Basic cause
Humans usually contract rabies after being bitten or scratched by rabies-infected animals (dogs, cats, etc.), and 99% of confirmed cases of rabies are transmitted from rabid dogs to humans. About 50% of wounding animals are domesticated, most of which have not been vaccinated against animal rabies, and stray animals account for about 25% of the total wounding animals.
When the virus initially enters the wound, it does not enter the bloodstream (rabies virus is usually undetectable in the blood), but replicates in the bitten muscle tissue and then invades the peripheral nervous system through the endplates and axons of motor neurons. Animal experiments have found that the rabies virus spreads rapidly from the spinal cord to the brain, and once it invades the brain, it proliferates rapidly. The brainstem is the first to be affected and the most heavily infected area.
Symptoms
There are no symptoms during the incubation period of rabies. Immediate post-exposure treatment is the only effective means of prevention after high-risk animals are exposed. The initial symptom of rabies is fever, and there is often pain at the wound site or abnormal, unexplained trembling, stinging or burning sensation. As the virus spreads in the central nervous system, the patient presents typical clinical symptoms of rabies, namely the manic type and the paralyzed type, and eventually dies of asphyxia or respiratory and circulatory failure due to spasm of the pharyngeal muscles.
Early symptoms
The early symptoms of rabies should refer to the clinical manifestations in the two stages of "latency period" and "prodromal period". During the incubation period of rabies (mostly 1-3 months) there is no sign, and in the prodromal period (usually 2-4 days), it usually starts with atypical symptoms such as anorexia, fatigue, headache, fever, etc. In addition, unreasonable fear, Anxiety, agitation, irritability, insomnia, depression and other manifestations.
Typical Symptoms
Incubation period symptoms
The asymptomatic period from infection to onset is mostly 1 to 3 months, and rarely within 1 week or more than 1 year. The incubation period of rabies is asymptomatic and there is currently no reliable diagnostic method during this period.
Prodromal symptoms
The onset of rabies patients usually begins with atypical symptoms such as discomfort, anorexia, fatigue, headache and fever, and 50% to 80% of patients will have specific neuropathic pain or paresthesia (such as itching, numbness and ant crawling) at the original exposure site. Infection, etc.), may be due to virus replication in the dorsal root ganglia or cause ganglion neuritis. Symptoms such as unprovoked fear, anxiety, agitation, irritability, nervousness, insomnia, or depression may also occur during this period. The prodromal period is 2 to 10 days (usually 2 to 4 days).
Acute neurological symptoms
Patients develop typical clinical symptoms of rabies, which generally last for 1 to 3 days. There are two manifestations, namely the manic type and the paralytic type.
Manic patient
Fever occurs accompanied by obvious neurological signs, including hyperactivity, disorientation, hallucinations, seizures, strange behavior, and neck stiffness. Its prominent manifestations are extreme fear, fear of water, fear of wind, paroxysmal pharyngeal muscle spasm, dyspnea, difficulty urinating and defecating, and excessive sweating and salivation.
Fear of water and wind are special typical symptoms of this disease. When a typical patient sees water, hears the sound of running water, drinks water, or just mentions drinking water, it can cause severe pharyngeal muscle spasm. Although the patient is extremely thirsty, he does not dare to drink, even after drinking, he cannot swallow, and is often accompanied by hoarseness and dehydration.
Bright light, noise, touch, or drafts may also trigger spasms, which can be painful convulsions all over the body in severe attacks. Dyspnea and cyanosis may result due to frequent spasms of the respiratory muscles.
Paralytic patients
There is no typical excited period and hydrophobia, but it starts with high fever, headache, vomiting, and pain at the bite site, followed by limb weakness, abdominal distension, ataxia, muscle paralysis, and incontinence, showing transverse myelitis or rising Guillain-Barré syndrome (GBS)-like manifestations such as spinal cord palsy. The lesions are limited to the spinal cord and medulla oblongata without involving the brainstem or higher central nervous system.
Symptoms of paralysis
In the late stage, the patient gradually enters a quiet state. At this time, the spasm stops, the patient gradually becomes quiet, and flaccid paralysis occurs, especially the limb flaccidity is the most common. Paralysis may be symmetrical or asymmetrical, being more severe on the side of the bitten limb. Eye muscles, facial muscles, and masticatory muscles can also be affected, manifested as strabismus, eye movement disorders, jaw drop, inability to close the mouth, and lack of facial expression.
Furthermore, the patient's breathing gradually becomes weak or irregular, and tidal breathing may occur; pulse breakdown, blood pressure drop, reflex loss, and mydriasis. Patients often enter a coma before dying, and respiratory arrest usually occurs shortly after coma. This session lasts 6-18 hours.
The whole natural course of rabies after onset is generally 7-10 days. The cause of death is usually suffocation or respiratory and circulatory failure due to spasm of the pharyngeal muscles.
Accompanying symptoms
Other abnormalities include fasciculations (particularly near exposed sites), hyperventilation, hypersalivation, localized or generalized spasms, and, less commonly, symptoms including priapism or increased libido, which are associated with autonomic related to dysfunction.
Seek medical attention
Clinically, it is impossible to quickly identify whether the injured animal is carrying the virus. It can only be comprehensively evaluated based on the results of local epidemiological investigations and whether it has been licked or bitten by dogs, cats, bats or other host animals. Therefore, when rabies exposure occurs, it is bitten, scratched, licked at the mucous membrane or damaged skin by a rabies, a suspected rabies host animal (dog, cat, bat, etc.), or an open When wounds and mucous membranes are in direct contact with saliva that may contain rabies virus, seek medical attention as soon as possible.
