Cholera is an acute intestinal infection that occurs when a person is infected with cholera vibrio. Cholera is manifested by pronounced frequent diarrhea, copious repeated vomiting, which leads to significant loss of fluid and dehydration of the body. Signs of dehydration are dryness of the skin and mucous membranes, a decrease in tissue turgor and skin wrinkling, sharpening of facial features, oligoanuria. The diagnosis of cholera is confirmed by the results of bacteriological sowing of feces and vomit, serological methods. Treatment includes isolation of a cholera patient, parenteral rehydration, therapy with tetracycline antibiotics.
Cholera is a particularly dangerous infection caused by the enteropathogenic bacterium Vibrio cholerae, occurring with the development of severe gastroenteritis and severe dehydration up to the development of dehydration shock. Cholera tends to spread epidemically and has a high mortality rate, therefore it is classified by WHO as highly pathogenic quarantine infections.
The most frequent epidemic outbreaks of cholera are registered in the countries of Africa, Latin America, and Southeast Asia. According to WHO estimates, 3-5 million people are infected with cholera annually, about 100-120 thousand cases of the disease end fatally. Thus, today cholera remains a global problem of world health.
Causes of cholera
Characteristics of the pathogen
To date, more than 150 types of cholera vibrions have been detected, differing in serological characteristics. Cholera vibrions are divided into two groups: A and B. Cholera is caused by vibrions of group A. Cholera vibrio is a gram-negative motile bacterium that secretes a thermostable endotoxin and a thermolabile enterotoxin (cholerogen) in the process of vital activity.
The pathogen is resistant to the environment, retains viability in a flowing reservoir for up to several months, up to 30 hours in wastewater. A good nutrient medium is milk, meat. Cholera vibrio dies during chemical disinfection, boiling, drying and exposure to sunlight. Sensitivity to tetracyclines and fluoroquinolones is noted.
The reservoir and source of infection is a sick person or a transient carrier of infection. Bacteria are most actively isolated in the first days with vomit and fecal masses. It is difficult to identify infected persons with easily flowing cholera, but they are dangerous in terms of infection. In the focus of cholera detection, all contacts are examined, regardless of clinical manifestations. The contagion decreases over time, and usually by the 3rd week there is a recovery and release from bacteria. However, in some cases, the carrier lasts up to a year or more. Concomitant infections contribute to the prolongation of the period of carriage.
Cholera is transmitted by household (dirty hands, objects, dishes), food and water by fecal-oral mechanism. Currently, a special place in the transmission of cholera is given to flies. The waterway (polluted water source) is the most common. Cholera is an infection with high susceptibility, most easily infecting people with hypoacidosis, some anemia, infected with helminths, alcohol abusers.
The incubation period for infection with cholera vibrio lasts from several hours to 5 days. The onset of the disease is acute, usually at night or in the morning. The first symptom is an intense painless urge to defecate, accompanied by an uncomfortable feeling in the abdomen. Initially, the stool has a liquefied consistency, but retains a fecal character. Quite quickly, the frequency of defecation increases, reaches 10 or more times a day, while the stool becomes colorless, watery.
In cholera, bowel movements are usually not fetid, unlike other infectious intestinal diseases. Increased secretion of water into the intestinal lumen contributes to a noticeable increase in the amount of excreted feces. In 20-40% of cases, the stool acquires the consistency of rice broth. Usually the bowel movements have the appearance of a greenish liquid with white loose flakes, similar to rice.
Rumbling, tumbling in the stomach, discomfort, transfusion of fluid in the intestine are often noted. Progressive loss of fluid by the body leads to symptoms of dehydration: dry mouth, thirst, then there is a feeling of cold limbs, ringing in the ears, dizziness. These symptoms indicate significant dehydration and require urgent measures to restore the body’s water-salt homeostasis.
Since diarrhea is often accompanied by frequent vomiting, fluid loss is aggravated. Vomiting usually occurs a few hours later, sometimes the next day after the onset of diarrhea. Vomiting is copious, multiple, 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 acquiring the appearance of rice broth.
When vomiting occurs, the body rapidly loses sodium and chlorine ions, which leads to the development of muscle cramps, first in the muscles of the fingers, then all the limbs. With the progression of electrolyte deficiency, muscle cramps can spread to the back, diaphragm, abdominal wall. Muscle weakness and dizziness increases until it is impossible to get up and walk to the toilet. At the same time, consciousness is completely preserved.
