River blindness

Pearlman, E., Lass,J.H., Bardenstein, D.S., Kopf, M., Hazlett, F.E. Jr, Diaconu, E. and Kazura, J.W. (1995) Interleukin 4 and T helper type 2 cells are required for development of experimental onchocercal keratitis (river blindness). Journal of Experimental Medicine 182, 931—940. 

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. 

Onchocerciasis (River blindness) Onchocerca volvulus Suramin,- Diethylcarbamazine, or Ivermectin-... 

It is mainly indicated in scabies, ascariasis trichuriasis, strongyloidiasis, enterobiasis, filariasis, onchocerciasis (River blindness) and elephantiasis. It is drug of choice for onchocerciasis producing long lasting reduction in microfilaria without affecting adult worm. 

The inadequacy or nonexistence of health tools to combat tropical diseases is a key factor preventing effective control efforts. This was not always the case. During the first part of the twentieth century, tropical diseases were a concern of European colonial administrators because of their impact on territorial expansion diseases such as river blindness, sleeping sickness, and malaria incapacitated workers and limited exploitation of natural resources. This led to the establishment of the study of tropical medicine and the development of the European drug industry. But, as western interests withdrew, so did concern for tropical disease control (Janssens, Kivits, and Vuylsteke 1992). 

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). 

Nematoda Ascaris, Ancylostoma, Oncho- River blindness, elephantiasis,... 

There are urgent economic reasons for trying to control predation in Africa by biting, sucking flies and acarines (ticks and mites). Among them are identified the vectors of mammalian parasitic and virus diseases such as trypanosomiasis (sleeping sickness), filariasis such as onchocerciasis (river blindness), leishmaniasis, malaria, Dengue fever and East Coast fever (Theileriosis) (ECF). 

But that s exactly what Merck did. On October 21, 1987, Roy Vagelos, then the CEO, declared that Merck would donate as much Mectizan as necessary, for as long as necessary, to treat river blindness and help bring the disease under control as a public health problem. The company also worked with the World Bank, UNICEF, the World Health Organization, and more than two dozen other groups to set up a distribution system. 

A fortunate fallout of the avermectin work was the finding that Ivermectin has activity against the black fly vector of human onchocerciasis ( river blindness ). It interferes with transmission of the filarial nematode. Onchocerca volvulus, to the human population. Since 40 million people are affected by this disease, the decision by Merck to supply ivermectin free of charge to the World Health Organization, for use in humans in the tropics, was met with great enthusiasm and hope for conquering this parasitic disease. 

Flies also harbor diseases that can be transmitted to humans and other mammals when they bite to obtain a blood meal for themselves. For example, black flies can carry river blindness, sandflies can carry leishmaniasis and kala-azar, and tsetse flies (found mainly in Africa), carry the trypanosomes that cause sleeping sickness. Livestock, such as horses and cattle, can be infected with a variety of botflies and warbles that can infest and feed on the skin, throat, nasal passages and stomachs of their hosts. 

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