What Causes Cholera?

Cholera is an acute diarrheal infectious disease caused by food or water contaminated with Vibrio cholerae. Each year, there are an estimated 3 to 5 million cases of cholera, and another 100,000 to 120,000 die. The peak of the disease is in summer, which can cause diarrhea, dehydration and even death within hours.

Basic Information

English name

cholera

Visiting department

Infectious Diseases

Common locations

Digestive system

Common causes

Caused by Vibrio cholerae infection

Common symptoms

Sudden diarrhea followed by vomiting; decreased blood pressure, weak pulse, etc.

Contagious

Have

Causes of cholera

Cholera is caused by Vibrio cholerae. Vibrio cholerae is Gram-negative and is sensitive to dryness, sunlight, heat, acids and general disinfectants. Vibrio cholerae produce endotoxin and exotoxin. Normal gastric acid can kill Vibrio. When gastric acid is temporarily low or the number of invading virus bacteria increases, Vibrio that is not killed by gastric acid enters the small intestine, rapidly multiplies in alkaline intestinal fluid, and produces a large amount of strong exotoxin. This exotoxin has ADP-ribosyltransferase activity. After entering the intracellularly catalyzed intracellular NAD + ADP ribosyl covalently bound subunit, it will prevent this subunit from hydrolyzing the self-bound GTP to GDP, thus making this This subunit is in a state of continuous activation, which continuously activates adenylyl cyclase, which causes the cAMP level in the small intestinal epithelial cells to increase, causing a large amount of sodium ions and water to continue to flow out. The effect of this exotoxin on the small intestinal mucosa causes a large amount of intestinal fluid secretion, which is large in secretion and exceeds the ability of the intestinal tube to reabsorb. It causes severe diarrhea and severe dehydration in the clinic, resulting in a significant decrease in plasma volume, lack of body salt, and blood Concentrated, peripheral circulation failure occurs. Due to severe vomiting, electrolyte loss, potassium and sodium deficiency, muscle spasm, acidosis and even shock and acute renal failure.

Clinical manifestations of cholera

Diarrhea

The diarrhea usually begins with sudden diarrhea and then vomits. Generally, there is no obvious abdominal pain, and there is no severe feeling after anxiety. It is even difficult to count stools several times a day, and the amount is large, 2,000 to 4000 ml per day, and more than 8000 ml in severe cases. Initially yellow water samples, and soon changed to rice water water samples, a few patients have bloody water samples or tar-like stools, spurting and borderline vomiting after diarrhea, initially stomach contents, followed by water samples, rice cakes . Vomiting is usually not accompanied by nausea. The contents are similar to those of stool. A small number of patients are not accompanied by vomiting during diarrhea. Due to the severe loss of body fluids and electrolytes caused by severe vomiting, circulatory failure occurs, which is manifested by decreased blood pressure, weak pulse, significantly increased hemoglobin and plasma specific gravity, decreased urine output and even anuria. Organic acid and nitrogen product excretion in the body is impaired, and patients often show early symptoms of acidosis and uremia. A large amount of electrolytes such as sodium and potassium were lost in the blood, and the patient developed systemic electrolyte disorders. Sodium deficiency can cause muscle spasms, especially the gastrocnemius and rectus abdominis muscles. Potassium deficiency can cause hypokalemia syndromes, such as loss of muscle tone throughout the body, disappearance of tendon reflexes, tympanic bowel, tachycardia, arrhythmia, etc. Due to the large loss of bicarbonate ions, metabolic acidosis can occur. In severe cases, consciousness is lost and blood pressure drops.

2. Dehydration phase

The appearance of patients with dehydration is very obvious. In severe cases, the eye sockets are deep, the voice is hoarse, the skin is dry, shrunken, and the elasticity disappears. The abdominal depression is boat-shaped. , Muscle cramps or convulsions.

3. Recovery period

A small number of patients (most common in children) may have a febrile reaction at this time, and the body temperature rises to 38 ° C to 39 ° C, which usually subsides after 1 to 3 days, so this period is also called the reaction period. The average disease duration was 3 to 7 days.

Cholera check

Blood test

Red blood cell count and hemoglobin increased, white blood cell count increased, and neutrophil and large monocyte counts increased. Serum potassium, sodium, chloride, and carbonate decreased, blood pH decreased, and urea nitrogen increased. Due to the intracellular potassium ion shifting out before treatment, serum potassium can be within the normal range. When acidosis is corrected, potassium ion moves into the cell and hypokalemia occurs.

2. Urine test

A small number of patients may have protein, red, white blood cells and casts in the urine.

3. Inspection of pathogenic bacteria

(1) Routine microscopy shows mucus and a few red and white blood cells.

(2) Smear staining Stools or early culture smears were taken for Gram staining microscopy, and Gram-negative slightly curved Vibrio were found.

(3) Hanging drop inspection Fresh droppings were examined by hanging drop or dark field microscopy. Vibrio vibrio was shown to be active and shuttle-like.

(4) Brake test: Take watery stools or alkaline superficially water-enriched bacteria for 6 hours, and perform dark field microscopy to observe the dynamics. If there is a shuttle-like moving object, add a drop of O1 group multivalent serum. If it is Vibrio cholerae O1 group, due to the action of antigen and antibody, it will agglomerate and Vibrio movement will stop. If you cannot stop exercise after adding O1 serum, you should repeat the test with O139 serum.

