What Is Epidemic Typhus?

Epidemic typhus is also called lice-borne typhus or "typical typhus". Relapses may occur months to years after the epidemic typhus is called recurrent typhus, also known as Brill-Zinsser disease. It is an acute infectious disease transmitted by rickettsialia through body lice. Its clinical features are persistent high fever, headache, petechiae-like rash (or maculopapular rash), and symptoms of the central nervous system. The natural course is 2 to 3 weeks.

Basic Information

nickname: Typhus typhus, typhus typhus
English name: epidemic typhus
Visiting department: Infectious Diseases
Common causes: Rickettsia

Common symptoms: Persistent high fever, headache, petechiae-like rash (or maculopapular rash), central nervous system symptoms
Contagious: Have
way for spreading: Human lice-borne

Causes of epidemic typhus

The pathogen of this disease is rickettsial Plasmodium, which is parasitic in the cytoplasm of vascular endothelial cells of humans and animals and in the epithelial cells of the intestinal wall of human lice. It also attaches to red blood cells and platelets during rickettsemia. The basic shape is a micro club shape, arranged in a chain shape along the long axis. However, the developmental stages in the lice intestine are polymorphic and can be spherical, short rod-shaped, rod-shaped, or long-lined. 0.3 1m × 0.3 0.4m, Gram staining was negative. The chemical composition and metabolites of pathogens include proteins, sugars, fats, phospholipids, DNA, RNA, various enzymes, vitamins and endotoxin-like substances. The lipopolysaccharide layer of its cell wall has an endotoxin-like effect. Platts rickettsia is very sensitive to heat, ultraviolet rays, and general chemical disinfectants. It can be inactivated at 56 ° C for 30 minutes, has a strong tolerance to low temperature and dryness, and can survive for several months in dry lice feces.

Clinical manifestations of typhus typhus

Generally can be divided into two types of typical and mild, and there are recurrent typhus.

Typical symptoms

The 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, and low fever. Most have rapid onset of illness, with chills, severe and persistent headaches, muscle pain throughout the body, conjunctiva and facial congestion.

(1) Fever body temperature reaches its peak (39 to 40 ° C or higher) on the 2nd to 4th days. It is stubborn in the first week and has a tendency to relax from the second week. The heat course is usually 14 to 18 days, and the body temperature quickly returns to normal within 2 to 4 days. In the cases reported in recent years, the thermal pattern is mostly relaxation or irregularity, which may be related to the application of antibiotics.

(2) Rash is an important sign. It is seen in more than 80% of cases. It appears on the 4th to 6th days of the disease course. It is first seen in the chest, back, axilla, and both sides of the upper arm. It quickly develops to the whole body within one day. There is usually no rash on the face and fewer rashes on the lower extremities. The rash is round or oval, with a diameter of about 2 to 4 mm. It is initially bright red maculopapular rash, which fades, and then turns to dark red or petechiae. The rash subsided in 5 to 7 days, and the petechiae-like rash lasted for 1 to 2 weeks, leaving brown spots or scaling.

(3) Nervous system symptoms are obvious and appear very early, manifested as panic, excitement, severe headache, and may be accompanied by dullness, delirium, occasional meningeal irritation, muscle and tongue tremor, coma, incontinence, difficulty swallowing, Hearing loss, etc.

(4) Symptoms of cardiovascular system Heart rate increase is generally directly proportional to temperature rise, and galloping and arrhythmia may occur when toxic myocarditis occurs. Shock or hypotension is the combined effect of dehydration, microcirculation disorders, cardiovascular and adrenal insufficiency.

(5) Other symptoms include cough, chest pain, shortness of breath, nausea, vomiting, subsistence, constipation, abdominal distension, and occasionally jaundice, cyanosis, and impaired renal function. The spleen is slightly enlarged and hepatomegaly is present in some cases.

2. Lightweight

Mild cases are more common and may be related to the immune level of the population. Its characteristics are:

(1) Short thermal range (8-9 days) and low heat content (about 39 ° C);

(2) Symptoms of venom are mild, but there is still obvious pain throughout the body;

(3) The rash is congestive maculopapular rash, which is found on the chest and abdomen, and a proportion of those who do not have a rash;

(4) The symptoms of the nervous system are light and short duration, mainly manifested as headache, excitement, etc .;

(5) Hepatosplenomegaly is rare.

3. Recurrent typhus

It is also called Brill-Zinsser disease. It is more common in foreign countries and people who migrate to the United States from Eastern Europe. There are few reports of this disease in China. The main clinical manifestations can be summarized as:

(1) Light passage, mild symptoms of toxemia and central nervous system;

(2) It is a relaxation heat, the heat range is 7-11 days;

(3) No rash or rare spotted pimples;

(4) Spread, no seasonality, the incidence rate is significantly higher in the older age group.

