By Melinda Smith
Environmental Biology Spring 2013
The infectious bacterium cholera is responsible for over 100,000 deaths each year. (CDS) Third world regions and areas with limited water management are the major targets of this disease. It is a water-borne bacterium of the intestine that causes severe diarrhea, vomiting, and eventually if unable to treat, can cause death from severe dehydration in hours. (CDS) Due to our modern water and sewage sanitation procedures, the United States does not experience outbreaks of cholera. It is still prevalent in Asia, Africa, and Latin America. They have been dealing with this disease for over 40 years. (CDS) History
Cholera is said to be documented first in India in the early 1800’s. This bacterium was spread by International ships pumping on contaminated water from the Bay of Bengal. Once these ships made it home to their various ports the water was released into their waters and eventually infected its’ people. Cholera had already spread globally before London’s famous John Snow figured out the infection was spread through the water system. Dr. Snow investigated the cities reported outbreaks and deaths and created the disease map to pinpoint the source of the illness to a water pump. He determined that sewage had leaked into the main water pipe and was shut down. Many scientists use this method today of mapping to monitor data and look for outbreak sources. Robert Koch, the author of the germ theory of disease, was the first to successfully isolate and identify the bacteria in a solid agar petri dish. He was later awarded the Nobel Prize for his contributions to science.
What causes it?
Cholera is often found in areas where the hygiene is poor, water and sewage treatment is minimal to non-existent, and there is lack of sanitation. Bacteria enter the body through the mouth by water or food. It is spread through feces contamination in water and food.
V. cholera’s natural habitat is a water environment, ranging from bays, rivers, lakes, water reservoirs, and oceans. It is found attached to zooplankton, water hyacinth, bird underbellies, and copepods. Research on cholera originally contested that it was only transmitted by water supplies, but in recent year’s evidence of mutated strains show ability to transfer through human contact. (Morris) Factors that affect its growth and viability include temperature, salinity and weather patterns. Vibrio cholera has 16 different strands and the two that are extremely toxic are O-group 1 and O-group 139. These two strands are the only reported groups linked to the original epidemics and pandemics globally. So far serogroup 0139 has only been linked to South-East Asia. The new El Tor strains are more residual than the original strains. They have a higher death rate and more severe symptoms. (Siddique) The main element in triggering this infection is the cholera toxin. It is found on the ctx element gene and allows the microorganism to bind to the intestinal mucosa. The intestine becomes inflamed and cannot reabsorb water. This microorganism is capable of changing its state after being expelled in feces back to a hyper-infectious state. Over time the strains 01 and 0139 have evolved into a bacteriophage that genetically has increased its’ viability, levels of cholera toxin, and ability to adjust to different environments.
Facts you should know
Cholera not only lives in our drinking water supplies but in our coastal waters and inlets. The bacteria can attach to shells containing chitin. Eating raw or undercooked shell fish can transfer the bacteria to humans. The bacterium originally was thought to only be ingested through water or food. This disease is currently being researched in regards to new strains that can be transferred by contact from person to person. Cholera can be diagnosed through stool samples or a swab of the rectum and then examined by a lab. If you have…