Study of the resistance acquired by rabbit does immunized with a precocious line of Eimeria magna and of its transmission to their litters
Fifty two coccidia free rabbit does were used in this experiment and 26 of them were immunized by repeated per os inoculations of 104 oocysts of Eimeria magna precocious line during gestation. The oocysts output was completely controlled after the third inoculation and signs of disease were never observed. The serum antibodies (Ab) were titrated by an ELISA method. In the controls, the Ab titers were constantly below the optical density 0,25 at the wave length 405nm. In immunized does, the Ab level began to increase 4 weeks after the first inoculation. Booster inoculations given 7 and 4 days before parturition produced a high increase of Ab level. 26 females received an injection of sporozoites 2 and 17 days after parturition; these injections produced a dramatic increase of the Ab level compared with that of the untreated females. The serum Ab of the weanlings were titrated at 29 and 39 days of age. In all groups, the Ab titers were very low but a slightly higher level was observed in the groups corresponding to the immunized does. The dramatic increase of the Ab titers of the does injected with sporozoites had no effect on the Ab titers of their litters. To test the protection transmitted by the mothers, the weanlings were inoculated with 10 oocysts of the same Eimeria magna precocious line and the oocysts output was measured. The whole excretion of oocysts was identical (6 x 10 oocysts) in all groups, and the decrease in weight gain was identical to that of inoculated controls. We can conclude that the does immunity did not protect the litter against an infection with E.magna.
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