Régulation des populations de Nématodes gastro-intestinaux ...

Abstract
Résultats
The sheep immune response towards gastro-intestinal nematodes has became of great
importance in the current context of extensive resistances to anthelmintic molecules in
parasite populations and the need of alternative strategies such as vaccination or selective
breeding for resistance. In this study, 3 month old INRA 401 lambs (n=79) were randomly
allocated into three groups: uninfected control, challenged either once (primary-infected
animals) or twice (previously-infected animals) with 10,000 Trichostrongylus colubriformis
L3. Uninfected control and once and twice challenged animals were sequentially sacrificed at
4, 10, 17 and 28 days post challenge. No clear polarization of the adaptive immune response
was detected in infected lambs. Nevertheless, delayed cellular and humoral responses
corresponding to well-known described Th2-type effectors were observed in previously-
infected sheep and were strongly correlated to a significant decrease in faecal egg excretion.
No differences in worms’ establishment or worms’ development were noticed between the
two challenged groups. We conclude that two successive exposures to this parasite are
probably not sufficient to induce an unequivocal and detectable Th2 cytokine response in
young lambs but that the effect of this response could limit the larval burden on pastures by
decreasing the faecal egg output.
Keywords : Trichostrongylus colubriformis / sheep / immune response / real-time
quantitative PCR / antibody response
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