largely a disease of poverty, as it is found and spread most commonly through contaminated water and poor sanitation. Given that poverty spans the globe, it’s no surprise that it is considered one of the most important diseases to address.
V. cholerae is curved, rod shaped gram negative bacteria with a powerful flagellum at one end, and has special pili called the “toxin-coregulated pilus” which helps the bacteria stick together in colonies. Some researchers are beginning to target these pilus connections in developing medications. The bacteria colonize on the intestinal lining, and release a toxin that directly targets the epithelial cells. The toxins activate the G protein inside the epithelial cells in a second messenger system, turning on adenylate cyclase, without the ability to shut off. In response, the cAMP causes electrolytes such as sodium, chloride, potassium, bicarbonate and water to rapidly leave the cells into the intestinal lumen via watery stool. Water can be lost into the stool in gallons, within hours. The treatment is rapid rehydration and restoring electrolyte balance. Antibiotics are not helpful beyond decreasing the length of time the patient experiences diarrhea.
Oral vaccinations have been developed that have positive results in preventing infection. A combination of antibodies and antitoxin molecules respond effectively, and memory has been good up to several years. People who are well-nourished are more likely to fend off infection because they have adequate mucus and acid secretions in their stomachs. This factor increases the rate of infection in areas of poverty in which people lack quality nutrition. As governments and aid organizations work to improve clean water supplies, inevitably cholera will decrease, however, with so much global poverty, political unrest, and natural disasters combined with the virulence and easy spread of cholera, it is still a major global health challenge.
Kenneth J. Ryan. Sherris Medical Microbiology. 5th edition. McGraw Hill. 2010.