Nobel 2015 and river blindness

Pubblicato il

Tuesday, 20 October 2015

Argomento

Eye infections

Prize-winning discovery of avermectin, effective in treating river blindness.

The 2015 Nobel Prize for Medicine and Physiology honoured the efforts of a number of scientists who have distinguished themselves in the fight against infectious diseases. First of all, the importance of the discovery by the Dr Youyou Tuof the artemisininwhich has played a key role in the halving of malaria-related deaths since 2000.
The Nobel Prize was also jointly awarded to the American William C. Campbell and the Japanese Satoshi Omura for their discoveries concerning the avermectineffective against certain nematode worms. Avermectin is in turn derived from a living organism, the Streptomycesa bacterium of which Dr Omura had bred thousands of strains during the 1970s in the hope of coming across a new anti-infective, since the very Streptomyces was behind one of the first antibiotics, streptomycin. Dr Campbell then followed up on this work by identifying among Dr Omura's compounds the one that was most effective in killing the nematode worms responsible for the filariasis (o filariasis) lymphatics and the river blindness o onchocerciasis.
The drug that descends directly from avermectin, theivermectinToday, it plays an essential role in the fight against this category of parasitosis, so much so that it is included by the WHO (Wealth Health Organisation) in the List of Essential Medicines.
Onchocerciasis or 'river blindness' is considered the world's second leading cause, after trachoma, of preventable blindness due to contagious diseases.
It is an infection caused by a nematode worm, theOnchocerca volvulus, especially common along large rivers, where brown flies of the genus SimiliumThey transmit the infection through bites from the infected female. The larvae (microfilariae) penetrate through the skin and mature into the adult form in subcutaneous nodules; in these they reproduce and spread throughout the body, causing local inflammation when they die.
The first ocular sign of the disease is a modest anterior uveitis. Over time, as microfilariae enter the eye, intraocular inflammation progresses, aggravated by scarring. Involvement of the posterior segment of the eye produces chorioretinitis and further aggravation of the disease leads to the appearance of chorioretinal atrophy, pigment accumulation, fibrosis and neovascularisation.
The lesions are generally symmetrical and tend to spare the macula until the terminal stages of the disease, which can lead to blindness, also due to the onset of sclerosing keratitis.
The disease is still endemic in several sub-Saharan African countries. A total of 31 African states, a dozen Central and South American states as well as Yemen (Arabian Peninsula) are affected. Some 25 million people are infected, while 123 million live in areas at risk. Around 300,000 sufferers have gone blind due to the parasite, while another 800,000 are visually impaired. Almost 99% of the infected people live in Africa (mainly in rural areas).
At present, there is no vaccine or other drug that can prevent infection.
Considerable progress has been marked since 1989 by the large-scale distribution in affected areas of ivermectin, which is to be administered as an annual dose (minimum dose) for a period of 10-15 years. The anti-infective therapy is combined with initiatives to clean up unhealthy areas and to spread the use of insecticides.
The APOC (African Programme for Onchocerciasis Control), launched in 1995, and the OEPA (Onchocerciasis Elimination Programme of the Americas), launched in 1992, have already achieved such important results that the WHO is now shifting the focus from control to eradication of this disease.
Major outbreaks are unfortunately still present in Yemen.