Serological response of chickens, turkeys and ducks to strain V4 of Newcastle disease virus.

The serological response of two different age groups of turkeys and ducks to strain V4 of Newcastle disease virus was markedly inferior to that of similar age groups of chickens. This suggested that this strain might not be a suitable vaccine strain for use in turkeys and ducks, even though the correlation between specific serum antibody and immunity in these species is not clearly understood. The 20-week-old group of chickens required two doses of 10(7.1) 50 per cent embryo infective doses (EID50) of the virus to develop a specific serum antibody titre comparable to 21-day-old chickens given one dose of 10(7.1) EID50 of virus.