Epidemic typhus

Introduction to epidemic typhus Epidemic typhus (epidemictyphus), also known as louse-bornetyphus or "typical typhus", is an acute infectious disease transmitted by body lice in Rickettsia prowazekii. Its clinical features are persistent high fever, headache, rash-like rash (or maculopapular rash) and central nervous system symptoms, and the natural course is about 2 to 3 weeks. basic knowledge Sickness ratio: 0.001%-0.005% Susceptible people: no special people Mode of transmission: insect vector transmission Complications: abortion acute nephritis

Epidemic typhus

Causes:

The pathogen of this disease is Platts rickettsia, which is parasitic in the cytoplasm of human and animal vascular endothelial cells and in the epithelial cells of human intestinal wall. It is also attached to red blood cells and platelets in rickettsialosis. The shape is a micro-clip shape, which is arranged in a chain shape along the long axis, but has a multi-form in the development stage of the calf, and can be spherical, short rod-shaped, rod-shaped or long-line-shaped, about 0.3 to 1 m × 0.3 to 0.4 m. Gram staining is negative. The chemical composition and metabolites of pathogens include protein, sugar, fat, phospholipid, DNA, RNA, various enzymes, vitamins and endotoxin-like substances. The lipopolysaccharide layer of the cell wall has an endotoxin-like effect. Platts rickettsia is sensitive to heat, ultraviolet rays and general chemical disinfectants. It can be inactivated at 56 ° C for 30 min. It is resistant to low temperature and dryness. It can survive for several months in dry manure, typhus The rickettsia and the Proteus OX19 antigen components cross, so the patient's serum can agglutinate with the Proteus OX19, that is, the external Fission reaction, the Platts rickettsia contains both the group's shared heat tolerance group specific Sexual antigen Heat-tolerant particulate antigens, which can be differentiated from rickettsial infection by serological tests.

Pathogens can grow in tissue culture, and grow vigorously in chicken embryo yolk sac. Animals can only be used in guinea pigs. After vaccination, they cause fever and vascular disease, and scrotal enlargement is not obvious. This is different from M. rickettsia infection. This can be distinguished from endemic typhus. Toxin-like substances can dissolve red blood cells of warm-blooded animals such as humans, monkeys, and rabbits in a test tube. When injected into a large, mouse vein, it can cause difficulty in breathing, convulsions, decreased blood volume, etc. Animals die within 6 to 24 hours.

Pathogenesis:

The pathogenesis of this disease is mainly caused by pathogen-induced vascular disease, and the toxemia caused by the toxin produced by the toxin and some immune, allergic reactions, P. striata from the skin, mucosal invasion of the human body, first in the local lymph Tissues or small blood vessels and capillary endothelial cells grow and multiply, causing cell rupture and pathogens to escape, resulting in initial rickettsialemia, and then pathogens invade the body, more organs, small blood vessels and capillary endothelial cells to establish new infections The lesions proliferated in a large amount, died, and released toxins caused symptoms of toxemia. In the second week of the disease, immune allergic reactions caused the vascular lesions to worsen.

Pathological changes:

Pathological changes are characterized by hyperplastic, thrombotic, necrotizing vasculitis, especially small blood vessel endothelial cells proliferate to form thrombus, segmental or ring necrosis of the vessel wall, plasma cells, mononuclear cells and lymphocytes infiltration There are certain characteristic and miliary "typhus nodules" or granulomas around the blood vessels. This lesion can be spread throughout the body, especially in the dermis, myocardium, testicular stroma, brain, meninges, kidneys and adrenal glands, liver. In the alveolar wall, etc., in the skin, depending on the degree of vascular damage, there may be a congestive maculopapular rash or a red small bleeding point or even a defect. Some organs or tissues have diffuse interstitial infiltration in addition to typhus typhus nodules. The central nervous system lesions are characterized by cerebral cortex, cerebellum, cerebral ventricle, basal ganglia, pons, and spinal cord lesions. The severity and diffuse changes make the patient's neuropsychiatric symptoms last for a long time after the body temperature drops, and in the sympathetic Typical lesions are occasionally seen in the ganglion, spinal ganglia and nerve pituitary. The meninges may be acute serous inflammation, and the lung may have interstitial inflammation or bronchitis. Muscle may be interstitial inflammation, the kidney is mainly interstitial inflammatory disease, may also be complicated by glomerulonephritis, basophilic mononuclear cell infiltration in the liver portal area, hepatic cells have varying degrees of steatosis and focal necrosis With monocyte infiltration, the spleen and lymph nodes are swollen due to the proliferation of reticuloendothelial cells, lymphoblasts, lymphocytes and plasma cells, and the adrenal glands may have hemorrhage, edema and degeneration of parenchymal cells.

