Pediatric Rabies

Introduction to Pediatric Rabies Rabies is a zoonotic acute infectious disease caused by rabies virus. Because rabies patients have a prominent clinical manifestation of fear of drinking water, this disease has also been called "hydrophobia", but Diseased animals do not have this characteristic. The main clinical manifestations are peculiar arrogance, fear and anxiety, fear of wind and water, drooling and pharyngeal muscle spasm, and eventually paralysis and life-threatening. basic knowledge Sickness ratio: 0.0012% Susceptible people: children Mode of infection: non-infectious Complications: hypertension, hypotension, arrhythmia, hypothermia, congestive heart failure, thrombosis

Causes of childhood rabies

Rabies virus (25%):

It belongs to rhabdoviridae, lyssavirus, virus-like bullet, 75-80 nm in diameter, 175-200 nm in length, inner core is core shell, contains 40 nm core, and outer layer is dense envelope. There are many filamentous protrusions on the surface, the distal end of the protrusion is braided, the whole virus has a honeycomb-like hexagonal structure, the genome of the virus is a negative-strand single-stranded RNA, the molecular weight is 4.6×106, and the viral genome is 11932 nucleosides. Acid, of which about 91% of nucleotides are involved in encoding five known structural proteins, namely glycoprotein (GP), envelope matrix protein (M2P), matrix matrix protein (M1P), nuclear protein (NP) and transcription Enzyme protein (LP), genomic RNA and 180 NP molecules bind to ribose nucleoprotein (RNP), which protects RNA from degradation and provides a suitable structure for genome replication and transcription. Basis, M2P is the smallest structural protein of rabies virus (molecular weight is only 25×103), it can connect the outer membrane of the virus and the GP and nucleocapsid on the membrane. GP is a typical transmembrane glycoprotein that can bind to acetylcholine receptor. Make the virus neurotoxic, while Inducing neutralizing antibodies and stimulating cellular immunity in the host, and protecting against rabies virus attack. NP is a group-specific antigen of rabies virus, which can make the body produce complement-binding antibody. NP-induced anti-rabies virus protection is caused by The interaction of various cytokines (such as antibodies, mononuclear factors and lymphocytes) is also involved; it can also promote neutralizing antibodies, and rabies virus GP and NP may also induce interferon production in the body.

Rabies virus nucleocapsid protein (25%):

Monoclonal antibodies can classify rabies virus and its related viruses into five serotypes: type 1 - typical rabies challenge virus standard (CVS); type 2 - lagos bat rabies virus (logosbat virus); Type 3 - Mokola virus; type 4 - Duvenhage virus; type 5 - including European bat rabies virus: EBL1 and EBL2, genotyping can be divided into six types: gene 1, Types 2, 3, and 4 correspond to serum types 1, 2, 3, and 4, respectively, and types 5 and 6 are EB1 and EB2 of serum type 5, and types 2, 3, 4, and 2 of serum 2, 3. Types 4, 5, and 6 are also known as rabies-associated viruses, and the wild distribution is mainly type 2, 3, and 4.

Other (30%):

The virus can be inoculated into chicken embryos, rat brain, and cultured in hamster kidney cells and diploid cells. The virus isolated from humans and animals is a wild strain that exists in nature, and is also a disease of human or animal. The pathogen, called "street virus", is characterized by strong virulence and long incubation period (inoculation for 15 to 30 days in the brain), which can be propagated in the parotid gland, and can cause disease after infection in various ways. After the street virus is continuously passaged in the animal brain (more than 50 generations), the virulence is reduced, the incubation period is shortened, and it is fixed for 3 to 6 days. It loses pathogenicity to humans and dogs, does not invade saliva, and does not form an inner matrix. As a "fixed virus", although the fixed virus has attenuated mutation, it still retains its main antigenicity and can be used for the preparation of live attenuated rabies vaccine for vaccination.

The rabies virus is easily inactivated by ultraviolet light, formaldehyde, 50% to 70% ethanol, mercury chloride and quaternary amine compounds such as benzalkonium bromide. The suspension loses its vitality after 56 ° C for 30-60 min or 100 ° C for 2 min. It is not easy to be killed by phenol and cresol soap solution. It can be stored for several years under lyophilization. The infected tissue can be stored in 50% glycerol for inspection.

Pathogenesis

Rabies virus has a strong affinity for nerve tissue, mainly through nerve retrograde, centripetal to the central transmission, generally does not enter the blood.

The pathogenesis of rabies can be divided into the following three stages:

1. Extraneural small-volume breeding virus After invading the skin or mucosa from the bite site, it firstly multiplies in the striated muscle cells of the local wound, and binds to the acetylcholine receptor of the neuromuscular junction to invade the nearby peripheral nerve from the local wound. Until the invasion of the peripheral nerve is not shorter than 72h.

