Associate Certified Entomologist (ACE) Practice Exam

Which of the following is a macrocyclic lactone used in veterinary medicine?

1. Chlorfenapyr

2. Fipronil

3. Ivermectin

4. Chlorantraniliprole

The correct answer is: Ivermectin

Ivermectin is a macrocyclic lactone that is widely used in veterinary medicine for its ability to control a variety of internal and external parasites. This compound works by interfering with the nervous system of parasites, leading to paralysis and death. Ivermectin is particularly effective against nematodes and ectoparasites, which makes it a valuable tool in the treatment and prevention of various parasitic infections in domestic animals. In comparison, while the other compounds listed also serve important roles in pest and parasite control, they do not belong to the macrocyclic lactone class. For instance, chlorfenapyr is an insecticide that operates by disrupting cellular processes in insects, while fipronil is a phenylpyrazole used to control fleas and ticks by blocking specific neurotransmitter functions. Chlorantraniliprole, on the other hand, is a diamide insecticide that targets insect ryanodine receptors and is primarily used in agriculture. None of these compounds share the same structural characteristics or mechanisms of action that define macrocyclic lactones like ivermectin.