What is Rabies?

Rabies (rabies) is an acute infectious disease caused by rabies virus. It is a common zoonotic disease. It is more common in carnivorous animals such as dogs, wolves, and cats. People are infected by bites from diseased animals. Clinical manifestations are peculiar fear of water, fear of wind, pharyngeal muscle spasm, and progressive paralysis. Because the symptoms of water phobia are more prominent, this disease is also called hydrophobia. Rabies virus belongs to the genus Rhabdovirus of the Rhabdoviridae family. It is a single-stranded RNA virus. Animals spread the virus by biting each other. Rabies is mainly transmitted by dogs in China, and domestic dogs can become asymptomatic carriers, so the appearance of "healthy" dogs is very harmful to human health. There is still no effective treatment for rabies. The mortality rate of people suffering from rabies is almost 100%. Patients generally die from respiratory or circulatory failure within 3 to 6 days, so preventive measures should be strengthened.

Basic Information

nickname

Hydrophobia

English name

rabies

English alias

hydrophobia

Visiting department

Infectious Diseases

Common causes

Caused by rabies virus transmitted from animal to human

Common symptoms

Fear of water, wind, paroxysmal pharyngeal spasm, dyspnea, etc.

Contagious

Have

way for spreading

Sick dog, sick cat, sick wolf, etc.

Causes of rabies

It is mainly caused by the transmission of rabies virus from animals to humans. Rabies virus contains 5 kinds of proteins, namely glycoprotein (G), nuclear protein (N), polymerase (L), phosphoprotein (NS), and matrix (M). The glycoprotein of rabies virus can bind to acetylcholine, which determines the neurophagicity of rabies virus. Sources of infection are mainly sick dogs, followed by sick cats and sick wolves. After a person is bitten by a diseased animal, the virus in the animal's saliva enters the human body through the wound and causes the disease. A small number of patients can also get sick due to the conjunctiva contaminated by the saliva of diseased animals.

Humans are generally susceptible to rabies, and hunters, veterinarians, and animal keepers are more susceptible. When rabies virus enters the human body, it first infects muscle cells, proliferates in small amounts in muscle cells near the wound, and then invades nearby peripheral nerves. Then, the virus spreads to the central nerve along the axon of the peripheral nerve, and does not spread blood. It mainly invades neurons in the brainstem and cerebellum. The virus replicates in a large amount in the gray matter, and descends along the nerves to the salivary glands, cornea, nasal mucosa, lungs, and skin. The main damage of the rabies virus to the host comes from the endosomes, that is, the eosinophilic particles formed by the abandoned protein shells in the cells, and the endosomes are widely distributed in the central nervous cells of patients. An indicator.

Not all of the people get sick after being infected. About 15% to 20% of people who are bitten by sick dogs without vaccination, and about 50% to 60% of those who are bitten by sick wolf. , Wound treatment, thin clothing, and whether or not the vaccine is injected.

Clinical manifestations of rabies

The incubation period varies, most of them are within 3 months. The length of the incubation period is different from the age (children are shorter), the wound site (early onset of head and face bites), the depth of the wound (the incubation period is shorter for those with deep wounds), and the number of invasive viruses. And virulence and other factors. Other diseases such as incomplete debridement, trauma, cold, and overwork may cause the disease to occur in advance. Typical clinical manifestations can be divided into the following three phases:

1. Prodromal or invasive phase

Prior to the state of excitement, most patients had low fever, loss of appetite, nausea, headache, burnout, and general discomfort, which resembled a "cold"; then they became frightened, sensitive to sound, light, wind, pain, and throat. Tightness. The more early diagnostic symptoms are paresthesia in the wound and its vicinity, numbness, itching, pain, and ants walking. This is caused by the stimulation of neurons during virus reproduction, which lasts 2 to 4 days.

