V. cholerae, bacteria responsible for cholera.
Photo taken from www.npr.org/blogs/health
Vibrio cholerae, the bacteria responsible for the disease cholera, claims over one hundred thousand lives every year and can spread explosively among populations. The virus is highly transmittable and must be ingested to spread infection. Many people act merely as carriers of the disease meaning they house the bacteria in their bodies but display no symptoms of infection, making the disease very difficult to eradicate. For those individuals unlucky enough to succumb to their bacterial guests, death comes as a result of dehydration caused by excessive watery diarrhea. The world has experienced 7 separate cholera pandemics since the 19th century.
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Due to its virulent nature and significant impact on human health and history, cholera has been studied and observed by the scientific community for quite some time. Scientists have developed used cholera to develop vaccines as well as learn more about the spread of diseases and the rapidity of bacterial evolution among infectious diseases. Much like Streptococcus pneumoniae, the bacteria responsible for diseases like pneumonia, V. cholerae evolves quickly to produce more effective and dangerous strains to infect human hosts. While the tendency of cholera causing bacteria to evolve rapidly may appear to have only negative implications, it actually helps epidemiologists track and control potential outbreaks. Scientists can draw on DNA databases filled with the genetic code for all current and past strains of V. cholerae to use as comparison with new outbreaks of the disease. This allows governments to determine the cause and track the spread of the disease in order to contain and treat it. Recently this method of using genetic information to compare strains of V. cholerae helped the Haitian government track the cause of the recent 2010 outbreak of cholera to UN workers from Nepal. (http://www.bbc.co.uk/news/world-latin-america-21542842)
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Has the genotype of carriers been analyzed and compared to the genotype of others? Did you come across any studies that discussed this? Carriers must possess some form of mutation that enables them to house the bacteria but not experience sickness. An understanding of this could help researchers develop new treatments.
ReplyDelete-Mary Morales
I haven't run into anything involving the genotypes of individuals affecting their carrier status. This article (http://www.ncbi.nlm.nih.gov/books/NBK8407/) gives a little overview on cholera and its ability to spread and deals with carriers ("asymptomatic individuals"). It states that the effectiveness of the disease depends upon, among other things, the bacteria's "toxigenicity" and it's "resistance to gastric acid." If a person with unusually low gastric acid pH levels were to be infected with a highly toxic and resistant bacteria, it would likely not end well. From my impression of this data it would seem like a person's chances of being asymptomatic depend more upon the bacteria and less on the person's genes, though both are involved.
DeleteIn what ways can the disease alterations be used to help fight it? a rapidly mutating gene is very dangerous when trying to create broad-spectrum antibiotics because you run having resistant strains take hold. How would be best to maybe use this high alteration frequency against the bacteria?
ReplyDeleteI think the evolution of developing drug resistance is really interesting. Are the cholera vaccines still effective as the bacteria has evolved, or are new vaccines constantly being released responding to the changes? (similar to the flu vaccine?)
ReplyDeleteIt would be really interesting to study this question through the lens of different countries' efforts to fight the disease. Perhaps if developed countries use sophisticated drugs to combat cholera and developing countries use more rudimentary systems, you could use the differences in the cholera strains in the two locations to assess how the cholera has responded to the various drugs present in countries like the US, for example.
DeleteI'm curious as to whether, following cholera eradication in the US and other developed countries, if cholera strains became more or less virulent as a result of public health efforts. It seems as if it could potentially go either way- more virulent strains may have the ability to infect water sources more effectively and therefore infect more people... or less virulent might be less noticeable and treated less vigorously and therefore allow more time for disease spread.
ReplyDeleteThere is a book called "Ghost Map" which does a good job of describing the circumstances on the early discovery of cholera (http://www.amazon.com/The-Ghost-Map-Terrifying-Epidemic--/dp/1594482691/ref=sr_1_2?ie=UTF8&qid=1362628694&sr=8-2&keywords=john+snow).
ReplyDeleteThe impression I got from this book is that the best way to stop cholera is to have good sanitization, especially on water. Cholera outbreaks today usually happen on developing countries where there is no effective sanitization system.
Though I have not read this book, the information I have seen agrees with this impression. Lack of quality sanitization is a major factor in the spread of cholera. That is why post-earthquake Haiti was such a vulnerable target. One of the reports I read claiming that UN workers brought cholera to Haiti noted that the outbreak may have been caused by their camp's makeshift toilet being too close to a water source (a stream or a river). Clearly, if the contaminated water had been properly sanitized (instead of being directly ingested by the population) the disease would've been unable to grab hold in Haiti.
DeleteIs the cholera genotypes pretty similar to other diseases genotypes? How exactly will scientists utilize this information in order to decide the evolution of other diseases? I really like this topic and I think it is a good idea to use cholera and try to study how diseases work more effectively in order to see the similarities between different diseases.
ReplyDeleteThis was interesting! I actually read a book, The Ghost Map on cholera so this was cool to see how it is actually helping in a way. I wonder what gene is actually mutating that is allowing it to live on and survive. Also, it would be interesting to know more about the specific differences between some of the strains of cholera that support evolutionary change.
ReplyDeleteWhat I find most interesting about this article is the last bit of information explaining how genetic coding now allows us to track the sequential mutations and use it as a tracking device and time stamp. With this in mind, I wonder if there is a any pattern to the mutations. We learned that not all mutations are random, (similar to the mechanisms in which humans develop certain forms of cancer) and this may also be the case for the Cholera bacteria. If this indeed is the case and we can somehow anticipate the evolution, we may be able to eradicate the bacteria, or at least its symptoms, by providing a cocktail vaccine that takes into account the possibility of future mutation. Does anyone have any information on the potential/feasibility of such a technique?
ReplyDeleteJust last night I sat in on the worlds leading expert and civic scientist on Cholera, Dr. Rita Colwell, and the work and findings she had about Cholera. She mentioned the exact information you had above and the fact that it is not really the strains of cholera bacteria but the genetic material itself that causes the phenotype in bacteria that causes the illness and symptoms! So she was basically saying that the bacterial strain data and medical data kept on Cholera all over the world is actually data tracking the genes that are passed into the bacteria that then cause the outbreaks! Just like influenza and thus new genetic material appears every year that advances and changes the face of the disease (bacterial strains) but not the overall negative outcomes.
ReplyDeleteCholera is an interesting topic, especially since it really brings to light the importance of sanitation and how important the availability of clean water is. Just like Rebecca, I also attended the Colwell lecture last night, and this post falls in agreement with the lecture very well. However, although cholera is constantly evolving, is there any information as to whether the evolution of cholera has resulted in any increase in virulence today as opposed to our ancestors? Or is there a possible coevolutionary aspect to the situation as well?
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