Endemic typhus

Introduction to endemic typhus Endemic typhus (endemictyphus), also known as sputum or mouse-type typhus, is an acute infectious disease caused by rickettsia. The patient is the only source of infection. The clinical manifestations are similar to those of epidemic typhus, but the symptoms are mild, the course of disease is short, the prognosis is good, and the mortality rate is low. The course of disease is 2--3 weeks. basic knowledge Sickness ratio: 0.0001% Susceptible people: no specific people Mode of transmission: insect vector transmission Complications: meningitis pneumonia hepatitis

Cause of endemic typhus

[pathogen]

The pathogen is Rickettsia mooseri, which is in the shape of a polymorphic globule, about 0.3--1×0.3--0.4 m, and up to 4 m. There are two main antigens in rickettsial: 1 soluble antigen, which is a group-specific antigen, which can be used to distinguish it from other groups of rickettsia; 2 granule antigen, containing species-specific antigen. Benike's corpuscles are similar in morphology, staining and resistance to heat and disinfectants, but are rarely arranged in long chains. Both contain 3/4 specific particulate antigens and 1/4 group of specific soluble antigens. Inoculation of pathogens in the peritoneal cavity of mice can cause rickettsial system and peritonitis, and pathogens can be found in various organs.

Although the morphology, staining characteristics, biochemical reaction, culture conditions and resistance of rickettsii are similar to those of Platts. But it can be distinguished in animal experiments.

1 Morse rickettsia can cause fever or death in rats, and survive in the brain for several months, so it can be used to preserve strains or passaging. The Platts rickettsia only caused the latent infection of the rats.

2 The scrotal reaction of guinea pig caused by rickettsial is far more obvious than that of Platts rickettsia. After vaccination of male guinea pigs with guinea pigs, the scrotum is highly edematous, except for fever. For the scrotum of guinea pigs. Moritz rickettsia multiplies in the plasma cells of the testicular sheath, and a large number of rickettsia can be found in the smear of the sheath exudate. Platts rickettsia only causes mild scrotal reactions.

3 Inoculation of M. rickettsia in the abdominal cavity of mice can cause lethal peritonitis and sepsis.

Since the Moritz rickettsia and the rickettsia have a common soluble antigen, the soluble antigen is heat-resistant and is common to both, so that a cross reaction can occur. Both can undergo agglutination reaction with Proteus OX19. However, the thermolabile particulate antigens are each specific, and they can be distinguished by an agglutination test and a complement binding test.

[Pathogenesis]

It is similar to epidemic typhus, but vascular lesions are mild, and thrombosis in small blood vessels is rare.

Endemic typhus prevention

1. Mainly to eliminate rodent, kill cockroaches, treat patients early and isolate.

2. The disease is scattered, so there is no need to prevent vaccination. If there is an outbreak, vaccination should be carried out for high-risk groups. Inactivated vaccine can be used.

Endemic typhus complications Complications meningitis pneumonia hepatitis

Concurrent gastrointestinal symptoms, joint muscle pain, lymphadenopathy, splenomegaly, meningitis, pneumonia, hepatitis and pericarditis, etc., a few cases are serious, can be complicated by multiple organ failure.

Endemic typhus symptoms Common symptoms Hepatomegaly diarrhea, rash, maculopapular rash, heat, nausea

The incubation period is 5 to 21 days, with an average of 10 to 14 days.

(a) typical typhus

Often acute onset, a small number of patients have headaches, dizziness, chills, fatigue and other prodromal symptoms.

1. Invasion period More fever, accompanied by chills, followed by high fever. The body temperature reaches 39 ° C ~ 40 ° C within 1 to 2 days, showing a heat retention type, and a few are irregular or relaxation heat type. It is usually found in the chest and abdomen and spreads rapidly to the neck, back, shoulders, arms, lower limbs, etc. within 24 hours. The face and palmar are rare. With severe toxemia symptoms, severe headache, restlessness, insomnia, dizziness, tinnitus, hearing loss. The words are vague and the muscles are sore. At this time, the patient's cheeks, neck, and upper chest are flushed, and the conjunctiva is highly congested, which is like drunkenness. There is a wet rales at the bottom of the lungs. The liver and spleen are swollen, soft and tender after 3 to 4 days of fever.

1) Frequent fever onset, a small number of patients have 1 to 2 days of fatigue, anorexia and headache and other prodromal symptoms. The body temperature gradually rises, reaching a peak on the first weekend, mostly around 39 °C, leaving heat or relaxation heat. The heat stroke is mostly 9 to 14 days, and the body temperature gradually returns to normal. With cold, headache, systemic pain and conjunctival congestion.

2) Patients with central nervous system symptoms have milder symptoms than epidemic typhus, which are characterized by headache, dizziness, insomnia, less irritability, paralysis, drowsiness and disturbance of consciousness. About 50% may be accompanied by mild swelling of the spleen. Hepatomegaly is less common.

