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Review: Targeting trachoma: Strategies to reduce the leading infectious cause of blindness

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Summary

The World Health Organisation (WHO) estimated that in 2002, 1.3 million people were blind due to trachoma, an eye infection caused by Chlamydia trachomatis. This review examines the evidence behind current strategies to reduce the global burden of trachoma. Trachoma disappeared from most western nations before the advent of antibiotics, probably due to improvements in water, sanitation and hygiene. The current effort to target trachoma, headed by the WHO and the Alliance for the Global Elimination of Trachoma by 2020, is called the SAFE (Surgery, Antibiotics, Facial cleanliness and Environmental improvement) strategy. Surgery for trachoma is more cost effective than extra-capsular cataract surgery and can reverse trichiasis (in-growing eyelashes), but needs to be repeated every few years. A single oral dose of azithromycin can eliminate trachoma infection, but cannot be used in infants under 6 months old, and needs to be given every few years in communities with a high prevalence of disease. Improved health education and facial hygiene has been linked to a lower incidence of trachoma, but the evidence is less clear than for surgery and antibiotics. Pit latrines and spraying with permethrin insecticide may reduce the spread of trachoma via eye-seeking flies.

Introduction

Trachoma no longer presents a significant burden of disease in western nations, but in the 19th century hospitals such as Moorfields Eye Hospital in London were founded primarily to combat this condition, which was brought back to Europe by troops returning from fighting during the Napoleonic wars in Egypt. Although trachoma is almost unheard of in London today, in 2002 the World Health Organisation (WHO) estimated that 1.3 million people were blind from trachoma, and an additional 1.8 million suffered from reduced vision.1 The reason trachoma disappeared from developed countries is thought to be improvements in water, sanitation and hygiene. It was eliminated in many countries before antibiotics appeared. Today trachoma is endemic in more than 50 countries, and it’s greatest burden falls on sub-Saharan Africa.2 The current effort to reduce the burden of trachoma is led by the WHO and the Alliance for the Global Elimination of Trachoma by 2020 (GET2020). It is called the SAFE strategy. SAFE stands for “Surgery, Antibiotics, Facial cleanliness and Environmental improvement”: four points targeted together to reduce the burden of trachoma. This essay provides some background on trachoma and the epidemiology of this disease, before going on to analyse the four points of the SAFE strategy.

Section snippets

Background

Trachoma is caused by four serovars of Chlamydia trachomatis: A, B, Ba and C. The genital serovars D to K can also cause conjunctivitis (opthalmia neonatorum in infants or inclusion conjunctivitis in adults), but these are more minor conditions, which do not lead to blindness. The blinding effect of trachoma is due to repeated infection and a chronic keratoconjunctivitis. Active disease occurs in childhood, whereas cicatricial or scarring manifestations are seen in older children and adults. In

Epidemiology

Trachoma used to occur in North America and Europe, but disappeared during the early 1900’s. This was presumed to be due to an increase in living standards and hygiene. Today trachoma is endemic in 56 countries, stretching across areas of South and Central America, Africa, India, China and Australia.4

Factors thought to increase the prevalence of trachoma include poor frequency of washing (often secondary to water scarcity), limited access to toilets and crowded living conditions.

It is hard to

WHO SAFE plan

The current strategy for trachoma control advocated by the WHO and the Alliance for the Global Elimination of Trachoma by 2020 (GET2020) is the SAFE strategy. The aim of this strategy is to eliminate blinding trachoma rather than aiming to eliminate the bacteria itself. Surgery is needed to correct trichiasis (interning of eyelids and scraping of eyelashes over the cornea) to stop corneal damage. Antibiotic treatment advocated for trachoma is a single dose of azithromycin, which has additional

Surgery

Surgery for trichiasis aims to reduce the gradual progression to corneal opacity and blindness, which can occur due to lashes abrading the cornea. The procedure with the best results for correction of trichiasis (and the procedure advocated by the WHO) is the bilamellar tarsal rotation. A study from Oman8 shows success rates for correction of trichiasis of 77%–80%. Unfortunately it has not been proven directly that trichiasis surgery reduces progression to corneal opacity,9 but it is assumed

Antibiotics

The use of a single oral dose of azithromycin to treat trachoma offers hope for effective widespread community level antibiotic retreatment. The six week course of tetracycline previously advocated faced major issues around compliance. A further benefit of azithromycin is that it protects against other infections. A cluster-randomised trial16 in Ethiopia looked at treatment with azithromycin in children aged 1–9 years, compared to a control group. Mortality in all groups was compared after one

Facial cleanliness

The idea behind an improvement in facial cleanliness is that without nasal and ocular discharge transmission is reduced by removing a source of infection. Increased facial cleanliness is thought to be one reason for the disappearance of trachoma from Europe and the United States during the last century. Health education and improved access to water are the main strategies currently used to help facial cleanliness. A study in Ethiopia22 on 1813 children found having a clean face was

Environmental improvement

Flies (specifically M. sorbens), which lay larvae in human faeces, have been linked with trachoma for many years. It therefore appears logical that reducing the prevalence of these flies through insecticide spraying and latrine construction should reduce the transmission of trachoma too.

A cluster randomized controlled trial24 in Gambia compared clusters with observation only, to those with pit latrines or permethrin spray. Areas sprayed with permethrin insecticide had an 88% reduction in the

Conclusion

In various areas where the SAFE strategy has been successfully implemented the prevalence of trachoma has fallen. Studies have shown this in areas of Ethiopa,26 Zambia27 and Sudan.28 The first three countries in the GET 2020 campaign to successfully stop trachoma (Mexico, Morocco and Oman) have achieved this using all four aspects of the SAFE strategy. Ideally this is clearly the template for success that should be followed. Unfortunately not all countries have the resources or willpower to

Conflict of interest

The author declare that there is no financial or personal relationship with other people or organisations that could inappropriately influence the work.

Acknowledgements

I would like to thank Michael Karampelas for his help in overseeing my writing of this article.

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