Chagas disease: symptoms, how it spreads, testing and treatment in the UK

UKHSA describes two phases. The acute phase, which commonly lasts around 2 months immediately after infection, has few or no symptoms in most people. UCLH says a small number experience a mild illness with fever that gets better by itself. The acute phase is unlikely to be seen in migrants who arrive in the UK.

The chronic phase causes no symptoms in the majority of patients, according to UKHSA, but 20 to 30% go on to develop heart and/or digestive problems over the next decades. UCLH says one in three people develop problems with the heart, the digestive system or both after years or decades, which is why detecting infection matters.

• Heart: UKHSA lists conduction disorders, arrhythmia, cardiomyopathy, heart failure, cardiac aneurysm and secondary thromboembolism. UCLH says symptoms can include breathlessness, ankle swelling, dizziness or collapse.

• Digestive system: UKHSA lists megaoesophagus and megacolon. UCLH mentions difficulty swallowing and constipation.

Chagas disease (American trypanosomiasis) is caused by the parasite Trypanosoma cruzi. UKHSA says it affects up to 8 million people worldwide, is endemic in large parts of Central and South America, especially in poor rural areas, and kills more people than any other parasitic disease in Latin America. UCLH gives an estimate of around 7 million people.

Once a person has the infection, UCLH says they remain infected for decades, often with no signs. Many people born or raised in Latin America and now living elsewhere may have Chagas disease without knowing. UCLH says the number in London is not known but may be several thousand. UKHSA says that fewer than 5% of people infected in the UK are thought to have been identified.

In Latin America, UKHSA says it is mainly transmitted by the infected faeces of a blood-sucking triatomine bug, which can enter through the bite site, another break in the skin, or mucous membranes such as the eye or mouth. UCLH says the bugs, known locally as vinchuca or chirimacha, live in cracks in walls and thatched roofs and usually bite at night. Less often it can spread through contaminated fruit juice, blood transfusion or organ transplantation.

UKHSA says the triatomine bug does not occur in the UK, so ongoing transmission from infected people by that route is not an issue. In the UK, transmission is possible through pregnancy and delivery, and less frequently through laboratory accident. All blood products and donated organs are tested in the UK, which UCLH says reduces the risk from transfusion and transplant.

Nothing in the sources used for this page suggests that Chagas disease spreads through ordinary contact such as touching, hugging or sharing a household.

UCLH says the only way to know for sure is a blood test, which can be arranged through a tropical diseases hospital, through GPs, or at community screening events. UKHSA advises that doctors consider the possibility in migrants from endemic Central and South American countries and request serology (a clotted blood sample).

UKHSA advises offering testing to Latin American migrants who are women of child-bearing age or pregnant, who have heart or gut disease, who are immunosuppressed (particularly with HIV, transplantation or cancer chemotherapy), or who wish to become organ donors. If the blood test is positive, UKHSA advises referral to a specialist service for definitive diagnosis and treatment.

There is currently no routine antenatal screening programme for Chagas disease in the UK, according to UKHSA. If you come from Latin America, UCLH advises you to tell your doctor.

UKHSA says two treatments exist, benznidazole and nifurtimox, used by specialist parasitology centres. UCLH says benznidazole is the drug used in the UK, a daily tablet for a course of up to 60 days, and nifurtimox is the alternative, also a daily tablet for up to 60 days. UKHSA says the schedule is long and has frequent side effects.

UCLH lists benznidazole side effects that are usually mild and get better by themselves: rashes, nerve problems, poor appetite and weight loss, nausea and vomiting, headache or dizziness, and sleep problems. For nifurtimox: aching muscles, pins and needles, headache, dizziness, difficulty concentrating, poor appetite and weight loss, nausea and vomiting, and sleep problems. You are closely monitored during treatment.

Timing matters. UKHSA says treatment is generally more effective in the acute or early chronic phase, and in reactivation if someone becomes immunosuppressed. Once characteristic damage is established, such as dilated cardiomyopathy or megaoesophagus, anti-parasitic treatment will not reverse it, and symptomatic treatment is the mainstay.

UCLH says that in a small proportion of pregnancies the parasite can be passed to the baby by an infected mother (congenital infection). UKHSA advises testing women of child-bearing age before pregnancy, because treating before conception can reduce the risk of congenital infection, and testing pregnant women from Latin America.

UKHSA states that treatment of Chagas during pregnancy is contraindicated, but identifying infection is important so that congenital infection can be detected and treated. Treatment of infants is highly effective and well tolerated, it says, and failing to identify and treat infected infants carries a risk of illness and early death from chronic Chagas later in life. UCLH adds that if your baby gets the infection, it can be cured with current treatment.

Pre-donation screening has been in place in the UK since 1999. UKHSA says a potential donor must not donate if they or their mother were born in South or Central America, if they had a blood transfusion there, or if they lived or worked in rural subsistence farming communities there for a continuous period of 4 weeks or more. However, donation is allowed if at least 4 months have passed since the last exposure and a validated test for T. cruzi antibody is negative.

Tell your GP if you were born or lived in Latin America and have never been tested, particularly if you are planning a pregnancy, are pregnant, or have a weakened immune system. See a GP promptly for breathlessness, ankle swelling, dizziness, fainting episodes, difficulty swallowing or persistent constipation; these can have many causes, and Chagas disease is one of the things your doctor may consider if you have lived in an affected area.

Call 999 if someone collapses, has severe chest pain or is struggling to breathe.

On the NHS, testing can be requested by a GP, and positive results are referred to specialist tropical disease and parasitology services for confirmation, anti-parasitic treatment and follow-up by cardiology or gastroenterology teams where needed. UKHSA notes that benznidazole and nifurtimox are used on a named-patient basis by specialist centres.

Private tropical medicine services also exist, but because the drugs are supplied through specialist routes, and long courses need monitoring, ask any provider how treatment and follow-up would be arranged and shared with your GP.