2. Excitement period

The patient gradually entered a state of high excitement, prominently manifested as extreme horror, fear of water, fear of wind, paroxysmal pharyngeal muscle spasm, difficulty breathing, difficulty urinating and defecation, and sweating and salivation. This period lasts 1 to 3 days.

Water phobia is a special symptom of rabies. The typical person can cause severe laryngospasm when he sees water, drinks water, listens to the sound of running water, or even only mentions drinking water. Fear of wind is also one of the common symptoms. Breeze or other stimuli such as light, sound, and touch can cause pharyngeal muscle spasm, and severe fashion can cause painful convulsions throughout the body.

3. Paralysis period

The spasms ceased, and the patient gradually became quiet, but he had delayed paralysis, especially limb paralysis. Eye muscles, facial muscles, and masticatory muscles can also be affected, showing strabismus, eye movement disorders, jaw drop, mouth not closed, lack of facial expression, etc. This period lasts 6 to 18 hours.

The entire course of rabies usually does not exceed 6 days, and occasionally more than 10 days. In addition, there are still "paralyzed" or "static" paralysis as the main manifestation, also known as dumb rabies. This type of patient has no excitement and waterphobia, but starts with fever, headache, vomiting, and pain at the bite. Then there were weakness of the limbs, abdominal distension, ataxia, muscle paralysis, and incontinence. The disease lasted for 10 days, and eventually died of respiratory muscle paralysis and bulbar palsy. Rabies caused by biting vampire bats is often of this type.

Rabies test

1. Blood, urine and cerebrospinal fluid examination

The total number of peripheral white blood cells (12-30) × 10 ⁹ / L, neutrophils generally account for more than 80%. Routine urine tests can find mild proteinuria, occasionally transparent casts, cerebrospinal fluid pressure can be slightly increased, and the cells The number is slightly increased, generally not more than 200 × 10 ⁶ / L, mainly lymphocytes, and the protein is increased to more than 2.0g / L, and sugar and chloride are normal.

2. Virus isolation

Saliva and cerebrospinal fluid are commonly used to isolate viruses, and saliva is separated at a higher rate.

3. Antigen check

Skin or brain biopsy was performed for immunofluorescence.

4. Nucleic acid determination

When the RNA was measured by PCR, the positive rate of saliva, cerebrospinal fluid, or skin tissue samples with hair follicles behind the neck was higher.

5. Animal inoculation

After the specimens were inoculated in mice, brain tissues were taken for immunofluorescence test to detect pathogens, and pathological sections were used to examine Negri bodies.

6. Antibody check

It is used to detect early IgM. On the 8th day after the disease, 50% of the serum were positive, and all were positive on the 15th. Serum neutralizing antibodies were measured on the 6th day after the illness. After the cell vaccine injection, the titer of the neutralizing antibodies can reach thousands, after vaccination, it can not exceed 1: 1000, and patients can reach 1: 10000 or more.

Rabies diagnosis

A medical history and a positive immunofluorescence test can confirm the diagnosis.

Differential diagnosis of rabies

The disease needs to be distinguished from rabies-like hysteria, tetanus, viral meningoencephalitis, and polio.

Rabies-like hysteria

Because rabies is a very scary disease, some people with rickets imagine they have it after exposure. It is characterized by a larynx tightening feeling from time to time after being bitten by an animal, drinking water is difficult and exciting, but not afraid of wind, salivation, fever and paralysis. After suggestion, persuasion, and symptomatic treatment, the patient's condition no longer develops.

Tetanus

The early symptoms of tetanus are tightly closed teeth. Later, a bitter smile and a reflexed horn bow appear, but they are not afraid of water. Tetanus-affected muscle groups maintain a high level of muscle tone during the spasm interval, but these muscle groups in rabies patients are completely relaxed during the interval.

3. Viral meningoencephalitis

There are obvious intracranial hypertension and meningeal irritation signs, obvious changes in mind, and cerebrospinal fluid examination can help identify.