Epidemic typhus prevention

The disease has experienced many pandemics in history, causing major harm. At present, epidemic typhus is still one of the epidemiological surveillance projects of the World Health Organization. The key to prevention is prevention of phlegm, mites and extensive public health. motion.

(1) Patients who manage the source of infection should be treated with cockroaches. After sputum mites, they can be quarantined, but they should still be concentrated in specialized wards or hospitals. Bathing, dressing, hair parts should be washed many times and sprayed with pesticides. For example, 1% to 3% malathion is equal to clothes and hair.

(2) Cut off the transmission route to strengthen health education, encourage the masses to bathe, diligently change clothes, clothes, etc. Available dry heat, damp heat, boiling and other physical methods to kill cockroaches, the temperature needs to be maintained at 85 ° C for 30 minutes; also available epoxy Ethane fumigation chemical sputum, fumigation 6 ~ 24h, the appropriate temperature is 20 ~ 30 ° C.

(3) Inactivated vaccines for susceptible persons include calf vaccine, chicken embryo or duck embryo vaccine and mouse lung vaccine. Domestically used are inactivated mouse lung vaccine, which is suitable for residents in endemic areas and newly entered epidemic areas. Force commanders, epidemic prevention medical staff, laboratory staff, etc., the first year of subcutaneous injection 3 times, each interval 5 to 10 days; 15 years of the first injection 0.5ml, the second and third times each 1ml; 14 years old The following are 0.3 to 0.4 ml and 0.6 (the second time) and 0.8 ml (the third time) respectively. After the next injection, the injection is the same as the third time. After 6 or more vaccinations, it will last longer. The immunity is also effective against Morax's rickettsial infection. The response after vaccination is mild, only mild redness in the local area. The live attenuated E vaccine has been widely used in some countries, subcutaneous injection once, immune effect It can last for 5 years.

Temporary preventive effects can also be obtained by taking tetracycline or chloramphenicol, but most scholars do not advocate the use of it, and can achieve satisfactory results due to early administration after onset.

Epidemic typhus complication Complications, abortion, acute nephritis

Bronchial pneumonia is a common complication of epidemic typhus. Others include otitis media, mumps, endocarditis, meningoencephalitis, etc. Occasionally, necrosis or gangrene, such as toes, fingers, scrotum, earlobe, nose, etc. , gastrointestinal bleeding, pleurisy, abortion, acute nephritis, etc., mild cases and recurrent typhus have few complications.

Epidemic typhus symptoms common symptoms hypothermia rash shock chest pain dysphagia green urine fatigue arrhythmia chills

Generally can be divided into two types, typical and light, and recurrent typhus.

(1) The typical incubation period is 5 to 21 days, with an average of 10 to 12 days. A few patients have prodromal symptoms of 2 to 3 days, such as fatigue, headache, dizziness, chills, low fever, etc. Most of the onset of illness is accompanied by chills and severe Lasting headache, muscle pain in the body, conjunctiva and facial congestion.

1. The body temperature of the fever reaches the peak on the 2nd to 4th day (39~40°C or higher), and the first week is the retention type. The relaxation trend appears from the 2nd week. The heat history is usually 14-18 days, and the heat is 2~. Within 4 days, it quickly returned to normal. In recent cases, the heat type was mostly relaxation or irregular, which may be related to the application of antibiotics.

2. The rash is an important sign. It is found in more than 80% of cases. It appears on the 4th to 6th day of the disease. It is first seen on the chest, back, armpits, upper arms and other places. It develops rapidly throughout the body, and the face usually has no rash. There are fewer rashes in the lower extremities. The rash is round or oval, with a diameter of about 2 to 4 mm. It is a fresh red maculopapular rash. It fades according to it, and then turns into a dark red or a sputum. The rash subsides in 5 to 7 days. The rash can last for 1 to 2 weeks, with brown spots or desquamation.

