The Collaborative International Dictionary of English v.0.48:

Louping \Loup"ing\n. [From Loup to leap.] (Veter.)
   An enzo["o]tic, often fatal, disease of sheep and other
   domestic animals, of unknown cause. It is characterized by
   muscular tremors and spasms, followed by more or less
   complete paralysis. The principal lesion is an inflammation
   of the membranes covering the brain and spinal cord.
   [Webster 1913 Suppl.]