Because Bacillus anthracis lives in rural areas and fauna, the infected population is limited to veterinarians, animal husbandry and field workers, and the general public need not worry. In addition, anthrax may be used in biological warfare, but it is very difficult to make it into extremely fine atomized particles, which requires highly specialized technology and special instruments.
route of transmission
Bacillus anthracis and spores usually exist in soil, sheep, cattle and horses. Humans can be infected by touching infected animals and their products, or inhaling anthrax spores. Anthrax does not spread from person to person.
Treat anthrax
If anthrax can be diagnosed early, appropriate antibiotics can cure it, but if it is ignored, it may be fatal, so patients should seek medical attention as soon as possible.
preventive measure
Avoid contact with infected animals or contaminated animal products.
Handle the wound properly.
Maintain good personal, food and environmental hygiene.
Wash your hands thoroughly before handling food.
Wash and cook food thoroughly before eating.
There is a vaccine to prevent anthrax, but the whole vaccination procedure takes 18 months to complete, and there are many side effects, so it is not recommended for the public to vaccinate. If you take antibiotics after exposure to anthrax, the chances of preventing anthrax are quite high.
Anthrax is an acute infectious disease of herbivores caused by Bacillus anthracis. An acute infectious disease of humans and animals. People are infected by touching sick animals and their products or eating the meat of sick animals. Clinically, the main manifestations are skin necrotizing ulcer, extensive edema and toxemia in eschar and surrounding tissues, and occasional acute infection of lung, intestine and meninges, which may be accompanied by sepsis.
[etiology]
Bacillus anthracis is an aerobic or facultative anaerobic flagella-free Bacillus, which is 4-8μm long and 1- 15μm wide. Both ends of the bacteria were arranged in bamboo-like long chains, and Gram staining was positive. Capsules are formed in human body, which is highly pathogenic, and non-toxic strains do not produce capsules. Bacillus anthracis has strong vitality and grows well on general culture medium. The propagule of Bacillus anthracis can be killed at 56℃ for 2 hours and at 75℃ for 65438 0 minutes. Disinfectants with ordinary concentration can also be quickly killed. Oval spores can be formed in unsuitable environment in vitro. Spores are extremely resistant and can survive for a long time in natural conditions or cured meat. You can live in dirt for decades and in fur for years. Direct sunlight 100 hour, boiling for 40 minutes, dry heat at l40℃ for 3 hours,10℃ high-pressure steam for 60 minutes, 10% formaldehyde solution 15 minutes, neophenol solution (5%) and 20.
The antigen of Bacillus anthracis consists of capsule antigen, bacterial antigen, protective antigen and spore antigen. Capsule antigen is a kind of polypeptide, which can inhibit the conditioning effect related to bacterial invasion, resist phagocytosis and be beneficial to the growth and diffusion of bacteria. Although bacterial antigen is non-toxic, it has species specificity; The protective antigen has strong immunogenicity; Spore antigen has immunogenicity and serological diagnostic value.
Bacillus anthracis propagules can secrete anthrax toxin, which is a complex polymer composed of factor I (edema factor, EF), factor II (protective antigen, PA) and factor III (lethal factor, LF). The three components are not toxic when injected into human animals, but the protective antigen plus edema factor or lethal factor can cause edema, necrosis or animal death respectively.
[epidemiology]
Anthrax is distributed all over the world, especially in pastoral areas such as South America, Asia and Africa. It is endemic and a natural focus disease. In recent years, due to the concentration of fur processing in cities and towns all over the world, anthrax also broke out in cities and became one of the important occupational diseases. At present, the incidence of the disease in China has gradually declined.
(1) Infected herbivores such as cattle, horses, sheep and camels are the main sources of human anthrax. Pigs can swallow contaminated green feed; Carnivores, such as dogs and wolves, can become a secondary source of infection by swallowing the meat of sick animals. The secretions and excretions of anthrax patients are also contagious.
