Oh, yes, parasites and parasitoids can be highly spezialised! We had some discussion about them in the “random interesting fact” thread, like here and in some posts before and after that:
Speaking of the Iberian Lynx where I take my avatar and name from, they were extremely specialised eaters, their diet being almost exclusively rabbits. Then myxomatosis hit the rabbits hard and the lynx almost went extinct. They are very good at catching rabbits, but they struggle with birds, it seems. Their life would be easier if they learned to diversify their diet.