Chagas disease, also known as American trypanosomiasis, is a potentially life-threatening illness caused by the protozoan parasite Trypanosoma cruzi.
An estimated 6 to 7 million people worldwide are infected with T. cruzi. Chagas disease is found mainly in endemic areas of 21 continental Latin American countries, where it is mostly transmitted when humans come into contact with faeces and/or urine of infected blood-sucking triatomine bugs (vector-borne transmission).
Chagas disease was once entirely confined to the Region of the Americas. In the last decades the epidemiological pattern of the disease changed from a rural to a mostly urban disease, mainly due to population mobility, urbanization and emigration. As a consequence, increased number of cases have been detected in Canada and the United States of America, and in many European and some African, Eastern Mediterranean and Western Pacific countries. Due to the high number of people who remain undiagnosed or untreated, combined with the areas with remaining active transmission, put an estimated 75 million people at risk of infection.
Triatomine bugs typically live in the wall or roof cracks of poorly constructed homes in rural or suburban areas, becoming active at night, biting exposed areas of skin, then defecating close to the bite.
The parasites enter the body when: i) the person inadvertently smears the bug’s waste into the bite or another skin break, the eyes or the mouth; ii) by consumption of food that has been contaminated with waste from infected triatomine bugs, typically infecting groups of people (causing outbreaks or oral transmission) with a higher frequency of severe disease and number of deaths.
Everywhere Chagas disease can be also transmitted through blood or blood product transfusion from infected donors; by congenital (mother to child) transmission during pregnancy or childbirth; by organ transplantation from infected donors; and also by laboratory accidents.
In May 2019, following up on decision of the 72nd World Health Assembly, the World Chagas Disease Day was established to be celebrated on 14 April (the date of the year 1909 when Carlos Chagas diagnosed the first human case of the disease, a two-year-old girl called Berenice).
After the infection is transmitted there is an initial, acute phase that lasts for about two months. In most cases, symptoms are absent or mild and unspecific. In people bitten by a triatomine bug, characteristic first visible signs of infection, such as a skin lesion or a purplish swelling of the lids of one eye (the so-called Romaña sign), can help in the diagnosis of new cases. With any transmission route, patients can present fever, headache, enlarged lymph glands, pallor, muscle pain, difficulty in breathing, swelling, and abdominal or chest pain.
During the chronic phase that succeeds the acute phase, up to 30% of patients suffer from cardiac disorders and up to 10% experience digestive, neurological or mixed disorders. In later years, the infection can lead to sudden death principally due to heart arrhythmia or heart failure caused by the destruction of the heart muscle and its nervous system.
Chagas disease can be treated with two antiparasitic medicines: benznidazole and nifurtimox. Both medicines are nearly 100% effective in curing the disease if given soon after infection, including the cases of congenital transmission. The efficacy of both diminishes, however, the longer a person has been infected and the adverse reactions are more frequent at older age.
Treatment is also indicated for those in whom the infection has been reactivated due to immunosuppression, and for patients during the early chronic phase. Infected adults, especially those with no symptoms, should be offered treatment because antiparasitic treatment can also prevent or curb disease progression and prevent congenital transmission in pregnant women. In other cases the potential benefits of medication in preventing or delaying the development of Chagas disease should be weighed against the duration of treatment (up to 2 months) and possible adverse reactions (occurring in up to 40% of treated adult patients).
Benznidazole and nifurtimox should not be taken by pregnant women or by people with kidney or liver failure. Nifurtimox is also contraindicated for people with a background of neurological or psychiatric disorders.
Additionally, specific treatment for cardiac, or digestive or neurological manifestations may be required.