Chagas disease

Introduction to Chagas disease Chagas disease is a protozoal infectious disease caused by trypanosomes infection. There are two types of trypanosomiasis, namely African trypanosomiasis and Chagas disease. The former is distributed in western and central Africa. The main source of infection is human. The medium of transmission is the tsetse fly. The latter is distributed in eastern Africa. Animals and humans are the source of infection. The medium of transmission is the genus. African trypanosomiasis is dominated by neurological diseases. basic knowledge The proportion of children: the incidence rate of children under 12 years old is about 0.004%-0.009% Susceptible people: no specific people Mode of transmission: insect vector transmission Complications: congestive heart failure, ventricular premature contraction, aneurysm, pulmonary embolism, arrhythmia

The cause of Chagas disease

Causes:

Blood-sucking locusts are infected by sucking the blood of animals or humans containing trypanosomes. The inhaled trypanosomes proliferate in the intestines of the mites and are excreted with the faeces. When the insect bites the wound or the mucous membrane of the skin is damaged, it is infected. When the worms are contaminated, the trypanosomes can be transmitted to the host. The locusts are commonly called vinchuca in Argentina, meaning falling by themselves. This worm lives on the walls and roof of the house, and can fall when it is ready for food at night. To the person who sleeps underneath, often biting the eye circumference, when the trypanosomes in the feces enter the human body through the skin, the human body is infected, and the skin lesion caused by entering the human body through the skin is called chagas nodule. In addition, the disease can also be transmitted through blood transfusion or congenital, but both approaches are rare.

Pathogenesis:

The pathogenesis of this disease is unknown. The positive rate of detection of trypanosomes in patients who died of the disease is not high. At present, the autoimmune mechanism of the disease has been proposed. It is believed that after infection with trypanosomes, autoreactive cells can be produced in vivo. Toxic T lymphocytes, which can dissolve normal cells in the host. In addition, various antibodies against myocardial cell sarcoplasmic reticulum, fibrin and other cellular components may also be involved in the development of Chagas myocarditis, denervation of the cardiac parasympathetic nerve. The effect is thought to be the cause of chronic Chagas disease.

Pathological changes:

Neurological and autonomic ganglia often have abnormal changes, and megacolon and giant esophagus can occur. Different strains of Trypanosoma gondii cause regional differences in the pathological manifestations of this disease, such as giant esophagus and megacolon are common in Brazil, but in Venezuela. However, it is rare to see that there are many denervation of the parasympathetic nerve in patients with chronic Chagas disease. Heart pathological examination shows enlargement of the whole heart and hypertrophy of the heart. More than half of the left ventricle (occasionally the right ventricle) has thinned and bulged apex. Such as ventricular aneurysm, this is a characteristic change of the heart of Chagas disease, there may be thrombosis in the heart cavity, common thrombus fills the apex, and there are often thrombosis in the right atrium.

Chagas disease prevention

1. Eliminate the habitat and breeding sites of cone mites in the epidemic areas, reduce their quantity, and timely spray the drugs to kill the mites to control the media, improve the living conditions of the residents, not live in the huts, hang mosquito nets, and reduce the chance of disease.

2. Strengthen the examination of blood donors and maternal blood trypanosomes and serum anti-trypanosome antibodies in the epidemic areas to reduce the incidence of Chagas disease and congenital Chagas disease after transfusion.

3. Closely observe the performance of cardiomyopathy during the period of 10 to 20 years after the occurrence of trypanosomiasis, early detection and active treatment.

Chagas disease complications Complications Congestive heart failure ventricular premature systolic aneurysm pulmonary embolism arrhythmia

1. Congestive heart failure: Chronic trypanosomiasis is characterized by enlarged heart, extensive myocardial damage, and abnormal cardiac structure. In addition to long-term arrhythmia or ventricular aneurysm, congestive heart failure can occur in the advanced stage of the disease. .

2. Arrhythmia: This disease is very easy to be complicated by malignant ventricular arrhythmia, especially ventricular premature contraction, ventricular tachycardia, ventricular fibrillation, etc.; 2 / 3 patients have heart block, often right bundle Branch conduction block and so on.