2. Invasion of the central nervous system from the peripheral nerve The virus spreads to the heart along the axis of the peripheral nerve at a rate of about 5 cm/d. After reaching the dorsal root ganglion, it begins to multiply and then invade the spinal cord and then spread throughout the central nervous system. It mainly invades neurons in the brain stem and cerebellum, but it can also terminate in a certain part during the process of diffusion, forming a special clinical manifestation.

3. From the central nervous system to the various organs during the diffusion period, the virus spreads eccentrically from the central nervous system to the peripheral nerves, invading various tissues and organs, especially the parotid gland, tongue taste buds, olfactory nerve epithelium and other viruses, due to the vagus nerve nucleus, Damage to the swallowed nerve nucleus and hypoglossal nucleus can occur in respiratory muscles and swallowing tendons. Clinically, patients develop symptoms such as water-induced fear, difficulty breathing, and difficulty swallowing. Sympathetic nerves are stimulated to increase salivation and sweating; vagus nerve Section, sympathetic ganglia and damage to the heart ganglion can cause cardiovascular system dysfunction and even sudden death.

At present, it is believed that the local presence of the virus is not the only factor that causes the difference in clinical manifestations. The humoral immunity and cell-mediated immunity have a protective effect in the early stage. However, when the virus enters a large number of nerve cells, the immune-mediated damage and the onset also have a certain relationship. The immunosuppressed mice were delayed after vaccination with rabies virus. After passive input of immune serum or immune cells, the death accelerated. In human rabies, the lymphocytes positive for rabies virus cell proliferation were mostly arrogant, and the death was faster. Myelin basic protein (MBP) has an autoimmune response and is also a manic type, and the disease progresses rapidly. Immunological damage mediated by antibodies, complement and cytotoxic T cells can be seen in the brain tissue.

Pediatric rabies prevention

1. Control and eliminate the source of infection

Strengthen the management of dogs, wild dogs should try to kill, dogs should be registered, vaccination, rabies should be immediately killed, burned or buried, can not be peeled, can not be sure of rabies for a while, should be observed for 10 days, take killing or death in isolation Animal brain tissue is examined for pathogens.

2. Vaccination

It is one of the important measures to prevent and control rabies.

(1) Rabies virus vaccine: Currently, cell culture vaccines are mainly used, including:

A human diploid cell (HDCV) vaccine has strong immunogenicity, few adverse reactions, and few injections, but it is difficult to prepare and expensive.

2 primary hamster kidney cell rabies vaccine: efficacy is above 2.5U, safe to use.

3 Refined Vero rabies vaccine: immunogenicity and adverse reactions similar to 1, but low prices, other refined chicken embryo rabies vaccine, refined duck embryo rabies vaccine and primary bovine kidney cell rabies vaccine.

(2) Immunization before exposure: those who are at occupational risk, those who are exposed to rabies virus and those who are in close contact with rabies patients, recommend 2 and 28 days, 0, 7, 28 or 0, 28, A 56-day 3-dose vaccination regimen, 1.0 ml intramuscular or subcutaneous injection, or 0.1 ml intradermal injection.

(3) Immunization after exposure: WHO recommended standard immunization program (HDCV vaccine) for intramuscular injection of 1 ml on days 0, 3, 7, 14 and 28, and once again on day 90, adjuvant hamster kidney cell vaccine recommendation The 2-1-1 procedure was used, that is, intramuscular injection of 2 doses (2 ml), and intramuscular injection of 1 ml on the 7th day and the 21st day. The injection site was taken by the adult deltoid muscle, and the child was injected into the anterior and lateral part of the leg. It should not be inoculated into the arm.

3. Injection of immune serum

WHO recommends that human rabies immunoglobulin (HRIG) be injected at the same time as vaccination at a dose of 20 U/kg (horse rabies immunoglobulin dose of 40 U/kg), first skin test, negative one intramuscular or half dose in wound Infiltration around the injection, the other half of the intramuscular injection, skin test positive need to desensitize treatment (0.05ml diluted 20 times, 0.05ml diluted 10 times, 0.1ml, 0.2ml, 0.5ml, undiluted antiserum, subcutaneous injection, each After 15 minutes of observation, it can be injected.

