How is rabies spread?
Rabies is prevalent in dogs, wolves, cats, rats and other animal groups. After being infected, these animals are manic and very easy to hurt people. Their saliva contains a lot of rabies virus. Once a person is bitten or scratched, rabies virus will invade the human body through damaged skin or mucosa. It is worth noting that many healthy animals, such as dogs and cats, also carry rabies virus and become "toxic animals". These animals are normal in appearance, but very dangerous. They often transmit rabies to people by licking their skin or mucous membranes.
How to prevent rabies
Rabies virus has strong vitality and is difficult to be killed in human body. Once a person is bitten or licked by an animal with rabies virus, he must go to the epidemic prevention station to get rabies vaccine in time, and even get anti-rabies serum in severe cases to treat the wound locally as soon as possible. Only in this way can we prevent diseases and save lives.
Basic survey of rabies
The pathogen of rabies belongs to Rhabdoviridae, which has a unique bullet shape and four serotypes. It is a negative-strand RNA virus. It can be inactivated under the conditions of strong acid, strong alkali, ethanol, formaldehyde, sunlight and ultraviolet rays. , 100 degrees for 2 minutes and 660 degrees 10- 15 minutes. But it can survive in brain tissue for months at a temperature of 4 degrees. Pathogenesis, symptoms, incubation period and prognosis;
The rabies virus first increases in value at the infected site, then penetrates into the adjacent nerve endings, moves along the axon to the central nervous system at a speed of 3 mm per hour, enters the brain tissue and multiplies in large quantities, and then spreads around along the nerve channels, and is discharged from secretions, which is common in saliva.
There are three forms of clinical symptoms:
Precursor symptoms: numbness, itching and pain in the wound, which spread all over the limbs along the nerve and may change behavior.
Spastic type: extreme excitement, light, sound and touch can all cause spasms and convulsions.
Dementia type: it looks like an acute attack of mental illness, sometimes accompanied by harmful behavior.
Paralysis type: characterized by progressive paralysis or complete paralysis, coma and failure.
Incubation period:
The clinical symptoms of rabies mostly appear between 10-90 days, but the incubation period can be very short (1 week) or very long (months or even years), and the shortest incubation period mostly occurs in children. Or fingers, head, face, neck, nerve-controlled sexual organs are bitten.
Results:
Once rabies is diagnosed, there is no doubt that 100% will die. There is no cure in the world at present,
Infected people can only survive if they are vaccinated immediately after being bitten.
Prevention methods:
Wound treatment+rabies vaccine+antiviral serum
Epidemic distribution and its characteristics
Rabies is an animal infectious disease. Wild animals are the main storage hosts of the disease, and dogs play a major role in carrying and spreading rabies. Usually infected animals secrete viruses and then transmit them to humans through biting. Animal rabies affects most parts of the world, and rabies exists in the whole United States, Africa, Asia and parts of Europe. Only a few island countries, such as Australia, New Zealand, Japan, Britain and other countries, are not affected because of their unique geographical location and strict laws and regulations. Human rabies is rare in industrialized countries, because there are comprehensive disease prevention measures such as vaccinating pets, eliminating unattended dogs, and vaccinating wild animals. The most important thing is to vaccinate immediately once you are suspected of being bitten. But rabies is still a public health problem in Africa, Asia and Latin America. In Thailand, although more than 10000 people are vaccinated with rabies vaccine in 10 laboratory every year, about 300 people still die. In India, more than 6 million people are bitten by dogs every year, and 500,000 people are vaccinated, but 30,000 people still die. In more than half of South America, about 300 million people and dogs are attacked by rabies, and 150-200 cases of human rabies are reported every year. It is reported that the number of deaths caused by rabies in the world is estimated to be 40,000-70,000 every year, and the vast majority of cases occur in developing countries, 98% of which are in Asia, and China ranks second in the world after Indian.
