Cholera is one of the serious epidemiological diseases that threatens humanity to this day. It spreads quickly and easily, for example, with food or water. The acute form of cholera can cause significant health problems. These include, for example, severe dehydration, which leads to an imbalance of minerals in the body and can cause death. Consequently, there are various cholera control and treatment measures. In addition, patients need to be isolated from other people as the disease is transmitted through physical contact. The prognosis may be favorable, but only if all necessary precautions and treatment are followed.
Cholera is an acute intestinal infection that occurs when a person is affected by cholera vibrio. Cholera is manifested by severe, frequent diarrhea, profuse repeated vomiting, which leads to significant loss of fluid and dehydration. Signs of dehydration are dryness of the skin and mucous membranes, decreased tissue turgor and wrinkling of the skin, sharpening of facial features, and oliguria. The cholera diagnosis is confirmed by the results of bacteriological inoculation of feces and vomit, or serological methods. Treatment includes isolation of the cholera patient, parenteral rehydration, and tetracycline antibiotic therapy.
Causes and Demographics of Cholera
Cholera is a particularly dangerous infection caused by the enteropathogenic bacterium Vibrio cholerae, which develops severe gastroenteritis and severe dehydration up to the dehydration shock. Cholera tends to spread epidemically and has a high mortality rate; therefore, WHO has classified it as a highly pathogenic quarantine infection. The most frequent epidemic outbreaks of cholera are recorded in Africa, Latin America, and Southeast Asia (Legros, 2018). According to WHO, every year 3-5 million people are infected with cholera, and about 100-120 thousand cases of the disease end in death (Berger, 2019). Thus, today, cholera remains a global problem of world health.
To this day, more than 150 types of Vibrio cholerae have been identified, differing in serological characteristics. Vibrio cholerae are divided into two groups: A and B, with Vibrios of group A causing cholera (Deen et al., 2020). Vibrio cholerae is a gram-negative motile bacterium that secretes a thermostable endotoxin in the process of vital activity, as well as a heat-labile enterotoxin (choleragen). The pathogen is resistant to the environment, remains viable in a flowing reservoir for up to several months and up to 30 hours in wastewater. For example, milk and meat are a good breeding ground. Vibrio cholerae is killed by chemical disinfection, boiling, drying, and exposure to sunlight; it is also sensitive to tetracyclines and fluoroquinolones.
The reservoir and source of infection is a sick person or a transient carrier of disease. The most active bacteria are secreted in the first days with vomit and fecal masses. It is difficult to identify infected individuals with mild cholera, but they pose a risk of infection (Von Pettenkofer, 2018). Infection decreases over time, and usually, by the 3rd week, there are recovery and release of bacteria. However, in some cases, carriage lasts up to a year or more. Concomitant infections contribute to the lengthening of the carrier period.
Cholera is transmitted by touching objects, food, and water through the fecal-oral mechanism. At present, flies have a special place in the transmission of cholera. The waterway (contaminated water source) is the most common one (Spellman, 2018). Cholera is an infection with high susceptibility, most easily infecting people with hypoacidosis, some anemias, helminths, or alcohol abuse (Shah, 2016). Cholera can be complicated by other infections, the development of pneumonia, thrombophlebitis, and purulent inflammation (abscess, phlegmon), mesenteric vascular thrombosis, and intestinal ischemia. A significant loss of fluid can contribute to the onset of cerebral circulation disorders, myocardial infarction.
The incubation period for Vibrio cholerae infection lasts from several hours to five days. The onset is acute, usually at night or in the morning. The first symptom is an intense painless urge to defecate, accompanied by an uncomfortable sensation in the abdomen. Initially, the stool has a thin consistency but retains the fecal character. Quite quickly, the frequency of bowel movements increases, reaching ten or more times per day, while the stool becomes colorless, watery. In cholera, bowel movements are usually not offensive, unlike other infectious bowel diseases. Increased water secretion into the intestinal lumen contributes to a noticeable increase in the amount of excreted feces. In 20-40% of cases, the feces acquire the consistency of rice water. The stool usually appears as a greenish liquid with white, rice-like flakes.
