I propose that this phenomena was caused by a parasite that created the desire to dance in the brains of the afflicted. There are many well-documented cases of parasitic bacteria and fungi. Tomentella vexes ants, bird-chasing parasites screw with snail's brains, and the "crazy cat-woman virus" has been in the news recently. In this case, I believe that the bacteria or virus in question targets another mammal to similar behavior, and simply hit these poor people by accident. For all we know, we other, similar bugs in us, causing other behavioral problems.
Check out:
http://www.mjt.org/exhibits/stinkant.htm
http://www.youtube.com/watch?v=xa0uxeHDgBg
http://www.mjt.org/exhibits/stinkant.htm
http://www.nytimes.com/2007/12/09/magazine/09_10_catcoat.html