Immune responses to an Eimeria acervulina infection in different broilers lines.

The (T-cell) immune responses of two different broiler lines to a primary Eimeria acervulina infection were investigated. The lines used were a commercial fast-growing broiler line and a slow-growing type of broiler as used in organic farming. Seven-day-old broilers of both lines were infected with 5 x 10(4) oocysts of E. acervulina. The animals were weighed and a species-specific real-time PCR was used to quantify the total amount of parasites in the duodenum. In the fast-growing line, a lower parasite load was seen from day 4 onwards compared to the slow-growing line. In both lines the intestinal peak of Eimeria DNA was observed at day 5 post infection (p.i.). In the duodenum no increase in CD4(+) T-cells was found in both infected lines, but a fast increase in CD8(+) T-cells was observed in the fast-growing line. At day 3 p.i. in the slow-growing broilers an IL-18 mRNA response was observed. At day 4 p.i. strong IFN-gamma and IL-8 mRNA responses were found in both lines. No IL-4 mRNA responses were found in the duodenum. In conclusion, both lines have different growth rates and control and infected conditions. Based on the kinetics of observed phenomena a primary infection with E. acervulina in 7-day-old broilers seems to generate an early CD8alpha(+) response in fast-growing broilers compared to the slow-growing broilers. This difference in immune reaction after an E. acervulina infection could result in a different Eimeria load in the duodenum.