Drug treatment of tropical parasitic infections - Recent achievements and developments

Drug development offers potential solutions to a number of tropical health diseases, although the expense of pharmaceutical research and lack of retur n on investment has limited the production of new agents. The greatest succ esses have been through the development of single dose therapy and mass tre atment control programmes for a number of diseases. We review some of the c urrent treatment regimens for malaria, intestinal helminth infection, oncho cerciasis, filariasis and schistosomiasis, and their use in clinical practi ce. Geographical spread and emergence of drug resistant parasites have hindered the control of malaria, the most important global parasitic infection. Art emisinin compounds have proved effective antimalarial agents producing rapi d reduction of parasite load and can be used in combination treatment regim ens to combat multidrug resistance. Intestinal helminth infections are widespread, giving rise to nutritional d eficiencies and impaired childhood cognitive development. Pregnant women in developing countries are at increased risk of morbidity. Treatment with a single dose benzimidazole such as albendazole or mebendazole has beneficial effects on morbidity and rates of transmission. Diethylcarbamazine has been used in the treatment of onchocerciasis and hum an filariasis. A complicated escalating dose regimen over several weeks is associated with systemic and allergic reactions and may require corticoster oid cover. Simplified regimens for mass population treatment with ivermecti n have proved useful and been used in combination with single dose albendaz ole and diethylcarbamazine. The African Programme for Onchocerciasis Contro l in West and Central Africa has been one of the most successful mass contr ol programmes virtually eliminating new infections by a combination of chem otherapy, education and vector control. Schistosomiasis is of increasing importance as a result of the creation of new snail habitats by agricultural and economic development. Praziquantel h as become the most widely available and effective chemotherapy for schistos omiasis. There have been a number of reports of persistent schistosome egg shedding after treatment posing concerns about the emergence of drug resist ance. Eflornithine has been successfully used in patients with human trypanosomia sis failing melarsoprol therapy however expense and availability have limit ed its potential. Mass control treatment programmes have targeted schoolchildren, adolescents and pregnant women. The integration of schistosomiasis, onchocerciasis, fi lariasis and helminth control programmes has been considered as a cost-effe ctive method of delivering treatment. It is likely that future control will be based on this optimisation and integration of existing regimens, rather than the development of new agents.