Description
Cholera is an acute infection of the small intestine caused by the gram-negative microorganism Vibrio cholerae, which secretes a toxin that causes profuse watery diarrhea, leading to dehydration, oliguria, and vascular insufficiency. Infection usually occurs through contaminated water or seafood. It is diagnosed by fecal culture or serologic testing and treated with abundant rehydration with electrolyte replacement, antimicrobial therapy, and doxycycline (Loharikar, 2015). The causative agent V. cholerae (serogroups 01 and 0139) is a short, curved, motile, aerobic gram-negative bacillus that produces enterotoxins – proteins that cause hypersecretion of isotonic electrolyte solution through the mucous membrane of the small intestine (Christian et al., 2017). Both El Tor and the classic V. cholerae 01 biotypes can cause severe illness. However, mild or asymptomatic infections are much more likely to be caused by the currently predominant biotypes El Tor and non-01, non-0139 V. cholerae serogroups.
Affected Populations
Cholera is spread by drinking water, seafood, or other foods contaminated with the feces of people with symptomatic or asymptomatic infection. Domestic cholera patients are at high risk of infection, which is likely through shared sources of contaminated food and water (Christian et al., 2017). Human-to-human transmission is less likely because it requires a large amount of pathogen material. Cholera is endemic to parts of Asia, the Middle East, Africa, South America, Central America, and the northern US Gulf Coast (“Cholera,” n.d.). In 2010, the outbreak occurred in Haiti and then spread to the Dominican Republic and Cuba. The infection, imported to Europe, Japan, and Australia, caused local outbreaks. According to the World Health Organization (WHO), more than 50 countries around the world suffer from cholera (“Cholera,” n.d.). Southeast Asia, China, and Vietnam are traditionally disadvantaged. In the countries of Europe, Japan, Korea, cases of cholera were imported from outbreaks, where it is registered continuously. Due to the high level of culture of the population, the spread of infection in these countries was not observed. The most unfavorable for cholera are currently: India, Yemen, Iraq, Iran, Nigeria, Uganda, Tanzania, Mexico, Brazil; in some CIS countries, cases of cholera are also reported (“Cholera,” n.d.). In endemic areas, outbreaks usually occur during the warmer months.
V. cholerae are sown from water bodies in various regions (including those that are not endemic for cholera), warm, brackish, stagnant water contributes to the reproduction of vibrios, in addition, vibrios can multiply in the chitinous cover of mollusks, zooplankton, which can serve as a factor in the transmission of infection (reservoir in the environment). In case of violation of sanitary and hygienic rules and low sanitary culture of the population, it is possible to increase the proportion of those infected by contact and household means up to 60–70% (“Cholera,” 2020). In the USA, Latin America, India, there are cases of foodborne infections (Fang, Ginn, Harper, Kane, & Wright, 2019). In areas with a high incidence, children are more likely to get sick: the highest incidence occurs at the age of 2-4 years (Christin et al., 2017). Men get sick more often than women, urban dwellers – more often than rural. The peak incidence occurs during the summer months and the rainy season (in the tropics).
People living in endemic areas gradually acquire immunity to the pathogen. The incidence is highest in children. In newly affected regions, epidemics can occur at any time of the year, with all ages being equally susceptible (“Cholera,” 2020). Susceptibility to infection varies; it is higher among people with blood group O (Christian, 2017). Since vibrios are sensitive to gastric acid, hydrochloric acid, hypochloridium, and achloridium are predisposing factors. To stop the spread of cholera, it is very important to isolate the sick person in time, observing appropriate precautions, since this avoids contamination of healthy people. With timely and complete treatment, after the suppression of the infection, recovery occurs. Currently, modern drugs effectively act on Vibrio cholerae, and rehydration therapy helps prevent complications.
Specific prophylaxis of cholera consists of a single vaccination with cholera toxin before visiting regions with a high prevalence of this disease. If necessary, revaccination is performed after three months. The transferred infection does not leave behind a strong immunity, and re-infection with cholera is possible at any period of life, and attempts to create an effective vaccine are still fruitless (Mosley, Smith, Brantley, Locke, & Como, 2017). The effectiveness of vaccination is currently estimated at 25-50% with a duration of action of 3-6 months (Mosley et al., 2017). Non-specific cholera prevention measures imply compliance with sanitary and hygienic standards in populated areas, at catering establishments, in water intake areas for the needs of the population. Individual prevention consists of maintaining hygiene, boiling the water used, washing food, and cooking them correctly.
Cholera in the US
In the United States, cholera cases are mostly associated with international travel. Thus, the infection does not correlate with specific social demographics in the US like gender, age, and others. It is not possible to calculate a statistically significant conclusion since the number of cases is not enough. Mosley et al. (2017) state that the number of cases in the US is low; however, the areas with a high incidence of cholera attract US tourists. As Loharikar et al. (2015) report, between 2001 and 2011, 81% of patients were infected due to their foreign trips. Travel-associated cases are mostly associated with trips to Asia; however, since 2010, Hispaniola-associated cases began to rise due to the epidemic in Haiti, which started in 2010 and spread to the Dominican Republic.
Domestic causes of infection mostly come from seafood consumption. The latter is regulated by examining oysters, fish, and seawater in the area where cases of infection become reported. In the example of Florida, Fang et al. (2019) report their survey and genetic characterization of a particular pathogen Vibrio Cholerae while comparing the results to data for Vibrio Vulnificus and Vibrio parahaemolyticus. Such steps help understand the cause of the reported case as well as possible health risks and virulence potential. These tests are placed in a broader framework of The Foodborne Diseases Active Surveillance Network (FoodNet) (“Cholera,” 2020). This policy aims at controlling and studying infections of specific bacteria and parasitic pathogens found in food.
Preventive Measures
At the same time, an essential measure for the prevention of cholera outbreaks in the US is vaccination. The first FDA-approved cholera vaccination in the United States is Vaxchora (Mosley et al., 2017). This vaccine is supposed to support travelers from getting infected in the high incidence areas and, subsequently, bringing it to the US. Inside the US, such measures as modern water and sewage treatment systems have eliminated possible pandemic outbreaks of cholera (“Cholera,” 2020). The overall policy of control and prevention of this disease has been formulated and implemented through The Choler and Other Vibrio Illness Surveillance System (COVIS) (“Cholera,” 2020). With these measures, cholera cases in the US remain relatively low.
References
Christian, K. A., Iuliano, A. D., Uyeki, T. M., Mintz, E. D., Nichol, S. T., Rollin, P., …Arthur, R. R. (2017). What we are watching-top global infectious disease threats, 2013-2016: An update from CDC’s global disease detection operations center. Health Security, 15(5), 453–462.
Cholera. (2020).
Cholera. (n.d.).
Fang, L., Ginn, A. M., Harper, J., Kane, A. S., & Wright, A. C. (2019). Survey and genetic characterization of Vibrio cholerae in Apalachicola Bay, Florida (2012–2014). Journal of Applied Microbiology, 126(4), 1265−1277. Web.
Loharikar, A., Newton, A. E., Stroika, S., Freeman, M., Greene, K. D., Parsons, M. B.,… Mahon, B. E. (2015). Cholera in the United States, 2001–2011: A reflection of patterns of global epidemiology and travel. Epidemiology & Infection, 143(4), 695−703.
Mosley, J. F., Smith, L. L., Brantley, P., Locke, D., & Como, M. (2017). Vaxchora: The first FDA-approved cholera vaccination in the United States. Pharmacy and Therapeutics, 42(10), 638−640.