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第17号公告板 - Winter 2003
Parasitology- No Category
MEJER H, ROEPSTORFF A, ERIKSEN L
Predisposition to Ascaris suum infections in neonatally exposed pigs.
Proceedings of the 19th International Conference of the World Association for the Advancement of Veterinary Parasitology, New Orleans, Louisiana, August 10-14, 2003, page 146
Earlier it has been shown that pigs may be predisposed to Ascaris suum. However, this phenomenon has not previously been investigated in pigs that have been exposed early in life. From the age of 3 weeks, 4 litters of outdoor pigs were infected with 25 A. suum eggs/kg body weight/day once weekly for 9-10 weeks. The pigs were weaned at the age of 7 weeks and allocated to 6 random groups. The pigs were then treated with piperazine and placed in individual cages for 48 hours for worm collection. Thereafter, the pigs were returned to their groups and re-infected with A. suum according to the earlier protocol. After 10 weeks all pigs were slaughtered for worm recovery. A. suum egg excretion was followed throughout the experiment. Though overall prevalence did not change much from treatment (81%) to slaughter (77%), all 4 litters did not respond equally well to the 2 infection periods. At treatment, infection levels varied considerably between pigs but to a lesser degree between litters. However, at slaughter 2 of the litters harboured a mean of only 1 worm/pig compared to 20 at treatment and prevalence decreased with 20%. In contrast, the 2 other litters had a mean of 23 and 17 worms at treatment and slaughter, respectively, and seemed to respond better to the second infection as prevalence (17%) and fecundity (12%) increased. Furthermore, they had a significant correlation between individual worm burdens at treatment and slaughter (p= 0.017). The results confirm that moderate neonatal exposure may result in high worm establishment and the strong litter effect may offer some confirmation that infection levels and patterns may be influenced by genetic factors so that some pigs are more susceptible to infections.
