We do not normally think of blindness as being infectious, but in many of the under-developed areas of our world, it certainly is. The disease trachoma is the world's leading infectious cause of blindness, hitting rural areas especially hard. About 6 to 9 million people worldwide are currently blind and many more have suffered partial loss of vision from the disease.
Trachoma is caused by a strain of bacteria called chlamydia trachomatis, which is genetically related to the sexually transmitted disease, chlamydia. The transmission of chlamydia trachomatis is mainly among children, and from children to women during child care.
Now the big – and bad – news. Researchers at the Wellcome Trust Sanger Institute and Menzies School of Health Research, Australia have discovered that genes can move from chlamydia strains in the eye to sexually transmitted strains of chlamydia. This allows them to then infect the eye and cause trachoma – making it, by genetic extension – sexually transmittable.
Up until this study, scientists believed that the trachoma and blindness causing version of chlamydia was of a completely separate variant from those that cause the sexually transmitted disease. Now, it's a new ball game.
Clinically, the impact of the results is very sobering. Trachoma, once a neglected tropical disease, will re-emerge onto the world stage if the sexually transmitted chlamydia remains common.
Worse yet, the study provides evidence that the acquisition of just one or two gene variants can change a sexually-transmittable strain into a trachoma associated strain. Because it is also now known that chlamydia can readily exchange DNA this shows that there is a continued potential for yet new variant trachoma strains to emerge.
Currently, trachoma is treated at the “village level” with tetracycline ointment, which is only effective in the short term. The disease usually returns to the community within 6 to 12 months. Trachoma can now also be treated with the antibiotic azithromycin. Promotion of increased face-washing helps further to control the disease. Surgery of the scarred eyelids can prevent continued damage to the cornea by turned-in lashes.