I don't think that's generally the case. As far as I know, the main salmon parasites that we care about are Anisakis (nematodes) and Diphyllobothrium (tapeworms). The former is much more common than the latter, especially in the US where as far as I know broad tapeworm has only recently been detected in a small fraction of Alaskan salmon.

Anisakis has no terrestrial hosts. Its lifecycle is crustacean -> fish -> aquatic mammal (whales, dolphins, seals) -> repeat.

Humans and other land mammals are the host of Diphyllobothrium, but, again, I don't think that's very common. From what I've read, most of the need to freeze salmon comes from wanting to deal with roundworms.