Description and Significance
Vibrio cholerae is a “comma” shaped Gram-negative bacteria with a single, polar flagellum for movement. There are numerous strains of V. cholerae, some of which are pathogenic and some of which are not. [SOURCE]
The bacteria infects the intestine and increases mucous production causing diarrhea and vomiting which result in extreme dehydration and, if not treated, death. It is usually transmitted through the feces of an infected person, often by way of unclean drinking water or contaminated food. Since water treatment and sanitation is more advanced in the United States, cholera is not nearly as high of a public health threat in the U.S. as it is in densely populated, economically reduced areas like India or sub-Saharan Africa where water and sewage treatment technology is low.
Filippo Pacini first discovered V. cholerae in Italy in 1854, though it was originally believed to be Robert Koch who discovered it thirty years later in Berlin in 1884.
V. cholerae thrives in a water ecology, particularly surface water. The primary connection between humans and pathogenic strains is through water, particularly in economically reduced areas that don’t have good water purification systems.
Non-pathogenic strains are also present in water ecologies. It is thought that it is the wide variety of strains of pathogenic and non-pathogenic strains that co-exist in aquatic environments that allow for so many genetic varieties. Gene transfer is fairly common amongst bacteria and recombination of different V. cholerae genes can lead to new virulent strains.
V. cholerae enters the human body through ingestion of contaminated food or water. The bacteria enters the intestine, embeds itself in the villi of absorptive intestinal cells, and releases cholera toxin. Cholera toxin (CT) is an enterotoxin made up of five B-subunits that form a pore to fits one A-subunit. CT is made from filamentous phage gene, CTXφ.9 A phage gene is also responsible for another virulence factor of V. cholerae, which is toxin co-regulated pilus (TCP), which acts as a receptor for CTXφ.
Physiological responses and symptoms that follow release of cholera toxin include stimulation of the mucosal lining of the intestine to secrete fluids. This causes vomiting and watery diarrhea that has a “rice water” quality. Death can occur from extreme dehydration and if not treated does occur 50-70% of the time.
Treatment includes rehydration and replacement of lost electrolytes, which are important ions, such as sodium and potassium, used in biochemical processes to keep the body alive. Because of the low quality of water treatment in many poverty ridden countries, rehydration with clean water can be impossible without medical aid and supplies.
The Outbreak Grows
The outbreak around Golden Square in 1854 hit a new peak before midnight on Thursday. Hundreds of the residents now had the disease and in some cases entire families in small, dark suffocating rooms.
Henry Whitehead’s social rounds had now become a death vigil. As dawn broke, Whitehead was called to one house where four people were already dead, their skin already taut and blue. As he made his way from house to house the horrors before him were difficult. However, while visiting one of the filthest houses on his route, the residents seemed to be doing just fine. He was amazed. Surely, they would have been sick too.
Back at 40 Broad Street, baby Lewis was silent. The disease had left her dead.
The neighborhood was under attack. Neighbors shuttered themselves up. By that afternoon, a yellow flag was raised to alert the residents that the cholera had struck.
But, you didn’t need to see the yellow flag to know there was trouble. You could see the dead being wheeled down the street by the cartload.
Next: Dr. John Snow