Overview.
Typhus is divided into epidemic typhus and endemic typhus. The former is transmitted by Rickettsia prowazekii through human lice, and is complicated by bronchopneumonia, second only to Q fever pneumonia; the latter, also known as murine typhus, is an acute infectious disease transmitted by Rickettsia motti through rat fleas, and its clinical features are similar to those of epidemic typhus, but the condition is milder and the complications of pneumonia are less frequent.
Epidemiology
Typhus occurs globally. The epidemiological characteristics of epidemic typhus and endemic typhus are different: in the former, the patient is the only source of infection of the disease, and the body louse is the main vector, the pathogen is present in the feces of the body louse and invades into the body by the skin lesions, and partly because of the teeth biting of the louse so that it invades into the human body from the mucous membranes of the oral cavity or the louse feces are dried and formed into aerosols through the respiratory tract and the conjunctiva; in the latter, the main source of infection is the mouse and the small mouse by the mouse – mouse-flea-mouse cycle, the epidemiological characteristics are similar to those of epidemic typhus. The main source of the latter is house mice and small house mice in the form of rat-rat flea-rat cycle, only when people are bitten or scratched by rat fleas resulting in skin breakage, feces containing Rickettsia mordecai contaminate the local area before the pathogen enters the body, through the digestive tract, the respiratory tract, and conjunctivae of the eye can also be invasive. People are generally susceptible to typhus and get a certain degree of immunity after the disease, but the immunity of epidemic typhus can not be maintained for a long time, resulting in recurrence of Brill’s disease.
Causes
The causative agent of epidemic typhus is Rickettsia prowazekii, which is a tiny bacillus-shaped bacterium with a length of 0.3-0.6 μm and a width of about 0.3 μm, and is usually parasitized in the vascular endothelial cells of patients and the epithelial cells of the intestinal wall of body lice.
Symptoms
The incubation period of the disease is 5 to 15 days. Most of the patients have a rapid onset of the disease, with high fever, chills, headache, muscle pain and generalized rash, often accompanied by neurological and gastrointestinal symptoms such as unresponsiveness, delirium, tremor of hands, etc. The disease is characterized by abdominal distension, abdominal pain, constipation, etc. The disease is usually associated with a high fever, chills, headache, muscle pain and generalized rash. Lung involvement can form typical rickettsial bronchopneumonia, manifested in the first few days of the disease appeared obvious cough, mostly dry cough or a small amount of mucous sputum, accompanied by chest tightness, shortness of breath, respiratory growth rate becomes shallow with the aggravation of the disease can appear lips and nail beds cyanosis. Chest auscultation can be heard wet rhonchi or twisted sound. In some patients, due to the mild condition, only bronchiolitis changes are manifested, which is more likely to occur in endemic typhus. In severe cases, signs and symptoms of heart failure and pulmonary edema are present.
Examination
(I) Laboratory tests
1. Blood tests
The white blood cell count is mostly in the normal range, a few are higher than 10×109/L, and occasionally below 5×109/L. The platelet count is decreased. Platelet count is decreased. Eosinophils are significantly reduced or absent.
2. Serologic tests
Exophilic reaction: Epidemic typhus patients can produce high efficiency agglutination reaction against Aspergillus OX19 strain, especially at the end of the second week of the disease, which can reach the highest peak (between 1:320 and 1:5120). Similar agglutination reactions can also occur in endemic typhus but with lower agglutination potencies, mostly between 1:160 and 1:640.
3. Animal inoculation
Guinea pigs are sensitive to Rickettsia prowazekii, early onset of the patient’s blood inoculated in the male guinea pig peritoneal cavity, 7 to 10 days after the guinea pig fever, peritoneal scraping examination of the cytoplasm can be found in a large number of pathogens in the guinea pig scrotum is only mild redness, there is no obvious swelling, in order to differentiate it from the endemic typhus.
(ii) Other auxiliary examinations
Chest X-ray examination may show speckled or patchy exudative hyperdense shadows in the lungs with generalized pneumonia or bronchopneumonia images, and occasional shadows of lobar and segmental pulmonary solid changes.
Diagnosis
Diagnosis is based on epidemiology, duration of fever, rash, chest symptoms and signs, and extrapyramidal reactions. Characteristics such as season of prevalence, severity of symptoms, nature of rash, and complement binding test guinea pig scrotal reaction are borrowed.
Differential diagnosis
Differentiate from typhoid fever, leptospirosis, scrub typhus, lobar pneumonia, influenza and other acute infectious diseases with rash.
Treatment
The treatment is the same as that for Q fever pneumonia. Chloramphenicol, tetracycline and doxycycline are effective. Accompanying bacterial infection should be based on sputum culture and drug sensitivity results to choose effective antibiotics. For those with severe neurological disorders such as coma, dysphagia, dyspnea and incontinence, nursing care should be strengthened with nasal feeding and oxygen intake, endotracheal intubation and mechanical ventilation if necessary, and ensure the airway is open. Complicated heart failure, shock, should be actively treated.
Prognosis
In recent years, the mortality rate of epidemic typhus has decreased greatly. As long as early diagnosis and timely treatment, the effect is satisfactory and the prognosis is good.
Prevention
Starting from the management of infectious sources and cutting off the transmission channels, vigorously carry out the activities of exterminating lice and preventing lice, exterminating rats and fleas, and enhancing the awareness of all people on hygiene and disease prevention. Inactivated vaccination is available for people living in areas where epidemic typhus is prevalent, and prophylactic vaccination is available for certain personnel engaged in the operation of pathogens and the extermination of rats.