2. The rash period of 3.50% to 80% of patients began to appear on the 5th day of the onset of rash, initially red spotted, about 1 ~ 4mm in diameter, followed by dark red maculopapular rash, pressure fading, rarely hemorrhagic. It is usually found in the chest and abdomen and spreads rapidly to the neck, back, shoulders, arms, lower limbs, etc. within 24 hours. The face and palmar are rare. Severe cases can be seen in the palms and soles of the feet, but there is no rash on the face and fewer lower limbs. The size and shape of the rash are different, about 1 to 5 mm, the edges are not uniform, most of them are isolated, and occasionally merged into pieces. From the beginning, it is often the fading of congestive rash or papules, and then it turns into dark red or hemorrhagic maculopapular rash. The pressure does not fade, and the rash lasts for about 1 week. There is a brown pigmentation in the back. In recent years, there have been less than 10% of reports of rashes in China. The time and characteristics of rash appear similar to epidemic typhus, but the number of rashes is small, mostly congestive, hemorrhagic rash is rare.

As the rash appears, the symptoms of poisoning increase and the body temperature continues to rise, reaching 40 to 41 °C. At the same time, neuropsychiatric symptoms worsened, mental retardation, paralysis, irritability, upper limb tremors and unconscious movements, and even coma or insanity. There may also be meningeal irritation, but the cerebrospinal fluid examination is normal except for increased pressure. The pulse of the circulatory system often accelerates with the increase of body temperature, and the blood pressure is low. In severe cases, it can be shocked. Some patients with severe poisoning may develop toxic myocarditis, which is characterized by low heart sound, arrhythmia, and gallop. There are also a small number of patients with bronchitis or bronchial pneumonia. The digestive system has loss of appetite, nausea, vomiting, bloating, constipation or diarrhea. Most patients have splenomegaly and less hepatomegaly.

3. Recovery period The disease begins to fever on the 13th to 14th day of the disease, usually 3 to 4 days to retreat, in a few cases, the body temperature can be suddenly reduced to normal. As the symptoms improved, the appetite increased, and the physical strength returned to normal within 1 to 2 days. In severe cases, mental symptoms, tinnitus, deafness, and hand tremors take longer to recover. The entire course of disease is 2 to 3 weeks.

(two) light typhus

A small number of epidemic typhus cases are mostly light. Its characteristics are 1 systemic poisoning symptoms, but the body is sore, headache is still more obvious. 2 The heat stroke is short, lasting for 7 to 14 days, with an average of 8 to 9 days, and the body temperature is generally around 39 °C. 3 rash is less, a small amount of congestive rash appears in the chest and abdomen. 4 nervous system symptoms are mild. Excitement, irritability, paralysis, and hearing loss are rare. 5 liver, splenomegaly is rare.

(three) recurrent typhus

Stronger immunity can be obtained after epidemic typhus. However, some patients may be latent in the body due to immune factors or improper treatment, and may recur after several years or decades after the first onset. Its characteristics are: 1 short course, about 7-10 days. 2 fever is irregular and the condition is mild. 3 rash is rare or no rash. 4 The external Fischer test is often negative or low titer, but the complement fixation test is positive and the titer is high.

(4) Others

About 1/3 to 1/2 of patients have mild splenomegaly. The myocardium is rarely affected, so the symptoms and signs of the circulatory system are rare. Complications rarely occur. However, Japan recently reported an outbreak of endemic typhus in a certain middle school student. More than 30 people have developed symptoms, and the clinical manifestations are fever, chills and sore throat. The diagnosis was confirmed by positive IgM and IgG of rickettsial. Most of the prognosis is good, cured with minoxidin. A small number of cases are seriously ill, and multiple organ failures occur and die. The United States reported the characteristics of endemic typhus in children. 49% of patients had fever, headache and rash, and 77% had digestive symptoms such as loss of appetite, nausea, vomiting and diarrhea. The course of disease is 12 days (5 to 29 days). Laboratory tests can present mild abnormalities in multiple organs, systems (such as liver, kidney, blood, and central nervous system), but serious complications are rare.

The diagnosis points of this disease:

1. There are rats in the living or working environment, or the disease has occurred.

2. Clinical manifestations such as fever, rash and other characteristics are similar to epidemic typhus, and are lighter.

3. Serological diagnosis has a positive result.

According to the above points, it is not difficult to make a diagnosis.

Endemic typhus examination

Early onset (within 7 days), 1/4 to 1/2 cases have mild leukopenia and thrombocytopenia. Subsequently, nearly one-third of patients have elevated white blood cells, prothrombin time can be prolonged, but DIC is less. See, 90% of patients with serum aspartate aminotransferase increased slightly, ALT, AKP and LDH also increased, other abnormalities still have hypoproteinemia (45%), hyponatremia (60%) ) and hypocalcemia (79%), elevated cases of elevated serum creatinine and urea nitrogen.

