Chapter 5 : The Blinding Neglected Tropical Diseases: Onchocerciasis (River Blindness) and Trachoma

Abstract:

Blindness in resource-poor settings is especially onerous because of the absence of support services found in the industrialized world. This chapter talks about the impact of blindness that results from two neglected tropical diseases (NTDs) that are entirely preventable with simple, safe, and effective preventive chemotherapy. Trachoma is a bacterial infection occurring in approximately 84 million persons living in the developing regions of Africa, the Middle East, Central Asia, India, and Southeast Asia. Onchocerciasis is a parasitic helminth infection occurring in an estimated 37 million people, primarily in West and Central Africa. Humans become infected with onchocerciasis when Simulium blackflies, which breed along rivers or streams, deposit Onchocerca volvulus larvae while biting and feeding on blood. Thus, whereas hookworm infective larvae enter human skin from the soil, both O. volvulus and Wuchereria bancrofti infective larvae gain entry into humans during the bite of an insect vector, a mosquito in the case of W. bancrofti and a blackfly for O. volvulus. Trachoma is a chronic infection that usually begins in childhood, sometimes with redness (pinkeye), itching, and pain. The disease and blindness result from recurrent and multiple infections with Chlamydia trachomitis which occur over a period of 10 to 20 years. During this time, recurrent infection leads to scarring of the eyelids. When the scarred eyelids turn inward, the lashes scratch the surface of the eyeball, leading to inflammation and scarring of the cornea (an ordinarily transparent part of the eye) and ultimately blindness.