Trachoma: An Overview

Dost Jarbakhyl

Trachoma is a form of keratoconjunctivitis and the leading infectious cause of blindness worldwide. This eye disease results from an infection with the bacterium Chlamydia trachomatis serotypes A-C. It continues to pose a substantial burden on global health, particularly in regions with poor sanitation, inadequate hygiene practices, and limited access to clean water and healthcare services (1).

Aetiology

The causative agent of trachoma is a gram-negative bacterium called Chlamydia trachomatis which infects humans at the epithelial layer of mucosal surfaces (2), and spreads through multiple transmission routes. Primary transmission of Trachoma to uninfected individuals occurs through direct contact with ocular or nasal secretions from infected individuals. This spread is often facilitated by close eye-to-eye or hand-to-eye contact (3).

Additionally, the bacterium can survive on contaminated objects (fomites), such as towels, clothing, or bedding, which act as vectors when shared and thus plays a role in indirect transmission of the disease (4). C. trachomatis is also known to be carried by eye-seeking flies, which contribute to transmission by landing on infected eyes and transferring the bacterium to uninfected individuals (5).

This multifaceted transmission mechanism contributes to the persistence and prevalence of trachoma, particularly in areas with poor sanitation and hygiene.

Epidemiology

Trachoma is a public health problem in 38 countries and is the cause of blindness or visual impairment in about 1.9 million people with approximately 103 million of people living in areas at risk of blinding trachoma (1). Although trachoma accounts for 1.4% of global blindness, as of October 2024, 21 countries have been validated by the WHO as having eliminated trachoma as a public health problem (1).

Active trachoma affects boys and girls at similar rates during childhood (6). However, when it comes to trachomatous trichiasis (TT), women are disproportionately affected compared to men (7). The heightened risk for women is generally attributed to their increased exposure to Chlamydia trachomatis (Ct) which is largely due to societal roles and responsibilities, particularly in regions where trachoma is endemic. Women often bear the primary burden of childcare, involving frequent and close interactions with young children, who are key reservoirs of the infection. These interactions, such as cleaning children’s faces or caring for those with active trachoma, significantly increase the likelihood of bacterial transmission to women (8).

Classification

Trachoma is categorised under the World Health Organization’s (WHO) Simplified Grading System, which provides a systematic method for identifying and assessing the disease’s progression. This framework outlines five distinct stages, each defined by observable clinical signs in the conjunctiva and cornea (9).

  • Trachomatous Inflammation – Follicular (TF): Five or more follicles, ≥0.5 mm in diameter, on the upper tarsal conjunctiva, indicating early active infection.
  • Trachomatous Inflammation – Intense (TI): Severe conjunctival inflammation obscuring >50% of deep tarsal vessels, signalling high bacterial load and risk of progression.
  • Trachomatous Scarring (TS): Visible scarring on the tarsal conjunctiva, resulting from chronic or repeated infections.
  • Trachomatous Trichiasis (TT): At least one eyelash touching the eyeball or evidence of epilation, posing a risk of corneal damage.
  • Corneal Opacity (CO): Corneal opacification obscuring the pupil, leading to irreversible blindness.

The WHO Simplified Grading System aids in identifying trachoma’s severity and guiding interventions. Early stages (TF, TI) require antibiotics to treat infection, while advanced stages (TT, CO) often necessitate surgery to prevent blindness. This framework supports disease surveillance, resource allocation, and progress in trachoma elimination efforts (9).

Clinical Findings

The clinical manifestations of trachoma can be divided into stages: active disease, recurrent infections, and late stages with scarring and residual damage.

Active Disease

  • Follicular Conjunctivitis: Dome-shaped follicles, consisting of lymphoid cells, form on the conjunctiva. These follicles have a central area without blood vessels, surrounded by a vascular base. They appear as yellowish-white bumps, most prominently on the everted upper eyelid. Large follicles near the upper corneal margin can cause indentations known as ‘Herbert’s pits,’ which are pathognomonic for trachoma (10).
  • Papillary Hypertrophy: Small blood vessels in the conjunctiva become engorged and swollen, causing oedema that may obscure deeper tarsal vessels (10).
  • Corneal Pannus: The upper cornea becomes vascularised, typically a late feature resulting from chronic corneal irritation and inflammation (11).

Repeat Infection and Inflammation

  • Conjunctival Scarring: White fibrous bands or lines appear on the upper tarsal conjunctiva due to scar tissue formation (12).

