River blindness, treatment

Nematode parasites present a serious problem for most animals and for humans in developing countries. These parasites produce various symptoms including ill thrift, poor growth, diarrhoea and, in around 1 % of cases, loss of life. The economic forces are such that new drugs for the treatment of nematode parasites have been developed first for animal use and only later for human use. A recent example is the development of the antibiotic anthelmintic, ivermectin, which was introduced first for the treatment of cattle nematode parasites and has subsequently been used to control river blindness , an eye condition seen in west Africa caused by farvae of Onchocerca volvulus. 

Ivermectin (Mectizan, Stromectol) is the primary treatment for filarial nematode infections (onchocerciasis) that invade ocular tissues and cause loss of vision (river blindness). Ivermectin may also be used in filarial infections in other tissues (lymphatics, skin). This drug is a secondary agent for treating intestinal nematodes such as strongyloidosis. 

Another important class of anti-infective natural products introduced in recent years is the avermectins, polyketide-derived macrolides that were originally isolated from several species of Streptomyces. The major drug in this class, ivermectin, was originally developed to treat and control nematodes and parasites in livestock. In recent years, however, the potential of ivermectin for the treatment of human disease has also been realized, and it is now used to treat onchocerciasis (river blindness), a disease that afflicts 40 million people worldwide (De Smet, 1997). 

Analogous to the derivation of Synercid from a veterinary antibiotic, another famous example of the use of a modified veterinary product in man as an antiparasitic is the oral use of ivermectin (Mectizan, Stromectol) (42a (80%), 42b (20%) Figure 9) in the treatment of strongyloidiasis, onchocerciasis (river blindness), and for the treatment of filariasis. In addition to these uses (predominately in Africa), in 2006 Banyu received approval of the product in Japan for the treatment of scabies. ... 

Ivermectin, a neurotoxic compound in animals with low P-gp expressions, has been safely used in Africa for the prevention and treatment of river blindness. The lack of neurotoxicity in African might be due to the high P-gp expression in African population (Ameyaw et al., 2001). Gene analysis showed a high frequency of the C allele in the African group than British Caucasian, Portuguese, southwest Asian, Chinese, Filipino, and Saudi populations, which implies overexpression of P-gp in African population. 

Two of the most successful new microbial compounds have come from the laboratories of Merck. Both the veterinary andielmintic ivermectin and the recently introduced hypocholesterolemic, lovostatin, have been hailed as revolutionary new drugs (2). Although Merck has developed ivermectin primarily as an antiparasitic agent for livestock and pets, Merck also found that this compound could be used to treat the human scourge of onchocerciasis, African river blindness (3). In what is one of the finest examples of corporate humanitarianism, Merck developed and now distributes ivermectin free of charge to African countries for use in the treatment of this affliction (. ... 

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