Chagas disease


Chagas disease, also known as American trypanosomiasis, is a tropical parasitic disease caused by Trypanosoma cruzi. It is spread mostly by insects in the subfamily Triatominae, known as "kissing bugs". The symptoms change over the course of the infection. In the early stage, symptoms are typically either not present or mild, and may include fever, swollen lymph nodes, headaches, or swelling at the site of the bite.[1] After four to eight weeks, untreated individuals enter the chronic phase of disease, which in most cases does not result in further symptoms.[2][4] Up to 45% of people with chronic infections develop heart disease 10–30 years after the initial illness, which can lead to heart failure. Digestive complications, including an enlarged esophagus or an enlarged colon, may also occur in up to 21% of people, and up to 10% of people may experience nerve damage.[2]

T. cruzi is commonly spread to humans and other mammals by the bite of a kissing bug.[5] The disease may also be spread through blood transfusion, organ transplantation, consuming food or drink contaminated with the parasites, and vertical transmission (from a mother to her baby).[1] Diagnosis of early disease is by finding the parasite in the blood using a microscope or detecting its DNA by polymerase chain reaction.[4] Chronic disease is diagnosed by finding antibodies for T. cruzi in the blood.[6]

Prevention focuses on eliminating kissing bugs and avoiding their bites.[1] This may involve the use of insecticides or bed-nets.[7] Other preventive efforts include screening blood used for transfusions. As of 2022, a vaccine has not been developed. Early infections are treatable with the medications benznidazole or nifurtimox, which usually cure the disease if given shortly after the person is infected, but become less effective the longer a person has had Chagas disease. When used in chronic disease, medication may delay or prevent the development of end-stage symptoms. Benznidazole and nifurtimox often cause side effects, including skin disorders, digestive system irritation, and neurological symptoms, which can result in treatment being discontinued.[2][8] As of 2019, new drugs for Chagas disease are under development, and experimental vaccines have been studied in animal models.[9][10]

It is estimated that 6.5 million people, mostly in Mexico, Central America and South America, have Chagas disease as of 2019,[1][3] resulting in approximately 9,490 annual deaths.[3] Most people with the disease are poor,[11] and most do not realize they are infected.[12] Large-scale population migrations have carried Chagas disease to new regions, which include the United States and many European countries.[1] The disease affects more than 150 types of animals.[13]

The disease was first described in 1909 by Brazilian physician Carlos Chagas, after whom it is named.[1] Chagas disease is classified as a neglected tropical disease.[14]

Chagas disease occurs in two stages: an acute stage, which develops one to two weeks after the insect bite, and a chronic stage, which develops over many years.[2][4][15] The acute stage is often symptom-free.[2] When present, the symptoms are typically minor and not specific to any particular disease.[4] Signs and symptoms include fever, malaise, headache, and enlargement of the liver, spleen, and lymph nodes.[1][2][4] Sometimes, people develop a swollen nodule at the site of infection, which is called "Romaña's sign" if it is on the eyelid, or a "chagoma" if it is elsewhere on the skin.[4][16] In rare cases (less than 1–5%), infected individuals develop severe acute disease, which can involve inflammation of the heart muscle, fluid accumulation around the heart, and inflammation of the brain and surrounding tissues, and may be life-threatening. The acute phase typically lasts four to eight weeks and resolves without treatment.[2]


An acute Chagas disease infection with swelling of the right eye (Romaña's sign)
Life cycle and transmission of T. cruzi
Triatoma infestans, a common vector of T. cruzi[19]
Large scale anatomy of a heart damaged by chronic Chagas disease
T. cruzi trypomastigotes seen in a blood smear
Bed nets can be used in endemic areas to prevent bites from triatomine bugs.[15]
A bottle of nifurtimox tablets
Epidemiology of Chagas disease circa 2011: red is endemic countries where spread is through vectors; yellow is endemic countries where spread is occasionally through vectors; blue is non-endemic countries where spread is through blood transfusions.[38]
Disability-adjusted life years due to Chagas disease in 2016. Grey indicates no data. Otherwise, colors get increasingly dark red for each order of magnitude increase in DALY burden: 0, white. Up to 1,000 DALYs, yellow. 1,001 to 10,000 DALYs, orange. 10,001 to 100,000 DALYs, light red. Greater than 100,000 DALYs, dark red.[39]
Carlos Chagas, in his laboratory at Instituto Oswaldo Cruz