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The broad benefits of trachoma elimination

Thursday, 5th of May 2016 Print

The Lancet Infectious Diseases, Volume 16, No. 5, p530–531, May 2016

The broad benefits of trachoma elimination

DOI: http://dx.doi.org/10.1016/S1473-3099(16)30017-2

The mapping of trachoma worldwide has highlighted where elimination efforts should be targeted, and potentially sets the scene for broader interventions. Talha Burki reports.

By the time an antibiotic to treat trachoma had arrived, most Europeans had no need for it—development had driven the disease from the continent. Elsewhere, progress has been slower. Today more than 21 million people are thought to harbour active trachoma. The disease is endemic to 50 or so countries worldwide. An estimated 2·2 million people have impaired vision or permanent blindness caused by trichiasis, the eyelid-inverting stage of trachoma that occurs after repeated infection.

In February, 2016, the Global Trachoma Mapping Project (GTMP) released its results. The project assembled data for 2·6 million individuals across 29 countries, representing a global population of 224 million people. More than 550 teams surveyed almost 2000 districts over a period slightly longer than 3 years. It is the largest infectious disease survey in history. The UK Government provided £10·6 million of funding, and the US Government came up with an additional £6 million.

“The survey was all done using android smartphones”, explains Sightsavers´ Caroline Harper. Questions were standardised, and included sections on sanitation and access to latrines. GPS technology allowed locations to be exactly pinpointed. “We could be confident that all the fieldworkers doing the survey were using the same approach”, notes Harper. It meant that the data could be quickly approved and disseminated.

The results broadly matched expectations. Sub-Saharan Africa remains by far the region at greatest risk. Ethiopia, one of the poorest countries on the continent and historically the nation with the highest trachoma prevalence, had more disease than previous estimates had suggested; swathes of the country showed rates in excess of 30%. Trachoma is disappearing from much of Nigeria, testament to burgeoning development in the country (the disease thrives in unsanitary and overcrowded conditions, spread by personal contact and flies). “The Nigerians have done great work in education, sanitation, and hygiene—they are really coming up”, points out Paul Emerson (International Trachoma Initiative, Decatur, GA, USA). Nonetheless, there remain areas of high endemicity in the country, and the surveyors were unable to enter the troubled northeastern states of Adamawa and Borneo, Nigeria. Trachoma distribution in places such as the Democratic Republic of the Congo and Côte d´Ivoire was mapped for the first time. In southeast Asia, Laos and Cambodia showed very low rates of the disease. But prevalence was high in several Pacific islands.

“It looks as if we will be able to reach elimination of trachoma more quickly than we had previously thought in a number of countries”, Harper told The Lancet Infectious Diseases. The goal of eliminating the disease as a public health problem by 2020 was set in a 1998 resolution by the World Health Assembly. It amounts to an intention to end trachoma blindness. Elimination was defined as a prevalence of active trachoma of less than 5% in children younger than 10 years, and less than one case of trichiasis per 1000 population. “The expectation is that at that kind of prevalence, the infection will gradually disappear without needing much more of a push in the way of interventions”, explains Anthony Solomon (WHO, Geneva, Switzerland).

WHO´s SAFE strategy is the basis of control efforts: surgery to correct the deformed eyelids and forestall blindness, antibiotics to treat the infection, and facial cleanliness and environmental improvements for prevention. The GTMP has boosted momentum, and brought a great deal of welcome publicity. “We now know where the disease is, we have a global strategy, tremendous collaboration among all the different non-governmental organisations and academics involved, sensitised ministries of health, and a very clear understanding of how to do it”, said Harper. Ethiopia, which carries roughly 30% of the global burden, has established a fast-track elimination programme. The country´s highly effective cadre of health extension workers are assisting. “Ethiopians are putting in a considerable amount of personnel and cash into tackling trachoma; it is a place where we can expect to see huge inroads”, said Emerson.

Commitment elsewhere is variable. There has been little recent information on disease prevalence in India—authorities in the country may have underestimated the scale of their trachoma problem (India was not part of the GTMP). Physicians from the trachoma programme in neighbouring Nepal report that roughly half their patients have crossed the border. Given the woeful sanitation and poverty that attends underdeveloped parts of India, it would not be surprising if trachoma infection and blindness lingered in the country.

Globally, funding levels remain low. “We still have only a quarter of the money that we really need to get to elimination”, said Harper. But the biggest challenge is insecurity. Afghanistan, the Central African Republic, parts of northern Nigeria, parts of northern Pakistan, and South Sudan are in varying degrees of chaos. Several of these places struggled to eradicate polio, a disease with a simpler intervention. The ongoing war in Yemen has devastated sanitation systems, and although the GTMP described a country with low trachoma prevalence, this could easily change. Then there are the places where access is problematic because of geography or a lack of roads—the Amazon rainforest, and parts of Ethiopia and Chad, for example.

“The elimination target is feasible, but only with very rapid support to implement programmes in countries where interventions are required”, stressed Solomon. Realistically, unless peace settles on most of the world´s troubled nations, 2020 will probably not see the target achieved. More likely, the disease will continue to be pushed back in most places by development and the SAFE strategy, but a few stubborn pockets of high prevalence will remain intact. In historical terms, this would still constitute a huge success. Besides, maintaining control efforts past 2020 would have benefits beyond trachoma.

“The rural sanitation component of the strategy is very important; its implementation will have an impact on peoples´ livelihood, diarrhoeal diseases, and lots of other neglected tropical diseases”, affirms Solomon. There is increasing evidence that azithromycin, the antibiotic used to treat trachoma, reduces all-cause mortality in children. “We are awaiting confirmation of that, but it would be fair to say that trachoma elimination interventions are good for people”, Solomon told The Lancet Infectious Diseases. Pfizer has thus far donated some 500 million doses of the broad-spectrum antibiotic, distribution of which has not been restricted to low-income countries. “Giving people access to a dose once a year [the schedule for trachoma] really does seem to improve their overall health status”, said Emerson.

Whether or not the 2020 target is attained, however, the crucial issue is sustainability. As yet, none of the countries to have thus far declared elimination were hyperendemic. If Ethiopia, say, or Tanzania can eliminate trachoma, and avoid recrudescence, it would indicate that blinding trachoma can be banished forever. Moreover, the preventative measures for the infection are the cornerstone of public health. Elimination could act as a springboard to tackle other diseases of poverty.