Cholera and Ebola: A Threat to Our Environmental Freedom

Topics: Cholera, Microbiology, Vibrio cholerae Pages: 6 (1553 words) Published: July 20, 2005
Cholera, aka Asiatic Cholera or epidemic cholera, is an infectious disease of the gastrointestinal tract caused by the Vibrio cholerae bacterium. From the family Vibrionaceae, the bacterium is characterized as a gram-negative rod. As with other gram-negative rods, Vibrio cholerae produces an endotoxin, known as cholera toxin. This bacterium is mobile due to the presence of a single polar flagellum and is highly infectious. The Vibrio cholerae bacterium grows in both freshwater and marine habitats and also in association with aquatic animals.

Originally discovered in 1824 by the Italian Anatomist, Filippo Pacini, Vibrio cholera most likely originated in India with the Ganges River serving as the primary contamination reservoir. Nearly 30 years later bacteriologists Robert Koch and John Snow found the link between Cholera and drinking water. Since its discovery in the early 19th century Cholera has claimed many lives due to its transmission via the drinking water supply. Through many years of research and chlorination of drinking water supplies, Cholera has not been considered a threat to the United States and Western Europe for nearly a century. However, purposeful introduction of the bacterium into a local water supply, could indeed cause contamination and mass spread of infection.

Ebola hemorrhagic fever (EHF) is a highly infectious, highly fatal disease caused by the Ebola virus. Ebola virus is a member of the family Fivoviridae and is named after the Ebola River in the Republic of Congo (formerly Zaire) which is where the first epidemic occurred in 1994. The virus is classified as follows:

Group: Group V ((-)ssRNA)

Order: Mononegavirales

Family: Filoviridae

Genus: Ebolavirus

Species:

Ivory Coast ebolavirus

Reston ebolavirus

Sudan ebolavirus

Zaire ebolavirus

The first two strains of the virus were identified in 1976 in Zaire and Sudan. Dr. F.A. Murphy was the first to isolate the virus and capture it for electron microscopy. Dr. Murphy noted that the virus was a simple-strand RNA virus with encoding for seven viral proteins. Since its discovery and initial outbreaks, four sub-species have been isolated (as outlined above) which are named after their respective outbreak locations. Due to its highly infectious nature and its ability to mutate rapidly, Ebola virus has a mortality rate of nearly 77%. Although, not a treat in the United States and other civilized nations, the Ebola virus could pose a serious health risk if purposely introduced into the water or food supply.

A protein on the surface of the virus has been discovered that is responsible for the severe internal bleeding (the death-dealing feature of the disease). The protein attacks and destroys the endothelial cells lining blood vessels, causing the vessels to leak and bleed. In fact, the virus has a very specific tropism for liver cells and cells of the reticuloendothelial system, e.g. macrophages. Massive destruction of the liver is the hallmark feature of Ebola virus.

The Ebola virus, once inside a host, begins to replicate. The seven proteins that make up the body of the virus begin to consume the host cell as the virus starts making copies of itself. These seven proteins attack the body of the cell and somehow attack the structural proteins of the body of the host. As the disease progresses, it manifests itself in the form of bleeding, especially in the mucosa, abdomen, pericardium, and vagina. The capillary leakage leads to loss of blood volume, bleeding from various points in the body, shock, and acute respiratory disorder. Infections with Ebola virus are acute with an incubation period ranging from 2 to 21 days.

Cholera is an acute illness characterized by watery diarrhea and is caused by certain members of the species Vibrio cholerae (bacteria). The cholera germ is passed in the stools. The toxin released by the bacteria causes increased secretion of water and chloride ions in the intestine, which can produce...
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