Trachoma

2 April 2020 | Q&A

Trachoma is a disease of the eye and the leading infectious cause of blindness worldwide.

The infection is transmitted by direct or indirect transfer of eye and nose discharges of infected people, particularly young children who harbour the principal reservoir of infection. These discharges can be spread by particular species of flies.

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.

The disease thrives especially in crowded living conditions where there are shortages of water, inadequate sanitation and where numerous eye-seeking flies are present. 

An individual’s immune system can clear a single episode of infection, but in endemic communities, re-acquisition of the organism occurs frequently.

 

Trachoma is a disease of the eye and the leading infectious cause of blindness worldwide. It is caused by an obligate intracellular bacterium called Chlamydia trachomatis.

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 scarring of the cornea. Left untreated, this condition leads to the formation of 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 of visual impairment between the ages of 30 and 40 years is more typical.

 

Trachoma is hyperendemic in many of the poorest and most rural areas of 37 countries of Africa, Central and South America, Asia, Australia and the Middle East.

It is responsible for the blindness or visual impairment of about 1.9 million people. It causes about 1.4% of all blindness worldwide.

Overall, Africa remains the most affected continent, and the one with the most intensive control efforts.

 As of 2 January 2020, 13 countries had reported achieving elimination goals. These countries are: Cambodia, China, Gambia, Ghana, Islamic Republic of Iran, Iraq, Lao People’s Democratic Republic, Mexico, Morocco, Myanmar, Nepal, Oman and Togo. Eight of those countries – Cambodia, Islamic Republic of Iran, Lao People’s Democratic Republic, Ghana, Mexico, Morocco, Nepal and Oman – had been validated by WHO as having eliminated trachoma as a public health problem.

 

Trachoma disease is usually clinically diagnosed. People are examined for clinical signs through the use of magnifiers (loupes). In most early stages, infection does not present visible signs of the disease. However, repeated infections cause scarring of the conjunctiva and it is during this phase that infected individuals get the feeling of irritation.

 

The infection is associated with inflammatory changes in the conjunctiva known as “active trachoma”.

The WHO grading system for trachoma classifies the disease in 5 grades, depending on the presence of visible signs of the disease. The treatment involves antibiotics to clear infection and surgery for the most advanced cases. Disease grades and associated treatment are listed below.

  • Trachomatous Inflammation – Follicular (TF) - which mostly requires topical treatment. 
  • Trachomatous Inflammation – Intense (TI) - during which topical and systemic treatments are considered.
  • Trachomatous Scarring (TS) - when scars are visible as in the tarsal conjunctiva and which may obscure tarsal blood vessels.
  • Trachomatous Trichiasis (TT) - when an individual is referred for eyelid surgery; and
  • Corneal Opacity - a stage during which a person is irreversibly blind.

 

Elimination programmes in endemic countries are being implemented using the WHO-recommended SAFE strategy. This consists of:

  • Surgery to treat the blinding stage (trachomatous trichiasis);
  • Antibiotics to clear infection, particularly mass drug administration of the antibiotic azithromycin, 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 elimination targets.