Although malaria has plagued humans since the beginning of civilization it was largely eliminated from much of the world during the 20th century by use of insecticides and other means of mosquito control. Synthetic drugs joined quinine for treatment. Nevertheless, the development of drug-resistant forms followed. The most recently discovered antimalarial drugs are derivatives of the natural product artemisinin. Most of the parasitic diseases are endemic to underdeveloped tropical and subtropical parts of the world and involve transmission by vectors. Vector control provides a means of prevention. Many of these diseases, including trypanosomiasis, leishmaniasis, schistosomiasis, lymphatic filariasis, and onchocerciasis, are considered “neglected diseases” by the World Health Organization.