3. ventricular aneurysm: myocardial fibrosis can be seen in the myocardium of the patient, cardiac hypertrophy, dilatation of the atrioventricular cavity, and aneurysm-like protrusion and thrombosis in the apex.

4. Embolization: Thrombosis that is detached from the apex and atrium can cause embolism of the brain or lungs. In severe cases, sudden death occurs.

Symptoms of Chagas disease Common symptoms Cardiac sudden cardiac failure Myocardial pain response Atypical chest pain ECG abnormal heart arrhythmia Tachycardia Atrioventricular block

Chagas disease can be divided into acute phase, occultation phase and chronic phase according to the natural history.

1. Acute trypanosomiasis : After the trypanosomes enter the human body, they begin to multiply and spread widely in the body, but less than 10% of the infected people can develop acute trypanosomiasis, which occurs most frequently in young children, and the symptoms are more than adulthood. Serious, mainly manifested as fever, myalgia, sweating, hepatosplenomegaly, myocarditis and its complicated heart failure, occasional meningoencephalitis, etc., most patients with clinical symptoms can be relieved after several months, the mortality rate is about 10 %.

2. Occult trypanosomiasis : The disease then enters the asymptomatic occult period. Electrocardiogram changes often occur in this period. It is currently considered that ECG abnormality is an important indicator of the ultimate occurrence of cardiomyopathy and advanced mortality.

3. Chronic trypanosomiasis: about 20 years after trypanosome infection, about 30% of infected people may have clinical manifestations of chronic trypanosomiasis, such as heart enlargement, heart failure, arrhythmia, thromboembolism, atypical chest pain , right bundle branch block and sudden death, the myocarditis of this disease is congenital heart disease, can also be segmental myocardial damage and ventricular dysfunction, clinical ventricular arrhythmia, atrioventricular block, congestive heart Failure and thromboembolism are its main manifestations.

(1) arrhythmia: this disease is prone to ventricular arrhythmia, and is the most common cause of sudden death. Frequent ventricular premature contraction can be the only clinical manifestation of this disease, and those with other heart disease, There is no ventricular premature contraction without exception. Compared with other cardiomyopathy, the ventricular premature contraction of this disease is more frequent, reaching tens of thousands of times per day, and it continues to occur frequently for a period of time, with left ventricle. Ventricular arrhythmias are more common in patients with ventricular aneurysm or cardiac dysfunction, or both, and the likelihood and severity of ventricular arrhythmia is related to the extent and severity of myocardial lesions, persistent ventricular Cardiac tachycardia is not uncommon, and is often associated with left anterior branch block or double bundle branch block, rather than simple right bundle branch block, the incidence of cardiac conduction system involvement can reach 80%, often expressed as Right bundle branch block, or left anterior branch block, or both, is considered to be a typical ECG manifestation of the disease. Studies have found that conduction block seems to be progressively aggravated, from incomplete right bundle Conduction block turns to complete right Branch block, from the left anterior branch block, and finally to complete atrioventricular block, the latter is common in patients with advanced heart failure, pathological Q wave on the ECG often indicates poor prognosis; ST segment elevation And T wave abnormalities usually suggest the presence of an aneurysm.

(2) Congestive heart failure: is the result of extensive and irreversible myocardial injury and abnormal cardiac structure, most of which occurs after 40 years of age, often later than atrioventricular block or ventricular aneurysm, which is the late manifestation of this disease.

(3) autonomic dysfunction: this disease often occurs early in the cardiovascular autonomic dysfunction, mainly due to the denervation of parasympathetic nerves, manifested as slow hemodynamic response to exercise, orthostatic hypotension, Heart rate variability decreased and pressure reflex test, atropine test abnormality, some studies have found that plasma norepinephrine level and the severity of autonomic dysfunction are related; some scholars pointed out that the sudden cardiac death of this disease may also be independent Related to neurological dysfunction.

