Studies towards infectious disease elimination on the Bijagos Archipelago of Guinea Bissau

So far, smallpox is the only infectious disease of humans that has been completely eradicated; but a number of so-called Neglected Tropical Diseases (NTDs), which cause a huge burden of disease among poor rural communities in low income countries, are targeted for global eradication, or at least for elimination from large parts of the world. Great progress has been made in reducing the number of cases of NTDs in some parts of the world but it has become clear that, for most of them, further research is needed to develop new tools and elimination strategies. Global eradication of malaria, which was attempted unsuccessfully in the 1960s, is back on the agenda, and malaria was eliminated from Sri Lanka in 2016, but it is clear that malaria will not be eliminated from Africa using the old methods.

We have been working on the elimination of blinding trachoma, one of the NTDs targeted for global elimination, in The Gambia since 1984, and showed that it could be cured with a single dose of the antibiotic azithromycin, given by mouth. 500 million doses of azithromycin have been donated to trachoma programmes by the manufacturer since then, and The Gambia has recently met the World Health Organization's elimination targets, but trachoma remains the leading infectious cause of blindness worldwide.

For the past 6 years we have been studying trachoma in the remote Bijagos Islands of Guinea Bissau where it remains an important cause of blindness, and have made considerable progress in understanding where it is being transmitted and how it might be controlled. Our aim in the next two years is to set up a trachoma elimination programme on the islands, using mass treatment with azithromycin and health education to reduce transmission, and a surveillance programme to make sure it is not re-introduced. We also plan to study the transmission of malaria on the islands, with a view to identifying the most promising strategies for malaria elimination in this setting, and to map the distribution of other NTDs. The programme will be led by Anna Last, a clinical lecturer in infectious diseases, who has recently completed a PhD on trachoma in the Bijagos Islands, and is fluent in the local language.

In two years time we will have established a laboratory and insectary on the islands, trained staff in how to do field surveys, how to diagnose malaria and NTDs and how to control mosquito populations, worked out where and how trachoma and malaria are being transmitted, and found out which other NTDs are present on the islands, we will be in a strong position to try out new interventions for eliminating these diseases. The islands are a particularly good place to evaluate the impact new tools and strategies for disease elimination, since they are relatively isolated, and can be randomly allocated to one strategy or another.

We have been studying the epidemiology of trachoma, a neglected tropical disease (NTD) caused by Chlamydia trachomatis infection, which remains the leading infectious cause of blindness worldwide, in the Bijagos Islands of Guinea Bissau since 2010. We used whole genome sequencing and geospatial analysis to map the transmission of ocular C. trachomatis in these communities, and have shown that elimination of blinding trachoma should be possible through mass treatment with azithromycin, as recommended by WHO, although it is likely that behavioural interventions and improved sanitation will be needed to ensure that elimination is sustained. These remote islands are an ideal setting in which to evaluate new tools and strategies for the elimination of infectious diseases through cluster-randomised trials, since there is little migration between the 20 inhabited islands, and each can be treated as an independent cluster. Over the next two years we propose to use a multi-disciplinary approach to map the geographical distribution, routes of transmission and socio-behavioural determinants of malaria, trachoma and other NTDs including yaws, lymphatic filariasis, schistosomiasis, scabies and soil transmitted helminths on the islands, with the aim of developing new strategies for disease elimination that can be evaluated through cluster-randomised trials. We will establish a laboratory and insectary on the islands and train staff in diagnostic parasitology, mosquito collection and identification, and the collection of qualitative and quantitative data in the field. We will conduct population-based surveys to map the epidemiology of these diseases, using two-stage cluster sampling, and collect information on hygiene related behaviours, local beliefs concerning disease causation and attitudes towards potential interventions through direct observation, semi-structured interviews, focus group discussions and interviews with key informants.

The results of these studies will inform the design of new strategies for the elimination of malaria and Neglected Tropical Diseases that can be evaluated in the Bijagos Islands, which could have a major impact on the burden of disease in West Africa and beyond. We will ensure that the results of these studies are made available to policy makers and control programme managers worldwide by publishing them in open access journals and presenting them at major international meetings, and through our close links with the World Health Organisation, the Bill and Melinda Gates Foundation, the International Trachoma Initiative and major NGOs such as SightSavers and the ChristophelBlinden Mission. The Guinea Bissau Ministry of Health (including the National Programme for Visual Health) and National Institute of Public Health will be able to use these data to define and plan health service provision and disease surveillance on the islands. All clinical, field and scientific staff involved in the studies will benefit from the research and clinical training. Foundation funding will be used to train clinical and field staff to conduct epidemiological and environmental surveys, train laboratory technicians (and provide a simple laboratory facility to perform basic diagnostics in a field setting), entomologists and social scientists, and to train an administrator/data manager to coordinate the studies. Through training and mentoring and support from research studies and collaborative partners, we aim to create a sustainable surveillance system on Bubaque, as we have shown to be possible with the development of a self-sufficient eye care unit in The Gambia as a result of our collaboration with Sightsavers and the Gambian National Eye Care Programme.