4. Poliomyelitis

Paralytic polio is easily confused with paralytic rabies. The disease was bidirectional onset of fever, asymmetric flaccid paralysis of both limbs, no symptoms of water phobia, and myalgia was more pronounced.

Rabies complications

Inappropriate antidiuretic hormone secretion may occur, but also may be complicated by pneumonia, pneumothorax, mediastinum emphysema, arrhythmia, heart failure, arteriovenous embolism, superior vena cava obstruction, upper gastrointestinal bleeding, and acute renal failure.

Rabies treatment

1. Strict isolation in a single room, special care

Rest quietly in bed to prevent all sound, light, wind and other stimuli. Large veins are intubated for high-nutrition therapy. Medical staff must wear masks, gloves, and gowns. Patients' secretions, excreta and their pollutants must be strictly disinfected.

2. Actively do symptomatic treatment and prevent various complications

(1) Nervous system Those who have water-phobia should fast and drink to minimize various stimuli. Seizures can be phenytoin, diazepam and so on. Cerebral edema can be given dehydrating agents such as mannitol and furosemide, and lateral ventricle drainage can be given when it is not effective.

(2) Pituitary dysfunction: Those with too much antidiuretic hormone should limit water intake, and those with diabetes insipidus should be given intravenous fluids and use pituitary vasopressin.

(3) Respiratory system: Difficulties in inhaling the tracheostomy, cyanosis, hypoxia, atelectasis, oxygen, artificial respiration, and pneumonia, physical therapy and antibacterial drugs. For pneumothorax, perform lung retension. Take care to prevent aspiration pneumonia.

(4) Cardiovascular system Most of the cardiac rhythm disorders are supraventricular, and those who are related to hypoxemia should be given oxygen. Patients with hypotension were given vasoconstrictor and volume rehydration. People with heart failure limit water and use heart strength agents such as digoxin. Arterial or venous thrombosis can be replaced by venous intubation; if the superior vena cava is obstructed, the venous cannula should be removed. Cardiac arrest is performed by resuscitation.

(5) Other transfusions for patients with anemia, transfusion and fluid replacement for patients with gastrointestinal bleeding. People with high fever should use cold mattresses, those with low body temperature should be given blankets, and those with low or high blood volume should be adjusted in time.

Rabies prevention

1. Manage the source of infection

Vaccinate home-raised animals and manage stray animals. Animals suspected of being killed by rabies should be taken for examination of their brain tissue and burned or buried deep. They must not be peeled or eaten.

2. Correct wound management

After being bitten or scratched by an animal, the wound should be repeatedly washed with 20% soapy water immediately. Those with deeper wounds need to be inserted with a catheter, and the soapy water is continuously perfused and washed to remove dog saliva and squeeze out blood. Generally, wounds are not sutured, antibacterial drugs are used when necessary, and tetanus antitoxin is used when the wound is deep.

3. Vaccination against rabies

Vaccination is of certain value in preventing disease, including active and passive immunization. Once a person is bitten, vaccination is critical, and severe cases require rabies serum.

(1) Active immunization Immunization is usually performed after the exposure on the bite 0 days (day 1, day), 3 days (day 4, and so on), 7 days, 14 days, and 28 days. Of 5 stitches. Adult and child doses are the same. Severe bites (head, face, neck, fingers, multiple site bites, or bites licking the mucosa), in addition to the rabies vaccine given above, should be doubled on days 0 and 3. Pre- exposure vaccination For healthy people who have not been bitten, rabies vaccine can be administered by 0, 7, 28 days, three injections, one year later, and then every other 1-3 years.

(2) Passive immune trauma is deep, severe, or occurs on the head, face, neck, hands, etc. At the same time, bites of humans have the possibility of rabies, you should immediately inject rabies serum, which contains high titer anti-rabies immune spheres Protein, which can directly neutralize rabies virus, should be applied as soon as possible and used immediately after injury, and it is almost ineffective after one week of injury.