Pronounced abdominal pain, unlike most intestinal infections, is not noted in cholera. 20-30% of patients complain of moderate pain. Fever is also not characteristic, body temperature remains within normal limits, sometimes reaches subfebrile figures. Pronounced dehydration is manifested by a decrease in body temperature.
Severe dehydration is characterized by paleness and dryness of the skin, decreased turgor, cyanosis of the lips and distal phalanges of the fingers. Dryness is also characteristic of the mucous membranes. With the progression of dehydration, hoarseness of the voice is noted (the elasticity of the vocal cords decreases) up to aphonia. The facial features sharpen, the stomach retracts, dark circles appear under the eyes, the skin on the fingertips and palms wrinkles (a symptom of “laundress’s hands”). During physical examination, tachycardia and arterial hypotension are noted. The amount of urine decreases.
Dehydration of the body varies by stages:
- at the first stage, fluid loss does not exceed 3% of body weight;
- on the second – 3-6%;
- on the third – 6-9%;
- at the fourth stage, fluid loss exceeds 9% of body weight.
With the loss of more than 10% of body weight and ions, dehydration progresses. There is anuria, significant hypothermia, the pulse in the radial artery is not palpable, peripheral blood pressure is not determined. At the same time, diarrhea and vomiting become less frequent due to paralysis of the intestinal muscles. This condition is called dehydration shock.
The increase in clinical manifestations of cholera can stop at any stage, the course can be erased. Depending on the severity of dehydration and the rate of increase in fluid loss, cholera of mild, moderate and severe course is distinguished. Severe cholera is observed in 10-12% of patients. In cases of lightning-fast course, the development of dehydration shock is possible during the first 10-12 hours.
Cholera can be complicated by the addition of other infections, the development of pneumonia, thrombophlebitis and purulent inflammation (abscess, phlegmon), thrombosis of mesentery vessels and intestinal ischemia. Significant loss of fluid can contribute to the occurrence of disorders of cerebral circulation, myocardial infarction.
Severe cholera is diagnosed based on the data of the clinical picture and physical examination. The final diagnosis is established on the basis of bacteriological sowing of feces or vomit, intestinal contents (sectional analysis). The material for sowing must be delivered to the laboratory no later than 3 hours from the moment of receipt, the result will be ready in 3-4 days.
There are serological methods for detecting infection with cholera vibrio (AR, RPH, vibrocidal test, ELISA), but they are not sufficient for final diagnosis, being considered methods of accelerated indicative determination of the pathogen. Accelerated methods for confirming a preliminary diagnosis can be considered luminescent serological analysis, microscopy in a dark field of vibrions immobilized by O-serum.
Since the main danger in cholera is progressive loss of fluid, its replenishment in the body is the main task of treating this infection. Cholera treatment is carried out in a specialized infectious diseases department with an isolated ward (box) equipped with a special bed (Philips’ bed) with scales and dishes for collecting feces. To accurately determine the degree of dehydration, their volume is recorded, hematocrit, serum ion level, acid-base index are regularly determined.
Primary rehydration measures include replenishing the existing shortage of fluids and electrolytes. In severe cases, intravenous administration of polyionic solutions is performed. After that, compensatory rehydration is performed. The introduction of liquid occurs in accordance with its losses. The occurrence of vomiting is not a contraindication to continued rehydration. After restoring the water-salt balance and stopping vomiting, antibiotic therapy begins. In cholera, a course of tetracycline preparations is prescribed, and in case of repeated isolation of bacteria, chloramphenicol.
There is no specific diet for cholera, in the first days table No. 4 can be recommended, and after the pronounced symptoms subside and intestinal activity is restored (3-5 days of treatment) – nutrition without peculiarities. Cholera survivors are recommended to increase potassium-containing foods in the diet (dried apricots, tomato and orange juices, bananas).
Prognosis and prevention
With timely and complete treatment, recovery occurs after suppressing the infection. Currently, modern drugs effectively act on cholera vibrio, and rehydration therapy helps prevent complications.
Specific prevention of cholera consists in a single vaccination with cholera toxin before visiting regions with a high level of spread of this disease. If necessary, revaccination is performed after 3 months. Non-specific cholera prevention measures imply compliance with sanitary and hygienic standards in populated areas, at catering establishments, in areas of water intake for the needs of the population. Individual prevention consists in observing hygiene, boiling the water consumed, washing food and their proper culinary processing. If a case of cholera is detected, the epidemiological focus is subject to disinfection, patients are isolated, all contact persons are monitored for 5 days to identify possible infection.