Abstract: Described is a system for efficiently producing live Enterocytozoon bieneusi (E. bieneusi) organisms using laboratory animals, preferably Mongolian gerbils. Some important steps are: providing at least one breeding pair; administering to each of such breeding pair a sufficient antibiotic in sufficient dosage to destroy essentially all parasites which might be passed to offspring, especially Trichomonas; permitting such breeding pair to produce and rear offspring as production animals; preventing breeding by the production animals by separating males from females in separate cages; immune-suppressing each production animal sufficiently to permit propagation of live E. bieneusi organisms; infecting each production animal with love E. bieneusi organisms administered in an amount sufficient for such organisms to propagate but insufficient to kill the production animal; and, during a production period following such infecting, collecting the feces of each production animal.