Late Stages and Complications

  • Cicatricial Entropion and Trichiasis: Scar tissue contraction causes the eyelid margin to turn inward, leading to eyelashes rubbing against the ocular surface, which can result in further damage to the cornea and conjunctiva (13).
  • Corneal Opacification and Vascularization: Repeated irritation from in-turned eyelashes can cause corneal scarring and the growth of new blood vessels, potentially leading to visual impairment or loss (14).

Symptoms

Most individuals with trachoma are asymptomatic or experience mild, variable symptoms depending on the severity of inflammation. When symptoms do occur, they may include persistent redness, Photophobia, excessive tearing, irritation, and mucopurulent discharge. However, In the advanced stages of the disease, visual impairment or loss can occur due to scarring (15).

Treatment

The public health approach recommended by the World Health Organization (WHO) to prevent and treat trachoma is called the SAFE strategy, which includes Surgery for trichiasis, Antibiotics for active infection, Facial cleanliness, and Environmental improvements (16). Surgery is essential for individuals with trachomatous trichiasis, as it prevents corneal damage and reduces the risk of blindness. WHO recommends the posterior lamellar tarsal rotation (PLTR) technique due to its lower recurrence rates compared to bilamellar tarsal rotation. This procedure can be performed effectively in local communities, ensuring greater accessibility and minimizing logistical challenges (17).

Given trachoma’s high transmission potential, a community-wide approach is essential, as individual treatment alone is ineffective due to rapid reinfection (18). WHO recommends mass antibiotic distribution when the prevalence of active trachoma exceeds 10% in children aged 1 to 9 years, with annual treatment of all individuals over 6 months of age for three years (19). The choice of oral antibiotic is azithromycin which is administered as a single dose of 20 mg/kg body weight (up to a maximum of 1 g) (23). Alternatively, tetracycline 1% eye ointment can be applied twice daily for 6 weeks, particularly in infants under 6 months of age who cannot receive azithromycin (23).

Although Azithromycin is preferred for its single-dose regimen, favourable safety profile, and comparable efficacy to tetracycline ointment, however monitoring for macrolide resistance in Streptococcus pneumoniae remains necessary (20–22). Trials show that quarterly treatment of children aged 1 to 9 years significantly reduces infection prevalence in both treated and untreated adults (24). Alongside antibiotics, public health interventions such as hygiene promotion and environmental improvements play a critical role in sustainable trachoma control. Ensuring access to safe water, improving sanitation facilities, managing waste disposal, and reducing fly populations are all essential measures to limit transmission and support long-term disease control (25,26).

References

1.            Trachoma [Internet]. [cited 2024 Dec 15]. Available from: https://www.who.int/news-room/fact-sheets/detail/trachoma

2.            O’Connell CM, Ferone ME. Chlamydia trachomatis Genital Infections. Microb Cell Graz Austria. 2016 Sep 5;3(9):390–403.

3.            Solomon AW, Burton MJ, Gower EW, Harding-Esch EM, Oldenburg CE, Taylor HR, et al. Trachoma. Nat Rev Dis Primer. 2022 May 26;8(1):32.

4.            Ahmad B, Zeppieri M, Patel BC. Trachoma. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 [cited 2024 Dec 15]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK559035/

5.            Hu VH, Harding-Esch EM, Burton MJ, Bailey RL, Kadimpeul J, Mabey DCW. Epidemiology and control of trachoma: systematic review. Trop Med Int Health TM IH. 2010 Jun;15(6):673–91.

6.            Adera TH, Macleod C, Endriyas M, Dejene M, Willis R, Chu BK, et al. Prevalence of and Risk Factors for Trachoma in Southern Nations, Nationalities, and Peoples’ Region, Ethiopia: Results of 40 Population-Based Prevalence Surveys Carried Out with the Global Trachoma Mapping Project. Ophthalmic Epidemiol. 2016;23(sup1):84–93.

7.            Cromwell EA, Courtright P, King JD, Rotondo LA, Ngondi J, Emerson PM. The excess burden of trachomatous trichiasis in women: a systematic review and meta-analysis. Trans R Soc Trop Med Hyg. 2009 Oct;103(10):985–92.

8.            Courtright P, West SK. Contribution of sex-linked biology and gender roles to disparities with trachoma. Emerg Infect Dis. 2004 Nov;10(11):2012–6.

