Effects of vaccination on the haematological parameters of cockerels and ducks infected with a Velogenic Newcastle disease virus

Abstract

This study investigated the effects of vaccination on haematologic responses of cockerels and Pekin ducks experimentally infected with a velogenic Newcastle disease virus (NDV). One hundred cockerels and ducks respectively were used for the study. The birds were randomly divided into six groups of three groups each. One group from both bird types was vaccinated against NDV with La Sota vaccine after three weeks of age. The vaccinated and unvaccinated cockerels and ducks were inoculated with a velogenic NDV after six weeks and observed for clinical signs and lesions. Blood samples were randomly collected from five birds in each group for haematological analyses at 3 days interval from day 0 to 15 and 21 post inoculation. Ten birds in each group were used for haemagglutination inhibition test weekly. Results showed signs of weakness and greenish diarrheoa from day 2 pi, torticollis, ruffled feathers and droopy wings with 13.33% and 100% mortality for vaccinated and unvaccinated infected cockerels respectively. There were leukocytosis, heterophilia and lymphopaenia in infected birds. The HI titres of vaccinated cockerels were far higher than the vaccinated ducks. The leukocytosis in vaccinated birds confirmed reports that vaccination did not prevent infection but reduced clinical signs, lesions, virus shedding and mortality. The transient leukocytosis in these birds could be seen as early signs of NDV infection in the absence of any clinical signs especially in ducks that are less susceptible and therefore may help in early detection of the disease before they constitute a risk to more susceptible birds.

Keywords: Vaccination, Velogenic Newcastle disease virus, Haematology, Cockerels, Ducks