Trachoma

What is trachoma?

Trachoma is an infectious eye disease caused by the bacterium Chlamydia trachomatis and is the leading infectious cause of blindness worldwide.

The infection, which is mainly found in children, is thought to spread through contact with fluid from the eyes or nose of a person carrying the infection. In trachoma-endemic settings (areas where trachoma is found more commonly), children will be reinfected many times, over many years. This can lead to eyelid inflammation and a build-up of scar tissue inside the eyelid, leading to the eyelashes turning inward and scratching the eyeball. This is called trachomatous trichiasis (TT).

TT causes intense pain and eventually, if left unmanaged, can lead to irreversible blindness - eventually, the cornea becomes too cloudy for light to pass through, causing the complete loss of sight. Therefore, vision loss from trachoma happens over time.

Trachoma is more likely to affect the most marginalised and vulnerable populations, in rural areas of Africa, Central and South America, Asia, and the Middle East.

How does Trachoma spread? 

Infection spreads through infected eye or nose fluids in areas where people come into close contact. Primarily, the infection is passed between young children when playing or sharing bedding, or through eye-seeking flies.

In communities where trachoma is endemic (where the infection occurs regularly), repeated infections can happen frequently. The environmental factors associated with the increased spread of infection include:

• Inadequate hygiene and cleanliness

• Crowded households

• Inadequate access to water

• Inadequate access to and use of sanitation

The bacterium that causes trachoma can also spread through different species of flies, such as the Bazaar fly.

What is trachomatous trichiasis?

Trachomatous Trichiasis (TT, the penultimate stage of trachoma progression) is characterised by eyelashes from the upper eyelid turning inward towards the eye. TT develops when an individual is repeatedly infected.

TT can have an impact on quality of life. Symptoms may include:

• Feeling like there is sand or something stuck in your eye

• Blurry vision

• A red, sore and watery eye

While there is a high risk of someone losing their sight from TT, it is not inevitable. As TT involves the eyelashes turning inwards, management includes surgery to correct the position of the eyelid, preventing these misdirected eyelashes from scratching the eyeball. If there are only a few (one or two) in-turned eyelashes, or the individual doesn’t want surgery, high-quality epilation can be done instead of surgery. If TT is left unmanaged, there is the ongoing risk of damage to the surface of the eye (cornea) from the eyelashes growing inwards. This could eventually lead to a permanent loss of vision.

What causes trachoma?

The cause of trachoma is a bacterium called Chlamydia trachomatis. This bacterium causes an infection, with infection mostly found in children. A single infection won’t lead to trachoma. However, in trachoma-endemic areas, children will be infected regularly over many years. If interventions are not implemented to stop transmission (such as antibiotics to treat infection and better hygiene and sanitation to limit transmission), these repeated infections can lead to trachomatous trichiasis (TT). The bacterial infection causes the lining of the eyelid (conjunctiva) to become inflamed and scarred, and over time, the infection can also damage the front of the eye (cornea).

The bacterium can spread through:

• Contact with the fluid from the eyes or nose of someone else with infection. This most commonly happens through someone carrying the infection touching their eyes and then touching another person on their face, or via clothing or a personal care item, for example, a towel.

• Flies landing on the face of someone with the trachoma infection and carrying the secretions to another person’s face.

• Direct mother-to-newborn transmission of Chlamydia trachomatis can occur – but only if the mother has the bacteria in her birth canal – as this is because the bacteria can directly come into contact with the baby as it is born. However, this will only cause a single self-limiting infection of the eye and will not lead to trachoma.

Who is at risk of trachoma?

Trachoma remains a pressing public health issue in many parts of the world. It is a disease of poverty, associated with inadequate access to water, sanitation and hygiene, particularly for rural communities. Crowded households and limited access to healthcare also increase the risk of contracting trachoma.

Infection is most common in young children aged between 1 and 9 years. Because children are often in close contact playing together, trachoma can easily spread between them.

Women are 1.8 times more likely to be affected by trachoma than men and are blinded by trachoma up to 4 times as often as men. This is thought to be because of the close contact between women and children, resulting in an increase in trachoma infections for this group.

What are the signs and symptoms of trachoma?

Trachoma symptoms can vary in severity depending on the stage of the infection. Most individuals with active trachoma have minimal or no symptoms.

Mild symptoms which may occur include:

• Eye redness

• Irritation and discomfort

• Excessive tearing

• Sensation of a foreign body in the eye

As the disease progresses, moderate to severe symptoms include:

• Swelling of the eyelids

• Thickening of the conjunctiva (the clear membrane covering the white part of the eye)

• Scarring of the eyelids

• Eyelashes growing inwards (trachomatous trichiasis)

• Scratching of the cornea (front surface of the eye)

• Reduced vision from corneal clouding (opacity)

What are the stages of trachoma?

The World Health Organization (WHO) has defined five signs to classify trachoma. This is known as the WHO simplified grading system and can be used for clinical diagnosis of trachoma.

• Trachomatous inflammation—follicular (TF): Five or more small bumps (follicles), at least 0.5 mm in diameter, that can be seen on the inner surface of the conjunctiva. This stage is most common in pre-school children.

