Foot-and-mouth disease (FMD), as an acute contagious disease, is widely prevalent in many countries and regions in the world. With the prosperity of international trade and the convenience of material exchange and tourism activities, many countries may be attacked by foot-and-mouth disease again. Foot-and-mouth disease seriously harms the development of animal husbandry, causing serious economic losses to pastoral areas, as well as heavy losses to foreign trade and tourism. The global direct economic losses caused by this can reach tens of billions of dollars every year. The outbreak of foot-and-mouth disease has affected international relations, national reputation and economic development. In some epidemic processes, the virus will mutate, which also brings difficulties to the prevention and control of foot-and-mouth disease. It is of practical significance to further understand the nature and epidemic law of the virus, the source and mode of transmission, clinical manifestations and preventive measures. In this paper, the research at home and abroad is reviewed to provide basic basis for the prevention and treatment of foot-and-mouth disease.

1 year foot-and-mouth disease epidemic

Foot-and-mouth disease is commonly known as aphtha, hoof ulcer and thrush. It is an acute contagious disease which is zoonotic. OIE and FAO listed it as the first of 18 A livestock infectious diseases in the International Code of Animal Health. Viruses are carriers of diseases, which spread quickly and in a wide range of ways. Almost 100% of susceptible animals are infected, and the mortality rate is only 2% ~ 3%. However, in addition to the direct economic losses caused by animal death, the reduction of meat and milk production and the loss of breeding value during and after illness will also cause huge losses. Foot-and-mouth disease was first discovered in Italy in 15 14, and then broke out from time to time, mostly in winter and spring, and rarely in summer. In recent years, foot-and-mouth disease has spread widely around the world, and some countries and regions in Europe, Asia, Africa and South America have become the hardest hit areas [1]. From 65438 to 0999, foot-and-mouth disease occurred in nearly 40 countries and regions around the world. In 2000, foot-and-mouth disease occurred in South Korea, Russia, Mongolia, Japan, South Africa and Taiwan Province Province. 200 1 foot-and-mouth disease has made a comeback in Britain and spread widely in Europe, causing economic losses of about 9 billion pounds in Britain. China is an old epidemic area of foot-and-mouth disease. In the half century before the founding of the People's Republic of China, the total epidemic situation of foot-and-mouth disease was less in agricultural areas and more in pastoral areas, which never stopped, and sometimes it was an epidemic situation. Since the founding of People's Republic of China (PRC), there have been four foot-and-mouth disease pandemics. In recent years, with the development of animal husbandry and foreign trade in China, the risk of foot-and-mouth disease outbreak has increased accordingly.

2 Pathogens and modes of transmission

Foot-and-mouth disease is caused by foot-and-mouth disease virus. The virus belongs to picornaviridae, a single-stranded DNA virus, which is symmetrical in equivalence plane and has no cyst. This is the earliest virus that causes human and animal diseases. It can be divided into seven main types: O, A, C, South Africa 1, South Africa 2, South Africa 3 and Asia 1. Among them, type O and type A are the most widely distributed and the most harmful. Each type produces similar symptoms, which can only be distinguished in the laboratory. There is no cross-immunity between viruses, and even viruses of the same serotype have different antigenicity. Each type can be divided into multiple subtypes, and 65 subtypes have been identified so far [2]. During the fever period of sick animals, feces, urine, milk, tears, saliva and exhaled gas all carry the virus, and then the virus mainly exists in blisters and lymph. Animals recovering from diseases can carry viruses for a long time. Foot-and-mouth disease virus (FMDV) is highly toxic, and fresh blister fluid diluted by 500-500,000 times can still cause the disease when inoculated into susceptible animals. Strong resistance to the outside world, dry and cold; But afraid of acid, alkali and heat, heat 85? /kloc-above 0/00℃? Min can kill people. Foot-and-mouth disease virus can enter the skin and mucosa, respiratory tract and digestive tract of susceptible animals through contact, air and food, causing diseases. The main susceptible targets are large cloven-hoofed mammals such as pigs and cows, and rats and rabbits are also high-risk groups. People can also be infected by touching animals infected with foot-and-mouth disease and their contaminated fur or eating the milk and meat of infected animals by mistake, but typical cases are rare. Most virus strains isolated from people are O type, followed by C type. In addition, people can transmit the virus to livestock, and people rarely infect each other. This is different from swine vesicular disease (SVD), which is highly contagious to humans.

