Cholera Vectors Cholera is an acute diarrheal infection caused by a bacterium called Vibrio cholerae that infects the intestines of human and causes massive dehydration. Most estimates believe that there are 3-5 million cases of cholera globally each year, with about 100,000 deaths. The infection varies between little or no symptoms to serious and life-threatening cases. In about 5% of the population, infected individuals will have massive watery diarrhea, vomiting, leg cramps, and resulting ancillary issues caused by shock and dehydration (Bjorklund, 2011).

Type of Pathogen

The bacterium that causes cholera, Vibrio cholerae, is a gram negative, non-spore forming, curved rod bacterium that is oxidase positive. From a biological perspective, it is quite mobile with a single point tail (flagellum). It is not toxic itself, but when it enters a host it produces a toxin that is poisonous to humans and causes symptoms. Not all cholera bacteria produce this toxin, however, and there are several sub-strains of the bacteria that vary in toxicity and danger to humans. Many of these subtypes are, in fact, endemic to different parts of the world, with the most toxic living in tropical areas, particularly near brackish or standing waters near ocean coasts. A number of the subtypes of the cholera bacteria do not produce the cholera toxin, but serve as a reservoir for that genome. Many of these, while not producing the full-fledged symptoms of cholera, do produce illness in humans (enteritis, etc.) and are thus serious when ingested. The cholera bacterium seems also to have evolved over time; reports of cholera outbreaks from the Ancient World describe similar symptoms, but there does not appear to have been the large amounts of subgroups, which may have evolved as humans populated certain areas more (Bjorklund, 2011).

Known Reservoirs

Cholera is typically found in water or food sources that have been somehow contaminated with feces from a human already infected with cholera. This is typically in areas with poor sanitation, inadequate water treatment and inadequate...

In some cases, depending on the microenvironment, cholera may life in brackish areas of coastal waters and manifest in shellfish. In fact, eating raw or undercooked shellfish is one vector that transcends economics and occurs in both the developed and developing worlds. Certainly, cholera is more endemic during high stress times (disasters, etc.) and is found in humans, water birds, shellfish, fish and even some herbivores (Krauss, H., et al., 2003).
Endemic and Environmental Factors

Cholera bacterium occur naturally in many coastal waters where they tend to attach to small crustaceans called copepods. The copepods are a food source for many small fish and crustaceans, and the cholera bacteria then travel up the food chain through hosts, often living in the gut of fish, etc. without negative effects to the organism. In certain tropical areas, there are more virulent types of cholera, thought to be due to certain types of algae and plankton that grow more in these climates and in warmer waters. Because algae growth is fueled by sewage and agricultural run-off, many countries that have fewer environmental regulations are more susceptible to toxic versions of cholera, as are areas hit with flooding or other disasters that limit the infrastructure of hygiene. Cholera is a global public health problem, but tends to be both endemic and virulent in poorer countries with a more tropical climate (e.g. Vietnam, Haiti, Zimbabwe, etc.). The primary endemic regions are in Central and Southern Africa and coast regions of the Indian Peninsula and Southeast Asia. The World Health Organization notes that the incidence risk environmentally is primarily based on the level of sanitation (Ali, M., et al., 2011).

Transmission and Dosage

The degree to which cholera is transmitted into humans varies based on the amount of acid in the individual's gut, their immune system function and age. Most research notes that the infection dose ranges between 106 and 1011 of ingested bacterium. Cholera is spread by consumption of water or drops of water that have been…