Trachoma

Key Facts

  • Trachoma is a chronic exacerbating and remitting chlamydial conjunctivitis (eye disease) caused by infection with the bacterium Chlamydia trachomatis that is common among children ages 3 through 6 in certain resource-limited areas worldwide.
  • About 7% of patients develop decreased vision or blindness; trachoma is the leading cause of preventable blindness worldwide.
  • Diagnosis is usually clinical, but standard methods to detect chlamydia can be done when available.
  • It is a public health problem in 39 countries and is responsible for the blindness or visual impairment of about 1.9 million people. Blindness from trachoma is irreversible.
  • Based on April 2024 data, 103 million people live in trachoma endemic areas and are at risk of trachoma blindness.
  • Infection spreads through personal contact (via hands, clothes, bedding or hard surfaces) and by flies that have been in contact with discharge from the eyes or nose of an infected person.
  • Initial symptoms are conjunctival hyperemia, eyelid edema, photophobia, and lacrimation. Later, corneal neovascularization and scarring of the conjunctiva, cornea, and eyelids occur.
  • With repeated episodes of infection over many years, eyelashes may be drawn in so that they rub on the surface of the eye. This causes pain and may permanently damage the cornea (trachomatous trichiasis).
  • For endemic areas, the World Health Organization (WHO) also advocates corrective surgery, mass administration of antibiotics, facial cleanliness and environmental interventions to reduce transmission.
  • In 2023, 130,746 people received surgical treatment for advanced stage of the disease, and 32.9 million people were treated with antibiotics. Global antibiotic coverage in 2023 was 29%.

Overview

Trachoma, a neglected tropical disease (NTD) is caused by Chlamydia trachomatis (serotypes A, B, Ba, and C). It is the leading infectious cause of blindness. Infection is transmitted by ocular and nasal secretions that are passed from person to person on fingers and fomites (such as hard surfaces and clothing) and by eye seeking flies (particularly Musca sorbens). Eye infection is associated with inflammatory conjunctivitis, known as “active trachoma”. Repeated episodes of active trachoma can scar the inner side of the eyelids. In some individuals, this leads to trachomatous trichiasis (trɪˈkaɪ.ə.sɪs) (TT), in which one or more eyelashes from the upper eyelid touch the eye. TT is extremely painful. It can be corrected surgically but, if left untreated, may lead to corneal opacification, vision impairment and blindness.

Trachoma is endemic in resource-limited parts of North Africa, the Middle East, the Indian subcontinent, Australia, and Southeast Asia, affecting 1.9 million people. It is also the cause of about 1.4 percent of blindness worldwide.

Symptoms and Transmission

In the United States, trachoma is rare, occurring occasionally among American Indians and immigrants. The disease occurs mainly in children, particularly those between the ages of 3 and 6. Older children and adults are much less susceptible because of increased immunity and better personal hygiene. Trachoma is highly contagious in its early stages and is transmitted by eye-to-eye contact, hand-to-eye contact, eye-seeking flies, or the sharing of contaminated articles (e.g., towels, handkerchiefs, eye makeup).

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 to 90%. Infection becomes less frequent and shorter in duration with increasing age. Infection is usually acquired when living in close proximity to others with active disease, and the family is the main setting for transmission. An individual’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 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.

Visual impairment or blindness results in a worsening of the life experience of affected individuals and their families, who are normally already amongst the poorest of the poor. Women are blinded up to 4 times as often as men, probably due to their close contact with infected children and their resulting greater frequency of infection episodes. Environmental factors associated with more intense transmission of C. trachomatis include: (i) inadequate hygiene; (ii) crowded households; (iii) inadequate access to water; (iv) inadequate access to and use of sanitation.

Distribution

Trachoma is hyperendemic in many of the poorest and most rural areas 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 21 October 2024, 21 countries – Benin, Cambodia, China, Gambia, Islamic Republic of Iran, Lao People’s Democratic Republic, Ghana, India, Iraq, Malawi, Mali, Mexico, Morocco, Myanmar, Nepal, Oman, Pakistan, Saudi Arabia, Togo, Vanuatu and Viet Nam – had been validated by WHO as having eliminated trachoma as a public health problem.

Economic Impact

The burden of trachoma on affected individuals and communities is enormous. The economic cost in terms of lost productivity from blindness and visual impairment is estimated at US$ 2.9 to 5.3 billion annually, increasing to US$ 8 billion when trichiasis is included.

Prevention and control

Trachoma can be eliminated as a public health problem with a set of interventions known as the “SAFE strategy”, consisting of:

  • Surgery to treat the blinding stage (trachomatous trichiasis).
  • Antibiotics to clear infection, particularly mass drug administration (MDA) of the antibiotic azithromycin, which is donated by the manufacturer, Pfizer to elimination programs, 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.

Surgery should be offered to any individual with trachomatous trichiasis considered likely to benefit from an operation

The requirements for these interventions are determined by population-based prevalence surveys in districts suspected of being endemic at baseline. Surveys are repeated at specified intervals after initiation of interventions. In particular, it is recommended that impact surveys be undertaken at least 6 months after the last planned annual round of antibiotic mass drug administration (MDA), in order to determine whether treatment should be continued or can safely be stopped.

