Chagas disease, also known as American trypanosomiasis, is a potentially life-threatening illness caused by the protozoan parasite, Trypanosoma cruzi (T. cruzi). It is named after Carlos Chagas, a Brazilian doctor who discovered the disease in 1909. The World Health Organization (WHO) estimates that about 6-7 million people are infected, predominantly in Latin America, but Chagas disease is already found on other continents due to population flows.
Chagas disease is characterised by two phases. For the first two months after infection, a large number of parasites circulate in the blood; this acute phase is mostly asymptomatic with less than 50% of people presenting mild symptoms such as skin lesions, a purplish swelling of the lid of one eye, fever, headache, enlarged lymph glands, pallor, muscle pain, difficulty in breathing, swelling and abdominal or chest pain. The parasites are hidden mainly in the heart and digestive muscles in the second, chronic phase, which is characterized by up to 30% of patients suffering from cardiac disorders and up to 10% from digestive, neurological or mixed alterations. Years later, the progressive destruction of the heart muscle and its nervous system can lead to sudden death or heart failure.
The currently available treatments, benznidazole (the first choice) and nifurtimox, are almost 100% effective if given soon after infection. Efficacy is over 90% in children and recent data has shown that response rates for chronically infected adults are up to about 80%. In both children and young people, treatment of Chagas disease is associated with fewer adverse effects than in adults. Despite this, currently only an estimated 1% of those affected are treated. Broad use of these drugs has been limited due to a lack of guidelines and policies supporting implementation.
Drawbacks include long treatment periods (60-90 days), dose-dependent toxicity, and a high drop-out rate of patients due to side-effects. Both treatments should always be given under medical supervision. There is currently no approved treatment for the chronic form of the disease with target organ involvement. Safe, effective, oral treatments for both stages of the disease are still needed.
There is no vaccine for Chagas disease. Vector control is the most effective method of prevention in Latin America. The large reservoir of T. cruzi parasites in wild animals in the Americas means that the parasite cannot be eradicated. Instead, the control targets are the elimination of transmission and health-care access for the infected and ill population.
T. cruzi parasites are mainly transmitted by contact with the faeces of infected blood-sucking triatome ‘kissing’ bugs. These nocturnal vectors, which typically live in the cracks of poorly-constructed homes in rural or suburban areas, feed by biting an exposed area of skin such as the face, and then defecate close to the bite. The parasites enter the body when the person instinctively smears the bug faeces into the bite, the eyes, the mouth, or into any skin break. Infection can also occur through eating contaminated food, blood transfusions, organ transplants, and from mother-to-child during pregnancy or childbirth.