9.            Solomon AW, Kello AB, Bangert M, West SK, Taylor HR, Tekeraoi R, et al. The simplified trachoma grading system, amended. Bull World Health Organ. 2020 Oct 1;98(10):698–705.

10.         Mohammadpour M, Abrishami M, Masoumi A, Hashemi H. Trachoma: Past, present and future. J Curr Ophthalmol. 2016 Dec;28(4):165–9.

11.         Derrick T, Holland MJ, Cassama E, Markham-David R, Nabicassa M, Marks M, et al. Can corneal pannus with trachomatous inflammation – follicular be used in combination as an improved specific clinical sign for current ocular Chlamydia trachomatis infection? Parasit Vectors. 2016 Dec;9(1):30.

12.         Butcher R, Tagabasoe J, Manemaka J, Bong A, Garae M, Daniel L, et al. Conjunctival Scarring, Corneal Pannus, and Herbert’s Pits in Adolescent Children in Trachoma-endemic Populations of the Solomon Islands and Vanuatu. Clin Infect Dis Off Publ Infect Dis Soc Am. 2021 Nov 2;73(9):e2773–80.

13.         Taylor HR, Burton MJ, Haddad D, West S, Wright H. Trachoma. Lancet Lond Engl. 2014 Dec 13;384(9960):2142–52.

14.         Mathew AA, Turner A, Taylor HR. Strategies to Control Trachoma: Drugs. 2009 Jun;69(8):953–70.

15.         Tabbara KF. Trachoma: a review. J Chemother Florence Italy. 2001 Apr;13 Suppl 1:18–22.

16.         2nd GLOBAL SCIENTIFIC MEETING ON TRACHOMA.

17.         Habtamu E, Wondie T, Tadesse Z, Atinafu B, Gashaw B, Gebeyehu A, et al. Posterior lamellar versus bilamellar tarsal rotation surgery for trachomatous trichiasis: Long-term outcomes from a randomised controlled trial. EClinicalMedicine. 2019 Dec;17:100202.

18.         Liu B, Cowling C, Hayen A, Watt G, Mak DB, Lambert S, et al. Relationship between Community Drug Administration Strategy and Changes in Trachoma Prevalence, 2007 to 2013. PLoS Negl Trop Dis. 2016 Jul;10(7):e0004810.

19.         Organization WH. Report of the 3rd Global scientific meeting on trachoma: Baltimore, USA, 19-20 July, 2010. 2010 [cited 2024 Dec 15]; Available from: https://iris.who.int/handle/10665/329074

20.         Porco TC, Gebre T, Ayele B, House J, Keenan J, Zhou Z, et al. Effect of mass distribution of azithromycin for trachoma control on overall mortality in Ethiopian children: a randomized trial. JAMA. 2009 Sep 2;302(9):962–8.

21.         Solomon AW, Mohammed Z, Massae PA, Shao JF, Foster A, Mabey DCW, et al. Impact of mass distribution of azithromycin on the antibiotic susceptibilities of ocular Chlamydia trachomatis. Antimicrob Agents Chemother. 2005 Nov;49(11):4804–6.

22.         Hong KC, Schachter J, Moncada J, Zhou Z, House J, Lietman TM. Lack of macrolide resistance in Chlamydia trachomatis after mass azithromycin distributions for trachoma. Emerg Infect Dis. 2009 Jul;15(7):1088–90.

23.         Solomon AW. Trachoma Control: A Guide for Programme Managers with 1 CD-ROM. LEARNER’S VERSION. Geneva: World Health Organization; 2006. 53 p.

24.         House JI, Ayele B, Porco TC, Zhou Z, Hong KC, Gebre T, et al. Assessment of herd protection against trachoma due to repeated mass antibiotic distributions: a cluster-randomised trial. Lancet Lond Engl. 2009 Mar 28;373(9669):1111–8.

25.         WoldeKidan E, Daka D, Legesse D, Laelago T, Betebo B. Prevalence of active trachoma and associated factors among children aged 1 to 9 years in rural communities of Lemo district, southern Ethiopia: community based cross sectional study. BMC Infect Dis. 2019 Dec;19(1):886.

26.         Emerson PM, Lindsay SW, Alexander N, Bah M, Dibba SM, Faal HB, et al. Role of flies and provision of latrines in trachoma control: cluster-randomised controlled trial. The Lancet. 2004 Apr;363(9415):1093–8.

Leave a Reply