( ( ( A ( ( recently described ) cause ) ) ( of ( diarrhea ( among ( certain travellers ) ) ) ) ) ( ( is ( a ( new ( protozoan pathogen ) ) ) ) . ) )
(ROOT (S (NP (NP (DT A) (ADJP (RB recently) (JJ described)) (NN cause)) (PP (IN of) (NP (NP (NN diarrhea)) (PP (IN among) (NP (JJ certain) (NNS travellers)))))) (VP (VBZ is) (NP (DT a) (JJ new) (NN protozoan) (NN pathogen))) (. .)))
A recently described cause of diarrhea among certain travellers is a new protozoan pathogen.
(ROOT (S (NP (NNS Trichomoniasis)) (VP (VBZ is) (VP (VB cause) (PP (IN by) (NP (DT a) (NN protozoa))))) (. .)))