Final answer:
Moxidectin targets glutamate-gated chloride channels unique to parasites, disrupting their nerve and muscle functions without affecting dogs, which lack these specific channels and have mechanisms to detoxify and eliminate the drug.
Step-by-step explanation:
Moxidectin harms the nerve and muscle cells of parasites but not the nerve and muscle cells of the dog due to differences in the composition of glutamate-gated chloride channels, which are present in invertebrates but not in mammals. Moxidectin binds to these channels in parasites, disrupting neurological function and muscle contraction, leading to the paralysis and death of the parasite.
Furthermore, dogs and other mammals have different cellular and molecular structures which render them less susceptible to the action of moxidectin. Parasites, on the other hand, have nerve and muscle cells that contain specific receptors sensitive to this class of drugs, which includes avermectins. Dogs have a physiological and metabolic capacity to detoxify and eliminate such drugs without causing harm to their body systems whereas parasites do not, allowing for targeted treatment of parasitic infections in dogs with compounds like moxidectin without detrimental effects to the dog itself.