- Trachoma is caused by ocular infection with the bacterium Chlamydia trachomatis.
- It is believed to be endemic in 51 countries, and is responsible for the visual impairment of about 1.8 million people, of whom 0.5 million are irreversibly blind.
- Approximately 232 million people live in trachoma endemic areas and are at risk.
- Infection spreads through personal contact (hands, clothing) and by flies that have been in contact with discharge from the eyes or nose of an infected person.
- With repeated episodes of infection over many years, chronic sequelae may occur, with pain and discomfort, and permanent damage to the cornea of the eye, leading to irreversible visual impairment or blindness.
- A 1998 World Health Assembly resolution targets trachoma for elimination as a public health problem by the year 2020.
- In 2013 nearly 234 000 received surgical treatment for advanced disease, and 55 million people were treated with antibiotics for trachoma.
Trachoma is the leading infectious cause of blindness in the world. It is caused by an obligate intracellular bacterium called Chlamydia trachomatis. The infection is transmitted through contact with eye and nose discharge of infected people, particularly young children who are the principal reservoir of infection. It is also spread by flies which have been in contact with the eyes and noses of infected people.
Clinical characteristics and morbidity
In areas where trachoma is endemic, active (inflammatory) trachoma is common among preschool-aged children, with prevalence rates which can be as high as 60–90%. Infection becomes less frequent and shorter in duration with increasing age. Infection is usually acquired through living in close proximity to others with active disease, and the family is the principal unit for transmission. A person’s immune system can clear a single episode of infection, but in endemic communities, re-acquisition of the organism occurs frequently.
After years of repeated infection, the inside of the eyelid can become so severely scarred (trachomatous conjunctival scarring) that it turns inwards and causes the eyelashes to rub against the eyeball (trachomatous trichiasis) resulting in constant pain and light intolerance. This and other alterations of the eye can lead to the scarring of the cornea. Left untreated, this condition leads to irreversible opacities, with resulting visual impairment or blindness.
The age at which this occurs depends on several factors including local transmission intensity. In very highly endemic communities, it can occur in childhood, though onset between the ages of 30 and 40 years is more typical.
Visual impairment or blindness results in a worsening of the life experience of affected individuals and their families, who are normally already among the poorest of the poor. Women are blinded 2 to 3 times more often than men, probably due to their close contact with infected children and the resulting greater frequency of infection.
Environmental risk factors influencing the transmission of the disease include:
- poor hygiene
- crowded households
- water shortage
- inadequate latrines and sanitation facilities.
Trachoma is hyperendemic in many of the poorest and most rural areas of 51 countries of Africa, Asia, Central and South America, Australia and the Middle East. It is responsible for the visual impairment of about 1.8 million people, of whom 0.5 million are irreversibly blind. This represents about 1.4% of the global total of blind individuals.
Overall, Africa remains the most affected continent and the one with the most intensive control efforts. In 2013, in the 29 endemic countries of WHO’s Africa Region, 204 000 cases of trichiasis were operated (87% of the global total operated), and 54 million people were treated with antibiotics (98% of the global total treated).
To date, 7 countries have reported achieving elimination goals, which signifies a major milestone in the campaign for trachoma elimination, signifying progression to the surveillance phase. These countries are: The Gambia, Ghana, Iran, Morocco, Myanmar, Oman and Viet Nam.
The burden of trachoma on affected individuals and communities is enormous. The economic cost in terms of lost productivity is estimated at between US$ 2.9–5.3 billion annually, increasing to US$ 8 billion when trichiasis is included.
Prevention and control
Control programmes in endemic countries are being implemented through the WHO-recommended SAFE strategy. This consists of:
- surgery to treat the blinding stage of the disease (trachomatous trichiasis),
- antibiotics to treat infection, particularly mass drug administration of antibiotics, which is donated by the manufacturer to elimination programmes through the International Trachoma Initiative,
- facial cleanliness, and
- environmental improvement, particularly improving access to water and sanitation.
Most endemic countries have agreed to accelerate the implementation of this strategy to achieve their elimination targets, all by the year 2020.
Data reported to WHO by Member States for 2013 show that nearly 234 000 people with trachomatous trichiasis were provided with corrective surgery that year, and 55 million people in endemic communities were treated with anti-chlamydial antibiotics to eliminate trachoma.
Elimination efforts need to continue to satisfy the target set by the World Health Assembly resolution (WHA 51.11), which is elimination of trachoma as a public health problem by 2020. Particularly important will be the full engagement of other sectors to improve sanitation and socioeconomic development.
WHO adopted the SAFE strategy in 1996. Its mandate is to provide technical leadership and coordination to the international efforts aiming to eliminate trachoma as a public health problem. The recommended strategy is a combination of interventions implemented as an integrated approach.
In 1997, WHO launched the WHO Alliance for the Global Elimination of Trachoma by the year 2020 (GET 2020). GET 2020 is a partnership which supports country implementation of the SAFE strategy and the strengthening of national capacity through epidemiological assessment, monitoring, surveillance, project evaluation and resource mobilization.