Rumbling, bubbling in the abdomen, discomfort, and fluid transfusion in the intestine are often noted. The progressive loss of fluid by the body leads to dehydration symptoms (dry mouth and thirst). Then, there is a feeling of cold extremities, ringing in the ears, dizziness. These symptoms indicate significant dehydration and require urgent measures to restore the body’s water-salt homeostasis (McMillen, 2016). Since diarrhea is often associated with frequent vomiting, fluid loss is exacerbated. Vomiting usually occurs several hours later, sometimes, the next day after the onset of diarrhea. Vomiting profuse, repeated, begins suddenly and is accompanied by an intense feeling of nausea and pain in the upper abdomen under the sternum. Initially, the remains of undigested food are noted in the vomit, then bile. Over time, the vomit also becomes watery, sometimes taking on the appearance of rice water.
With vomiting, the body quickly loses sodium and chlorine ions, which leads to the development of muscle cramps, first in the muscles of the fingers, then in all extremities. With the progression of electrolyte deficiency, muscle cramps can spread to the back, diaphragm, and abdominal wall. Muscle weakness and dizziness grow up to the inability to get up and walk to the toilet; at the same time, consciousness is completely preserved. Severe pain in the abdomen, unlike most intestinal infections, is not noted with cholera while 20-30% of patients complain of moderate pain. Fever is also not characteristic; the body temperature remains within normal limits, sometimes reaches subfebrile numbers. It is important to note that a decrease in body temperature manifests severe dehydration.
Severe dehydration is characterized by paleness and dryness of the skin, decreased turgor, cyanosis of the lips, and distal phalanges of the fingers. Additionally, dryness is also a characteristic of the mucous membranes. With the progression of dehydration, the voice’s hoarseness is noted (the elasticity of the vocal cords decreases) up to aphonia. Facial features sharpen, the abdomen is pulled in, dark circles appear under the eyes, the skin on the fingers’ pads and palms wrinkles. On physical examination, tachycardia and arterial hypotension are noted; the amount of urine decreases.
Dehydration of the body differs in stages: at the first stage, the loss of fluid does not exceed 3% of the bodyweight; at the second – 3-6%; at the third – 6-9%; at the fourth, it exceeds 9% of the body weight. With a loss of more than 10% of body weight and ions, dehydration progresses (Davies et al., 2017). Anuria, significant hypothermia occurs, and the radial artery’s pulse is not palpable, and peripheral arterial pressure is not detected. Simultaneously, diarrhea and vomiting become less frequent due to paralysis of the intestinal muscles, which is called dehydration shock. The increase in cholera’s clinical manifestations can stop at any stage, and the course can be erased. Depending on the severity of dehydration and the rate of increase in fluid loss, cholera is distinguished from mild, moderate, and severe. Severe cholera occurs in 10-12% of patients. In cases of a fulminant course, dehydration shock development is possible during the first 10-12 hours.
Severe cholera is diagnosed based on clinical findings and physical examination. The final diagnosis is established based on bacteriological culture of feces or vomit, intestinal contents (sectional analysis). The material for inoculation must be delivered to the laboratory no later than 3 hours after receipt; the result will be ready in 3-4 days. There are serological methods for detecting infection with Vibrio cholerae, but they are not sufficient for the final diagnosis, being considered methods of accelerated approximate determination of the pathogen. Luminescence-serological analysis, microscopy in the dark field of Vibrios immobilized by O-serum can be considered as accelerated methods for confirming the preliminary diagnosis.
Primary rehydration measures include replenishing existing fluid and electrolyte deficiencies. In severe cases, intravenous administration of polyionic solutions is performed, after which, compensatory rehydration is required; vomiting is not a contraindication to continued rehydration. After restoring the water-salt balance and stopping vomiting, antibiotic therapy is started. In cholera, a course of tetracycline drugs is prescribed, and in case of re-isolation of bacteria, chloramphenicol should be used (Van Heyningen, 2019). There is no specific diet for cholera: in the first days, doctors may recommend a moderate diet, but after the pronounced symptoms subside and the restoration of intestinal activity (3-5 days of treatment), a patient can eat normally. Cholera survivors are advised to increase their dietary intake of potassium-containing foods (dried apricots, tomato and orange juices, bananas).
With timely and complete treatment, after the suppression of the infection, recovery occurs. 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. Non-specific cholera prevention measures imply compliance with sanitary and hygienic standards in populated areas, at catering establishments, and in areas of water intake for the population’s needs. Individual prevention consists of maintaining hygiene, boiling the water used, washing food, and cooking properly (Koch et al., 2017). If a case of cholera is detected, the epidemiological focus is subject to disinfection, patients are isolated, and all contact persons are monitored for five days to detect possible infection.
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