New atlas working to assist in trachoma eradication

Global atlas displays up-to-date information on trachoma distribution.

Issue: May 2012

An atlas dedicated to trachoma control facilitates monitoring of trachoma distribution and may play an important role in supporting disease control strategies.

“This new atlas, a joint effort of the International Trachoma Initiative and the London School of Hygiene & Tropical Medicine (LSHTM), displays the most up-to-date information on the global distribution of trachoma,” Sarah Polack, PhD, lecturer at the LSHTM, said. “Compared with the first trachoma atlas, develop in 2005 by LSHTM and the [World Health Organization], it provides extensive updates, including data of four times the number of districts.”

For her contribution to the project, Dr. Polack was awarded the Gold Medal of Trachoma by the International Organization Against Trachoma and the French League Against Trachoma.

Dr. Polack received the Gold Medal of Trachoma from the International Organization Against Trachoma and the French League Against Trachoma.

Image: Polack S

Trachoma is the most common infectious cause of blindness worldwide, with the active stages of the disease occurring in children and the blinding trichiasis stages occurring in later life. According to recent estimates, 1.3 million people are blind and 1.8 million have low vision due to the disease.

Today, it is most prevalent in Africa, but it is also found in the Middle East, Latin America, Southeast Asia and the Western Pacific, typically in the most economically disadvantaged and marginalized communities.

Useful tool

“In 1997, the WHO implemented a program for the Global Elimination of Trachoma by 2020 (GET 2020), based on the so-called SAFE strategy,” Dr. Polack said at the French Society of Ophthalmology meeting in Paris. “SAFE includes a combination of interventions to address both long-term morbidity and transmission of the chlamydia trachomatis bacterium: surgery for trichiasis, antibiotics, face washing and environmental improvement.”

The recommendation for the implementation of SAFE is based on the district-level prevalence. Initial control activities are implemented in the WHO’s districts, with subsequent focus on the specific needs of individual communities.

“An awareness of district-level prevalence is very important for guiding control, and this is primarily provided by surveys being conducted to derive population-based estimates of the disease. Surveys have been carried out by many national trachoma control programs, researchers and [non-governmental organizations]. But this information tended to be held by the organization [that] had undertaken them or the countries in which the data were available,” Dr. Polack said.

“The aim of this updated atlas was to gather and collate all this information worldwide, to present a global, up-to-date picture of trachoma,” she said.

Maps have the advantage of describing the distribution in a clear, visible way, highlighting where data is missing. They are a visual way of showing where more information and control efforts are needed, of monitoring trends over time, documenting progress and ultimately engendering political and financial support for control of the disease.

In addition, maps can help assess geographical overlap with other diseases, facilitating the integration and optimization of resources for disease control programs, Dr. Polack said.

Another key aim of the work is to make these maps accessible and easy to update through the Internet. They are available at www.trachomaatlas.org.

Broader geographic coverage

A total of 175 population-based surveys were identified, providing information of active trachoma in 42 countries and trachoma trichiasis in 39 countries. In six additional countries for which data were not available, rapid assessment or anecdotal collection of information from health authorities or non-governmental organizations was carried out. The majority of data included in the maps were from trachoma control programs.

“We were positively surprised by the increased geographic coverage of trachoma surveys, which has risen from 205 districts prior to 2005 to 895 currently. This reflects a rise in the number of large-scale national or regional surveys taking place in recent years,” Dr. Polack said.

Based on available data, Africa has the highest prevalence of trachoma, mostly in the savanna areas of East Africa and Central Africa and in the Sahel area of West Africa. Successful control programs have greatly reduced the incidence in some areas: Morocco has achieved trachoma elimination status, Ghana is moving toward elimination, and there is evidence of reduced prevalence in Mali.

However, prevalence estimates are still lacking in some areas, Dr. Polack said.

Only incomplete information is available for Asia and the Western Pacific. Accurate survey data have been collected in Australia, where trachoma persists in the indigenous aboriginal community. While data are still lacking in India and China, Nepal has conducted extensive surveys of suspected endemic areas in the last 5 years and has made encouraging progress in control.

A fairly low prevalence has been reported in the Middle East, but data are limited and outdated. In Latin America, trachoma is limited to Brazil, Guatemala and one district in Mexico.

“The atlas is a work in progress. We are relying on new information coming in to continuously update these maps, and any contribution will be welcome,” Dr. Polack said. – by Michela Cimberle

References:

Frick KD, Basilion EV, Hanson CL, Colchero MA. Estimating the burden and economic impact of trachomatous visual loss. Ophthalmic Epidemiol. 2003. 10(2):121-132. Resnikoff S, Pascolini D, Etya’ale D, et al. Global data on visual impairment in the year 2002. Bull World Health Organ. 2004. 82(11):844-851.

For more information:

Sarah Polack, PhD, can be reached at London School of Hygiene & Tropical Medicine, 50 Bedford Square, London WC1B 3DP, UK; email: sarah.polack@lshtm.ac.uk.

Disclosure: Dr. Polack has no relevant financial disclosures.