Trachoma in Asia-A disappearing scourge.

Trachoma is an ancient blinding eye disease. With improvements in hygiene and living conditions and development of targeted strategies by the World Health Organization, trachoma is being progressively eliminated. Great progress is being seen in Asian countries, many of which are becoming trachoma free.

1. Introduction

Trachoma is the blinding infection caused by Chlamydia trachomatis1 C. trachomatis is a Gram-negative bacteria that first evolved at the time of the dinosaurs.2 Basically, every vertebrate species has evolved around its own particular species of Chlamydia.3 The human strains separated into a predominantly ocular strain and general strains some 2–5 million years ago at about the time when early human ancestors were evolving; however, modern humans evolved only some 100,000 years ago.

Given this extraordinary history of coevolution, infection with Chlamydia does not seem to have presented a major problem with the evolution and health of early mankind. However, with the development of early settlements and the start of agriculture at the end of the past Ice Age some 12,000 years ago, things changed.

References to trachoma in China date back to the 27th century BC when Emperor Huang Ti Nei Ching underwent surgery for trichiasis.4 Some of the earliest written records of trachoma are found in bone writing from the Chang Dynasty (16th–11th century BC). Trachoma became a common and important condition in the Yangtze and Yellow River Valleys in China. Similarly, trachoma also appeared in the small farming communities developing in the Euphrates Valley in Mesopotamia, along the Nile Valley in Egypt, and along the Indus and Ganges Rivers in South Asia.1 As people started to live in settlements, with increased crowding and poor hygiene, chances of individuals repeatedly being infected with Chlamydia increased, leading to the development of trachoma. A single episode of chlamydial eye infection will usually resolve without serious sequelae, but repeated episodes of reinfection lead to blinding trachoma.

Clinically significant outbreaks of chlamydial infection are also seen in a variety of other animal species, particularly when they are crowded together.5 When birds are crowded together, they develop psittacosis; when cows, pigs, or sheep are crowded, they develop problems such as chlamydial abortions. Even koalas and crocodiles, when overcrowded, develop symptomatic chlamydial infections.6

2. Pathogenesis

The key to understanding the pathogenesis of trachoma is that frequent and repeated episodes of reinfection are needed for the development of severe disease.78 Repeated episodes of infection induce a marked and sustained inflammatory response that, with time, leads to scarring and structural damage.1 The changes in trachoma are an immune response to the chlamydial antigens released, as the Chlamydia organisms divide in the conjunctival epithelial cells.9 In the eye, of course, this is characterized by the characteristic inflammation, with follicles in the upper tarsal conjunctiva lid, and scarring later. The more severe the inflammation and the longer it persists, the more severe the scarring. With time, the scars will contract to turn in the eye lashes, causing trichiasis, corneal scarring, and blindness.

The key to preventing trachoma is to prevent the repeated episodes of reinfection by preventing transmission. Trachoma is transmitted from one child to another through contact with to infected ocular and nasal secretions. This usually occurs by direct contact with fingers, while children play or sleep together, or by the use of shared towels or other materials used to clean children’s faces.

3. The 19th and 29th centuries

Although trachoma persisted in many areas over the past 2000 years, it was really 200 years ago after the Napoleonic Wars, particularly during the fighting in Egypt, that trachoma was seen as a major health problem and also a military problem in Europe.1 Although trachoma seems to have existed in many cities, it was not until a large number of soldiers became incapable of fighting because of their ocular infections that the authorities really took notice of it. This coincided with the start of the Industrial Revolution in Europe, a time when a large number of people moved from the countryside and crowded into slums and tenements on the outskirts of newly developing industrial towns. Trachoma became a major problem in the civilian population too.

