Article

Problématique du contrôle et de la prévention de la coccidiose du poulet

ABSTRACT La coccidiose chez le poulet est une pathologie digestive causée par les sept espèces du genre Eimeria dont les plus pathogènes sont: E. tenella, E. acervulina, E. brunetti et E. maxima. Le cycle de vie des coccidies est direct et très court souvent réalisé en sept jours et qui débouche sur la formation des oocystes excrétés à travers les fèces. L’incidence économique de la maladie est estimée à 2,3 milliards d’Euro mondialement avec 70% des pertes attribuables à la coccidiose sub-clinique, difficilement perceptible, qui déprime le gain de poids vif corporel et l’indice de consommation alimentaire du poulet. L’utilisation du PCR (Polymerase Chain Reaction) permet d’identifier les espèces de coccidies par l’analyse du génome. Les mesures de prévention et de contrôle sont basées sur l’utilisation des anticoccidiens et des vaccins. Toutefois, les problèmes de résistance des coccidies aux médicaments, la présence de résidus médicamenteux dans les produits avicoles et la forme sub-clinique de la maladie engendrée par la réplication des coccidies vaccinales dans les entérocytes, constituent de graves menaces pour la filière poulet. D’autres moyens de lutte continuent de faire l’objet d’expérimentation à travers les plantes médicinales, et les vaccins recombinés. L’utilisation de la résistance naturelle aux coccidies de certains génotypes de poulet est une perspective envisageable qui peut définitivement mettre l’aviculture à l’abri des pertes énormes engendrées par les mesures de contrôle actuelles et la forme sub-clinique de la maladie.
Mots clés: Eimeria, anticoccidien, vaccin, plante médicinale, résistance naturelle.

0 Bookmarks
 · 
338 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: During chicken coccidiosis, the growth of the parasite in the intestinal epithelium cells leads to the development of host immune response. Cell-mediated immune mechanisms appear to be mainly responsible for the acquired resistance to disease. The action of two species of Eimeria, with two different intestinal localizations, on T-lymphocyte subsets was followed by fluorescent antibody cell-sorter analysis, locally at the intestinal site of the parasitic development and systemically in spleen and blood. An Eimeria acervulina infection, localized in duodenum, induced a significant increase in the proportion of CD4+ (up to 15%), CD8+ (up to 12%) and TCR gamma/delta (up to 6%) in the duodenal intraepithelial leucocytes (IEL) from day 4 to day 8 Pl, and an increase in the proportion of IgM+ cells (12%) on day 8. At the same time, the proportion of CD8+ cells dropped significantly in the blood and spleen (-5 to -10%) on days 4 and 6 Pl and then increased with the proportion of CD4+ cells on day 8. An E tenella infection, localized in caecum, increased the proportion of CD4+ cells on day 8 Pl (20%) and of CD8+ cells (10%) on days 6 and 8 Pl in caecal IEL. A negative or zero effect on the proportion of TCR gamma/delta + cells was observed as well as on the IgM+ cells. At the same time, the proportion of CD4+ cells dropped in the spleen on day 8 Pl (-10%) and that of CD8+ cells dropped in the blood on day 6 (-15%). In conclusion, Eimeria infection seems to rapidly induce, locally at the site of the parasite development, a dramatic modification of the proportion of T-cell subsets in IEL, accompanied by systemic variations that are generally opposing, in the lymphocyte populations. The timing of the changes seems to follow the phases of the parasitic cycle for the Eimeria species considered.
    Veterinary Research 02/1996; 27(4-5):503-14. · 3.43 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The timing and magnitude of a coccidian infection, judged by the numbers of oocysts of Eimeria present in the litter, were affected by the duration of medication. In birds medicated for 6 wk and infected at 35 d of age, fewer oocysts were produced than in birds medicated for 4 or 5 wk whether infected at 18 or 35 d of age. Feed conversion at 6, 7, and 8 wk of birds infected at 18 d and medicated for 6 wk was less than that of birds medicated for 4 or 5 wk. Birds infected at 35 d and medicated for 6 wk had a lower feed conversion than birds medicated for 5 wk. Immunity to Eimeria tenella had developed by 8 wk in birds medicated for 4, 5, or 6 wk if infected at 18 d of age. Immunity did not develop in those birds medicated for 6 wk when infected at 35 d.
    Poultry Science 06/2004; 83(5):761-4. · 1.52 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Current methods for sustainable control of avian coccidiosis, whether by prophylactic medication or parasite vaccination, are suboptimal. In this study, we describe an alternative immunization strategy against Eimeria tenella infection using parasite antigen (Ag)-loaded dendritic cells (DCs), or their derived exosomes, in the absence of free Ag. CD45(+) intestinal DCs were isolated from E. tenella-infected chickens and loaded ex vivo with an extract of sporozoites as parasite Ag. Extracellular vesicles purified from the Ag-pulsed DCs expressed surface proteins associated with DC-derived exosomes, including major histocompatibility complex proteins (MHC I and MHC II), CD80, flotillin, and heat shock protein (HSP70). Following intramuscular immunization of chickens with Ag-pulsed DCs or Ag-pulsed DC-derived exosomes, Ag-containing cells were observed diffusely localized in the lymphoid tissue and concentrated in germinal centers of caecal tonsils, and restricted to germinal centers (GC) in the spleen. Chickens immunized with pulsed DCs or exosomes exhibited (a) higher numbers of caecal tonsil and spleen cells expressing IgG and/or IgA antibodies that were reactive with E. tenella Ag, (b) greater numbers of IL-2-, IL-16-, and IFN-γ-producing cells, and (c) higher E. tenella Ag-driven cell proliferation, compared with chickens immunized with Ag in the absence of DCs or exosomes. Chickens immunized with Ag-pulsed DCs or Ag-pulsed DC-derived exosomes and subsequently given a live E. tenella challenge infection at 10d post-immunization displayed (a) increased body weight gains, (b) decreased feed conversion ratios, (c) reduced fecal oocyst shedding, (d) diminished intestinal lesions, and (e) lower mortality, compared with animals given Ag alone. This is the first demonstration of Ag-specific protective immunity against avian coccidiosis using parasite Ag-loaded DCs or DC-derived exosomes.
    Vaccine 03/2011; 29(21):3818-25. · 3.77 Impact Factor

Full-text

View
172 Downloads
Available from
May 27, 2014