Doxycycline is used to treat nematodes, but I never heard of tapeworm. The reason is because some nematodes, like strongyloides, live on a wohleria (sp?) bacteria in the body. Kill the bacteria and they starve to death. ICU's protocols explicitly state that you should never do her ABZ/Iver protocol without the Doxcy. If you do, the worms die, spill all their guts, and you get very sick from the bacteria.