Anthelmintic resistance and the future for roundworm control.

Anthelmintic resistance has emerged as the most important problem confronting the successful control of nematode parasites of grazing animals. Although the significance of the problem varies between, and within, countries and farming enterprises, there is little likelihood that it will disappear of its own accord. On the contrary, it is reasonable to assume that it will increase if there is no change in traditional methods of parasite control. Although progress is being made in non-chemotherapeutic methods of control, these are unlikely to provide any practical alternatives in the short-term future. Nor can the pharmaceutical industry be expected to solve the problem because of the long period and the exceedingly high costs involved in bringing a completely new class of drug on to the market. The answer must lie in carefully husbanding the currently available anthelmintics, by providing farmers with programs which give good levels of parasite control and maintain high productivity in animals with fewer anthelmintic treatments. To be enthusiastically adopted by farmers, the programs require a commitment by both research and advisory workers. Such success can be achieved, as exemplified by the "Drenchplan" and "Wormkill" programs in Australia. It behoves workers in all countries which have a significant grazing livestock industry, not only those with an existing resistance problem, to consider how such schemes could be implemented.