The parasite's eggs, released into the water with the loon's feces, will mature and swim away to penetrate mollusks such as snails and occasionally clams, which are the first intermediate hosts.
In the mollusks, the parasite matures and eventually migrates and penetrates into the tissues of the second intermediate host, which is most often a fish.
Once in the tissues of a fish, the parasite causes obvious mechanical damage and hemorrhaging. While the damage caused is usually negligible, infestations in greater numbers may occasionally kill the host fish.
Loons are a key component in the parasite's life cycle, since the infected fish must be eaten by the final host to complete its lifecycle. Unfortunately, there is no practical treatment or control of the parasite at this time. It is important to note that the parasite does not infect humans, other mammals or birds, even though it can live for 4 years in a fish.
In most trout species, the parasite rarely appears in the meat of the fish, and cooking the fish kills the parasites evident on the skin.
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