Rabies Lecture

2021-01-31 12:00 AM

Human immunity is only obtained after a full dose of vaccination. Neutralizing antibodies persist in water for 3 months. If the second injection is repeated, the antibody can last for many years.

Define

Rabies is an acute infectious disease caused by rabies virus, disease mainly in warm-blooded animals (dogs, cats ...) transmitted to humans through the skin and mucous membranes.

The main clinical manifestation of the disease is psychomotor stimulation or a Landry-type paralysis syndrome. When sick, death is 100%.

Research history

Rabies is known from the 23rd century BC. In 1885 Pasteur researched to create immunity against rabies. It was not until 1903 that rabies was clinically clearly described by Adechi Negri. Through the fluorescence antibody test, rabies pathology was known in 1958.

Epidemiology

According to the World Health Organization, every year, the world, 100,000 people die from rabies, mainly in Africa and Asia. Approximately 4 million people require rabies exposure treatment each year.

In 1996, there were 32,209 people globally with rabies (according to WHO).

High-risk epidemiological areas are countries such as Afghanistan, Bangladesh, Brazil, Bolivia, China, Colombia, Ecuador, El Salvador, Guatemala, Haiti, India, Indonesia, Mexico, Myanmar (Burma), Nepal, Pakistan, Peru, Philippines, Sri Lanka, Thailand, Vietnam, Yemen.

Pathogens

A rabies virus, belonging to the family Rhabdovirus, has an RNA structure and has an outer shell.

Pasteur divides wild viruses into two categories:

Street rabies virus: Has a strong virulence, causing rabies in animals and humans.

Fixed rabies virus: A rabies virus that is cultured and adapted in the laboratory, has reduced, loses its virulence and does not cause rabies. Used to make the vaccine because it has the same antigen as the street rabies virus.

Resistance:

Has poor resistance: Inactivated quickly by soap, Ether, iodine, at 60 0 C die in 5 minutes, at 100 0 C die in 1 minute.

However, at room temperature: the virus can survive for 1-2 weeks. Therefore, objects contaminated with rabies' saliva are considered dangerous.

Inoculum

As wild animals such as wolves, weasels, foxes, civets, raccoons ... and vampire bats that suck blood from South America.

Are rabid cattle: The most common are dogs, cats and possibly donkeys, horses, cows, sheep, pigs ...

Infection

Skin and mucous membranes: The rabies virus contained in the saliva of rabid animals never passes through healthy skin, but the rabies virus is spread from animal to animal and to person through damaged skin and mucous membranes (though very small) by being bitten, scratched, licked by a rabid animal or when rabed by an animal. It is very rare to get rabies through intermediate objects contaminated with rabies saliva, rabies ... but on the healed there is already wound ...

Inhalation through inhalation of rabies-contaminated air: in South America, when people enter caves, there are bats carrying rabies virus.

In addition, there are some patients with rabies due to corneal transplantation of people with rabies. In animals that can cross the placenta or breast milk, there is no evidence of this transmission in humans.

Sense of the body

Pathogenicity: All warm-blooded animals such as humans, animals, and wild animals (especially predators) can get rabies.

It is not known if there is natural immunity in humans and animals, but some species of bats in South America carry the benign but infectious rabies virus.

After the onset of illness in people 100% die.

Human immunity is only obtained after a full dose of vaccination. Neutralizing antibodies persist in water for 3 months. If the second injection is repeated, the antibody can last for many years.

Mechanism of pathogenesis and pathology

Mechanism of pathogenesis

Penetrates into the body through the wound (due to being bitten, scratched, licked), the virus proliferates in muscle cells, along the peripheral nerve pathways to the brain, causing damage to central nerve cells, especially in the region. Amon horn, brain onion. Then from here the virus also travels through the nerve pathways to the salivary gland and spreads across the nervous system. The virus is present in saliva, urine, cerebrospinal fluid, concentrated in the brain. The virus is present in the saliva of a rabid dog 10 days before the onset of illness.

The clinical picture is inflammation of the brain (encephalitis) caused by the rabies virus. The time from when the virus invades until onset depends on the location, number and nature of the bite and on the patient's resistance.

Pathological anatomical injury 

The main organ of damage in rabies is the brain and spinal cord. With local inflammatory encephalopathy, both gray matter and white matter are damaged. Common brain areas are: Amon horn, cerebral cortex, brain.

Microscopic injury: Like other neurotropic viruses, the inflammatory brain caused by the rabies virus has white blood cell infiltrates, phagocytosis and perivascular inflammation. But the particular lesion of rabies is the Negri corpuscles located in the cytoplasm of brain cells (Anoon horn, medulla). Negri corpuscles are the cell responses around the rabies virus, which are round or oval microbes with a pink color when stained with Giêmsa, found in 80% of cases of rabies.