(II) Transmission route People infected with Bacillus anthracis mainly pass through industry and agriculture. Contact infection is the main route of disease transmission. Direct contact between skin and diseased animals and their fur is the most susceptible to infection. Inhaling dust and aerosol containing a large number of anthrax spores or eating contaminated meat can cause pulmonary anthrax or intestinal anthrax respectively. Using an unsterilized brush or being bitten by an insect with bacteria can occasionally cause illness.
(3) Susceptible people are generally susceptible, mainly depending on the degree and frequency of exposure to pathogens. Young and middle-aged people have more opportunities to contact sick animals, such as their fur and excrement, dust with spores and so on. Because of their occupations (farmers, herders, veterinarians, workers in slaughterhouses and fur processing factories, etc.). ), and their incidence is also very high. There will be lasting immunity after infection.
Incidence occurs all year round, with the peak in July-September. Inhalation is more common in winter and spring.
[Pathogenesis and Pathology]
When a certain number of spores break into the skin, swallow into the gastrointestinal tract or inhale into the respiratory tract, if the human body's resistance is low or weakened, the pathogenic bacteria will first propagate locally under the protection of its capsule, producing a large number of toxins, leading to hemorrhagic infiltration, necrosis and severe edema of tissues and organs, forming primary cutaneous anthrax, intestinal anthrax and pulmonary anthrax. When the body's resistance drops, pathogenic bacteria will spread rapidly to the whole body along lymphatic vessels and blood circulation, forming sepsis and secondary meningitis. Because of ischemia and toxin, nerve fibers in dermis degenerate, so the focus often has no obvious pain. If people are healthy, but the number of spores entering the body is small or the toxicity is low, they may not get sick or have recessive infection.
The pathogenicity of Bacillus anthracis is mainly related to the synergistic effect of various components in its toxin. Anthrax toxin can directly damage microvascular endothelial cells, increase the permeability of blood vessel wall, and lead to insufficient effective blood volume; In addition, the release of some bioactive substances increases during acute infection, which dilates small blood vessels, increases vascular permeability and reduces tissue perfusion; The common DIC and septic shock of anthrax are caused by toxins damaging the intima of blood vessels, activating the coagulation system in vivo, releasing tissue thromboplastin substances, and the blood is in a hypercoagulable state. In addition, Bacillus anthracis itself can block capillaries, causing tissue hypoxia and ischemia and microcirculation thrombosis.
The main pathology of anthrax is hemorrhagic infiltration, necrosis and edema of various organs and tissues. Cutaneous anthrax is a carbuncle-like lesion, surrounded by coagulative necrosis, acute serohemorrhagic inflammation of subcutaneous tissue and obvious interstitial edema. Due to the effect of toxin, the sensitivity of peripheral nerves is reduced, so local pain does not exist. Pulmonary anthrax is characterized by hemorrhagic bronchitis, lobular pneumonia and infarcted area, highly gelatinous edema in mediastinum, highly swollen lymph nodes in bronchi and mediastinum, and hemorrhagic infiltration, and pleura and pericardium may also be involved. The lesions of intestinal anthrax are mainly distributed in the small intestine, showing localized carbuncle-like lesions and diffuse hemorrhagic infiltration in the intestinal wall, high edema and bleeding in the intestinal wall around the lesion, and enlarged mesenteric lymph nodes; There is serous bloody exudate in the abdominal cavity, which contains a large number of pathogenic bacteria. When the meninges are involved, both the dura mater and the pia mater are extremely congested and edematous. Besides extensive bleeding, a large number of bacteria and inflammatory cells infiltrate into the subarachnoid space. When septicemia occurs, other tissues and organs of the whole body are widely bleeding and infiltrating, edema and necrosis, liver and kidney turbidity and splenomegaly.
[Clinical manifestations]
The incubation period is 1-5 days, the shortest is only 12 hours, and the longest is 12 days. Clinically, it can be divided into the following five types.