In China, the epidemic situation of human rabies has experienced two ups and downs since the founding of the People's Republic of China. 5 1 year, the national unified campaign to eradicate dogs has greatly reduced the incidence of rabies. Only five provinces in China have rabies, and only more than 3,000 rabies vaccines are produced each year. In 1950s and 1970s, the total number of cases was less than 1000. However, by the mid-1970s, the incidence had expanded to 14 provinces, and all 28 provinces and cities in China had19,91cases. The death rate of rabies has risen to the top of legal infectious diseases, and the number of cases has increased significantly with the expansion of the scope of the disease. Eighty years later, about 50,000 people died of rabies in 1 year. According to the report of Shanghai Epidemic Prevention Station, the number of people bitten by dogs in 1992 increased by 80.6 1% compared with 9 1 year, and the number of outpatients in our hospital increased by 39.62% compared with 9 1 year, reaching 13200. After 90 years, due to the widespread use of rabies vaccine, the vaccine titer increased (0.32-2.5 international units) and local governments have successively issued regulations restricting dog keeping, which has greatly reduced the incidence of rabies. 1995, the death rate of rabies dropped to the ninth place, and the epidemic situation was effectively controlled in China. According to the statistics of Chinese Academy of Preventive Science, the number of rabies cases in China was 60 18 in 1984, 3,520 in 1990 and 500 in 1993.
Judging from the geographical distribution of rabies in China, there are great differences from place to place, with the Yangtze River as the boundary, high in the south and low in the north. Most of the high-incidence provinces in China are located in the south, such as Guangdong, Guangxi, Hunan, Hubei, Guizhou and Jiangsu. Before 9 1 year, the average number of cases was about 300. The incidence rate in these provinces accounts for 50% of the total incidence rate in China. However, the incidence rate in the northern region is very low. For example, Gansu, Ningxia, Xinjiang, Tibet, Qinghai and other provinces sometimes have no cases or a small number of cases all the year round, while Shandong, Hebei, Northeast China and other provinces are between the two regions. The reason may be that the four seasons in the south are warm and humid, the population density is high, the contact time between people and animals is long, and the animals themselves carry many toxins, which is one of the important factors for the high incidence of rabies. Both the World Health Organization and the old textbooks suggest that "when the injured dog does not appear rabies after observing 10- 14 days, the injured person may not be vaccinated or stop injecting rabies vaccine". In recent years, more and more scholars think that the prevention of rabies is a problem that can not be ignored after the incident that the injured dog is dead but still alive and the detection of brain tissue of healthy dogs by fluorescence blocking method. Ethiopian experts reported that five apparently healthy dogs survived for 3-39 months after the rabies virus was first isolated from saliva. Guangdong Luo Huiming et al. investigated the brain virus carrying rate of 65438 0258 healthy dogs by fluorescent antibody method, and the average positive rate was 65438 07.73%. In addition, according to Chu's statistics, 909 rabies deaths were all bitten by seemingly healthy dogs before death. At the same time, 10 of the 29 rabies deaths in Beijing in 1989 were caused by asymptomatic dog bites.
Development progress of rabies vaccine
In view of the short and dangerous course of rabies, no special treatment, extremely high mortality and long incubation period after infection, immunization can play a very good protective role. Scientists all over the world have made great progress in the process of preventing rabies after more than 100 years of efforts, and rabies has been controlled and eliminated in some countries and regions. 1885, French scientist louis pasteur successfully applied the attenuated rabies vaccine prepared from rabbit brain bone marrow to human body for the first time, which was the first time to conquer rabies in human history, thus creating a precedent for vaccine to prevent rabies. With the progress of cell culture technology, molecular biology and concentration and purification technology, the quality and yield of rabies vaccine have been greatly developed and improved. Before 1960s, rabies vaccine was mainly prepared from animal brain tissue. This vaccine has poor immunogenicity, needs multiple injections, and has great toxic and side effects, which easily leads to serious complications and hinders its wide application in clinic. After 1960s, cells obtained from chicken embryos and hamster kidneys were cultured in vitro to make rabies vaccine, which replaced brain tissue vaccine. At present, this concentrated rabies vaccine is widely produced and used in China. 