Clinical

Divide the clinical form

Aggressive or spastic form: Manifestation is a predominant psychomotor stimulation.

Paralysis: less common than the above. Common in people bitten by rabies who have been vaccinated but late. Usually there is no fear of water or wind.

Clinical symptoms

The incubation periods

From 10 days to over 1 year. Average from 20 days to 60 days. If the number of bites is large, deep and the bite site is close to the central nervous system and rich in the neural network (head, face, neck, hands), the incubation period will be short.

Before the onset of illness, there may be aura: Anxiety, mood changes, an itchy, painful sensation at the site of the bite.

Full-blown period

There are 2 following diseases:

Aggressive or spastic form: Manifestation is a predominant psychomotor stimulation.

At times, the patient becomes violent, insane, quarrels, and quickly goes into a coma and dies.

At times, in the state of motor stimulation is mainly with manifestations: spasticity, tremor of limbs, convulsions, spasm of the throat and trachea causing hydrophobia. Thirst, not daring to drink, just seeing or hearing the sound of running water also causes increased throat spasm and pain. This spasm increases when there are even very small stimuli to the senses such as: light wind (fear of wind), taste, light, etc. Facial expression is always tense, panic, eyes bright and red, hearing ears, possibly a state of arousal (signs of sail, spontaneous ejaculation). There may be hallucinations, disorientation, fighting, struggling, and tearing. Increased fever, sweating, increased secretion of phlegm (spitting, foamy mouth), cardiovascular and respiratory disturbances.

All of the above symptoms appear in bouts, getting thicker and stronger. The patient may experience alertness between attacks. Symptoms worsen and average death after 3 to 5 days due to respiratory arrest and cardiac arrest.

Paralysis: Less common than the above. Common in people bitten by rabies who have been vaccinated but late. Usually there is no fear of water or wind.

At first, there may be pain in many areas of the spine, then appear Landry-type paralysis syndrome: First, lower limb paralysis, then sphincter disorder, then upper limb paralysis. When damage to the brain, cranial nerve paralysis appears, respiratory arrest and circulation. Death after 4 to 12 days.

Test:

Leukocytes usually increase, multiple nuclei increase. The urine contains proteins and white blood cells. Cerebrospinal fluid manifests itself as viral encephalitis-meningitis (slightly increased protein, white blood cells)

Determining the rabies virus from the following specimens: Tears, saliva, cerebrospinal fluid, brain and skin biopsy fragments by immunofluorescence method. Reply results after 2 hours. Isolation of the rabies virus from the above specimens by cell culture method. Reply in 24 hours. In fact, both of the above methods are less applicable and difficult to implement.

If patient dies: Look for Negri corpuscle in brain in Amon horny region and nonspecific encephalitis lesions by electron microscope.

Implementing the quadrants

Based on the following factors:

Having a history of being bitten, scratched, licked or eaten by animals (dogs, cats ...) such as: Dogs, cats suddenly became aggressive for no reason, ripped apart, biting many people or changing personality traits such as tickling, moody, lying in the dark.

Clinical symptoms of rabies: Note that in children often bitten in the face, the incubation period is usually short (9-12 days). Clinically presents very few contractions, so there may be no signs of fear of water. The child is still calm, only uncomfortable, gagging, dizzy, sad, may have a short stimulus period. Cardiovascular collapse and death.

Testing: Determining rabies virus from specimens: Tears, saliva, cerebrospinal fluid, brain biopsy piece. Isolation of the rabies virus from the above specimens by cell culture method.

Differential diagnosis

Aggressive forms must have a differential diagnosis

Acute alcohol poisoning: Also, suddenly mad with many hallucinations. But the difference is that there is no throat spasm, no breathing disorder. The madness was constant, not the same as rabies. Have a history of alcoholism. There is no history of being a dog or a cat.

Acute psychosis: Also provokes smashing, constantly screaming, but no history of dog bites ... If bitten by a dog, it is difficult to distinguish, must try treatment and monitor progress to distinguish.

Spasticity with hydrophobia requires differential diagnosis

Encephalitis caused by other viruses: No history of being bitten or scratched by a dog or cat.

Tetanus can be afraid of water: There is the first sign of stiffness in the jaw before the throat spasm appears. Continuous whole muscle contraction. Not temporary like rabies.

The thought of having rabies after being bitten by dogs is common in people with excessive fear. The patient is also afraid of water but not wind. Sedation may be lessened. Sometimes it takes a while to get to know them.

Polio needs a differential diagnosis

Polio in children: Headaches often have high fever, respiratory tract inflammation. Gastrointestinal disturbances and muscle pain. When paralysis appears, it has the following properties: There is no certain order, paralysis, asymmetry, often paralyzed at the base of the limb - no history of being bitten by a dog or scratched by a cat.