Data reported to WHO by Member States for 2023 show that 130,746 people with trachomatous trichiasis were provided with corrective surgery in that year, and 32.9 million people in endemic communities were treated with antibiotics to eliminate trachoma. In 2019, when COVID-19 did not affect the ability to undertake community-based work, 92,622 people with trachomatous trichiasis were provided with corrective surgery, and 95.2 million people were treated with antibiotics.

National Status of Trachoma

To date, elimination of trachoma as a public health problem has been validated by WHO in 18 countries (Benin, Cambodia, China, Gambia, Ghana, Iraq, Islamic Republic of Iran, Lao People’s Democratic Republic, Malawi, Mali, Mexico, Morocco, Myanmar, Nepal, Oman, Saudi Arabia, Togo and Vanuatu).

A further 10 countries (Botswana, Burundi, Guatemala, India, Mauritania, Namibia, Pakistan, Papua New Guinea, Tunisia and Viet Nam) report having achieved the prevalence targets for elimination.

As of 15 April 2024, based on the most recent district level prevalence data, trachoma was a public health problem in at least part of 39 countries. A further 3 countries may require interventions, but the necessary investigations in suspected trachoma endemic areas have not yet been completed. Efforts are being made to undertake those investigations.

Regional Highlights and Milestones

  • National trachoma programs continue to make progress towards trachoma elimination.
  • Overall, the number of people worldwide who require the A, F and E components of SAFE fell from 204.4 million in 2014 to 103.2 million in April 2024: a 49% fall in a decade.
  • No estimate of the global burden of trachomatous trichiasis was made for 2014, but the estimate for 2016 was 2.8 million. Against that 2016 baseline, the April 2024 estimate of 1.5 million people represents a 47% fall.
  • In July 2023, Iraq was validated by WHO as having eliminated trachoma as a public health problem. Iraq’s milestone increased the number of countries having eliminated at least one neglected tropical disease to 50: the half-way point towards the 2030 target of 100 countries having recorded such success.

Source: Adapted primarily from Weekly Epidemiological Record, 12 July 2024, WHO alliance for the global elimination of trachoma: progress report on elimination of trachoma, 2023: World Health Organization (WHO); https://tinyurl.com/y6ce94jv; Ref #: WER No 28, 2024, 99, 363–380; Licence: CC BY-NC-SA 3.0 IGO and (ii) ) Trachoma, World Health Organization website, 21 October 2024, Accessed 6 March 2025 at https://tinyurl.com/mr23vtxu. Additional information from (a) Trachoma, Wikipedia, The Free Encyclopedia, 14 January 2025, Accessed 6 March 2025 at https://tinyurl.com/5bjybn77; (b) Syed ZA, Trachoma, The Merck Manual Professional Version, Reviewed/Revised April 2023, Accessed 6 March 2025 at https://tinyurl.com/ydvhu8u4; (c) Al-Khatib T, Bella AL, Saboyá-Díaz MI, Solomon AW. Trachoma: The Last Decade? Ophthalmic Epidemiol. 2023 Dec;30(6):541-543. Epub 2023 Dec 12. PMID: 38085790; (d) Bilchut AH, Burroughs HR, Oldenburg CE, Lietman TM. Trachoma Control: A Glass Half Full? Am J Trop Med Hyg. 2023 Jan 9;108(2):237-238. doi: 10.4269/ajtmh.22-0760. PMID: 36623481; PMCID: PMC9896326; (e) West SK. Milestones in the fight to eliminate trachoma. Ophthalmic Physiol Opt. 2020 Mar;40(2):66-74. doi: 10.1111/opo.12666. Epub 2020 Feb 3. PMID: 32017172; (f) Oldenburg CE. One Size Does Not Fit All: Achieving Trachoma Control by 2030. Am J Trop Med Hyg. 2019 Dec;101(6):1189-1190. doi: 10.4269/ajtmh.19-0684. PMID: 31595872; PMCID: PMC6896881; (g) Renneker KK, Abdala M, Addy J, Al-Khatib T, Amer K, Badiane MD, Batcho W, Bella L, Bougouma C, Bucumi V, Chisenga T, Dat TM, Dézoumbé D, Elshafie B, Garae M, Goepogui A, Hammou J, Kabona G, Kadri B, Kalua K, Kanyi S, Khan AA, Marfo B, Matendechero S, Meite A, Minnih A, Mugume F, Olobio N, Omar FJ, Phiri I, Sanha S, Sharma S, Seife F, Sokana O, Taoaba R, Tesfazion A, Traoré L, Uvon N, Yaya G, Logora MY, Hooper PJ, Emerson PM, Ngondi JM. Global progress toward the elimination of active trachoma: an analysis of 38 countries. Lancet Glob Health. 2022 Apr;10(4):e491-e500. doi: 10.1016/S2214-109X(22)00050-X. PMID: 35303459; (h) Solomon AW, Burton MJ, Gower EW, Harding-Esch EM, Oldenburg CE, Taylor HR, Traoré L. Trachoma. Nat Rev Dis Primers. 2022 May 26;8(1):32. doi: 10.1038/s41572-022-00359-5. PMID: 35618795; and (i) Toumasis P, Vrioni G, Tsinopoulos IT, Exindari M, Samonis G. Insights into Pathogenesis of Trachoma. Microorganisms. 2024 Jul 28;12(8):1544. PMID: 39203386; PMCID: PMC11355952.