Further studies on resistance to Fasciola hepatica and Echinostoma revolutum in mice infected with Schistosoma sp.

Schistosoma sp. induced cross-resistance to a challenge with Fasciola hepatica and Echinostoma revolutum was studied in mice. Primary patent 56-days-old S. intercalatum and S. bovis infections stimulated a statistically significant level of resistance to a challenge with F. hepatica, and primary patent 100-day-old S. bovis infections induced an almost complete resistance to a challenge with E. revolutum. Primary single-sex S. mansoni infections, either male or female, aged 90 days did not stimulate any resistance to a challenge with E. revolutum. A primary infection with S. mansoni aged 70 days induced a marked reduction (94.1--100%) in the E. revolutum worm recovery already 2 h post-challenge as compared with that of the E. revolutum challenge control group and complete elimination of the echinostome worm population in S. mansoni infected mice had taken place 24 h after challenge. E. revolutum worm populations established in mice harbouring newly patent 36-day-old S. mansoni infections persisted unchanged for a period of at least 33 days into the patent period of the schistosome infection in spite of development of a complete resistance to a challenge with E. revolutum metacercariae during this period.