MICROBIOLOGY WRITING PROJECT

MICROBIOLOGY WRITING PROJECT

MICROBIOLOGY WRITING PROJECT

Onchocerciasis, or river blindness, caused by the filaria Onchocerca volvulus, affects more than 17 million people in Africa, Latin America, and Yemen. The microfilaricidal agent ivermectin is the principal means of controlling the disease, through mass treatment. Wolbachia endosymbiotic bacteria in filarias have emerged as a new target for treatment with drugs that lead to long term sterilisation of adult female filarias. Participants at recent international meetings have agreed that anti- Wolbachia chemotherapy with doxycycline (currently for six weeks) could be used to treat infected individuals. This approach holds promise for new developments based on registered antibiotics that are affordable in resource poor settings, as extensive registration processes are not needed. Recent experimental findings also indicate that endotoxin-like molecules from Wolbachia have a role in the pathogenesis of the disease and in adverse reactions after treatment (Hoerauf, 2001).

Outline

Onchocerciasis is almost certainly a disease that originated in Africa and has spread to Arabia and the New World as an unintended by-product of the slave trade. Skin lesions caused by onchocerciasis were first described in the Gold Coast (modern Ghana). The organism was first described in 1893 by eminent German parasitologist Friedrich Rudolf Leuckart. In 1916, the disease was first recognized in the Americas by Guatemalan investigator Rodolfo Robles. Robles linked nodules to eye disease and suggested that the distribution of infection implicated two species of Simulium as vectors. D. Blacklock, working in Sierra Leone, showed in 1926 that S. damnosum was the vector (Prichard, 2001).

In 1931, J. Hissette, working in Congo, linked onchocerciasis with blindness for the first time in Africa, but despite confirmation in the Sudan a year later, colonial doctors generally considered onchocerciasis only a skin disease. Just before World War II, French doctors in what is now Burkina Faso began to link the disease with mass blindness and river valley abandonment. Their colleagues across the frontier in the British Gold Coast did not make a similar discovery until 1949.

Although British physicians and administrators were aware of river valley depopulation, onchocerciasis, and substantial blindness in the northern part of the colony, they did not link these phenomena, partly because doctors who became interested in the problem in the 1930s were repeatedly distracted by other duties or transferred. After the war, the association was finally made. A series of investigations in the 1950s confirmed the widespread incidence and serious consequences of the disease in a number of African countries, and Latin American foci were delimited.

In 1975 the World Health Organization began the Onchocerciasis Control Programme, an ambitious and expensive 20-year effort to eliminate onchocerciasis in the entire Volta Basin. The basic strategy was to kill fly larvae by aerially spraying temephos (an organophosphate) over breeding sites throughout a huge and repeatedly extended portion of West Africa. The absence of an effective agent to kill adult flies has not prevented tremendous success in reducing and sometimes eliminating Simulium populations (Hoerauf, 2001).

Although treatment of victims was less successful until recently because existing drugs were too dangerous for ...