Eimeria adenoeides and E. meleagrimitis: effect of poult age on susceptibility to infection and development of immunity.

Beltsville small white and Nicholas turkey poults, 1, 7, and 14 days old, were inoculated with mixed cultures of Eimeria adenoeides and E. meleagrimitis. Weight gain and feed conversion of 1-day-old poults were affected as severely as those of the older poults, and mortality was heaviest in this group, ranging from 25 to 45%. One dose of oocysts (2 x 10(4)-1.5 x 10(5], given at 1, 7, or 14 days of age, protected even the 1-day-old poults against challenge with 3 x 10(5) oocysts. Protection was comparable to that afforded by multiple immunizing doses given over 3 weeks. After challenge, little weight reduction or mortality was observed in immunized poults. Average feed conversions of the immunized challenged poults were 1.52 to 1.69 as compared with 2.98 to 5.14 for unimmunized challenged poults.