3 Clinical manifestations

3? 1 animal

After pigs and cattle are infected with foot-and-mouth disease, their typical symptoms are fever and blisters on oral mucosa, breast and hoof skin. The course of disease can be benign, malignant or complicated. Newborn calves show acute and subacute myocarditis, without thrush, and usually end in death [4]. The acute process of foot-and-mouth disease can be divided into incubation period, precursor period and clinical period. The incubation period ranges from a few days to half a month, usually 2 ~ 7? D incubation period is the stage of foot-and-mouth disease virus amplification at the invasion site and in vivo. The prodromal stage is characterized by listlessness, loss of appetite, increased body temperature and decreased milk production. Typical blisters appear in clinical stage, which gradually fuse and rupture, showing bright red rotten face. At this time, the body temperature rises, the gait is compact or limping, the pulse and breathing times increase sharply, the milk production decreases, and the animal's physique deteriorates [5]. The most important thing of malignant foot-and-mouth disease is the destruction of heart activity, which often leads to rapid death due to myocardial failure. The complication of foot-and-mouth disease is mainly the process of bacterial suppuration-necrosis in infected tissues. Patients with chronic diseases may have heart disease, endocrine diseases (diseases such as pancreas and adrenal gland) and infertility.

3? 2 Clinical manifestations of human body

After the human body is infected with foot-and-mouth disease, after 2 ~ 18? The incubation period of D is characterized by sudden onset, and the initial symptoms are similar to those of influenza [6]. 2~3? Blisters may appear in the mouth, pharynx, fingers and toes after D, and will not leave scars after healing. Severe cases may be complicated by gastroenteritis, neuritis and skin and lung infections. Generally, the course of disease does not exceed 1 week, and the prognosis is good.

4 Prevention and control measures

Foot-and-mouth disease prevention and control measures are a kind of national behavior, and countries formulate corresponding prevention and control and eradication measures according to their own actual conditions. Main measures to prevent foot-and-mouth disease: (1) Prohibit the import of animals and their products from foot-and-mouth disease-stricken areas, and strengthen the quarantine of imported animals and their products [7]. (2) Regular and detailed animal epidemic reporting records, and establish an epidemic reporting system. (3) Strictly control the preservation and use of pathogenic microorganisms. (4) After the foot-and-mouth disease is eliminated, no immunization will be carried out to prevent the outbreak and epidemic of foot-and-mouth disease caused by vaccine. (5) Do a good job in personal hygiene protection, such as good food hygiene, and eat livestock meat after it is cooked. The main measures to control and extinguish foot-and-mouth disease [8]: (1) block the epidemic area, eliminate the same group of sick animals and susceptible animals, and carry out harmless treatment. (2) prohibit the outflow of animals and their products from epidemic areas, and strictly implement the disinfection system for vehicles, personnel and goods. (3) Animal products, forage grass and bedding burned or buried in epidemic areas shall be thoroughly disinfected with 1% ~ 2% formalin. (4) Strict epidemic investigation and quarantine shall be conducted around the epidemic spot (10km), animal activity control area (20km) and monitoring area (50km), and all positive and contaminated animal products shall be culled and destroyed. (5) Strict serological and clinical investigation and monitoring shall be carried out in areas related to epidemiology outside the monitoring area to identify and eliminate the source of infection. (6) Vaccinate susceptible animals in a certain range around the epidemic spot with the same vaccine as the local epidemic virus type. Foot and mouth disease vaccine can effectively prevent its outbreak. 1925 vaccine was successfully developed, but it was not put into mass production until 1940 technical breakthrough [9]. Traditional foot-and-mouth disease vaccines include attenuated vaccine and inactivated vaccine. The research of new vaccine began in the early 1980s, but it has not been put into use so far. At present, the new vaccines explored include synthetic peptide vaccine, genetic engineering expression vaccine, live vector vaccine, DNA vaccine and so on. The immune duration of foot-and-mouth disease vaccine is less than 6 months. The antigenicity of vaccine strain and epidemic strain is different, and the immune duration is also different. The greater the antigen difference, the shorter the immune duration [10].

5 conclusion

The Trial Measures for Meat Hygiene Inspection jointly issued by China's Ministry of Agriculture, Ministry of Health, Ministry of Foreign Trade and Ministry of Commerce clearly stipulates the treatment of livestock carcasses with foot-and-mouth disease: "Livestock carcasses with elevated body temperature will have internal organs and by-products after high temperature treatment; The boneless carcasses and viscera of animals with normal body temperature will appear after acid production and harmless treatment. " The choice of methods to control foot-and-mouth disease in a country depends on the situation of foot-and-mouth disease and the danger of being harmed. It is feasible to eliminate epidemic foot-and-mouth disease by various methods and achieve a foot-and-mouth disease-free state. The prevention and control of foot-and-mouth disease is a major event involving national reputation and safe production of animal husbandry, which must attract the attention of government departments at all levels, breeding units and animal owners. Effective implementation of foot-and-mouth disease prevention measures, rapid eradication of the epidemic situation and consolidation of the results of eliminating the epidemic situation are the touchstones for testing the control ability and effectiveness of the national epidemic prevention system.

[07-08-1310: 02: 00] Author: Yao Yuhong