Why do host-specific parasites tend to co-evolve with their hosts?

Step-by-step solution

Many parasites have evolved to be host-specific (they can parasitise only a single species of host) in such a way that both host and the parasite tend to co-evolve; that is, if the host evolves special mechanisms for rejecting or resisting the parasite, the parasite has to evolve mechanisms to counteract and neutralize them, in order to be successful with the same host species . In accordance with their lifestyles, parasites evolved special adaptations such as the loss of unnecessary sense organs, presence of adhes