New diagnostic tool has potential to improve treatment of trachoma

12 May 2006

The development of a pioneering new diagnostic tool for trachoma could help to eradicate the most common cause of blindness due to an infectious agent.

The Wellcome Trust has funded the work of Dr Helen Lee and Claude-Edouard Michel of the University of Cambridge and their collaborators that has resulted in the development of a rapid-test that can diagnose the presence of infection within half an hour. The new point-of-care (POC) test uses eye swabs, and a positive sample gives an easy to read stable purple line in a specially designed sample tube. This dipstick test was compared to the gold standard PCR (polymerase chain reaction) method in remote, trachoma-endemic villages in Tanzania with no running water or electricity. The findings, published in The Lancet this week, could profoundly influence the future diagnosis and treatment strategies for trachoma worldwide.

Trachoma is hyperendemic in many of the most remote poor rural areas of Africa, Asia, Central and South America, Australia and the Middle East. If the infection is caught in time, a single dose of the antibiotic azithromycin results in a complete cure.

The new test was developed at the Diagnostic Development Unit at the University of Cambridge, headed by Dr Lee, for use in developing countries, as it is cheap, quick and simple to perform and requires no expensive equipment or skilled labour. She collaborated with Professor David Mabey of the London School of Hygiene and Tropical Medicine, Professor Sheila West's group from the Johns Hopkins University, Baltimore, and institutions in Tanzania including the Kilimanjaro Centre for Community Opthalmology, to compare the accuracy of the new test with PCR in remote trachoma-endemic villages in Tanzania. The trial involved testing 664 children aged between one and nine, and showed that the rapid test completed at the trial site was more accurate in identifying the presence of infection with a positive predictive value of 97.3 per cent, against 43.6 per cent for the current method based on visual inspection of the clinical signs.

Co-Director of the Kilimanjaro Centre in Moshi, Tanzania, Dr Paul Courtright said: "The findings from this study are likely to lead to a major rethink on how we conduct trachoma control in Africa. It will help us become more targeted in our approach and save time and money - both are in very short supply in Africa."

Dr Lee said: "Trachoma is a disease of the poorest of the poor. Therefore, we have designed the test so that it can work effectively in the most difficult circumstances without even the most basic laboratory infrastructure."

Director of Technology Transfer at the Wellcome Trust, Dr Ted Bianco said: "This is a terrific development in the diagnosis of trachoma and a great example of how the private sector can contribute to healthcare, even of the poorest communities, by adapting core technologies created for more lucrative markets. A test that detects active trachoma infection has the potential to transform our approach to the control of this cruel and preventable condition."

The World Health Organization (WHO) estimates that six million people worldwide are blind due to trachoma and more than 150 million people are in need of treatment. Trachoma results from infection of the eye with Chlamydia trachomatis. Infection is spread by flies that feed on the discharge of infected eyes, or as a result of poor hygiene and lack of running water. Infected eyelids become inflamed and the thickened and scarred upper eyelids turn inwards so the eyelashes scratch the cornea, ultimately leading to blindness.

WHO aims to eliminate trachoma by 2020 through its SAFE strategy: surgery for those at immediate risk of blindness; antibiotics to treat individual active cases and reduce the community reservoir of infection; facial cleanliness and improved hygiene to reduce transmission; and environmental improvements. Effective community testing makes mass treatment of endemic regions a viable option and could help to eradicate trachoma.

The word 'trachoma' means 'rough eye' in ancient Greek, and was identified as early as 27 BCE. It often strikes the most vulnerable members of communities - women and children. Women are at much greater risk of developing the blinding complication of trachoma than men as they are in closer contact with small children, who are the main reservoir of infection.

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Notes for editors

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The Wellcome Trust is the most diverse biomedical research charity in the world; spending about £450 million every year both in the UK and internationally to support and promote research that will improve the health of humans and animals. The Trust was established under the will of Sir Henry Wellcome, and is funded from a private endowment, which is managed with long-term stability and growth in mind.