3. The nervous system symptoms are obvious, and appear very early, manifested as panic, excitement, severe headache, can be accompanied by mental retardation, convulsions, occasional meningeal irritation, muscle and tongue tremor, coma, incontinence, difficulty swallowing, Hearing loss, etc.

4. Cardiovascular symptoms The rate of heart rate increases is generally proportional to the increase in body temperature. In toxic myocarditis, there may be galloping, arrhythmia, shock or hypotension, loss of water, microcirculatory disorders, cardiovascular and adrenal insufficiency. The combined consequences of such.

5. Other symptoms include cough, chest pain, shortness of breath, nausea, vomiting, reduction, constipation, abdominal distension, etc. Occasionally, jaundice, cyanosis, renal dysfunction, mild splenomegaly, and hepatomegaly in some cases.

6. After the body temperature drops, in addition to the neurological symptoms of severe patients, various symptoms are improved, headaches are reduced, and appetite is restored.

(2) Light-weight domestic light cases are more common in recent years, which may be related to the population's immune level. Its characteristics are:

1 The heat stroke is short (8-9 days), the heat is low (about 39 °C); 2 The symptoms of venom are mild, but there is still obvious pain in the whole body.

3 rash is a congestive maculopapular rash, found in the chest, abdomen, no rash also accounted for a certain proportion.

4 The nervous system has mild symptoms and short duration, mainly manifested as headache and excitement.

5 hepatosplenomegaly is rare.

(3) Recurrent typhus typhus is also called Brill-Zinsser disease. It is more common in countries in Eastern Europe and Eastern Europe. It is rarely reported in China. The main clinical manifestations can be summarized as follows:

1 is mild, and the symptoms of toxemia and central nervous system are mild.

2 is a relaxation heat, the heat range is 7 to 11 days.

3 no rash, or only rare maculopapular rash.

4 Dissipated, no seasonality, the incidence rate of the older age group was significantly higher.

Epidemic typhus

(1) The routine white blood cell count of hematuria is mostly within the normal range, about 1/4 is above 10,000/mm3, a few are below 5000/mm3, the number of platelets is generally decreased, eosinophils are significantly reduced or disappeared, proteinuria is common, even There are red, white blood cells and casts.

(2) Serum immunology test should take two or three serum samples (first admission, the second week of the disease course and recovery period), and the increase in titer of more than 4 times has diagnostic value. The commonly used ones have external test, supplement Test, Rickettsia agglutination test, indirect hemagglutination test, etc., although the specificity of the external Fiji test is poor, but because the antigen is easy to obtain and preserve, it is still widely used; its principle is that some Rickettsia and Proteus OX19 The antigenic part of OXK or OX2 is the same, so the patient's serum can produce agglutination reaction on the strained strain. The agglutination titer of the serum of the epidemic typhus patient to the OX19 strain generally exceeds 1:320, but often at the 2nd weekend or recovery. The period begins with a meaningful level or peak; then the titer falls rapidly, turning negative in 3 to 6 months, non-rickettsial diseases such as Proteus urinary tract infection, leptospirosis, relapsing fever, malaria, typhoid fever Positive reactions can also occur, the titer is mostly low, and there are few dynamic changes. Other rickettsial patients can also produce agglutination reaction on OX19 strain, but in addition to endemic typhus, its agglutination titer is generally Also lower, recurrent rash Although cold also caused Platts Rickettsia, but often Felix test was negative, or agglutination titer <1:160.

In the first week of the disease, the tonifying body can reach a meaningful titer (1:40), the positive rate in the first week is 50% to 70%, the second week can reach more than 90%, and the low titer can be maintained at 10~. 30 years, it can be used for epidemiological investigations, and the purified P. rickettsia granule antigen as a complement test, not only has group specificity, but also has specificity, so it can be used to distinguish epidemic typhus and Endemic typhus, recurrent typhus patients with latent antibodies appear earlier, mostly peaked on the 8th to 10th day after the disease, the composition of which is mainly IgG, while epidemic typhus is mainly IgM .

