A recent study from researchers at University of Florida's Emerging Pathogens Institute has it that a non-virulent Vibrio cholerae O1 strain could be present in Haitian aquatic environments for centuries, long before cholera epidemic emerged in Haiti.
It noted that the non-pathogenic V. cholerae O1 strain could have become virulent through the transfer of genetic material from virulent strains from U.N. peacekeepers.
Dr. J. Glenn Morris, the senior author of the study, said that it has been a question of debate since the cholera outbreak in Haiti following the 2010 earthquake, whether virulent V. cholerae strain already existed in Haiti's water environment.
Morris added that though it is certain that V. cholerae strain that caused cholera back in 2010 was introduced by U.N. peacekeepers, the study suggests a possibility that non-pathogenic V. cholerae strain was present in Haiti as early as Columbus' period.
Though the ancient strains are non-toxigenic to cause infection, the findings pave way for a speculation whether the non-virulent strains became pathogenic after interacting with the virulent strains from the U.N. peacemaking troops.
While several strains of V. cholerae are found worldwide, the strains that have the potential to cause infection are found mostly in Africa and Asia. V. cholerae O139 and V. cholerae O1 are the two common strains that cause cholera in humans.
When the non-virulent V. cholerae O1 strain was isolated from estuaries in Port-au-Prince Bay, the researchers thought that it was toxigenic strain from Asia or Africa that lost its virulence eventually. It was later identified that the strains were more related to the ones that caused the first cholera pandemic in the world than the modern pandemic strains.
Meanwhile, Taj Azarian, from the Harvard School of Public Health, said the genomic data analysis suggests that the newly found strain has the common ancestors as that of the 1548 modern cholera strain, which was way before the emergence of cholera in Hispaniola.
According to Afsar Ali, the study's co-first author, the non-toxigenic V. cholerae is the progenitor for toxigenic El Tor and Classical biotypes.
"To analyze the isolates we used a computational technique called molecular clock analysis, which allows us to date the origin of strains isolated from the environment," said Marco Salemi, the senior author of the study, in a press release.
According to Salemi, it is sensible to think that the non-virulent strains of V. cholerae were present in Haitian aquatic environment with the potential to become pathogenic on interaction with toxigenic strains, which could pave way for the emergence of new epidemic strains over time.
The study was published in Scientific Reports on Oct. 27.