Inflammation of the encephalitis, spinal cord, polyvalent and neuralgia after vaccination, made from the nervous organization of adult animals (sheep, goats ...). Occurrence of paralysis 1 to 4 weeks after the first injection. Corticoid treatment has hope to cure it.

Landry's myelitis is caused by other causes.

Symptoms

Respiratory

Difficulty breathing, asphyxiation due to lack of oxygen, spasm.

Pneumonia, bronchitis, pneumothorax.

Cyclic

Cardiac arrhythmia, supraventricular tachycardia, atrioventricular block.

Lower blood pressure, acute pulmonary edema, heart failure.

Nerve

Increased intracranial pressure due to cerebral edema.

Treatment

Currently, there is no medicine that can save lives when a patient has a rabies attack. Symptomatic treatment only: sedation, cardiovascular and respiratory support, keep in a quiet, separate place.

Prevention

General prevention

Control rabid animals. Compulsory rabies vaccination for livestock, especially dogs and cats.

Avoid contact with animals of unknown origin, not to be bitten, vaccinate immediately when in doubt, follow up with animals suspected of being bitten for 10 days.

Rabies vaccination for some people who have a lot of contact with animals such as: Veterinary medicine, livestock husbandry (dogs, cats ...), professional, etc. ...

Rabies is considered a very dangerous disease, so when taking care of the patient, it is necessary to wear full equipment (hat, net, clothes, gloves, boots), wash hands and soap thoroughly after taking care and then disinfect with alcohol. Ether.

Objects (cloth, patient's own tools ...) need to be burned. Iron items, beds, wardrobes, floors ... need to be cleaned with soap and spray disinfectant.

Specific   

Spot the wound after being bitten by an animal

After being bitten or scratched by animals (dogs, cats ...), wash and rinse the wound thoroughly with soapy water; Then rinse the wound with filtered water and dry, disinfect the wound with available drugs such as alcohol, iodine, Ether ... Avoid premature stitches except for facial wounds. Tetanus shots and antibiotics can be given.

Serum anti-rabies

Only for severe bites: such as a wide, deep, multiple bites, bitten on the head, face, neck, or hands by an animal with a rabid expression.

Request:

Injections as soon as possible after being bitten are effective.

Inject before vaccination.

How to inject:

There are 2 types of rabies serums:

The anti-rabies serum is different from the highly immunogenic horse strain. Single injection of 40 UI / kg heavy. Can be injected around the bite.

To avoid anaphylaxis can be injected by the Besredka method and using synthetic antihistamines and only injected in rabies centers.

Immune globulin, co-strain, specific against rabies. Intramuscular injection, the buttock position is a single dose of 20 UI / kg weight. Advantages: No complications, good tolerance, but the downside is high drug prices.

Get vaccinated

Point:

When licked, wound on the skin, was scratched, bitten by an animal with rabies or suspected of having been rabed for which the animal was killed (without testing to confirm rabies), or has escaped or been bitten by a wild animal.

When bitten by seemingly healthy animals, the animal should be monitored for 10 days. If you see any signs of illness or change in personality, need to inject immediately. If still healthy, no need to inject.

Some vaccines and injections:

The classic Pasteur vaccine: is made from a fixed virus, cultured in the nervous system of an adult animal that has been reduced to toxicity (such as Fermi or Hemip vaccines) or has been killed (Semple vaccine). This type requires multiple injections and has a nerve accident, so it is rarely used today.

Fuenzalida vaccine: Prepared from fixed virus implanted in the brain of newborn mice inactivated by b Propiolactone. 6 injections in the skin every day with a dose of 0.2 ml / nose for adults and 0.1 ml / 1 nose for children. This is a Vietnamese vaccine. This vaccine can cause a stroke:

Allergies: At the injection site: Lumpy, halo, itchy. Body as a whole: Fever, rash. Treatment with antihistamines.

Neurological complications: Neuritis, inflammation of multiple roots and nerves, myelitis, encephalitis. This type of accident is severe but uncommon; Corticoid treatment.

Vaccine of Merieux Institute (France): is made from virus transplanted on human diploid cells (very safe injection) inactivated by b Propiolactone. Each injection: 1ml, subcutaneously (not intramuscularly). How to inject:

In case of mild and moderate bites: 5 shots in (N): N0, N3, N7, N14, N30 or N0 2 shots (morning-afternoon), N7, N21 (4 shorter shots).

During severe bites: N0 injected with the rabies-resistant serum, then vaccinated N0, N3, N7, N14 and N30; or N0x2, N7, N21.

Pasteur Institute vaccine (France): is made from fixed virus implanted on kidney cells of bovine fetuses, inactivated by b Propiolactone, injected very safely. Each 2 ml injection under the skin (not intramuscularly). Date of injection: Same as Merieux vaccine.