Source : Webster's Revised Unabridged Dictionary (1913)

Catarrhal \Ca*tarrh"al\, a.
   Pertaining to, produced by, or attending, catarrh; of the
   nature of catarrh.

Source : WordNet®

catarrhal
     adj : of or relating to a catarrh; "catarrhal fever is any of
           several respiratory or oral diseases of livestock such
           as bluetongue in horses and sheep"