Onchocerca volvulus infection, treatment

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. 

Metrifonate, which is given orally, is effective in Schistosoma hematobium infections in three doses of 7.5-10 mg/kg 14 days apart. When metrifonate was used in daily doses, as in the treatment of Onchocerca volvulus infections, it produced muscarinic effects, and in one case there was proximal weakness due to a nicotinic effect. The combination of polyarthritis, fever, and a raised sedimentation rate was described in 11 of 34 patients treated. Metrifonate inhibits blood cholinesterase activity for up to 48 hours, and common reactions that probably result from this effect comprise nausea, vomiting, abdominal pain, diarrhea, dizziness, weakness, headache, and muscle cramps. Because of its prolonged inhibition of brain cholinesterase and increased steady-state concentrations of acetylcholine in the cortex and the hippocampus, it is now also increasingly used in the treatment of Alzheimer s disease. 

A study in 28 healthy subjects given levamisole 2.5 mg/kg alone or with albendazole 400 mg found that albendazole produced a modest reduction in the AUC of levamisole but no other pharmacokinetic parameters were affected. However, the AUC of albendazole sulfoxide (the active metabolite) was 75% lower when given with levamisole than historical values in subjects who had received levamisole alone. An associated study in 44 patients found that levamisole with or without albendazole was not effective against Onchocerca volvulus infections. Both treatments caused a similar number of adverse effects. The clinical relevance of these findings is unclear, but they suggest that caution is needed if both drugs are to be given for systemic worm infections. 

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. 

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]. 

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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