The patient's serum can also undergo agglutination reaction with Proteus OX19 strain, the titer is 1:1601:640, which is lower than epidemic typhus; the positive reaction appears on the 5th to 17th day, the average is 1115 On the sick day, the foreign Filipino test is sensitive, but its specificity is poor. It can not be used to distinguish it from epidemic typhus. The more sensitive and specific tests include indirect immunofluorescent antibody detection, latex agglutination test, complement binding test, solid phase immunoassay. Etc., the antigen used is a specific Mohs rickettsial antigen, the indirect fluorescent antibody titer increased by 50% within 1 week after onset, and increased by almost 100% within 15 days. Conditional units can be detected by PCR. A rickettsial-specific nucleic acid in a blood sample.

It is not advisable for the general laboratory to perform guinea pig scrotal reaction tests to avoid the spread of infection between animals and the infection of laboratory workers.

1. Blood picture Most patients have a normal white blood cell count, which is rare or rare.

2. Serological examination

(1) OX19 was positive in the exo-fi reaction, and the titer was lower than epidemic typhus. The positive reaction occurred on 5-17 days, with an average of 11-15 days.

(2) The agglutination test is carried out with the sera of the patient and the serum of the patient, and the complement binding test and the indirect immunofluorescence test can be distinguished from the epidemic typhus.

(3) Some patients may have elevated serum alanine aminotransferase.

(4) DNA probe hybridization combined with PCR gene amplification technology, detection of blood rickettsial DNA in patients can also be used for early diagnosis of this disease.

3. Animal inoculation Inject the patient's blood into the abdominal cavity of male guinea pigs. The animals usually start to heat 5-7 days after inoculation. The scrotum is swollen due to testicular meningitis. The smear of the sac exudate shows a large number of pathogens in the swollen cytoplasm. It is necessary to pay attention to the fact that the general laboratory is not suitable for animal testing.

Electrocardiogram can show low voltage, ST-T changes, etc., chest X-ray examination common signs of pulmonary interstitial infection.

Diagnosis and diagnosis of endemic typhus

It is mainly distinguished from epidemic typhus. The pathogen is Platts rickettsia, the source of infection is the patient, and the body is used as the medium. It occurs mostly in winter and spring and is popular. Symptoms are similar to local typhus, but the condition is heavier, the rash is more, the hemorrhage is more common, the nervous system symptoms are obvious, and the agglutination of Platts rickettsia is positive.

In addition, it needs to be distinguished from typhoid, flu, ascariasis, and leptospirosis.

1. Typhoid fever: It is an acute infectious disease caused by Salmonella typhimurium. It is characterized by persistent bacteremia, reticuloendothelial involvement, and minimal abscess and ulceration at the distal ileum. Typical clinical manifestations include persistent high fever, abdominal discomfort, hepatosplenomegaly, low white blood cells, some patients with rose rash and relatively slow pulse. However, the clinical manifestations of this disease are mainly caused by the spread of pathogens through the blood to the whole body organs, but not caused by local intestinal lesions. Clinical diagnosis can be made based on epidemiological data, clinical and immunological examination results, but the diagnosis of typhoid fever is based on the detection of pathogenic bacteria.

2. Influenza: referred to as influenza, is an acute respiratory infection caused by influenza virus. The flu can cause upper respiratory tract infections, pneumonia, and various conditions outside the respiratory tract. Typical flu, violent fever, generalized pain, significant fatigue, and mild respiratory symptoms. Facial flushing, conjunctival congestion, pharyngeal congestion, and follicles on soft palate. The disease is caused by influenza virus, which belongs to the family of Orthomyxoviridae, 80 to 120 nm in diameter, spherical or filamentous. Influenza viruses can be divided into three types: A (A), B (B), and C (C). The type A virus often undergoes antigenic variation, which is highly contagious, spreads rapidly, and is prone to widespread epidemics.

3. tsutsugamushi disease: Also known as scrub typhus, it is an acute infectious disease caused by rickettsia tsutsugamushi. It is a natural epidemic disease, rodents are the main source of infection, and larvae are the vector. Clinical features include hyperthermia, toxemia, rash, eschar and lymphadenopathy.

4. Leptospinosis: is an acute infectious disease caused by various types of pathogenic Leptospira (abbreviated as hooks). It is exposed to infected wild animals and livestock, and the hooks enter the human body through the skin of the exposed parts to obtain infected zoonotic diseases. Rats and pigs are the main source of infection. The clinical manifestations vary depending on the level of individual immunity and the strains affected. The typical onset is rapid, early high fever, fatigue, body aches, conjunctival hyperemia, diaphragmatic tenderness, superficial lymphadenopathy; middle stage may be associated with diffuse hemorrhage of the lungs, obvious liver, kidney, central nervous system damage, late Most patients recover, and a small number of patients may have post-fever, uvitis, and occlusion of the cerebral artery. Diffuse pulmonary hemorrhage, liver and kidney failure are often the cause of death.

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