• Trachomatous inflammation—intense (TI): The upper inner eyelid becomes inflamed and swollen, appearing red, rough and thickened, and obscuring more than half the normal deep-lying blood vessels. The eye becomes highly contagious and the risk of blindness increases.

• Trachomatous scarring (TS): Repeated infections lead to scarring of the inner eyelid. TS is defined as “the presence of easily visible scarring in the upper tarsal conjunctiva”, with scars appearing as white lines, bands, or sheets in the upper inner eyelid.

• Trachomatous trichiasis (TT): TT is defined as “at least one eyelash from the upper eyelid touches the eyeball, or evidence of recent plucking out of in-turned eyelashes from the upper eyelid”.

• Corneal opacity (CO): The cornea becomes cloudy after being scratched by the eyelashes. There is a high risk of blindness if this is not managed urgently.

How is trachoma diagnosed?

In non-endemic settings, the early stages of trachoma are not normally looked for. TT is usually clinically diagnosed by a doctor trained in eye care, or more specifically, an ophthalmologist.

In trachoma-endemic areas, trained healthcare workers may diagnose trachoma with the use of the WHO simplified grading system. Diagnosis is normally done as part of surveys that are carried out at a district level to work out how much trachoma there is. This is because trachoma is a community disease, rather than a disease that is managed at an individual level. The exception is for TT, where individual diagnosis of in-turned eyelashes is important, so that appropriate management can be offered to prevent the person from going blind.

Diagnosis is almost always based on clinical assessment. However, the collection of swabs from the inner eyelid for testing with nucleic acid amplification tests (NAATs), such as polymerase chain reaction (PCR), is increasingly being used by national trachoma programmes to test for current infection. Also, the collection of a small amount of blood from the finger for testing with serology tests are also being increasingly used.

What are the treatments for trachoma?

Trachoma management depends on what stage the disease is at.

• Early stages:
  At the early stages of trachoma, antibiotics can be used to clear the infection. Antibiotics used to treat trachoma include tetracycline eye ointment or oral azithromycin.
  
  Since trachoma is a community disease, antibiotic treatment is recommended at the district level, known as antibiotic mass drug administration (MDA).
  
  

• Later stages:
  At the later stages of trachoma, where there have been repeated infections, surgery may be required to manage the TT. The surgery results in eyelashes being turned away from the eyeball to stop them rubbing against the cornea. This helps prevent further vision loss by reducing the progression of scarring on the eye.
  
  If there are only a few (one or two) in-turned eyelashes, or the individual doesn’t want surgery, high-quality epilation can be done instead of surgery. This involves removal (plucking out) of the eyelashes. This is more often used for individuals with minor trichiasis, rather than a severe form of the condition, as the eyelashes tend to grow back within 4-6 weeks, so it is only a temporary solution.

How can I reduce my risk of developing trachoma?

Those who live in trachoma-endemic areas are at risk of developing trachoma. Trachoma is considered to be a public health problem when prevalence surveys have shown the prevalence of TF to be at least 5% in children aged 1-9 years, or of TT “unknown to the health system” to be at least 0.2% in adults aged 15 years or above.

The SAFE strategy is recommended by WHO for trachoma control. The “F” and “E” components relate to limiting transmission of infection.

• ‘S’- is “surgery” to manage TT.

• ‘A’ - relates to “antibiotics”, generally given in MDA campaigns, to treat infection.

• ‘F’ - “Facial cleanliness”, encouraging children to practise good facial hygiene, including cleaning their faces daily, ideally with soap.

• ‘E’- “Environmental Improvement”, including having access to clean water for drinking and cleaning, and access to sanitation facilities for going to the toilet.

Reducing the risk of trachoma is best done through the following prevention methods:

• Facial cleanliness: Encouraging children to practise good facial hygiene, including cleaning their faces daily.

• Personal hygiene: Washing your hands regularly with soap and clean water, while avoiding touching your eyes with dirty hands and sharing towels or bedding.

• Access to clean water and sanitation: Ensuring access to clean and safe drinking water.

What research is there into trachoma?

The number of people requiring interventions against trachoma has dropped below 100 million for the first time since global records started. The target year from trachoma elimination globally is 2030. Modelling work has indicated that although many countries will achieve this, there will be some places where continued interventions will be needed.

One of the key research areas is to understand why the elimination thresholds are not being met, even though many years of antibiotic MDA have been conducted. Surveys are now collecting samples to test for current infection and past ocular C. trachomatis infection exposure, to try and better understand what is going on, as the clinical signs are not always a good indicator of infection.

Fight for Sight funded research by Dr Maryse Bailly investigated whether targeting a protein called Rac1 (responsible for making eye tissue tighten and scar) could be a safer way to prevent scarring after eye surgery. Dr Bailly and her team found that Rac1 plays an important role in driving this tightening and scarring response and found by blocking this protein, cells that create scar tissue (fibroblasts) are stopped from entering the scarring phase and therefore, reducing the damage to the eye tissue.