And helminth is what a parasitic worm is called in medical terminology, which tend to be specifically nematodes (roundworms) and tapeworms (flatworms) -- rather than all the other kinds of worms like earthworms, polychaetes, and nemerteans. Not to mention maggots, which are not worms at all but the larvae of insects. Another more general term for studying worms is vermeology, but this is less common, even though vermiform, shaped like a worm, can be found in the wild without too much trouble. Vermeology and helminthology are two halves of the same coin in another way: the latter is from Greek and the former form Latin for worm (helminth, the stem form of hélmins, and vermis). Per Wikipedia, with parasitology being considered of much less interest than that of infectious diseases, the great days of helminthology are over -- most of the big names were in the 19th century. Sic transit gloria helminth.
He also contributed much to helminthology with his study of the trematodes which cause schistosomiasis.