Examination of typhus typhus

Hematuria routine

Most white blood cell counts are within the normal range. Platelet counts generally decrease and eosinophils significantly decrease or disappear. Proteinuria is common, with occasional red and white blood cells and casts.

2. Serum immunological test

It is advisable to take two or three serum samples (first admission, the second week of the disease course, and the recovery period), and those with a titer of 4 times or more have diagnostic value. Commonly used are Wai Fei test, complement binding test, Rickettsia agglutination test, indirect hemagglutination test and so on. Although the Wai Fei test has poor specificity, it is still widely used because the antigen is easy to obtain and preserve; the principle is that some of the rickettsial body is the same as the antigenic portion of Proteus OX19, OXK or OX2, so the patient's serum is not suitable for the relevant deformation. Strains can produce agglutination reactions. The agglutination titer of OX19 strain in patients with epidemic typhus generally exceeds 1: 320, but often reaches a meaningful level or peak at the beginning of the second week or the recovery period; the titer then decreases rapidly, within 3 to 6 months. Go negative.

3. Pathogen isolation

Not suitable for general laboratories. Rickettsiaemia usually occurs within 1 week after the disease. It is advisable to collect blood and inoculate the guinea pig's abdominal cavity or chicken yolk sac before the application of antibacterial drugs; or to collect body lice from patients and observe them in the laboratory until the lice die. After that, the rickettsial body was examined by smear staining. Guinea pigs are sensitive to Pritzeri, and 3 to 5 ml of blood from early-stage patients can be injected into the abdominal cavity of male guinea pigs. After 7 to 10 days, the animal develops a fever reaction. Take the sheath and peritoneum for scraping tests, or take the brain and adrenal glands Spleen, spleen and other tissues are smeared, and microscopic examination after staining can find a large number of Rickettsia in the cytoplasm. The scrotal reaction of the guinea pigs was negative, or there was only slight redness without obvious swelling, which can be used as a reference when identifying endemic typhus.

4. Molecular biology inspection

The use of DNA probes or PCR methods to detect Plasmodium rickettsii specific DNA is fast, specific, and sensitive.

5. Other

Those with meningeal irritation should be examined for cerebrospinal fluid. The appearance is mostly clear, white blood cells and protein are slightly increased, and glycoproteins are generally normal. ECG can show myocardial damage, such as low voltage, T wave and ST segment changes, etc. A few patients may have changes in liver and kidney function.

Diagnosis of typhus typhus

Epidemiological information

The local epidemic situation, the season of occurrence, the history of residence in the epidemic area, the contact history with lice and the possibility of being bitten by lice, etc., have important reference values for diagnosis.

2. Clinical manifestations

Fever and heat course characteristics, date of rash, rash characteristics, and obvious central nervous system symptoms are helpful for diagnosis.

3. Laboratory inspection

Hematological characteristics, Wai Fei reaction positive, especially in the recovery period serum titer increased more than 4 times earlier than the diagnostic value, but can not be typed. Conditions can be used for Platts agglutination reaction, complement binding test and immunofluorescence indirect staining to detect specific antibodies for type identification. Positive results from animal vaccination are particularly diagnostic.

Epidemic typhus treatment

General treatment

After the patient was admitted to the hospital, he changed his clothes, lice, and stayed in bed. Keep mouth and skin clean. Critically ill patients should turn over frequently to prevent complications. Provide a nutritious and digestible diet, supplement a large amount of vitamin B, C and sufficient water and electrolytes.

2. Pathogen treatment

Chloramphenicol and tetracycline drugs have specific effects on this disease. Symptoms generally begin to decrease after more than ten hours after administration, and fever is completely reduced within 2 to 3 days. Chloramphenicol is taken orally 3 to 4 times, and the amount of chloramphenicol is reduced after fever, continued for 3 days, or extended to 5 to 7 days to prevent recurrence in the near future. Doxycycline is taken once a day, and another dose is taken 2 to 4 days if necessary. Although the clinical effect of chloramphenicol is good in clinical practice, it is no longer preferred because of its prominent side effects. Doxycycline is more commonly used, with simple treatment, fewer side effects, and satisfactory results. Recently, erythromycin, fluoroquinone drugs (such as norfloxacin, enoxacin, ciprofloxacin) and minocycline have also achieved good results in treating the disease.

3. Symptomatic treatment

High fever is mainly based on physical cooling, and small doses of antipyretic and analgesics can be given when necessary. Adverse corticosteroids can be given to those with severe symptoms of toxemia, with hypovolemic tendency or shock treated as septic shock. For those with heart failure, we should pay attention to reduce the load on the heart. Cardiotonic drugs such as lanolin C or lanolin K can be used. Pain medicine can be given for headaches. Dexamethasone and other treatments can be given to those with mental symptoms.