Comparative studies on the development of Oesophagostomum dentatum in vitro and in vivo

Although in vitro cultivation of Oesophngostomum dentatum provides defined material of third- (L3) and fourth- (L4) stage larvae, these are morphologi cally and biochemically different from larvae recovered ex vivo. The develo pment of pre-cultivated larvae was investigated by rectal transplantation i nto worm-free pigs with subsequent recovery of worms from intestinal conten ts after different time periods and determination of worm burdens and sizes . Additionally, the in vitro maintenance of L4 and adults recovered from in testinal contents of orally infected pigs in different media was investigat ed. Although growth and development rates of cultivated L4 are lower than t hose of larvae recovered from intestinal contents after oral infection, pre -cultured L4 are able to develop into egg-laying adults in the large intest ines (without nodule formation) within 9-14 days in rates comparable with t hose after oral infection. In contrast, rectally transplanted L3 only estab lish in low numbers without egg excretion. L4 and adult worms recovered fro m intestinal contents cannot be maintained in cultivation medium for more t han 1 week, although most L4 grow and moult during the first 3 days. Althou gh the standard cultivation conditions for mass production of L4 are not su itable for development or maintenance of preadult and adult stages, L4 reco vered from cultures have the ability to establish in vivo as fertile adults , indicating that the basic biological functions are retained in vitro.