(a) skin anthrax is the most common, accounting for about 95%, which can be divided into anthrax carbuncle and malignant edema. Anthrax carbuncle is more common in the skin of exposed parts such as face, neck, shoulders, hands and feet. At first it was a papule or macula. The next day, blisters appeared on the top, containing yellowish liquid, and the surrounding tissues were hard and swollen. On the third day, the central area was hemorrhagic necrosis, slightly sunken, surrounded by groups of small blisters, and the edema area continued to expand. On the 5th and 7th day, the blister was necrotic and ruptured into a superficial small ulcer, the secretion of blood sample formed a black carbon-like dry scab, and the granulation tissue under the carbuncle formed an anthrax carbuncle. There is non-concave edema in the surrounding tissue. The diameter of necrotic area of black scab varies from 65,438+0-2 cm to 5-6cm, and the diameter of edema area can reach 5-20cm, which is characterized by firmness, no pain and no suppuration of ulcer. Then the edema gradually subsided, and the black scab fell off within 1-2 weeks, and became a scar after 1-2 weeks. 1-2 days after onset, fever, headache, local lymphadenopathy and splenomegaly occurred.
A few cases showed large area edema without black scab formation, and most of the affected parts were slack eyelids, neck and thighs. The affected area is swollen, transparent and tough, and spreads rapidly, which can cause large area necrosis. Systemic toxemia is obvious and the condition is critical. If the treatment is delayed, you may die of circulatory failure. If pathogenic bacteria enter the blood, sepsis may occur, followed by pneumonia and meningitis.
(2) Pulmonary anthrax is mostly primary, which is caused by inhalation of Bacillus anthracis spores and can also be secondary to cutaneous anthrax. The onset is often sudden, but generally there are cold-like symptoms for 2 14 days first, and then they suddenly attack after remission, showing bipolar type. The clinical manifestations are chills, high fever, shortness of breath, dyspnea, wheezing, cyanosis, blood phlegm, chest pain and so on. Sometimes subcutaneous edema occurs in the neck and chest. The lungs only smell moist rales, or there are signs of pleurisy, which is often out of proportion to the severity of the disease. Most patients are critically ill, often complicated with sepsis and septic shock, and occasionally meningitis. If not diagnosed and rescued in time, people often die of respiratory and circulatory failure within 24-48 hours after acute symptoms appear.
(3) The clinical symptoms of intestinal anthrax are different, including acute gastroenteritis and acute abdomen. The incubation period of the former is 12- 18 hours, and the same eater may have severe vomiting, abdominal pain and watery diarrhea at the same time or successively, and recover quickly for several days. The latter has sudden onset, severe toxemia symptoms, persistent vomiting, diarrhea, bloody stool, abdominal distension and abdominal pain, abdominal tenderness or signs of peritonitis. If not treated in time, Emperor Huang died of septicemia and septic shock within 3 14 days after onset.
(4) Meningeal anthrax is mostly secondary to various anthrax complicated with septicemia, and primary anthrax is rare. Clinical symptoms include severe headache, vomiting, convulsion and obvious meningeal irritation. The disease is dangerous and develops rapidly, and the patient can die within 2 14 days of onset. Cerebrospinal fluid is mostly bloody.
(5) Septic anthrax is mostly secondary to pulmonary gangrene or intestinal anthrax. Skin anthrax causes fewer people. May be accompanied by high fever, headache, bleeding, vomiting, toxemia, septic shock, DIC, etc.
[Laboratory inspection]
(1) The total number of white blood cells in peripheral blood is mostly increased (10-20)× 109/L, and a few of them can be as high as (60-80)× 109/L, with neutrophils as the highest.
(2) Smear examination Take blisters, exudates, secretions, sputum, vomit, feces, blood, cerebrospinal fluid and other contents as smears to find pathogens. When pathogens are found in smear, Gram staining or capsule staining can be used, as well as various specific fluorescent antibodies (antibacterial, anti-capsule, anti-spore, anti-phage, etc.). ) for further identification.