Pediatric rabies complications Complications hypertension hypotension arrhythmia hypothermia congestive heart failure thrombosis

The main complications are increased intracranial pressure, hypothalamic involvement caused by excessive or too little antidiuretic hormone secretion (causing diabetes insipidus), autonomic dysfunction caused by hypertension, hypotension, arrhythmia (ventricular supraventricular tachycardia, Bradycardia, or even arrest) or hypothermia, common sputum, may be systemic or focal, respiratory dysfunction, such as hyperventilation and respiratory alkalosis are common in the prodromal and acute phases, and later occur Hypoxia, reported complications include congestive heart failure, acute renal failure, superior vena cava thrombosis, secondary infection of the lung or urinary system, and gastrointestinal bleeding.

Pediatric rabies symptoms common symptoms fatigue radiation pain low fever sore throat sputum water fear abdominal pain heart rate increase circulatory failure dyspnea

The incubation period varies from 4 days to 19 years, and most of them are within 1 year. The factors affecting the incubation period are age (small children), wound site (early onset of head and face), nature of wound (short bite) and The number of invading viruses, virulence and host defense mechanisms, etc., can be divided into three phases.

1. Prodromal period: 1 to 4 days, often with low fever, headache, fatigue, sore throat, abdominal pain, irritability, etc., followed by glare, high sound and other sensitization and throat sensation, mild throat phlegm when eating However, it can still be swallowed, and about 80% of patients have radioactive pain, numbness, itching and paresthesia on the wound and its nerve pathway.

2. Excitatory period: Reflective throat sputum gradually worsens. Whenever you drink water, you even hear water, see water and pharyngeal movements, or wind, light, sound, and smoke stimuli can cause severe paralysis of the throat. Hydrophobia, often accompanied by respiratory muscle spasm, difficulty in breathing, high muscle tension, strong neck, often alternating mania and lethargy, violent abnormalities during seizures; seizures are quieter, clear language, due to sympathetic hyperactivity There are sweating, increased heart rate, increased blood pressure, enlarged pupils, increased salivary secretion, etc., patients can have high fever 39 ~ 40 ° C, most of the mind is clear, some patients have mental disorders, can die of respiratory failure or circulation in the attack Depletion, this period lasts about 1-3 days.

3. Paralysis period: When the sputum is reduced or stopped, the patient becomes quieter and gradually becomes flaccid paralysis, especially in the soft palate of the limbs. The feeling is diminished, the reflex disappears, the breathing becomes slow and uneven, the heart beats weakly, the blood pressure drops, and the mind Unclear, and eventually died of respiratory paralysis and circulatory failure, this period lasts about 6 to 18 hours.

The whole course of rabies is 3 to 5 days, rarely more than 10 days. Very few cases of "paralysis" are found. The latter is characterized by high fever and progressive paralysis, and eventually died of exhaustion. The whole course of disease is about 8 to 9 days.

Pediatric rabies examination

1. Blood, urine and cerebrospinal fluid

The total number of white blood cells varies from (12 ~ 30) × 109 / L, the percentage of neutrophils is mostly above 80%, the percentage of large mononuclear cells can also be increased, urine protein routine examination can often find mild proteinuria, occasionally transparent tube Type, the pressure of cerebrospinal fluid is in the normal range or slightly increased, the protein is slightly increased, the number of cells is slightly increased, but rarely exceeds 200 × 106 / L, mainly lymphocytes.

2. Immunological test

(1) Determination of serum neutralizing antibody or fluorescent antibody: It has diagnostic value for uninjected vaccine, anti-rabies serum or immunoglobulin. The disadvantage is that it is difficult to detect before the 8th day of the disease, and the patient who has been vaccinated, such as When the antibody titer exceeds 1:5000, it is still valuable for the diagnosis of rabies. Because the vaccine is only low in antibody titer, ELISA is also used for antibody detection.

(2) Detection of rabies virus antigen: using fluorescent antibody to examine brain tissue smear, corneal print, frozen virus skin antigen, positive results can be obtained before onset, the method is simple, can be completed within a few hours, and with mice The intracerebral vaccination method has a high coincidence rate, so it is a kind of experiment with a large practical value. In an experienced laboratory, the reliability of the immunofluorescence test can reach more than 95%. Recently, it has been adopted. Rapid rabies enzyme immunological diagnosis (RREID) can be used to detect rabies virus antigen in brain tissue, which can be determined by visual observation or microplate reader. For example, the positive reaction shows orange color, and the negative reaction is negative. Colorless, very fast and easy.

3. Virus separation

Although the virus can be isolated from the brain tissue, spinal cord, parotid gland, lacrimal gland, muscle, lung, kidney, adrenal gland, pancreas and other organs and tissues, but the chances are not much, it is more difficult to isolate the virus from cerebrospinal fluid and saliva; The longer the patient's survival time, the more difficult it is to isolate the virus. The isolated virus can be inoculated with tissue culture or animal, and the virus can be isolated and identified by neutralization test.

