Latent rheumatic heart disease in West Africa: a pilot multi-country study Rheumatic heart disease (RHD) is a disease of poverty affecting the poorest countries in the world, with Sub-Saharan Africa bearing a heavy toll. In 2015, over 33 millions clinical cases and >300,000 deaths worldwide were estimated to be due to RHD. RHD is caused by an excessive immune reaction ("rheumatic fever" (ARF)) to throat or skin infections by Group A Streptococcus (GAS) which further damages the heart valves. Complications include heart failure and stroke that result in premature death, usually before 25 years old, and  women with RHD are at higher risk of complication during delivery.  RHD patients with early symptoms can be treated with monthly injections of benzathin penicillin G which stops the evolution of the heart lesions. However, in many countries, including The Gambia, RHD is usually diagnosed in patients attending health facilities at a late stage, with heart failure or other complications, when the efficacy of penicilllin treatment to prevent RHD adverse outcomes is limited. Ideally, penicillin treatment should be started as early as possible although its benefits in individuals with latent RHD, i.e. with cardiac lesions diagnosed by echocardiography but without symptoms, is unknown. Latent RHD represents a potential window of opportunity for early treatment with penicillin to prevent its progression towards overt clinical disease. This intervention needs to be evaluated with a large randomized clinical trial that will recruit hundreds of individuals with latent RHD. Therefore, considering the prevalence of latent RHD is probably 0.5-1% in children (up to 3% in young adults), the study team would need to rapidly screen thousands of individuals to attain the required sample size within a reasonable time period. Handheld echocardiography (HHEC) by non expert users has been proved as a reliable tool to detect RHD and is considered the best option for mass screening. This Trial Development Grant (TDG) will determine i) the prevalence of RHD (latent- and symptomatic) among school-aged children and young adults in peri-urban areas of The Gambia, Senegal and Nigeria; ii) whether non-experts users in the three study sites can be adequately trained for RHD screening using HHEC, and iii) the feasibility and acceptability of community-based screening by HHEC in the three study sites. After HHEC training (3 months), 3,000 children and 3,000 adults per country will be screened and all suspected RHD cases will be confirmed by standard EC before referral to the nearest teaching hospital for adequate management. The feasibility and acceptability of HHEC screenings will be evaluated as an ongoing process through early and regular engagement with participants and all stakeholders involved. Therefore, this TGD will provide useful information on RHD prevalence (both latent and symptomaticin different age groups) and the feasibility and acceptability of mass screening with HHEC, allowing to adapt accordingly the future trial design in the three West African countries. Results of such trial are crucially needed to issue new consensus guidelines on the management of latent RHD and further improve the control of RHD. The Global Challenges Research Fund (GCRF) supports cutting-edge research to address challenges faced by developing countries. The fund addresses the UN sustainable development goals. It aims to maximise the impact of research and innovation to improve lives and opportunity in the developing world.