Treatment:
Once rabies attacks, there is no effective clinical treatment. In the "Treatment" section, the treatment measures after exposure to rabies are introduced, and this section is to a certain extent post-exposure prophylaxis. Pre-exposure precautions will be highlighted in the "Prevention" section.
After exposure to rabies, the focus should be on timely implementation of post-exposure treatment, including wound treatment and vaccination. For class III exposures, it is very important to inject passive immunization preparations (anti-rabies serum, immunoglobulin for rabies patients, etc.) correctly and in a timely manner. In addition, for deep wounds, it is also very important to prevent tetanus infection at the same time.
If the patient is diagnosed with rabies, he should be given isolation care, keep quiet and rest in bed, avoid all sound, light, wind and other stimuli, and perform high-nutrition therapy with large vein catheterization. Medical staff must wear masks, gloves, and isolation gowns. The patient's secretions, excretions and pollutants must be strictly disinfected.
Wound management in the acute phase after exposure
Wound management after being injured by an animal is very important. The main purpose of wound treatment is to reduce the number of rabies virus and other microorganisms in the wound through mechanical, physical and chemical methods, thereby reducing the risk of rabies and other infections, promoting wound healing and early recovery of function.
Wound washing: Use soapy water (or weak alkaline cleaner) and running water to wash the wound thoroughly and effectively. In order to ensure the flushing effect, it is recommended to rinse for about 15 minutes. In order to avoid non-sterile water, soapy water or other cleaning agents remaining, rinse the wound with normal saline at the end. In order to achieve the best effect of irrigation and reduce medical risks, it is recommended to use a irrigator with Class II medical device qualification and a special irrigant to thoroughly rinse the wound.
Wound debridement: Professional medical workers follow the principle of debridement to clean the wound, and use surgical techniques to reduce the rate of wound infection and promote healing.
Wound disinfection: Use iodine products or special flushing fluid or disinfectant to disinfect the wound.
Primary wound closure: Due to the high rate of wound infection after animal injury, primary suture should be cautious, that is, the wound may not be sutured immediately after debridement. Primary suture is recommended for large wounds within 6 hours, especially those located on the head and face. Primary suture can also be considered for dog bite wounds other than the head and face, but not for cat bite wounds.
Application of passive immunization agents after exposure
Apply passive immunization preparations and rabies vaccines according to the level of rabies exposure. The former is often overlooked. In fact, passive immune preparations are exogenous rabies virus antibodies. The real mechanism of action is to form a high-concentration antibody environment locally through local action, neutralizing the virus remaining in the wound after wound washing and debridement. Thereby reducing the incidence rate to the greatest extent and prolonging the incubation period, so as to gain precious time for the production of antibodies after vaccination.
There are three levels of rabies exposure: level I exposure, level II exposure and level III exposure.
Class I exposure: Intact skin contact with animals and their secretions or excretions belongs to Class I exposure, no risk, no post-exposure disposal, but the contact area needs to be cleaned carefully.
Class II exposure: Bites and scratches without obvious bleeding, wounds without obvious bleeding or closed but incompletely healed wounds that come into contact with animals and their secretions or excretions belong to Class II exposures, and wound treatment and vaccination are required .
Class III exposure: including penetrating skin bites or scratches, clinically manifested as obvious bleeding; unclosed wounds or mucous membranes contacting animals and their secretions or excretions; exposure to bats. Wound management, vaccination and, where appropriate, passive immunization are required.
Note: Alcohol wipes can be used to distinguish grade Ⅰ or grade Ⅱ wounds. No pain belongs to grade Ⅰ exposure, and pain belongs to grade Ⅱ exposure. Class II or III exposure can be distinguished by whether there is obvious bleeding at the time. No bleeding from the wound, a small amount of blood oozing, and blood oozing after squeezing belong to Class II exposure, and obvious bleeding or full-thickness skin rupture belongs to Class III exposure.
Dosage of passive immunization preparations
The maximum dose of rabies passive immunization preparations should be calculated according to body weight, human rabies immunoglobulin (HRIG) is calculated at 20 IU per kilogram of body weight, and equine rabies immune globulin (ERIG) is calculated at 40 IU per kilogram of body weight.
Application method of passive immunization preparation
Apply a single dose to the injured area:
All wounds should be covered;
Do not inject passive immunization preparations and rabies vaccine at the same site;
It is forbidden to inject rabies vaccine and passive immunization preparation with the same syringe;
If the total dose used is not enough to infiltrate all the injection wounds, it can be appropriately diluted with normal saline;
When a sufficient amount of injection cannot be given to the terminal parts such as fingers, toes, nose tip, auricle and male external genitalia, use the maximum locally acceptable dose;
It is recommended to use it on the same day as the vaccine. If it is not possible, the vaccine should be injected first. Passive immunization preparations can still be injected within 7 days after the first dose of vaccine is injected.
The clinical use of passive immunization preparations should be carried out at the same time as the first vaccination (as soon as possible after exposure), and the injection of passive immunization preparations is still effective within 7 days after the start of vaccination; try to avoid injecting passive immunization preparations more than 1 day before vaccination. It should be emphasized that the medical and health institutions that implement animal-derived antiserum injections must have the ability to rescue allergic reactions.
Vaccination: If the re-exposure occurs during the immunization process, continue to complete the full vaccination according to the original procedure, without increasing the dose and dose. Re-exposure within 3 months after the completion of the last dose of the previous immunization program does not require booster immunization. Those who are exposed again 3 months or more after the last dose of the last immunization program need to receive 1 dose of vaccine on days 0 and 3 respectively.
Passive immunization preparations: Those who have completed at least 2 doses of rabies vaccine vaccination according to the pre-exposure or post-exposure procedures do not need to use passive immunization preparations for re-exposure, except for HIV-infected patients in the clinical stage or hematopoietic stem cell transplantation cases.
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