Endectocides in goats: Pharmacology, efficacy and use conditions in the context of anthelmintics resistance

Endectocides (avermectins/mibemycins) are today one of the most important anthelmintic families for the control in livestock nematodes and their use is increasing in goats because of the high frequency of benzimidazole resistance. Goat has specific pharmacological parameters for endectocides compared to sheep or cattle (absorption and elimination). The behaviour of the drug in the organism, represented by pharmacokinetic parameters, is affected through several ways including the route of administration and drug formulation, and the host animal (nutrition, parasitism, physiological status, amount of fat tissue). For each species, the determination of specific dose rates is needed to insure an optimal activity against nematodes (particularly those inhabiting the small intestine). This scientific knowledge is a prerequisite to a better use of the different anthelmintic families in goats. An important objective in the chemical control of nematodes is to define the best deworming practices that reduce the risk of nematode resistance occurrence through a decrease of selection pressure on nematode populations. The main points of a rational use of anthelmintics include the dose rate, the route of administration, the annual frequency and the period of treatment, the alternative use of families and the selective treatment of high excreting animals.