NEMATOSPIROIDES-DUBIUS IN MICE SELECTED FOR LIABILITY TO INFECTION - MODIFICATION OF PARASITE BIOLOGY THROUGH HOST SELECTION

Mice selected as liable (L) and refractory (R) over 10 generations voided significantly more and less N. dubius eggs compared with randomly mated (Rd) mice after primary infections with 100 larvae. There was little difference between the number of parasite eggs voided/g feces (epg) by individual mice on day 14 compared with day 15 after infection. There was a significant diurnal variation in the egg values for individual mice but the mean differences observed between the R, Rd and L mice were maintained over a 24 h period. There was a strong correlation between both the total number and the number of female worms, surviving 21 days after infection, and the mean epg 14 and 15 days after infection. Female N. dubius produced more eggs in L mice and fewer eggs in R mice compared with worms in Rd mice. Worms grew longer in L mice and were shorter in R mice compared with parasites in Rd mice.