Free Access
Vet. Res.
Volume 38, Number 4, July-August 2007
Page(s) 647 - 654
Published online 13 June 2007
How to cite this article Vet. Res. (2007) 647-654
Vet. Res. 38 (2007) 647-654
DOI: 10.1051/vetres:2007019

Short Note

In vitro pre-exposure of Haemonchus contortus L3 to blood eosinophils reduces their establishment potential in sheep

Getachew Terefea, Christelle Grisezb, Françoise Prevotb, Jean-Paul Bergeaudb, Philippe Dorchiesb, Jean-Claude Brunelc, Dominique Françoisd, Isabelle Fourquauxe and Philippe Jacquietb

a  Addis Ababa University, Faculty of Veterinary Medicine, Debre Zeit, PO Box 34, Ethiopia
b  UMR INRA/DGER 1225, Interactions Hôtes-Agents Pathogènes, École Nationale Vétérinaire, 23 Chemin des Capelles, 31076 Toulouse, France
c  INRA, UE332, Domaine expérimental de la Sapinière, 18 390 Osmoy, France
d  INRA, UR631, Station d'Amélioration Génétique des Animaux, BP 27, 31326 Castanet-Tolosan, France
e  Département de microscopie électronique, Faculté de Médecine de Rangueil, 31403 Toulouse, France

(Received 8 August 2006; accepted 2 February 2007 ; published online 13 June 2007)

Abstract - Different authors have reported that eosinophils are capable of immobilising infective larvae of different species of nematodes in vitro. However, classifying larvae as mobile or immobile is so subjective that it does not always mean all apparently immobile larvae are dead or those that are mobile are capable of surviving further immune responses if administered to their natural hosts. The objective of this experimental study was therefore to substantiate the role of eosinophils in the killing of Haemonchus contortus infective larvae by comparing the infectivity in sheep of larvae that had been incubated with eosinophil-enriched cell suspensions with control larvae. Since it was not possible to isolate pure eosinophils from sheep blood, we were compelled to evaluate the effects of other blood cells contaminating our eosinophil-enriched suspensions. Although eosinophils and neutrophils were the only cells found adherent to H. contortus infective larvae in vitro, induced eosinophils in the presence of immune serum were primarily responsible for the drastic reduction in larval motility compared to the minor effects of neutrophils and mononuclear cells. Corresponding reductions in faecal egg count and worm numbers were observed when the incubated larvae were transferred intra-abomasally to sheep. Interestingly, the proportion of larvae that failed to establish was much higher following incubation with induced eosinophils compared with other cells or with immune serum alone. Although this study did not address the in vivo role of eosinophils in sheep, the results strongly indicate that sheep blood eosinophils have a larval killing potential in vitro, and a larval mobility test alone may not fully explain the level of damage inflicted on the larvae.

Key words: Haemonchus contortus / eosinophils / in vitro / intra-abomasal / sheep

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© INRA, EDP Sciences 2007