(3) Culture samples should be inoculated on blood agar plates respectively. Ordinary agar plate, sodium bicarbonate plate. Blood samples should be enriched and cultured in advance. If the sample is obviously polluted, it can be heated at 65℃ for 30 minutes to eliminate miscellaneous bacteria, and then inoculated on a flat plate after 4 hours of enrichment in the broth. If suspicious colonies are found, they should be identified according to biological characteristics and animal tests, such as penicillin bead formation and inhibition test, phage lysis test, etc.
(IV) Inoculation of animals Secretions, tissue fluids or pure cultures obtained from patients are inoculated into subcutaneous tissues of animals such as mice or guinea pigs. If there is typical edema and bleeding in the injection area within 24 hours, most animals will die within 36-48 hours, and there are a large number of encapsulated Bacillus anthracis in animal viscera and blood. The isolated suspected anthrax should be identified and tested.
(5) Identification test is used to distinguish anthrax from various anthrax-like bacilli (Bacillus subtilis, Bacillus cereus, Bacillus Agaricus, Bacillus thermophilus, etc. ), mainly including bead wet method, specific fluorescent antibody staining method (antibacterial, anti-capsule, anti-spore, anti-phage, etc. ), W phage lysis test, sodium bicarbonate agar plate CO2 culture method, penicillin inhibition test, animal pathogenicity test, capsule swelling test and so on.
The above inspection should be carried out in a specially protected laboratory.
(6) Immunological tests include indirect hemagglutination test, ELISA, ELISA -SPA and fluorescence immunoassay. Used to detect various antibodies in serum, especially capsular antibodies and serum antitoxin antibodies, and generally used for retrospective diagnosis and epidemiological investigation.
Ascoli sedimentation test, which can be used when it is difficult to cultivate tiny bacteria from corrupt or dry specimens. For example, samples of scab skin, corpse tissue, blood, infected fur and its products of patients and sick animals, after boiling in water or high pressure, are put forward for circulating precipitation test with antigen components and anthrax precipitant serum to indirectly prove whether there is anthrax infection, but this method often leads to some false positives, and the results need to be carefully judged.
[Diagnosis and differential diagnosis]
The occupation, work and living conditions of patients, such as farmers and herdsmen who often come into contact with cattle, horses and sheep, and workers in fur leather and leather processing factories who work in the environment with spore dust, have important reference value for the diagnosis of this disease. Skin anthrax has certain characteristics, and it is generally not difficult to diagnose. When factory workers have respiratory tract infection, especially when the symptoms are not commensurate with the signs, they should be vigilant and think about the possibility of pulmonary anthrax. The diagnosis depends on the smear examination and nursing of various secretions, excreta, blood and cerebrospinal fluid. Smear examination is the easiest. If a typical E.coli with capsule is found, the diagnosis can be basically established. Fluorescent antibody staining, bead wet test, specific phage test and animal inoculation can further establish the diagnosis.
Skin anthrax should be differentiated from carbuncle, cellulitis, scrub typhus and rabbit fever ulcer. Pulmonary anthrax should be differentiated from pneumonia and pneumonic plague. Intestinal anthrax should be differentiated from acute bacillary dysentery and acute abdomen. Meningitis anthrax and sepsis anthrax should be differentiated from meningitis, subarachnoid hemorrhage and sepsis.
[Prognosis]
The prognosis of this disease depends on the clinical type and whether the diagnosis and treatment are timely. The mortality rate of cutaneous anthrax has decreased to about 65438 0%, but the prognosis of cutaneous anthrax located in neck, face, complicated with sepsis or malignant edema is poor. Acute abdominal anthrax, pulmonary anthrax, meningitis anthrax, septic anthrax, etc. Due to the rapid development of the disease and the difficulty in early diagnosis, the mortality rate can be as high as 90%, and patients often die within a few days after onset.
