What is Chagas Disease?
Chagas disease (American trypanosomiasis) is a disease caused by trypanosomes of the species Trypanosoma cruzi (simple colorless organisms having a spindle-shaped form).
Chagas disease, first discovered a century ago by Dr. Carlos Chagas in 1909, results from infection with the parasite Trypanosoma cruzi. Worldwide, it is estimated that between 16 and 18 million people are infected with this parasite; of these infected, 50,000 people die each year.
Causes of Chagas Disease
Chagas disease is caused by trypanosomes of the Trypanosoma cruzi species. T. cruzi strains vary considerably in host circle, geographic distribution, virulence and tropism to tissues, as well as in specific antisera, zymotypes and type of restrictive DNA.
Chagas disease can be infected in countries such as Argentina, Belize, Bolivia, Brazil, Colombia, Costa Rica, Ecuador, El Salvador, French Guiana, Guatemala, Guyana, Honduras, Mexico, Nicaragua, Panama, Paraguay, Peru, Suriname and Venezuela ( Bolivarian Republic). Due to the migration of the population, there has been an increase in the number of cases in Europe and the United States of America, and this increase is the cause of the additional risk of transmission of the disease through blood transfusion and organ transplantation.
The disease is transmitted by the bugs of the subfamily Triatominae from a sick person or infected wild animals (armadillos, opossums, forest rats, monkeys, etc.). The bugs themselves become infected when they are bitten by sick people and can transmit trypanosomes in a week or two, and then throughout life (up to two years).
The habitat of triatomic bugs (“kissing” bugs) in the territory from southern Argentina to the southern states of the United States is dilapidated living spaces, where they find favorable conditions for themselves in the cracks of the walls and in the roof of disadvantaged dwellings in rural areas or slums on the periphery of cities. “Kiss” bugs attack a person at night and usually bite the face in places where the skin enters the mucous membrane (most often in the area of the lips or the outer canthus).
The disease is dangerous throughout the year, at all ages, but more often in children. Asymptomatic form is characteristic for adults. Single cases are characteristic, but with a massive attack of infected triatomid bugs on people, epidemic outbreaks are possible. The disease occurs mainly in rural areas or on the outskirts of cities, where there are adobe and other dilapidated buildings inhabited by triatomid bugs. The patient himself becomes infectious 9-11 days after infection, and the level of danger decreases only in the second stage of the disease.
Pathogenesis during Chagas Disease
A person becomes infected with T. cruzi in several ways:
– people can carry the parasite on the eyes, mouth or cuts, if before they touched the feces of an infected triatom bug;
– Klopovye feces can get people in the eye in a direct way;
– if consumed food does not pass heat treatment, infected with klopovye feces, the parasite can get into the esophagus;
– mothers can pass on T. cruzi to children during pregnancy or at birth;
– The parasite can be transmitted through contaminated blood through blood transfusion or organ transplantation.
The risk of T. cruzi infection is directly related to poverty. The migration of the rural population to the cities, which took place in Latin America in the 1970s and 1980s, changed the traditional epidemiological picture of Chagas disease, which became an urban infection that is transmitted through blood transfusion. The degree of contamination of blood banks in some cities of the Americas can range from 3% to 53%, indicating the fact that in the blood supply the prevalence of blood infected with T. cruzi may exceed the prevalence of the HIV and Hepatitis B and C viruses.
The natural susceptibility of people is high; transmission mechanisms include transfusion of contaminated blood, congenital form, or milk from an infected mother.
Symptoms of Chagas Disease
Chagas disease is slow, sometimes not manifesting itself for years, sometimes even decades, and often asymptomatic – until a critical moment when a patient, exhausted by pains in the heart, stomach, and often recurring episodes of fever, see a doctor. Alas, at a late stage, the doctor can only state irreversible changes in the internal organs – myocardium, liver, esophagus, spleen, intestines. In 5-10% of cases, the disease develops very acutely – meningitis, meningo-encephalitis or severe heart failure lead to a fatal outcome in a matter of days. Approximately 30% of infected individuals are “lucky” more – their disease manifests itself quickly, but not fatally, sharply …
In a person with Chagas disease, there are two stages: an acute period in which symptoms appear soon after infection, and a chronic period in which symptoms appear after a quiet period, which can last for several years. In the chronic course of the disease, irreversible damage to the internal organs, in particular the heart, the esophagus, the colon and the peripheral nervous system, occurs. After several years of asymptomatic infection, 27% of those infected develop heart symptoms (which can lead to sudden death), 6% impair digestive functions (mainly, hypertrophy of internal organs), and 3% manifest disturbances of the peripheral nervous system.
