Studies on the pathogenesis of chicken infectious anaemia virus infection in six-week-old SPF chickens

The pathogenesis of chicken infectious anaemia virus (CAV) infection was st udied in 6-week-old and one-day-old SPF chickens inoculated intramuscularly with graded doses of Cux-1 strain (10(6)-10(2) TCID50/chicken). Viraemia, virus shedding, development of virus neutralizing (VN) antibodies and CAV d istribution in the thymus were studied by virus isolation, polymerase chain reaction (PCR), immunocytochemistry (IP) and in situ hybridization until p ostinfection day (PID) 28. In 6-week-old chickens infected with high doses of CAV, viraemia and VN antibodies could be detected 4 PID and onward witho ut virus shedding or contact transmission to sentinel birds. However, virus shedding and contact transmission were demonstrated in one-day-old infecte d chickens. In the 6-week-old groups infected with lower doses, VN antibodi es developed by PID 14, transient viraemia and virus shedding were detected . The thymus cortex of all 1-day-old inoculated chickens stained with VP3-s pecific mAb. Cells with positive in situ hybridization signal were fewer an d scattered throughout the thymus tissue of the one-day-old inoculated chic kens as compared to IF-positive cells. These results suggest that early imm une response induced by high doses of CAV in 6-week-old chickens curtails v iral replication and prevents virus shedding.