[therapy]
(a) patients with general and symptomatic treatment should be strictly isolated, and their secretions and excreta should be disinfected according to spore disinfection method. Give high fever and liquid or semi-liquid, intravenous rehydration if necessary, and appropriate blood transfusion for severe bleeding. Patients with skin malignant edema can use adrenocortical hormone to effectively control the development of local edema and reduce toxemia. Hydrocortisone 100-200mg/ day is generally available for short-term intravenous drip, but it must be used under the protection of penicillin. In case of DIC, heparin and dipyridamole should be used in time.
(2) In addition to taking specimens for diagnosis, local skin lesions should not be squeezed, nor should they be cut and drained to prevent septicemia from spreading. The local area can be washed with 1:2000 potassium permanganate solution, coated with tetracycline ointment and wrapped with sterile gauze.
(3) Penicillin is the first choice for pathogen treatment. Cutaneous anthrax, adults were given intramuscular injections of 7- 1.6 million and 3.2 million u every day for 7- 10 days. For pulmonary anthrax, intestinal anthrax, meningitis anthrax and septicemia anthrax, the daily dose should be increased to1001200,000 u for intravenous drip, and aminoglycosides (streptomycin, gentamicin, kanamycin, etc. ) should be used at the same time, and the course of treatment should be extended to more than 2 13 weeks.
Those who are allergic to penicillin can use ciprofloxacin, tetracycline, streptomycin, erythromycin, chloramphenicol and other antibiotics.
Anti-anthrax serum therapy is rarely used at present. If conditions permit, patients with severe toxemia can be treated by intramuscular injection or intravenous injection of anti-anthrax serum, the first 1 day 100 ml, the second13 day 30 150 ml, and skin test is needed before application.
[prevention]
(a) isolation treatment of patients who manage the source of infection until the wound heals, scab skin falls off or symptoms disappear, and secretion or feces culture is negative twice (5 days apart).
Strictly isolate and treat sick animals and don't use their milk. Dead animals are strictly forbidden to be skinned or cooked, and they should be burned with a large amount of quicklime or buried below 2 meters underground.
(two) when necessary, cut off the route of transmission and block the epidemic area. Disinfection and sterilization measures such as boiling, chlorine-containing lime (bleaching powder), ethylene oxide, peracetic acid, high-pressure steam, etc. Used in patients' clothes, utensils, discarded dressings, secretions and excretions. Samples such as fur and bone meal were detected by Ascoli precipitation test. Those who are infected or suspected to be infected with bacteria should be strictly disinfected, preferably with 0.8kg/m3 formaldehyde and sealed for 24 hours, which can kill germs and spores. Animal products processing plants must improve working conditions, strengthen protective facilities, and wear work clothes, masks and gloves at work.
(3) Protect the susceptible population
1. Strengthen health education and educate people in epidemic areas. Individuals should develop good hygiene habits to prevent skin injuries. If the skin is damaged, apply 3-5% iodine immediately to avoid infection.
2. Healthy animals and sick animals should be grazed separately, and herds in contact with sick animals or those with frequent anthrax should be inoculated with non-toxic budding vaccine.
3. Employees engaged in animal husbandry, livestock product acquisition, processing and slaughtering industries and people in epidemic areas are vaccinated with live attenuated anthrax vaccine 1 time every year. At present, the method of scratching on the skin is adopted, and the vaccine is 0. 1ml each time, and it is dripped on the skin outside the upper arm, marking a "well". The quadruple vaccine (Bacillus anthracis, Bacillus tularensis, Yersinia pestis and Brucella) has also proved effective.
In foreign countries, protective antigens are used for vaccination. In the first year, intramuscular injection was given 3 times with an interval of 3 weeks. Inoculate for the fourth time after 6 months, and then inject 1 time every year, with 0.5ml each time.
Close contacts should be kept for 8 days, penicillin and tetracycline should be used early if necessary, and the same measures can be taken for suspected patients.