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 massive diarrhea. Death can result from the severe dehydration brought on by the diarrhea.
The symptoms may appear 1 to 7 days after eating food or drinking water contaminated with the bacteria, typically within 2 to 3 days. Contamination is from contact with the feces or vomitus of someone infected with cholera. Cholera is transmitted by fecal-oral route (eating or drinking food or water contaminated by the fecal waste of an infected person). Vibrios are sensitive to acid, and most die in the stomach. Surviving virulent organisms may adhere to and colonize the small bowel, where they secrete the potent cholera enterotoxin (CT, also called “choleragen”).
This toxin binds to the plasma membrane of intestinal epithelial cells and releases an enzymatically active subunit that causes a rise in cyclic adenosine 51-monophosphate (cAMP) production. The resulting high intracellular cAMP level causes massive secretion of electrolytes and water into the intestinal lumen. Symptoms of cholera are an acute, diarrheal illness caused by infection of the intestine with the bacterium Vibrio Cholerae. One of 20 persons will have severe disease with profuse watery diarrhea, vomiting, and leg cramps. The rapid loss of body fluids and weight lead to dehydration and circulatory collapse.
Death can occur within hours. Symptoms of Ebola are fever, headache, joint and muscle pain, sore throat, weakness, which are followed by diarrhea, vomiting, and stomach pain. Some patients have a rash, red eyes and internal and external bleeding. A person becomes infected with cholera bacteria by consuming contaminated food or water. In most epidemics the infection comes from human feces, which contaminate inadequately treated sewage. The bacteria can also live in rivers and costal waters where it contaminates shellfish. Undercooked shellfish have been a source of cholera.
The disease is not likely spread by direct person-to-person contact. Cholera is diagnosed by laboratory isolation of the bacterium from a stool sample or by finding antibodies in serum indicating recent infection. The toxigenic forms of Cholera are O group 1 or 139 and can be identified through gram strain or culture. Darkfield of phase contrast microscopy can directly visualize motile vibrio. Generally diagnosis is clinical by water diarrhea and dehydration. Cholera is most effectively treated through rehydration of fluids and salts lost through diarrhea.
An oral rehydration solution that combines sugar and salts n prepackaged formula is mixed with water and used throughout the world resulting in a 1% mortality with treatment compared to 20-25% without. Sever cases may require intravenous fluid replacement. Antibiotics may shorten course and reduce severity of symptoms as well as decrease shedding of virus but must target organism susceptibility as antibiotic resistance is a growing problem. The natural reservoir of the virus is unknown as is the manner in which it fist appears during an outbreak.
It has been hypothesized that the index patient becomes infected through contact with an ill animal. After the first case patient, the virus can be transmitted through direct contact with infected blood or secretions or through contact with contaminated objects such as needles. Nosocomial transmission is common in outbreaks when healthcare workers do not wear proper protective clothing. Ebola is form of viral hemorrhagic fever that is usually clinically diagnosed by the constellation of symptoms described.
Laboratory diagnosis is through ELISA testing for IgM antibodies and PCR and virus isolation can be used to identify virus within a few days of symptom onset. Later in course of disease IgG antibodies can be tested. There is no curative treatment for Ebola. Only supportive treatments including fluid and electrolyte balancing, and maintenance of oxygen status and blood pressure are available. In March 1999, cholera was detected in the country for the first time in 10 years and was moving fast throughout the country. Poor water quality and sanitation infrastructure were the major contributing factors to high rates of cholera.
By November 1999, 30 of the poorest communities in urban Antananarivo, which is the capital of Madagascar, was chosen as the target population for piloting the Safe Water System in the country. The system consisted of behavior change techniques along with point-of-use treatment and safe storage of water. The organizations who collaborated on this project were the CARE Madagascar (Community Assistance for Relief Everywhere), Population Services International (PSI) and the Centers for Disease Control and Prevention (CDC).
CARE Madagascar implemented and combined community mobilization, Population Services International took care of the social marketing and the US Center for Disease Control and Prevention handled the program evaluation. The social marketing involved local production of a 0. 5% sodium hypochlorite solution packaged in a 500-mL bottle, and amount sufficient to treat approximately 2000 L of water. A local company was then contracted to produce 20-L narrow-mouthed plastic jerry cans. The brand name given was Sur’Eau, French for “safe water”. The program was launched months ahead of schedule because of the rapid increase in the disease.
The bottle of water was sold to wholesalers and retailers in the communities participating in the program and provided the product to CARE-trained community-based sales agents. The organizations designed radio and TV spots and gave out brochures and posters. Originally the project was limited to the 30 neighborhoods, but PSI and CARE broadened the intervention to cover all of Antananarivo. In nine months the sales ranged form 8,000 to 80,000 bottles per month. The success of the project was due to the waters usefulness and the project’s easy deployment in response to emergencies.
The organizations did not want the communities to look at this water as a cholera prevention product. They wanted the people to use the water all the time, not only during cholera season. This is where the behavioral change comes in to play.
References http://images. google. com/images? q=Vibrio+cholerae+photos&hl=en&lr=&sa=N&tab=ii&oi=imagest http://bact. wisc. edu/Bact330/lecturecholera http://en. wikipedia. org/wiki/Cholera http://en. wikipedia. org/wiki/Ebola http://www. astdhppe. org/infect/ebola. html http://www. cdc. gov/ncidod/dvrd/spb/mnpages/dispages/ebola. htm.