From the USDA Bulletin 19, Inspection of Meats for Animal Parasites, 1898 we find that the tapeworm stage Coenurus cerebralis called the Gid Bladder worms would infect the brains of sheep, cattle, and dogs. The phrase feeling giddy referred to the erratic behavior and movements of animals that had parasites eating their way through them like termites inside lumber. Some manifestations of the brain decay results in what can only be described as the Three Stooges Curly Shuffle where the animal spins in a circle and ends up falling down. Thing of it is: in the early days of investigating the lifecycles of parasites it was thought that Coenurus cerebralis of the grazing animals was A COMPLETELY DIFFERENT ORGANISM from Taenia coenurus the fully formed adult tapeworm stage found in the dogs that dogged the flocks.
That's the tricky thing about parasites. Many different hosts harboring what appear to be COMPLETELY DIFFERENT ORGANISMS that SHAPESHIFT when they encounter their intermediate or primary host. What a gig! To be able to avoid detection by detectives hunting you because you change your entire look and lifestyle, and to be able to avoid immune systems because you either look different or in the case of something like schistosome blood flukes you simply slather on the host antigens to make the patrolling white blood cells think that you are one of them.
Below is what they knew just before the beginning of the 1900s. It seems that in the entire history of mankind, Science knew hardly anything of an aspect of this world that plagues mankind to this day. It should not be surprising then to find out that bacteriophage viruses out-mass all living things on the planet, yet, due to their microscopic size and the ability of the whore of science to occult all necessary knowledge most people don't even know of the existence of something that outnumbers them and outthinks them. More on that after you 'digest' what I have excerpted from the USDA below without my colorful comments that you will find only in my book.