The Collaborative International Dictionary of English v.0.48:

Nagana \Na*ga"na\ (n[.a]*g[aum]"n[.a]), n. [Prob. native name.]
   (Med.)
   A disease of horses and other domestic animals, transmitted
   by the tsetse fly; any trypanosomiasis, especially the
   variety caused by Trypanosoma brucei. [South Africa]
   [Webster 1913 Suppl.]