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

Although in vitro cultivation of Oesophagostomum dentatum provides defined material of third- (L3) and fourth- (L4) stage larvae, these are morphologically and biochemically different from larvae recovered ex vivo. The development of pre-cultivated larvae was investigated by rectal transplantation into worm-free pigs with subsequent recovery of worms from intestinal contents after different time periods and determination of worm burdens and sizes. Additionally, the in vitro maintenance of L4 and adults recovered from intestinal contents of orally infected pigs in different media was investigated. Although growth and development rates of cultivated L4 are lower than those of larvae recovered from intestinal contents after oral infection, pre-cultured L4 are able to develop into egg-laying adults in the large intestines (without nodule formation) within 9-14 days in rates comparable with those after oral infection. In contrast, rectally transplanted L3 only establish in low numbers without egg excretion. L4 and adult worms recovered from intestinal contents cannot be maintained in cultivation medium for more than 1 week, although most L4 grow and moult during the first 3 days. Although the standard cultivation conditions for mass production of L4 are not suitable for development or maintenance of preadult and adult stages, L4 recovered from cultures have the ability to establish in vivo as fertile adults, indicating that the basic biological functions are retained in vitro.