Onchocerca volvulus ivermectin

Avermectins and Ivermectin. The avermectias are pentacycHc lactones isolated from fermentation products of Streptomjces avermitilis and ivermectin is a semisynthetic chemical, 22,23-dihydroavermectia (46). Ivermectin is effective in very low doses for the control of red spider mites on deciduous fmits, in baits for the control of imported fire ants, and as a parasiticide for Onchocerca volvulus in humans and for catde gmbs. These insecticides appear to function as agonists for the neuroinhibitory transmitter y-aminobutyric acid (GABA) (see Antiparasitic agents, avermectins). 

Table 4. Ivermectin and Diethylcarbamazine Against Onchocerca volvulus Infections ...

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-... 

When CNS involvement occurs, the poor penetration of suramin and pentamidine into the CSF requires alternative forms of chemotherapy, such as melarsoprol in combination with suramin. In treating Onchocerca volvulus infections, suramin kills adult worms and is an alternative to ivermectin. Suramin is used after initial treatment with diethylcarbamazine, which is used to kill the microfilariae. It produces favorable results in pemphigus and prolongs the time to disease progression in hormone-refractory prostate cancer. 

Basanez MG et al Effect of single-dose ivermectin on Onchocerca volvulus A systematic review and meta-analysis. 

Osei-Atweneboana MY Prevalence and intensity of Onchocerca volvulus infection and efficacy of ivermectin in endemic communities in Ghana A two-phase epidemiological study. Lancet 2007 369 2021. [PMID 17574093]... 

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. 

Gardon J, Boussinesq M, Kamgno J, Gardon-Wendel N, Demanga-Ngangue, Duke BO. Effects of standard and high doses of ivermectin on adult worms of Onchocerca volvulus, a randomised controlled trial. Lancet 2002 360(9328) 203-10. 

Collins RC, Gonzales-Peralta C, Castro J, Zea-Flores G, Cupp MS, Richards FO Jr, Cupp EW. Ivermectin reduction in prevalence and infection intensity of Onchocerca volvulus following biannual treatments in five Guatemalan communities. Am J Trop Med Hyg 1992 47(2) 156-69. 

Ivermectins B1 are derived from the avermectines Bl, the natural fermentation products of Streptomyces avermitilis. The avermectins Bl have double bonds between carbon atoms at 22 and 23, whereas the ivermectins Bl have single bonds in these positions (Fig. 2a). They have an intermediate polarity. The ivermectins Bl are a mixture of two major homologs, ivermectins Bla (>80%) and ivermectins Bib (<20%), but a crude ivermectin complex also contains various minor components. Ivermectins Bl are broad-spectrum antiparasitic agents used against Onchocerca volvulus in human medicine and for food production animals such as cattle, swine, and horses. 

Filariasis Wudiereria bancrofti, Brugia malayi, Loa loa, Onchocerca volvulus, Mansonella ozzardi, Dipetalonema perstans Suramin, diethylcarbamazine mebendazole, levamisole, ivermectin... 

Onchocerca volvulus River blindness (not in United Kingdom) Ivermectin... 

Ivermectin has found wide use as a systemic antiparasitic agent against endo and ectoparasites of animals. Ivermectin is also used as a treatment for human filarial worm infections Onchocerca volvulus) [220]. The monosaccharides were 2 to 4 times less active than the disaccharide, and dihydroavermectin B1 aglycone was 30 times less potent [219]. 

Newland, H. S., White, A. T., Greene, B. M., D Anna, S. A., Keyvan-Larijani, E., Aziz, M. A., Williams, P. N., and Taylor, H. R. (1988). Effect of single-dose ivermectin therapy on human Onchocerca volvulus infection with onchocercal ocular involvement. Br. J. Ophthalmol. 72, 561-569. 

Ivermectin prevents onchocerciasis and is the drug of choice in the individual and mass treatment of the disease. The only other dmgs effective against Onchocerca volvulus are suramin and diethylcarbamazine (not listed in the question). The World Health Organization no longer recommends diethylcarbamazine for onchocerciasis, since it is less effective and more toxic than ivermectin. Suramin is toxic to the kidney, liver, and nervous system and would not be used prophylactically in this case. The answer is (B). 

Awadzi K, Edwards G, Duke BOL, Opoku NO, Attah SK, Addy ET, Ardrey AE, Quarty BT. The co-administration of ivermectin and albendazole— safety, pharmacokinetics and efficacy t Onchocerca volvulus Ann TropMedParasitol(2003) 97,165-78. 

In humans infected with O. volvulus, ivermectin causes a rapid, marked decrease in microfi-larial counts in the skin and ocular tissues that lasts for 6—12 months. The drug has little discernible effect on adult parasites, even at doses as high as 800 ig/kg, but affects developing larvae and blocks egress of microfilariae from the uterus of adult female worms. Regular treatment with ivermectin also may act prophylactically against the development of Onchocerca infection. 

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