The soluble antigen is used for the rickettsia agglutination test, the specificity is high, the operation is simple, and the micro-method can save the antigen. The positive reaction is earlier than the external Fiji test, and more than 80% of the cases can be positive on the 5th day of the disease; The test tube method>1:40, the micro method>1:4 is a positive reaction, the positive rate is up to 100% at 2 to 3 weeks, the titer peaks in the course of the disease around 1 month, and then disappears rapidly and disappears within a few months. Not suitable for retrospective studies, this test has group specificity, can be used to distinguish with other groups of rickettsial diseases such as tsutsugamushi, various spot heat, Q heat, etc., patients with endemic typhus can have lower titers The positive reaction, the agglutinating antibody in patients with epidemic typhus is IgM, and the agglutinating antibody in patients with recurrent typhus is mainly IgG.

Some characteristics of the indirect hemagglutination test are the same as those of the microagglutination method, and only have group specificity. The hemagglutination antibody appears on the 5th to 7th day of the disease, and rises rapidly. The high value is maintained for 2 to 10 weeks, and the decrease is faster than the complement antibody. Generally, the titer of >1:100 is a positive standard.

Other serum immunological tests include indirect immunofluorescence assay, rocket immunoelectrophoresis, and staphylococcal protein A (SPA) slide synergistic agglutination.

(3) Isolation of pathogens is not suitable for general laboratories. Rickettsia is usually present within 1 week after the disease. It is advisable to inoculate blood into the guinea pig abdominal cavity or chicken embryo yolk sac before the application of antibiotics; After 7-10 days, the animals developed a fever reaction. The sheath and peritoneum were used for scraping, or the brain, adrenal gland, spleen and other tissues were used as smears. After staining, microscopic examination revealed a large number of rickettsia located in the cytoplasm. The scrotal reaction of guinea pigs is negative, or only mild redness without significant swelling, which can be used as a reference for identification of endemic typhus.

(4) Molecular biological examination The DNA probe or PCR method is used to detect the rickettsia-specific DNA, which is fast, specific and sensitive.

(5) Other meningeal irritation should be examined for cerebrospinal fluid. Most of the appearance is clear, white blood cells and protein are slightly increased, sugar is generally normal, and electrocardiogram can show myocardial damage, such as low voltage, T wave and ST segment changes, etc., a few patients may have Liver and kidney function changes.

Diagnosis and diagnosis of epidemic typhus

diagnosis

The following points should be noted:

1. The prevalence of epidemiological data, the season of good development, the history of travel in the epidemic area and the history of contact with the deaf and the possibility of being bitten, have important reference value for diagnosis.

2. Clinical manifestations of fever and heat history, rash date, rash characteristics and obvious central nervous system symptoms can help diagnose.

3. Laboratory examination of blood characteristics, external Fiji reaction, especially in the recovery period, serum titer is more than 4 times higher than the early growth has diagnostic value, but can not be typed, conditional for Platts rickettsia agglutination, complement Combining tests and immunofluorescence indirect staining to detect specific antibodies for type identification, the positive results of animal vaccination are particularly diagnostic.

Differential diagnosis

1. Typhoid summer, more incidence in autumn, slower onset, body temperature rises stepwise, relatively slow pulse, rash appears later, rosy rash, less, psychiatric symptoms appear relatively late, course Longer, bone marrow, blood, urine, and fecal cultures have typhoid bacillus growth, positive for fat.

2. Returning to the heat and returning to the heat is also spread by the cockroaches. The epidemic season is the same as this disease, but there is a typical periodic high fever, rash is rare, occasionally jaundice, peripheral blood white blood cell count increases, there is a large amount of blood in fever The spiral body should also pay attention to the occasional two diseases in the epidemic season.

3. Leptospirosis is summer, autumn is popular, there is history of contact with infected water, no skin rash, gastrocnemius tenderness is obvious, and there are many jaundice, hemorrhage, hemoptysis, leptospirosis complement test and agglutination dissolution test.

4. Endemic typhus is mostly regional epidemic or sporadic, with more incidence in summer and autumn, milder symptoms, shorter heat history, generally 9 to 14 days, rash is thinner, mostly congestive, less bleed and small The scrotum reaction of guinea pigs is obvious, and even the testicles are swollen. The serum of patients has specific complement binding and agglutination effects on rickettsia.

5. Others must be differentiated from tsutsugamushi, epidemic cerebrospinal meningitis, lobar pneumonia, epidemic hemorrhagic fever and other viral infections.

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