, ▁as ▁did ▁the ▁Gi ard ia ▁from ▁their ▁st ool ▁samples . ▁In ▁ 1 9 5 4 , ▁Dr . ▁R . C . ▁R end tor ff ▁ ▁performed ▁experiments ▁on ▁prisoner ▁volunte ers , ▁inf ect ing ▁them ▁with ▁Gi ard ia . ▁ ▁In ▁the ▁experiment , ▁although ▁some ▁prisoners ▁experienced ▁changes ▁in ▁st ool ▁hab its , ▁he ▁concluded ▁that ▁these ▁could ▁not ▁be ▁conclus ively ▁linked ▁to ▁Gi ard ia ▁in fection , ▁and ▁also ▁indicated ▁that ▁all ▁prisoners ▁experienced ▁sp ont aneous ▁clear ance ▁of ▁Gi ard ia . ▁ ▁His ▁experiments ▁were ▁described ▁in ▁the ▁E PA ▁Sym pos ium ▁on ▁Water bor ne ▁Trans mission ▁of ▁Gi ard ias is ▁in ▁ 1 9 7 9 : ▁ ▁In ▁ 1 9 5 4 – 5 5 , ▁an ▁out break ▁of ▁Gi ard ia ▁in fection ▁occurred ▁in ▁Oregon ▁( US ), ▁sick ening ▁ 5 0 , 0 0 0 ▁people . ▁ ▁This ▁was ▁documented ▁in ▁a ▁communication ▁by ▁Dr . ▁L yle ▁Ve az ie , ▁which ▁wasn ' t ▁ ▁published ▁until ▁ 1 5 ▁years ▁later ▁in ▁the ▁New ▁England ▁Journal ▁of ▁Medicine . ▁ ▁In ▁the ▁communication , ▁Ve az ie ▁notes ▁that ▁he ▁was ▁unable ▁to ▁find ▁a ▁publish er ▁for ▁his ▁account ▁of ▁the ▁ep ide mic . ▁ ▁The ▁communication ▁was ▁re - pub lished ▁in ▁the ▁E PA ▁Sym pos ium ▁on ▁Water bor ne ▁Trans mission ▁of ▁Gi ard ias is