(5) Bacteria culture All stools of patients with suspected cholera should be cultured in addition to microscopy. Feces should be collected before use of antibacterial drugs and should be sent to the laboratory for cultivation as soon as possible. The bacteria-enriching medium generally uses alkaline peptone water with a pH of 8.4, and the surface can form a bacterial film after being cultured at 36 ° C to 37 ° C for 6 to 8 hours. At this time, further separation and cultivation should be performed, and dynamic observation and braking test should be performed.

(6) Gentamicin agar plates or alkaline agar plates are commonly used for separation and culture . The former is a highly selective medium. Vibrio cholerae can be grown into small colonies when cultured at 36 ° C to 37 ° C for 8 to 10 hours. The latter requires 10 to 20 hours. Select suspicious or typical colonies and apply the antiserum of the "O" antigen of Vibrio cholerae as a slide agglutination test. If positive, a report can be made. In recent years, DNA probes using the cholera toxin gene have also been used abroad for colony hybridization, which can quickly identify the toxin producing O1 group V. cholerae.

(7) PCR detection Recently, PCR technology has been used to rapidly diagnose cholera. Among them, the C. cholera toxin gene subunit CtxA and the toxin synergy pili gene (TcpA) are identified in the PCR product to distinguish the cholera strain and the non-Vibrio cholerae, and then the classical biotype and El are distinguished according to the different DNA sequences of the TcpA gene. Support bio-type Vibrio cholerae. Results are available within 4 hours.

(8) Identification test The identification of classical biotype, Elto biotype, and O139 type Vibrio cholerae.

4 Serology

Can be used for serum agglutination test. Take 1 serum on the 1st to 3rd and 10th to 15th onset of the disease. If the antibody titer of the second serum is 4 times or more than that of the first serum, it has diagnostic reference value.

Cholera diagnosis

Diagnosis criteria

Those who have diarrhea and vomiting and who have positive stool culture of Vibrio cholerae; Those who have typical cholera symptoms in the epidemic area and negative stool culture for no other reason can be checked. If conditions permit, double serum lectin test A titer of 4 or more can be diagnosed; those who have symptoms of diarrhea within 5 days before a positive stool culture test can be diagnosed as mild cholera.

2. Suspected standards

All cases of non-endemic areas with typical symptoms of diarrhea should be diagnosed before the pathogenic examination; During the epidemic of cholera, patients who had contact with cholera and had symptoms of diarrhea without any other cause can be checked.

3. Other

Serological examination is suitable for retrospective diagnosis after illness and does not help early diagnosis. The diagnosis must identify the following diarrheal diseases: dysentery; bacterial food poisoning caused by salmonella, staphylococcus, proteus, etc .; diarrhea caused by Vibrio parahaemolyticus; enterotoxigenic coliform diarrhea; viral (Especially rotavirus) gastroenteritis; parasitic diarrhea; diarrhea caused by certain poisons (such as organophosphorus pesticides, arsenic trioxide, etc.). Diagnosis and identification of mild atypical cholera cases are difficult. Generally, there is only mild diarrhea without vomiting, normal blood pressure and pulse, clear consciousness, short course of disease, and healed by itself within three or two days. Fulminant cholera or dry cholera is relatively rare, and no vomiting or dehydration is seen after the onset, but it quickly switches to shock and severe toxic circulatory failure, with a very high mortality rate.

Cholera treatment

The treatment principle of this disease is strict isolation, rapid replenishment of water and electrolytes, correction of acidosis, supplemented by antibacterial treatment and symptomatic treatment.

1. General treatment and nursing

(1) Close isolation and isolation according to infectious diseases of the digestive tract until 6 days after the symptoms disappear, Vibrio faecalis is negative for 3 consecutive times before the isolation can be released. The patient's materials and excreta should be strictly disinfected, and the staff in the ward must strictly observe the disinfection and isolation. System to prevent cross infection.

(2) Absolutely rest in heavy patients until symptoms improve.

(3) Suspended diet with severe vomiting. When vomiting stops and diarrhea is relieved, a liquid diet can be given. Slowly increase the diet if the patient can tolerate it.

(4) Water replenishment is the basic treatment of cholera. Light patients can be rehydrated orally, while heavy patients need intravenous rehydration. After the symptoms improve, change to oral rehydration.

(5) Specimen collection The fecal specimen of vomitus is collected immediately after admission to the hospital and sent to routine examination and bacterial culture. Note that the specimen should be submitted for inspection immediately after collection.

(6) Closely observe the changes in the condition and measure the vital signs once every 4 hours, accurately record the amount of in and out, and indicate the frequency, quantity and traits of defecation.

2.Treatment and nursing of infusion

Principles of infusion treatment: early, rapid and moderate, salt first, sugar first, fast first, then slow, acid correction and calcium supplementation, see urine potassium supplementation.

3. Symptomatic treatment and nursing

(1) Atropine can be given to frequent vomiting.

(2) Adrenocortical hormone can be used as appropriate for severe diarrhea.

(3) Muscle spasm can be intravenously injected with 10% calcium gluconate, hot compress and massage.

(4) Those with peripheral circulation failure who have not recovered their blood pressure after a large amount of fluid replacement to correct acidosis, can use alamin or dopamine drugs.

(5) Those with uremia should strictly control the body weight, prohibit protein diet, strengthen oral and skin care, and use dialysis therapy if necessary.

4. Etiology treatment and nursing

Tetracycline can shorten the course of treatment to reduce diarrhea, shorten the time of fecal bacterial elimination, and reduce the incidence of bacteria. It can be intravenously infused until the condition improves. It can also be treated with doxycycline, compound neonomine, and piperacic acid.

5. Notes

Common complications of this disease include acidosis, uremia, heart failure, pulmonary edema, and hypokalemia syndrome.