What is trachoma?

Trachoma is a form of chronic conjunctivitis (inflammation of conjunctiva of eye) caused by infection with Chlamydia trachomatis. Generally serovar A, B, Ba, or C of Chlamydia trachomatis causes trachoma. Trachoma is the commonest cause of preventable (avoidable) blindness in the world. Certain strains of sexually transmitted C. trachomatis cause an acute ocular infection known as inclusion conjunctivitis (generally serovar D through K of C. trachomatis). Inclusion conjunctivitis in adults is generally caused by exposure to infected genital secretions and in newborn offspring also it can occur.

Global problem of trachoma:

Trachoma generally occurs in hot, dry and dusty areas of tropics and subtropics. The incidence and severity of trachoma vary according to different geographical areas. Trachoma is estimated to be responsible for more than 20 million preventable blindness cases throughout the world, especially in poor and developing countries where there lack of basic health facilities and also poor personal hygiene. The incidences of trachoma and resultant blindness have reduced in last four decades due to improved economic conditions and resultant improvement in health and hygiene. But trachoma is still endemic in many parts of the world like Africa (especially in northern Africa and sub-Saharan Africa), Middle East, and some areas of Asia.

Children with active disease act as reservoir of trachoma.

How trachoma is transmitted?

Trachoma (infection of Chlamydia trachomatis) is transmitted from eye to eye via fomites (hands, flies, towels, and many others), especially in trachoma endemic areas and serovar A, B, Ba, or C are involved. Transmission of trachoma mainly occurs through close personal contact. Transmission of trachoma is common especially in young children in rural areas where water is of limited availability. In endemic areas, trachoma generally occurs with repeated exposure or reinfection.

Acute relapse of old trachoma can sometimes occur after treatment with cortisone eye ointment. Sometimes trachoma can develop in very old individuals who were exposed to Chlamydia trachomatis in their youth. Trachoma can sometime become chronic.

Incubation period of trachoma:

The incubation period of trachoma is 5-12 days.

Who are at risk of trachoma?

Children of 2 to 5 years are most commonly affected by trachoma, although infants of few months can also be infected.

What are the predisposing factors of trachoma?

Dust, direct sunlight, irritants like smoke and application of kajal or surma (a blackening agent used by Indians to make the lining of the eyes black) by Indians are the predisposing factors of trachoma.

What is sex difference in the rate of incidence of trachoma & why?

Among children the prevalence of trachoma is same for boys and girls. Among adults the incidence is higher among females; the reason may be the longer contact period with children in whom trachoma is common as females look after the children. Also females are more exposed to irritants like smoke than men.

What are the clinical manifestations of trachoma?

Trachoma, especially endemic trachoma starts with a conjunctivitis the characteristic feature of which is small lymphoid follicles in the conjunctiva. But in highly endemic areas where blindness is common due to trachoma, the disease starts insidiously before the age of 2 years. Reinfection is common in this type.

Pannus formation, which is inflammatory leukocytic infiltration and superficial vascularization (formation blood vessel in cornea where normally no blood vessels are present) of cornea occurs next. The inflammation of conjunctiva continues and scarring of conjunctiva eventually distorts the normal anatomy of conjunctiva, which causes eyelids to turn inward so that the inwardly turned eyelashes constantly abrade the eyeball and cause trichiasis and entropion. Finally the corneal epithelium is also abraded which than cause ulceration of cornea and subsequent corneal scarring and ultimately blindness. Eyes become dry due to destruction of lacrimal ducts, and lacrimal gland. “Dry eye” syndrome occurs if there is xerosis or opacity of cornea due to drying of cornea or secondary bacterial infection of cornea (which also produce corneal opacity).

In trachoma endemic areas seasonal epidemics of conjunctivitis due to H. influenzae can make the intensity of the inflammatory process more severe due to Chlamydia trachomatis. In these endemic areas the infection usually resolve by age of 10-15 years, but the scar in conjunctiva continues to shrink which cause trichiasis and entropion due to continuous aberration and ultimately cornea is also abraded which ulcerate and cause opacity and blindness. But in non endemic areas the process is much slower and continues till adulthood and only rarely cause blindness.

How trachoma is diagnosed?

Trachoma (classical type) can be diagnosed clinically if any of the 2 signs are present (out of 4 signs):

1. Presence of lymphoid follicles on the upper part of conjunctiva.
2. Scarring of conjunctiva which is typical to trachoma.
3. Presence of Herbert's pits, which are limbal follicles or their sequelae.
4. Presence of vascular pannus (leukocytic infiltration and superficial vascularization).

In endemic areas clinical diagnosis of trachoma, especially in children should be supported (or confirmed) by laboratory investigation like chlamydial NAATs (nucleic acid amplification tests) or demonstration of intracytoplasmic chlamydial inclusions, which are seen in up to 60% of Giemsa-stained conjunctival smears in endemic areas. PCR (polymerase chain reaction) can confirm diagnosis by detecting clamydial DNA.

How trachoma is treated?

Trachoma can be treated effectively by ophthalmic ointment or oily drops of tetracycline 1-3%, which should be applied twice a day fro 3 months. Oral azithromycin (1 gram single dose), doxycycline (100 mg twice a day for 7 days), tetracycline (15 mg/kg/day for 2 weeks) are also very effective in treating trachoma. In some countries (where trachoma is endemic) mass treatment programs topical application tetracycline twice daily for 3-6 consecutive days every month for 6 months are undertaken with excellent results.

The scarring of the eyelids, opacity of cornea, ulceration of cornea, scarring of cornea may require surgical correction, which is done after control of infection.

How to prevent trachoma?

At present there is no vaccine for trachoma. The WHO (World Health Organization) has started “Global Campaign to Eliminate Trachoma” and introduced S-A-F-E strategy. S-A-F-E means Surgery for deformed eyelids due to trachoma; mass treatment with Azithromycin periodically; Face washing and improvement of Environmental condition and Environmental sanitation. S-A-F-E strategy WHO shows the importance of face washing (sometimes adequate water supply for personal cleanliness can make a great difference in the incidence of trachoma in a community) and general and personal hygienic measures along with improvement of living standards can eliminate trachoma from a community. Reduction of number of house flies can also be of great benefit in preventing trachoma. In some endemic areas mass treatment of entire villages with single-dose azithromycin has caused marked decline in chlamydial infection (trachoma).