The epidemiology of Chagas disease in the UK: a mixed methods study to inform equitable and evidence-based approaches to migrant health screening

Chagas disease is a long-term infection caused by a parasite (Trypanosoma cruzi) which is spread mainly by insects which live in South America, Central America and Mexico. It can also be passed from mother to child in pregnancy, and through blood transfusions and organ transplantations. The UK is home to 250,000 people from parts of the world where they may have been infected before they migrated. Most people live with the infection for years without any symptoms. About a third of people infected will go on to develop heart and gut disease, often 20-40 years later. Six different genetic types of the parasite exist in different parts of the Americas and these may influence disease type and severity. It is estimated that 97% of people with Chagas disease in the UK are undiagnosed and this project looks at how we can best find people with Chagas disease to get them tested and linked into specialist care.

Early diagnosis and treatment can prevent heart and gut complications and the risk of passing on the infection to babies during pregnancy. A screening test (a blood test), can tell us whether someone has the infection but - as we don't know exactly where in Latin America most people are infected, we don't know who it's most important to screen in the UK. This project aims to answer the following questions:
1. How common is Chagas disease in migrants from Latin America living in the UK?
2. How common is it when we test different people in different settings (at the GP surgery, pregnant women at their antenatal appointments and people attending community events with local charities)?
3. What types of people are most at-risk of Chagas disease?
4. What genetic types of parasite are people infected with?
5. What is the best way to find people with Chagas disease and get them tested and treated?

To answer these questions, I will invite people from at-risk countries to complete a questionnaire and have a blood test for Chagas disease. I will invite people through their GP surgeries, pregnant women at their antenatal appointments and I will also organise testing events with local charities. People who test positive will be referred to a specialist clinical for further tests and treatment. They will also be invited for a different blood test, to look at the parasite genetics. Finally, I will interview people invited to screening, and professionals responsible for designing and delivering screening programmes, to understand what they think are the key components of a good screening programme for Chagas disease.

At the end of this study, we hope to have all of the information required in order to design a screening programme for Chagas disease which reaches the people at greatest risk.

Chagas disease is a chronic disease endemic in the Americas, caused by the parasite Trypanosoma cruzi. Due to globalisation and migration, Chagas disease is increasingly recognised as a public health problem among migrants in Europe such as the 250,000 Latin American migrants in the UK. In endemic settings it is principally transmitted via triatomine vectors. In all settings, T. cruzi can be transmitted through vertical transmission and, in the absence of screening, through blood transfusion and organ transplantation.

Left undiagnosed and untreated, Chagas disease leads to cardiac and gastrointestinal complications in 30-40% of infected individuals, typically 20-40 years after initial infection. Disease phenotype may be related to parasite genetics, as gastrointestinal complications are only rarely reported outside of regions where the TcII genetic lineage T. cruzi predominates. The complex pathophysiology and gaps in diagnostic coverage of Chagas disease have led to a lack of any granular data on where people are (or could have previously been) exposed to T. cruzi infection. This "epidemiological silence" presents a major challenge in developing evidence-based screening policies in non-endemic settings.

This Fellowship aims to generate the knowledge required to design an equitable and impactful screening intervention for Chagas disease in the UK, through:
- Three sero-epidemiological cross-sectional studies to determine the burden of Chagas disease in core groups of migrants living in London (in primary care, antenatal care and community-based), and identify factors associated with increased risk of infection.
- A nested serological study of parasite-lineage on cases identified through these cross-sectional studies.
- A nested qualitative study with migrants from endemic countries and key stakeholders in the screening pathway to understand their perspectives on the barriers and facilitators of a successful screening programme