USAID's NTD Program

Trachoma

• Overview
• Epidemiology
• Life Cycle
• Symptoms
• Diagnosis
• Treatment, Prevention, and Control

Overview

Trachoma is the leading cause of infectious blindness worldwide. This crippling disease is an infection of the eye caused by the bacterium Chlamydia trachomatis (C. trachomatis), which spreads through direct contact with infected people and through eye-seeking flies. While the disease usually clears up on its own, infections can scar the inside of an infected person’s upper eyelid so that with repeated infections the lid turns inward causing the eye lashes to scratch the cornea, which can lead to blinding trachoma.

Epidemiology

In 2010, the World Health Organization (WHO) estimated 40 million people across 57 endemic countries needed treatment for the disease. Nearly half of the global burden of active trachoma is found in five countries: Ethiopia, Guinea, India, Nigeria, and Sudan, with about half of the global burden of trichiasis, the stage of the disease where eyelashes turn inward and scratch the cornea, is concentrated in China, Ethiopia, Nigeria, and Sudan. In some areas of Ethiopia and Sudan, more than half of children less than 10 years of age are infected with trachoma, and up to 19 percent of adults suffer from trichiasis.  WHO estimates the economic cost of trachoma in terms of lost productivity is $2.9 billion annually.  

Source: World Health Organization

Life Cycle of C. trachomatis

C. trachomatis spreads through direct contact with the eye, nose, or throat secretions of infected people and through eye-seeking flies. Infection is frequently passed from child to child and from child to mother, especially where there are shortages of water for people to wash their hands and faces regularly, numerous flies, and crowded living conditions. Because women spend more time with children, who are most frequently infected, women are at greater risk of developing blinding complications from trachoma than men.

House flies, especially Musca sorbens (M. sorbens), are the primary vectors of C. trachomatis infection. M. sorbens breed in human feces, as well as in livestock and pet feces, but do not breed in pit latrines. Therefore, environmental control plays an important role is reducing disease transmission.

Symptoms

The principal signs and symptoms in the early stages of trachoma include mild itching and irritation of the eye and discharge from the eye containing mucus or pus. As the disease progresses, later trachoma symptoms include marked light sensitivity, blurred vision, and eye pain.

Trachoma often begins during infancy or childhood and can become chronic. Though young children are particularly susceptible to infection, the disease progresses slowly in childhood and the more painful symptoms may not emerge until adulthood. Single episodes of infection usually do not cause permanent damage, but repeated infections can result in chronic conjunctivitis, which scars the upper eyelid causing the eyelid to turn inwards. Repeated conjunctivitis also irritates the eyes and creates a mucous discharge that is easily spread and very contagious.

Trichiasis becomes more common as a person gets older, ultimately leading to irreversible blindness, typically between 30 and 40 years of age. While only about 1 percent of people with trachoma develop trichiasis, a person’s risk of trichiasis increases in relation to the total number, duration, and intensity of C. trachomatis infections during his or her lifetime.

Diagnosis

While sensitive diagnostic tests, such as the polymerase chain reaction and the ligase chain reaction, are available for diagnosing trachoma, they are not practical or readily available where trachoma is prevalent. WHO has identified a grading system with five stages of trachoma based on clinical examination.

• Inflammation – follicular. The infection is just beginning. Five or more follicles – small bumps that contain lymphocytes, a type of white blood cell – are visible with magnification on the inner surface of the upper eyelid (conjunctiva).
• Inflammation – intense. During this stage, the eye is now highly infectious and becomes irritated, with a thickening or swelling of the upper eyelid.
• Eyelid scarring. Repeated infections lead to scarring of the inner eyelid; the scars often appear as white lines when examined with magnification. The eyelid may become distorted and may turn in.
• Trichiasis or ingrown eyelashes. The scarred inner lining of the eyelid continues to deform, causing the lashes to turn in so they rub on and scratch the cornea.
• Corneal clouding. The cornea becomes infected by an inflammation that is most commonly seen under the upper lid. Continual inflammation – compounded by scratching from the in-turned lashes – leads to clouding of the cornea. Secondary infection can lead to development of ulcers on the cornea and eventually partial or complete blindness.

Treatment, Prevention, and Control

Because blindness due to trachoma is caused by scarring of the cornea it is irreversible, but it can be prevented and the disease can be treated during its early stages. In 1997, WHO established the Alliance for Global Elimination of Trachoma (GET), which seeks to eradicate the disease by 2020.  Its strategy has been summarized with the acronym SAFE:

Surgery for trichiasis
Antibiotics for active infection
Facial cleanliness
Environmental change

The SAFE strategy combines individual and community-oriented measures that consist of four inter-related components:

• Surgery for trichiasis: Persons with trichiasis need to be identified and operated on to reduce the pain and to prevent or slow the progression toward blindness. If trachoma has been found in children, a search should be conducted for trichiasis in persons over 15 years of age and especially those over 40 years of age.


• Antibiotics for active infection: The basis of active trachoma treatment is antibiotics.  The two recommended antibiotics, oral azithromycin (single dose of 20 mg/kg) and a tetracycline eye ointment (6-week course), eliminate chlamydia infection and decrease the occurrence of clinical signs.
  
  According to WHO guidelines, if the prevalence of trachoma is greater than 10 percent in children ages 1 through 9, everyone in the community should be treated with antibiotics annually for at least 3 years. Annual mass treatment should continue until the prevalence of trachoma is less than 5 percent. If available, azithromycin should be used, as compliance may be an issue with tetracycline. While azithromycin is expensive, a donation program set up by Pfizer provides the drug, in the form of Zithromax®, free of charge to many countries where trachoma is endemic.


• Facial cleanliness: Facial cleanliness should be promoted within the community through behavior change communication and low-cost hygienic interventions. Adequate facilities need to be provided for children to clean their faces.  It has been shown that clean face campaigns can significantly reduce trachoma. Children with dirty faces are two to three times more likely to have trachoma. Many trachoma control programs advocate for general improvements in water supply for face washing and sanitation to suppress fly populations.


• Environmental changes: The transmission of trachoma by flies can be reduced by limiting the number of flies people come into contact with by building covered latrines, discouraging people from sleeping close to their livestock, and encouraging villagers to regularly collect and burn trash.

References

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