Immunization against coccidiosis in pheasants with low-dose live sporulated oocysts of Eimeria colchici.
Low-dose immunization of pheasants with live Eimeria colchici oocysts was observed to be effective against massive challenge infection. Fourteen-day-old pheasants, in groups of 28, were orally inoculated with about 100, 250, 500, 1000 and 2000 sporulated oocysts. These birds were then challenged homologously with about 120 000 sporulated oocysts 18 days after the immunization. During the 12-day observation period after the challenge infection, over 92% of the immunized pheasants were still alive, but only 11% of the non-immunized control birds survived the challenge infection. Moreover, the number of oocysts produced after challenge infection of the immunized group was only 10 to 19% of the positive non-immunized control group. The crowding effect of E. colchici infection in pheasant was thought to occur based on the significant difference of the relationship between inoculation doses, daily oocysts excretion and the amount of the faeces discharged, as analyzed by Pearson correlation analysis. Our results showed that immunization of pheasants with a low dose of E. colchici oocysts is feasible to help protect the birds from massive homologous infection, which can be fatal.
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