Cholera

Cholera (cholera) is an acute infectious disease of the small intestine caused by cholera vibrio. This microorganism secretes a toxin that causes the appearance of copious watery (secretory) diarrhea, which leads to dehydration, oliguria and collapse. In typical cases, contamination occurs through contaminated water and marine products. Diagnosis of cholera is based on a culture or serological study. Treatment of cholera includes intensive rehydration and compensation of electrolyte losses on the background of therapy with doxycycline.

ICD-10 codes

• A00. Cholera.
• A00.0. Cholera, caused by cholera vibrio 01, biovar cholerae.
• A00.1. Cholera, caused by cholera vibrio 01, biovar eltor.
• A00.9. Cholera, unspecified.

Causes of Cholera

Cholera is caused by the vibrio cholera of serogroups 01 and 0139.

This microorganism is a short, curved, labile aerobic bacillus that produces an enterotoxin. Enterotoxin is a protein that causes hypersecretion of an isotonic electrolyte solution by the small intestine mucosa. Both El Tor and the classical biotypes of the vibrio cholera can cause acute illness. However, mild or asymptomatic infection is much more common with El-Tor biotype.

Cholera spreads by consuming water, seafood and other foods contaminated with excrement of people with severe or asymptomatic infection. Cholera is an endemic disease in selected regions of Asia, the Middle East, Africa, South and Central America and the northern coast of the Gulf of Mexico in the United States. Cases of transfer of infection to Europe, Japan and Australia led to local outbreaks. In endemic regions, outbreaks of cholera usually occur during the warm months. The highest incidence is observed in children. In young regions, epidemics can occur at any time of the year for this causative agent, and susceptibility to the causative agent is the same in children and adults. Moderate form of gastroenteritis is due to non-cholera vibrios.

The sensitivity to infection can be different. It is higher in people with I (ABO) blood group. In view of the fact that the vibrio is sensitive to gastric acid, hypochlorhydria and achlorhydria are predisposing factors to the onset of the disease. People living in endemic regions gradually acquire natural immunity.

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What are the symptoms of cholera?

Cholera has an incubation period of 1-3 days. Cholera can be a subclinical, moderate, uncomplicated episode of diarrhea or a lightning, potentially fatal disease. Usually the initial symptoms of cholera are sudden, painless, watery diarrhea and vomiting. Severe nausea is usually absent. Losses with stools can reach 1 L per hour in adults, but usually they are much less. This leads to a sharp loss of water and electrolytes, which causes intense thirst, oliguria, muscle cramps, weakness and a pronounced decrease in the turgor of tissues, which is accompanied by sunken eyeballs, wrinkling of the skin of the fingers. Appear hypovolemia, hemoconcentration, oliguria and anuria, as well as acute metabolic acidosis with a drop in the level of ionized potassium (the concentration of sodium in the blood remains normal). If there is no treatment for cholera, then a circulatory collapse with cyanosis and stupor may follow. Prolonged hypovolemia can cause tubular necrosis.

How is cholera diagnosed?

Diagnosis of cholera is carried out with the help of culture studies of stool and subsequent serotyping. Cholera differentiates from a similar disease caused by enterotoxin-producing strains of E. Coli and, sometimes, salmonella and shigella. It is necessary to measure the levels of electrolytes, residual urea nitrogen and creatinine.

How is cholera treated?

Cholera is treated using the basic principle - replenishment of lost fluid. Cases of moderate disease can be treated by a standard oral remedy. Rapid correction of hypovolemia is vital. Very important prevention and correction of metabolic acidosis and hypokalemia. Patients with hypovolemia and acute dehydration are shown intravenous administration of isotonic solutions (for details on replacement therapy). Water should also be given freely through the mouth. To compensate for potassium losses to intravenous administration of solutions, KCL at a dose of 10-15 meq / L or KNSO 1 ml / kg may be added orally in a solution of 100 g / l four times a day. Reimbursement of potassium is especially important in children, because they are very poorly tolerated hypokalemia.

When the lost volume is reimbursed, it is necessary to carefully determine the amount of compensation for continuing losses, which is based on the determination of losses with stool. The adequacy of hydration is confirmed by frequent clinical research (pulse frequency and strength, tissue turgor, volume of urine received). Plasma, plasma substitutes and vasopressors should not be used in place of water and electrolytes. Oral glucose-saline solutions are effective to compensate for losses with stool. They can be used after initial intravenous rehydration, and in endemic regions where the amount of intravenous solutions is limited, they can be the only sources of rehydration. Patients with mild or moderate dehydration and drinkable can be rehydrated exclusively with glucose-saline solutions (approximately 75 ml / kg for 4 hours). Patients with more acute dehydration require large volumes of solutions, so sometimes it becomes necessary to put a nasogastric tube. Oral solution according to WHO recommendations should contain 20 g of glucose, 3.5 g of NaCl, 2.9 g of ternary citrate and dihydrate (or 2.5 g of NaHCO), and 1.5 g of potassium chloride per 1 liter of drinking water. These appointments should continue as required, {ad libitum) after rehydration in volumes adequate to losses with stool and vomiting. Hard food can be given to the patient only after vomiting has ceased and appetite is restored.

Early treatment of cholera with an effective oral antibiotic allows to achieve eradication of the vibrio, reduces losses with feces by 50% and stops diarrhea within 48 hours. The choice of an antibiotic is based on determining the sensitivity of the cholera vibrio, provided that the latter is isolated from the microbial community. Drugs effective against sensitive strains include doxycycline (one dose of 300 mg orally for adults), furazolidone (100 mg orally 4 times a day for 72 hours for adults, 1.5 mg / kg 4 times a day for 72 hours for children), trimethoprim-sulfamethoxazole (2 tablets 2 times a day for adults, 5 mg / kg 2 times a day (trimethoprim) for children for 72 hours).

Most patients are released from cholera vibrio within 2 weeks after cessation of diarrhea, but some become chronic biliary carriers.

How is cholera prevented?

Cholera is prevented by correct elimination of human excrement and cleaning of water supply systems. Drinking water must be boiled or chlorinated, and vegetables and fish must be carefully prepared.

The killed oral whole cell, based on the B subunit, cholera vaccine (not available in the US) provides 85% protection from the serogroup within 4-6 months. Protection lasts up to 3 years in adults, but quickly disappears in children. This protection is more pronounced from the classical biotype, rather than from El Tor. Cross-reactivity between 01 and 0139 serogroups does not occur. Vaccines with proven efficacy against both groups are the hope of the future. The parenteral cholera vaccine provides only a short-term partial protection, and therefore is not recommended for use. Forced prophylaxis of doxycycline 100 mg orally every 12 hours in adults (for children under 9 years of age for prevention, trimethoprim-sulfamethoxazole may be used) may reduce the incidence of secondary cases in households where there have been contacts with a sick cholera, but massive prevention of cholera is impractical some strains are insensitive to these antibiotics.