After an incubation period of 2 weeks, a local inflammatory reaction in the form of swelling, redness, a small nodule (a so-called erythematous node) appears, sometimes a swelling of the eyelids and conjunctivitis at the site of the introduction of the trypanosome into the body. However, in such cases it is easier for the infectious disease doctor to make a diagnosis and start treatment promptly.
At the site of infection, a small inflammation is formed without suppuration, accompanied by inflammation of the lymphatic vessels.
The acute stage of the disease begins (1-2 months) – fever and regional lymph nodes increase, extensive edema and skin rash may occur. This stage is most dangerous – there is a high probability of death or a serious illness, especially in young children.
Further, approximately for the second month, against the background of the development of antibodies, the patient’s condition improves. The disease goes into a chronic stage that lasts for months without symptoms. Parasites gradually spread throughout the body, often causing heart and gastrointestinal diseases, damage to the nervous system and respiratory organs. The more time passes, the more serious the disease, including appear autoimmune. Fatal organ damage occurs in a third of such infections.
Diagnosis of Chagas Disease
The diagnosis of Chagas disease is based on the detection of trypanosomes in a patient or on the positive results of serological tests. In the acute phase of the disease, trypanosomes can be detected in peripheral blood samples by the same methods as in African trypanosomiasis. Effective microhematocrit enrichment method. If these methods do not give positive results, you can spend blood cultures on a number of artificial media or enter it to rats, mice or guinea pigs.
The causative agents of Chagas disease grow well in blood broth at 28 ° C. In endemic areas, xenodiagnosis is often used; a carrier grown in a laboratory free of trypanosome is allowed to drink blood from a patient with suspected Chagas disease, and after 2 weeks the contents of the insect’s intestine are checked for the presence of the pathogen. Detection of trypanosomes in the blood sometimes leads to confusion. The fact is that many children in Venezuela and other countries of South America are carriers of a harmless species of trypanosome (T. rangeli), which does not cause illness, but can be kept in the blood for many months.
With repeated application of cultivation and xenodiagnostics methods, trypanosomes are found in the majority of patients in the acute phase and in 40% of cases in the chronic phase of infection. Using a biopsy of the affected lymph node or the gastrocnemius muscle, pathogens can be detected in the initial period of the disease, when trypanosome cannot be isolated from the blood. The Mashad-Guerreiro test (complement fixation test) is most effective in diagnosing chronic cases and conducting special examinations.
The reaction of fluorescent antibodies and the reaction of inhibition of hemagglutination, apparently, are more sensitive, but less specific. Accelerated agglutination test on a glass slide was designed for use at blood transfusion stations. In all these serological reactions, unpurified epi-astigot antigens are used, which cross-react with the sera of patients with leishmaniasis or infection caused by T. rangeli. These false-positive results can be avoided by applying a new enzyme immunoassay using purified glycoprotein antigen.
Treatment of Chagas Disease
There are no effective ways to treat Chagas disease. Drugs reduce mortality, but do not provide confidence that the doses transferred will destroy the parasites localized intracellularly.
Today, there are two drugs that are effective for the treatment of Chagas disease: benznidazole and nifurtimox. However, there is no confirmed clinical evidence that, in tolerated doses, they have the ability to destroy intracellularly localized parasites; in addition, they have pronounced side effects.
With regard to chronic changes in the internal organs in Chagas disease – they are irreversible, in the late stages of the disease, the sick part of them die from acute heart failure, heart attack, stroke.
Prevention of Chagas Disease
There are no vaccines for Chagas disease. Prevention consists in the treatment by insecticides of the residual action of the walls and roofs of houses – the main vector habitats. When using insecticides with the addition of latex, a colorless film is formed, which significantly prolongs the activity of the drug. Using fumigants will help prevent the reappearance of insects. Plastering of walls, cementing of earthen floors, transferring to a large distance from residential buildings of stacks of firewood also significantly reduce the concentration of bug bed vectors in the rooms.
Transfusion transmission of infection can be prevented by adding gentianoviolet or its analogues to blood products. In endemic areas of patients with leukemia, before starting immunosuppressive therapy, it is necessary to check for the presence of trypanosomiasis using serological methods.