PHYSIOLOGY, PHARMACOLOGY AND PARASITOLOGY

The developing resistance to current chemical classes of broad-spectru m anthelmintics and insecticides presents an undeniable threat to the long-term viability of the animal health industry. Alternative treatme nt strategies including vaccines, biological control and breeding of p arasite-resistant animals are unlikely to be widely available in the n ear future and even then they will be integrated with chemotherapy. Th e significant cost of research and development of new therapeutics for food-producing animals, together with the small market share of anima l health products, particularly in Australia and New Zealand, is a pos itive disincentive for drug development. The chemical actives that are currently available are all that we are likely to have for the forese eable future and they must be used more efficiently. Understanding the pharmacokinetic behaviour of antiparasitics and recognising the poten tial for the animal's physiological characteristics to assist drug act ion is crucial. Careful administration, coupled with a reduction of fe ed intake before oral anthelmintic treatment, maximises drug availabil ity and therefore increases efficacy of the benzimidazole and ivermect in compounds. This is a cost-effective option that can be employed imm ediately, which not only increases efficacy of ''older'' compounds but will be instrumental in prolonging the useful life of the newer drugs . Taking care to apply topical insecticide formulations directly along the backline immediately after shearing will maximise even diffusion of active around the sheep flanks to contact lice inhabiting sites rem ote from the point of drug application. The use of ''intelligent'' for mulation and delivery of existing compounds, based on knowledge of hos t physiological and pharmacological responses, holds the key to effect ive antiparasitic treatment. (C) 1997 Australian Society for Parasitol ogy. Published by Elsevier Science Ltd.