Clinical and bacteriological findings among families of cholera patients

Cholera rages in Africa and the Middle East: A narrative review on challenges and solutions

Background and Aim

Cholera is a life-threatening infectious disease that is still one of the most common acute watery diarrheal diseases in the world today. Acute diarrhea and severe dehydration brought on by cholera can cause hypovolemic shock, which can be fatal in minutes. Without competent clinical therapy, the rate of case fatality surpasses 50%. The purpose of this review was to highlight cholera challenges in Africa and the Middle East and explain the reasons for why this region is currently a fertile environment for cholera. We investigated cholera serology, epidemiology, and the geographical distribution of cholera in Africa and the Middle East in 2022 and 2023. We reviewed detection methods, such as rapid diagnostic tests (RDTs), and treatments, such as antibiotics and phage therapy. Finally, this review explored oral cholera vaccines (OCVs), and the vaccine shortage crisis.

Methods

We carried out a systematic search in multiple databases, including PubMed, Web of Science, Google Scholar, Scopus, MEDLINE, and Embase, for studies on cholera using the following keywords: ((Cholera) OR (Vibrio cholera) and (Coronavirus) OR (COVID-19) OR (SARS-CoV2) OR (The Middle East) OR (Africa)).

Results and Conclusions

Cholera outbreaks have increased dramatically, mainly in Africa and many Middle Eastern countries. The COVID-19 pandemic has reduced the attention devoted to cholera and disrupted diagnosis and treatment services, as well as vaccination initiatives. Most of the cholera cases in Africa and the Middle East were reported in Malawi and Syria, respectively, in 2022. RDTs are effective in the early detection of cholera epidemics, especially with limited advanced resources, which is the case in much of Africa. By offering both direct and indirect protection, expanding the use of OCV will significantly reduce the burden of current cholera outbreaks in Africa and the Middle East.

Prolonged colonization of mice by Vibrio cholerae El Tor O1 depends on accessory toxins

Cholera epidemics caused by Vibrio cholerae El Tor O1 strains are typified by a large number of asymptomatic carriers who excrete vibrios but do not develop diarrhea. This carriage state was important for the spread of the seventh cholera pandemic as the bacterium was mobilized geographically, allowing the global dispersion of this less virulent strain. Virulence factors associated with the development of the carriage state have not been previously identified. We have developed an animal model of cholera in adult C57BL/6 mice wherein V. cholerae colonizes the mucus layer and forms microcolonies in the crypts of the distal small bowel. Colonization occurred 1 to 3 h after oral inoculation and peaked at 10 to 12 h, when bacterial loads exceeded the inoculum by 10- to 200-fold, indicating bacterial growth within the small intestine. After a clearance phase, the number of bacteria within the small intestine, but not those in the cecum or colon, stabilized and persisted for at least 72 h. The ability of V. cholerae to prevent clearance and establish this prolonged colonization was associated with the accessory toxins hemolysin, the multifunctional autoprocessing RTX toxin, and hemagglutinin/protease and did not require cholera toxin or toxin-coregulated pili. The defect in colonization attributed to the loss of the accessory toxins may be extracellularly complemented by inoculation of the defective strain with an isogenic colonization-proficient V. cholerae strain. This work thus demonstrates that secreted accessory toxins modify the host environment to enable prolonged colonization of the small intestine in the absence of overt disease symptoms and thereby contribute to disease dissemination via asymptomatic carriers.

Clinical characteristics and risk factors for Vibrio cholerae infection in children

Surveillance was conducted during February and March 1991 in the pediatric emergency department of Cayetano Heredia Hospital, Lima, Peru, to contrast the characteristics of children with epidemic cholera with those of children with noncholera-associated diarrhea. Among 626 patients 14 years of age or younger, Vibrio cholerae O1 was isolated from stool specimens of 310 patients (49%), more commonly from children older than 24 months of age (66%; p < 0.0001) than from younger children. Cholera was clinically characterized by a more sudden onset; watery diarrhea; and associated abdominal pain, muscle cramps, and vomiting, which led to more severe dehydration and hospitalization more often than in noncholera cases. Only one patient with cholera died, for a case-fatality rate of 3.2 deaths per 1000 persons. Nonpotable water and uncooked foods were identified as probable vehicles for V. cholerae. The frequency of diarrhea among relatives of patients with cholera suggested intrafamily transmission. This study of epidemic cholera describes the clinical features and the risk factors for acquisition of the infection, and points out the low case-fatality rate with prompt and appropriate treatment.

Waterborne transmission and the evolution of virulence among gastrointestinal bacteria

Diarrhoeal diseases are primary contributors to millions of deaths annually. Yet, little is known about the evolutionary reasons for the differences in virulence among gastrointestinal pathogens. Applying the comparative, cost/benefit approach of evolutionary biology this paper proposes that waterborne transmission should favour evolution towards high virulence. This hypothesis is supported by a cross-specific test, which shows that waterborne transmission is strongly correlated with the virulence of bacterial gastrointestinal pathogens of humans. Alternative explanations of this correlation are not supported by available data. These findings bear on public health policy because they draw attention to a previously unrecognized long-range benefit gained from purification of water supplies; diarrhoeal pathogens may evolve to lower levels of virulence.

Foodborne transmission of cholera in Micronesian households

During a cholera epidemic in Truk (Micronesia), in a survey of 1 village, transmission of Vibrio cholerae O1 in the 28 households with illness appeared to be through food contaminated in the home. Households in which the index case was a foodhandler had significantly higher attack rates than households in which the index case was not a foodhandler. Members of households with illness were significantly more likely to become ill if they had eaten food prepared by a foodhandler who had recently been ill. A matched-pair case-control study on several adjacent islands confirmed this relation. Those who had tended an ill person were not at increased risk of cholera in either study. This study suggests that in this outbreak, foodborne transmission of V cholerae O1 was more important than contact spread.

Cholera transmission near a cholera hospital

A review of the incidence of cholera from 1964 through 1974 in Matlab, Bangladesh, revealed that among the villages several had very high incidence-rates. Investigation indicated that high cholera-rates in two of these villages were probably related to water contamination from a nearby cholera hospital established in 1963. The data imply that heavy contamination can overcome any immunity resulting from repeated exposure.