Chagas disease check

1. Direct examination method: In the acute phase, fresh blood can be used to check the active pathogen, or the thick blood smear can be examined by Giemsa staining, or the blood can be centrifuged to check the supernatant floating on the blood clot to find the trypanosome flagellum. Tissue biopsies can also be used to find the amastigotes in the pseudocysts.

2. Animal vaccination: The "golden index" is diagnosed, and the laboratory-trained scorpion worms are suspected to be the blood of the person infected with Trypanosoma cruzi. After 4 to 6 weeks, the rectum of the stag beetle is examined, and trypanosomes can be found. Very specific, as long as there is a very small amount of trypanosomes in the peripheral blood to confirm the diagnosis.

3. Polymerase chain reaction: measuring the specific DNA fragment of Trypanosoma in blood and tissues. Using this method, one trypan to 10 ml of blood can be found. As with animal vaccination, the specificity of the method is as high as 100%, high sensitivity, can even replace animal vaccination, but the sensitivity of patients with advanced, chronic Chagas disease is not satisfactory.

4. Serum experiment: It is the main clinical diagnosis method. It can detect the IgG antibody against the Trypanosoma cruzi antigen in the infected person. This antibody appears 4 to 6 weeks after infection and survives, even though The method has higher value in diagnosis, but its titer has nothing to do with the severity of the disease. There is no evidence to show how the antibody affects the course of the disease. Common methods include: complement binding assay, indirect immunofluorescent antibody assay, and Enzyme-linked immunosorbent assay, etc.

5. Right ventricular endocardial myocardial biopsy: This method can be used to understand the degree of myocardial damage in mild or advanced cases, but trypanosomes are usually not found.

6. X-ray examination: can show the giant esophagus and megacolon, can be found in the heart enlargement and special apical aneurysms and other signs.

Diagnosis and identification of Chagas disease

Diagnostic criteria

Cardiac trypanosome infection can be confirmed by pathological examination of cardiac tissue or animal vaccination, but the positive rate of pathological diagnosis is very low, animal vaccination can not be widely used, and it is not sensitive to advanced patients, so it is usually based on epidemics The data, serological examination and clinical manifestations are considered together to make a diagnosis. The main criteria are as follows (in non-popular areas, the standard should be enforced more strictly):

1. I have lived in a prevalent area of Chagas disease.

2. The serological test of Trypanosoma cruzi is positive.

3. The clinical manifestations of the heart are consistent with Chagas heart disease.

4. Although various cardiac manifestations can be attributed to other heart diseases, there is no evidence of these heart diseases.

Differential diagnosis

Should be differentiated from coronary heart disease, idiopathic dilated cardiomyopathy, alcoholic cardiomyopathy.

1. Coronary heart disease: This disease, like the trypanopathic myocarditis, can affect the myocardium, causing the heart to expand, and can have arrhythmia, heart failure, etc. Coronary heart disease is more common in men over 45 years old and postmenopausal women, older More common, coronary heart disease often has a variety of disease factors, such as hyperlipidemia, hypertension, diabetes, obesity, family history, etc., while trypanosomiasis has been prevalent in the fungus of Trypanos The history of living in the area, the serological test of Trypanosoma cruzi is positive, and the clinical manifestations of Chagas heart disease can often be distinguished from the disease.

2. Dilated cardiomyopathy: may have a family history, long course of disease, slow progress, heart of dilated cardiomyopathy is often enlarged, may have arterial embolism, negative virus isolation, serum virus neutralizing antibody titer does not increase in a short period of time, ECG There are often a variety of arrhythmias, sometimes pathological Q waves, late heart enlargement and heart failure symptoms, trypanosomiasis have lived in the epidemic area of Trypanosoma, the serum of Trypanosoma Experimental positive and typical clinical signs and symptoms.

3. Alcoholic cardiomyopathy: The patient has a large amount of alcohol consumption, long-term drinking history (more than 10 years, the amount of pure ethanol is 125ml per day); heart enlargement, arrhythmia, chest pain, high blood pressure, etc., and congestion can occur in the late stage. Heart failure, although similar to some of the symptoms and signs of this disease, it should be identified from the epidemiological history, the serological test of Trypanosoma cruzi and the multiple organ expansion.

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