4. Brain tissue animal inoculation and examination

After the death, the animals were inoculated into the brain of the mouse by making the brain tissue of the deceased into a 10% suspension (the 2 to 3 weeks old suckling mice are more sensitive than the adult rats), and the positive mice are 6-8. Within a day, tremors, vertical hair, strong tail, paralysis and other phenomena, died within 10 to 15 days due to failure, and the nematode can be found in the brain tissue sections of dead mice.

5. Reverse transcription polymerase chain reaction (RT-PCR) for detection of rabies virus nucleic acid

In order to detect most rabies virus and rabies-associated virus, the most conserved region of the rabies virus nucleoprotein gene (N) can be selected to design primers: N1( )(587)5'-TTTTGAGACTGCTCCTTTTTG-3'(605), N2(- (1029) 5'-CCCATATAGCATCCTAC-3' (1013), take brain tissue or virus-infected cells, first obtain viral RNA, N1 primers for cDNA synthesis, and then carry out PCR reaction, agarose gel electrophoresis detection results.

The brain tissue of the deceased brain tissue or the bite of the human animal was used for pathological sectioning or tableting, and the Neisseria was examined by Seller staining and direct immunofluorescence, and the positive rate was up to 70%.

Routine X-ray, B-ultrasound, electrocardiogram, brain CT examination should be done routinely.

Diagnosis and diagnosis of rabies in children

diagnosis

In the case of an episode, the diagnosis may be preliminarily established according to the past history of rabies or suspected rabies or cats, wolves, foxes, etc. If you can understand the condition of the bite and the health of the animal, then Diagnosis of this disease is more valuable. If you are not sure whether the biting dog or cat is suffering from rabies, the animal should be kept in a cage. If the animal does not develop within 7 to 10 days, the animal can generally be excluded from rabies. The clinical symptoms such as excitement, arrogance, fear of water, fear of the wind, throat muscle spasm, a large number of sputum, sputum, etc., can make a clinical diagnosis of rabies, especially for those with obvious symptoms, whether there is "three fears" (fear of water, Light, wind) phenomenon, if necessary, using fan wind, pouring water and lighting test, madness symptoms are not obvious should pay attention to pharyngeal muscle edema and hair erection phenomenon, such as prenatal immunological antigen, antibody detection positive, post-mortem brain tissue animal inoculation and The discovery of the Neissular body in the cytoplasm of neurons can be confirmed.

Differential diagnosis

In some cases, the history of bite is not clear, and it is often misdiagnosed as neurosis in the early stage. After the onset, the symptoms are atypical, sometimes misdiagnosed as mental illness, tetanus, viral meningitis and leptospirosis, and quiet limb paralysis. Cases can be misdiagnosed as polio or Guillain-Barré syndrome. The latent period of tetanus patients is shorter, mostly 6 to 14 days. Common symptoms are closed jaws, bitter smile, and systemic muscle spasm lasts for a long time. There is a horned arch reversal, and rabies muscle spasm is intermittent, mainly in the pharyngeal muscle, tetanus patients are not highly excited and fear of water, active treatment can be cured.

Severe changes in consciousness (coma, etc.), meningeal irritation, cerebrospinal fluid changes and clinical outcomes may contribute to the identification of neurological diseases such as viral meningitis, immunological antigens, antibody detection, and virus isolation.

Rabies should be differentiated from rabies-like snoring (pseudorabies), which has a history of dogs and is often identified as a history of rabid bites or contact with diseased animals. Similar rabies occurs in hours or days. Symptoms, such as throat tightness, drinking water, mental excitement and other symptoms, but no fever, no drooling, not afraid of the wind, or showing drinking water, can not cause throat muscle spasm, such patients are suggested, persuaded, symptomatic treatment, It will soon return to health.

In addition, after Semple vaccination, complications involving the central nervous system may occur, which should be differentiated from rabies. The incubation period for patients with concurrent myelitis is 1 to 3 weeks after the start of the injection, and the shortest 6 days from the first injection. The longest person is 52 days. The clinical manifestation is sudden fever during the inoculation with ascending paralysis or incomplete transverse spinal cord disease. There are paraplegia and sphincter incontinence. If the diffuse meningitis is complicated, the onset is 5-8. Week, the clinical symptoms are headache, fever, viral infection, and myelitis. Both of the above complications are easily confused with paralytic rabies. The presence of neutralizing antibodies in cerebrospinal fluid is conducive to the diagnosis of rabies, dynamic observation during the course of disease, and The judgment of the efficacy of adrenocortical hormones is helpful for clinical identification. The death cases must rely on animal vaccination to make a diagnosis based on the presence or absence of the inner corpuscle and viral antigen.

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