Cholera is an infectious disease caused by the bacterium Vibrio cholera and is responsible for thousands of deaths every year. A study conducted in Bangladesh has provided researchers evidence that the human body has developed ways to combat this disease. Researchers have discovered that, due to the high prevalence of cholera, the genomes of individuals in Bangladesh have been altered to fight off cholera. These findings also exemplify how human evolution is still occurring in this day-and-age.
Cases of cholera have been discovered all throughout the world, but the most prevalent area of cholera infections is the Ganges River of India and Bangladesh. In fact, cholera has been prevalent in this area for more than a thousand years. The microbe is responsible for causing diarrhea and promoting severe dehydration, which can cause death within a few hours if not treated.
Cholera’s endemic and enduring attributes among Bangladesh residents provided researchers an evolutionary framework to conduct the study. These researchers suspected that cholera has been exerting an evolutionary pressure on Bangladeshi individuals living near the Ganges similar to the evolutionary pressure malaria has shown to inflict on individuals in Africa. Infectious disease specialist Regina LaRocque also found that many Bangladeshi experience mild symptoms or do not get sick. with cholera, also supporting the idea of evolutionary pressure.
To determine if cholera has been inflicting evolutionary pressure, LaRocque and several other researchers used a statistical technique that selected portions of the human genome that are affected by natural selection. These researchers analyzed the genomes of 36 Bangladeshi families and compared these genomes with the genomes of individuals from Europe, Africa, and Asia. They found that natural selection has allowed for changes in 305 regions in the genome of the Bangladeshi subjects.
Researchers also compared DNA from Bangladeshi cholera patients with the DNA of individuals who remained healthy despite living in the same household as an infected individual and discovered that those susceptible to cholera carried DNA types that were within the region that shows the greatest impact by natural selection.
This study has provided a valuable example of how infectious diseases can impact human evolution. Although these findings will not lead to new cholera treatments, they may help researchers create more effective vaccines that allow for better protection against cholera.
Author: Ravneet Singh