Natural infection of broiler breeder chickens with endemic apathogenic Newcastle disease virus and their subsequent response to vaccination with a live V4 Newcastle disease virus vaccine.
Flocks of broiler breeder chickens housed on a commercial farm were monitored from 13 w of age for natural infection with endemic lentogenic Newcastle disease virus (NDV). Seroconversion was first detected at 17 w. By 24 w, all 8 flocks had achieved peak log2 mean haemagglutination inhibiting antibody titres of up to 4.8. Antibody titres then declined and rose again over several months, suggesting cyclic reinfection with NDV. A lentogenic NDV indistinguishable from V4 was isolated from the cloaca of one bird at 18 weeks of age. At 54 weeks of age, 6 of 8 flocks were vaccinated en masse with live V4 NDV vaccine, 3 flocks by drinking water and 3 flocks by aerosol. All flocks were serologically monitored for a further 8 w. Drinking water vaccination induced an anamnestic response in 3 flocks, showing that flocks with pre-existing active immunity to NDV may be successfully vaccinated with V4. However, in all aerosol vaccinated flocks, the procedures failed to induce a response different to that observed in unvaccinated flocks. The serological response to vaccination was greater in sires than in dams.
Bell
I G
IG
New South Wales Department of Agriculture and Fisheries, Elizabeth Macarthur Agricultural Institute, Menangle.
Nicholls
P J
PJ
Norman
C
C
Cross
G M
GM
D000818:Animals; D000914:Antibodies, Viral / Q000096:biosynthesis*; D002645:Chickens; D005260:Female; D008137:Longitudinal Studies; D008297:Male; D009521:Newcastle Disease / Q000453:epidemiology* / Q000276:immunology; D009522:Newcastle disease virus / Q000276:immunology*; D014611:Vaccination / Q000662:veterinary; D014765:Viral Vaccines / Q000276:immunology*
D000914:Antibodies, Viral; D014765:Viral Vaccines