Final answer:
The most likely cause of otoacariasis in a rabbit is Psoroptes cuniculi, a parasite known for causing ear infections.
Step-by-step explanation:
The most likely causative agent of otoacariasis in a rabbit is A. Psoroptes cuniculi. While Otodectes cynotis can also cause ear mite infections, it's more commonly found in dogs and cats. Cheyletiella yuasguri is a parasitic mite that causes skin disease, often referred to as walking dandruff, rather than ear infections. Lastly, Sarcoptes scabiei is responsible for scabies, which also typically affects skin rather than the ears.