Immune protection provided by a precocious line trivalent vaccine against rabbit Eimeria

A pilot study was conducted to evaluate the pathogenicity and immunogenicity of vaccinated rabbits with different doses of oocysts (5 × 10², 1 × 10³, 1 × 10⁴, and 5 × 10⁴) of a precocious line, including Eimeria magna, E. intestinalis or E. media following the challenge with their corresponding parent strains. Our results showed that each precocious line had weak pathogenicity but good immunogenicity in terms of clinical symptoms, average daily weight gains (ADGs), and oocyst outputs. Therefore, a precocious line trivalent vaccine, including E. magna, E. intestinalis, and E. media was formulated. A total of sixty 40-day-old coccidia-free rabbits were allocated to ten treatments with a 2 × 3 factorial arrangement that included 2 vaccination doses (5 × 10² or 1 × 10³ oocysts of the precocious line). Groups I to Ⅷ and Unimmunized Challenged Control group were challenged with mixed oocysts of their corresponding parent strains (1 × 10⁴ oocysts of each parent strain) 14 days after vaccination. No clinical symptoms were observed in the immunized groups after vaccination. Average daily weight gains (ADGs) were similar to those of unimmunized unchallenged controls (P > 0.05) after vaccination or after challenge. Oocyst outputs in the vaccinated challenged groups were significantly different from those of unimmunized challenged controls (P < 0.01) after challenge. These results indicated that the trivalent vaccine could provide immune protection against coccidiosis and therefore, it could be used as a candidate vaccine.