The first International Congress of Ophthalmology was held in 1857, and one of the two key agenda items was what to do about trachoma.10 From the military perspective, trachoma could be curtailed by having soldiers wash separately using clean water and not sharing towels.11 In the 1890s, the United States established a quarantine service for incoming emigrants from Central and Eastern Europe who were examined and sent back if they were found to have trachoma.12

For the general population, there was little advancement in the treatment of trachoma other than cauterization of the inflamed conjunctiva with silver nitrate or copper sulfate, or at times curetting of follicles. Many variations of lid surgery that dated back to ancient times were used to correct trichiasis.1

Although trachoma became widespread around the world in the 1920s, it started to disappear in most developed countries as living conditions improved during the first half of the 20th century.1 The advent of sulfonamides in the 1930s and then the development of tetracyclines in the 1940s sped up this process so that trachoma had disappeared from most developed areas by the 1950s and 1960s. Data collected in Japan track the disappearance of trachoma during the 20th century (Figure 1).13 Similar findings came from Taiwan.14 It has still remained an ongoing problem in most of the less developed areas despite many attempts by the World Health Organization (WHO) to combat it.15

Figure 1

Trachoma prevalence in Japanese school children.13

4. Identification of Chlamydia

Chlamydia was first identified in conjunctival scrapings in studies undertaken in Indonesia, which used a Giesma stain to show the now characteristic intracytoplasmic inclusions.16 The inability to culture Chlamydia led investigators to assume that it was a virus; although it is still not possible to culture the organism, a number of experimental studies were undertaken to confirm its infectious nature and understand some of its epidemiology.1

The organism that caused trachoma was not identified until 1957 following the ground breaking research of four Chinese ophthalmologists and scientists, Drs T’ang, Chang, Huang, and Wang,17 at Tongren Eye Hospital, Beijing, China. They were the first group in the world to be able to culture Chlamydia. They showed that Chlamydia is a Gram-negative bacterium that can grow only within the cytoplasm of cells and divide by binary fission. The ability to culture Chlamydia led to an explosion in the research of Chlamydia with the development of a variety of new and improved tests to identify infection and efforts to develop a vaccine.1

5. Trachoma in the 21st century

In 1998, the World Health Assembly passed a resolution calling for global elimination of blinding trachoma by the year 2020.18 It called on all member states to work and make that commitment a reality. The figures pulled together by WHO in 2003 suggested that some 49 million children in the Asia Pacific region had active trachoma and that over 3.5 million adults had trichiasis.19

WHO advocated the use of the SAFE strategy to eliminate blinding trachoma, which includes surgery for inturned lashes, antibiotic treatment, promotion of facial cleanliness, and environmental improvement.2021 Many countries undertook mass drug administration using an annual dose of azithromycin. Pfizer (New York, NY, USA), the manufacturer of this drug, committed to provide azithromycin free of charge for this work, and the distribution is coordinated through the International Trachoma Initiative. So far, Pfizer has donated over 500 million doses of azithromycin.22

National representatives of endemic countries and nongovernment organizations meet each year under the auspices of WHO at the Global Alliance to Eliminate Trachoma. Over the past decade, remarkable progress has been made and trachoma has been eliminated from a number of African and Middle East countries.21 Striking progress has also been made in the Asia Pacific region. Most striking of all is the oral announcement of elimination of trachoma from China that was made in September 2015 at the International Agency for the Prevention Blindness meetings held in Beijing. Great progress has also been made in Cambodia and Nepal that seem to have eliminated trachoma, and Vietnam and Laos where trachoma is now reported to be seen only in some small, more remote areas in the northern part of each country.23 Data are still awaited from India where much progress is thought to have been made. Published reports of recent surveys are still awaited.

Although active trachoma has been reduced in, or has disappeared from, most areas, trichiasis still continues to be a major problem. The need to identify and provide trichiasis surgery to older people, who had severe trachoma in their childhood and progress to develop trichiasis, will continue for many years.24

However, active trachoma still remains a problem in some countries in the Asia Pacific region. It persists in Afghanistan, Myanmar, Pakistan, Papua New Guinea, and the Pacific Island countries of Fiji, Kiribati, Solomon Islands, and Vanuatu. Of course, trachoma has been a significant problem in the Australian Aboriginal population for many years, but significant progress has been made over the past few years.25 The prevalence of trachom-atous inflammation—follicular is now less than 5%, although some Aboriginal communities still have higher levels of trachoma.

6. Summary

Trachoma is an ancient disease that occurs in areas of poor personal and community hygiene, where frequent exchange of infected eye secretions is facilitated. The global efforts to eliminate trachoma together with the continuing improvement in living conditions and housing have seen a rapid decline of trachoma in many regions in the Asia Pacific and around the world. With continuing efforts on the remaining “hotspots,” we can feel confident of eliminating trachoma as a blinding disease from the Asia Pacific region by the year 2020.