1972, the French Merieult Institute developed a diploid vaccine for subculture cell lines, which was only used in some developed countries because of its high cost. 1984, the institute developed a high-purity rabies vaccine with VERO passage cells, that is, Wilport rabies vaccine. This vaccine is recommended by the World Health Organization and has been widely used in all countries in the world. After continuous improvement, the dosage of cell vaccine was reduced from 2 ml to 0.5 ml, and the number of injections was reduced from 14 to 5 times. At present, there are vero cell vaccine and diploid cell vaccine produced in France, and chicken embryo cell vaccine produced in Germany and Japan. In addition, the vero cell vaccine with higher purity developed by chromatography technology in France will be on the market soon. These vaccines are welcomed by many countries because of their strong antigenicity, stable effect, long antibody maintenance time and few side effects. Since 1995, 6,000 copies of Wilbaut rabies vaccine produced in France have been used in prevention clinics, targeting different groups of people, such as the elderly, children, pregnant women and people with severe allergies. Clinical observation shows that there are no other adverse reactions except slight redness or low fever at the local injection site of a few users, and the effect is satisfactory. In China, the development of new vaccines is also stepping up. 1999, Shenyang first produced a refined rabies vaccine for human use with hamster kidney cells as raw materials, and the injection volume was reduced to 65438±0ml. According to reports, provinces such as Northeast China and Hebei are developing vero cell vaccines, which will be used in clinic through identification this year. In addition, in the 1990s, French scientists screened a two-site non-toxic mutation sag from the derivative strain of rabies vaccine sad. The toxin has good safety and immunogenicity, and is currently undergoing oral immunization tests. Once successful, it has made great contributions to the prevention and treatment of rabies. It can not only save a lot of manpower, material resources and financial resources, but also reduce the pain of patients with repeated injections. With the upgrading of rabies vaccine, the scope of prevention work is more extensive, such as pre-exposure preventive injection for veterinarians, animal experimenters, foresters and people in high-risk areas to reduce the infection rate of rabies.
Improvement of immune method
Since 1993, the World Health Organization has recommended several new injection methods, 1 and Pinedo point injection, that is, two parts were injected intradermally in both forearms on 0, 3 and 7 days, each part was 0. 1-0.2 ml, and each part was intradermally on 30 and 90 days. 2. Inoculate 8 4 1 1 loci at 0. 1 ml on the 0th, 7th, 28th and 90th days respectively. This method requires less vaccine and can produce antibodies quickly. 1998, Dr. Du Jing, an outpatient in our hospital, injected 155 patients with Pinedo acupoints. After 8 days, the positive conversion rate of antibody test was 100%. The time of antibody production is 6 days earlier than that of routine injection. 3. intramuscular injection, that is, one dose is injected into the deltoid muscles of both arms on the 0 th day, and one dose is injected into the deltoid muscles on the 7 th day and the 2 nd1day. This method can produce antibodies at an early stage and is more effective for patients who have not been injected with antiviral serum. 1In June, 1996, the World Health Organization put forward a new suggestion on the re-division and prevention of exposed wounds, that is, I-touch or feeding animals to lick the skin. If there is a reliable medical history, this does not require treatment. Second degree unprotected skin was bitten, no bleeding, slight scratches or abrasions, and damaged skin was licked. This kind needs to be vaccinated immediately. If you are vaccinated within five years, you only need 2 injections to get the third grade. One or more skin penetrating bites or scratches, and animal saliva pollutes mucosa. Such patients should be vaccinated immediately and injected with anti-rabies serum at the wound. At the same time, new requirements are put forward for wound treatment. In the aspect of rabies prevention, local treatment+anti-rabies serum+vaccine can ensure safety. Since the establishment of 1988, under the leadership of CDC, more than 65438+ million people have been vaccinated with rabies vaccine for all kinds of animal bites, and the immunization success rate is 654.38+000%, which has contributed to the prevention of rabies. According to the introduction of the national professional academic conference, the outpatient department of our hospital is at the advanced level of the national professional system in the aspects of rabies immunization prevention methods, the use of new vaccines, the quantity and quality of professional academic papers, clinical experience and vaccine response treatment. In short, rabies is a serious threat to human life, because once it happens, almost everyone will die. Therefore, all countries in the world attach great importance to it. Over the past century, due to people's unremitting efforts, great progress has been made in the prevention of rabies, especially the successful development of safe, effective and high-quality vaccines and the improvement of immunization procedures, which have expanded the immune range before exposure and greatly improved the immune effect of vaccination after exposure. With the cooperation of antiviral serum and proper treatment of wounds, the immune failure rate can be minimized. The successful development of oral rabies vaccine is very likely to fundamentally control and eliminate human rabies.