Tag: Cholera

Research Suggests Close Link Between Cholera Outbreaks and Phage Levels

Research published in the February 2005 issue of Proceedings of the National Academy of Science provides intriguing insight into cholera outbreaks, and may someday lead to a method of predicting or even preventing such epidemics.

After studying levels of cholera bacteria (Vibrio cholerae) in water, researchers at the International Center for Diarrhoeal Disease Research and Harvard Medical School noticed a relationship between the level of cholera bacteria and the presence of phage — a virus that uses bacteria to reproduce itself.

There was an inverse relationship between the two: as the level of phage increased, the number of cholera bacteria declined. Similarly, when phage levels fell, cholera bacteria levels increased.

It is somewhat of mystery why cholera plagues are self-limiting and tend to end of their own accord. This research provides one possible answer, namely that cholera outbreaks might begin when phenomena such as monsoons dilute the amount of phage in water, and then end of their own accord once phage levels again increase.

Much more research needs to be done to establish the precise relationship between phage and cholera bacteria, but this study provides intriguing clues that may help to predict and ultimately prevent cholera outbreaks.

Sources:

Cholera understanding ‘improved’. The BBC, January 16, 2005.

New insights: Why are cholera epidemics self-limited?. Press Release, International Center for Diarrhoeal Disease Research, March 7, 2005.

WHO Launches Cholera Vaccination Test in Mozambique

In January the World Health Organization announced it was launching its efforts at mass vaccination against cholera using a new oral vaccine against the disease.

For this demonstration project, WHO is focusing on Mozambique which has been hit particularly hard by the disease in recent years. In 1999, it reported 45,000 cases out of a world total that usually hovers between 100,000-200,000 annually.

The vaccination project will focus on the city of Beria and will vaccinate about 50,000 of the half million people living there against the disease. WHO will be able to gauge the success of its efforts there in early 2005.

Should the vaccine prove effective, it is likely to play a key role in reducing worldwide cholera incidence.

Source:

WHO launches first oral-vaccination cholera campaign. UN Wire, January 15, 2004.

Mozambique mass campaign tests the theory. Press Release, World Health Organization, January 14, 2004.

Sari Cloth Can Filter Cholera

In a test conducted by the US National Science Foundation, folded up sari cloth was found to be just as effective as more expensive materials in filtering out cholera from water in Bangladesh.

According to the BBC, the cholera bacteria lives in a symbiotic relationship with plankton. The theory was that by filtering the plankton out of the water, the amount of cholera bacteria would be decreased as well.

This was put to the test in a Bangladesh village where a filter made of simply taking sari cloth and folding it four times was compared with more expensive nylon filters. The result — in villages where training in using the sari cloth was given, incidence of cholera was cut in half. The nylon filters had slightly poorer results.

The main advantage of the sari cloth is that it is cheap and widely available. Dr. Rita Colwell, who headed up the research, told the BBC that, “The method can save thousands of lives during massive [cholera] epidemics, particularly those of children under the age of five.”

Source:

Cloth filter could cut cholera deaths. The BBC, January 14, 2003.

Cholera Gives Up Its Secrets In Mice

Cholera still sickens about 300,000 people every year, mostly in developed countries with poor water treatment systems. Efforts to create a vaccine for the disease have been always been stymied. But results from a cholera model in mice appears to offer a clue as to why that is so.

Researchers at Tufts University infected one group of mice with a cultured strain of the cholera bacteria and a second group of mice with a strain of the bacteria taken from the feces of cholera patients.

The strain taken from patients was as much as 700 times more infectious than the cultured strain. Moreover, when the patient strain was placed in a culture, within 18 hours it reverted to the relatively low-infectious version.

The implication is that the cholera bacteria has evolved a behavior usually seen in complex parasites such as malaria that use different forms for transmission between individuals than they have for infecting individuals once they are in the body (cholera has two chromosomes where most bacteria only have a single chromosome which may play a role in the transformation it makes once inside its hosts).

Since vaccines for cholera have focused on causing an immune response to the cultured form of the bacteria, they likely have failed to cause an immune response to the infectious form of the bacteria.

If the results in mice also hold for human beings, then researchers might be able to finally create an effective vaccine by targeting the proteins of the infectious form of the disease.

Source:

Cholera needs guts to survive. Tom Clarke, Nature, June 6, 2002.

Cholera bacterium’s quick change revealed. Deborah MacKenzie, New Scientist, June 2, 2002.

Cholera Gives Up Its Secrets In Mice

Cholera still sickens about 300,000 people every year, mostly in developed countries with poor water treatment systems. Efforts to create a vaccine for the disease have been always been stymied. But results from a cholera model in mice appears to offer a clue as to why that is so.

Researchers at Tufts University infected one group of mice with a cultured strain of the cholera bacteria and a second group of mice with a strain of the bacteria taken from the feces of cholera patients.

The strain taken from patients was as much as 700 times more infectious than the cultured strain. Moreover, when the patient strain was placed in a culture, within 18 hours it reverted to the relatively low-infectious version.

The implication is that the cholera bacteria has evolved a behavior usually seen in complex parasites such as malaria that use different forms for transmission between individuals than they have for infecting individuals once they are in the body (cholera has two chromosomes where most bacteria only have a single chromosome which may play a role in the transformation it makes once inside its hosts).

Since vaccines for cholera have focused on causing an immune response to the cultured form of the bacteria, they likely have failed to cause an immune response to the infectious form of the bacteria.

If the results in mice also hold for human beings, then researchers might be able to finally create an effective vaccine by targeting the proteins of the infectious form of the disease.

Source:

Cholera needs guts to survive. Tom Clarke, Nature, June 6, 2002.

Cholera bacterium’s quick change revealed. Deborah MacKenzie, New Scientist, June 2, 2002.