ABSTRACT

The incidence of Newcastle disease (ND) in Nigeria is high and is a persistent cause of mortality

and (or) morbidity among vaccinated chickens causing huge economic losses. This study was

carried out to evaluate the persistence of maternally derived antibody (MDA) against Newcastle

Disease Virus (NDV), thermo-stability of the test vaccines, comparative analysis of humoral

immune response against four La Sota NDV vaccines as well as the effect of time with respect to

vaccination schedule. In study group I; four experimental groups A, B, C and D each which

consisted of 10 birds were vaccinated with corresponding vaccines on day 14 (primer) and 28

(booster) and group E of 10 birds was maintained as unvaccinated control. Serum samples

collected from five randomly selected birds among the vaccinated groups on day 17, 21, 24, 28

and 35 and from the unvaccinated group E on day 1, 3, 10, 14, 24, 28 and 35 were subjected to

haemagglutination inhibition (HI) titre test. Study group II; two experimental groups i and ii

consisted of 10 birds each primed on day 14 and boosted on day 35 with vaccines A and B.

Serum samples were obtained on day 17, 21, 28 35 and 42 and HI titre measured. The test

vaccines were subjected to varying storage temperature and Haemagglutination (HA) titre

measured. It was found that MDA against NDV persisted till day 24. The results showed a

significant decrease (p<0.05) in HI titre of chickens which were vaccinated at day 14 and 28.

Chickens vaccinated at day 14 and boosted at day 35 produced better immune response.

Haemaggltuination (HA) titre measured after vaccines were subjected to high temperature was as

low as 0. This study has shown that MDA can serve as protection against infective form NDV in

chickens for first two weeks of life and none of the test La Sota vaccine was thermo-stable. In

conclusion, primary vaccination at day 14 followed by booster dose at day 35 may be followed

for better immune response and protection against ND in broilers.

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CHAPTER ONE

1.0       INTRODUCTION

1.1       Background

Newcastle Disease (ND) is a viral disease of poultry. Mayo (2002) described the causative agent;

Newcastle Disease Virus (NDV) as a member of the genus Avulavirus. It can present as a super

acute, acute and sometimes sub-clinical contagious disease of poultry (Health et al., 1991).

Newcastle Disease infection takes place through direct contact with secretions of infected birds;

principally via ingestion (feacal/oral route) and inhalation; fomites (feed, water, implements,

sacks among others); hatching chicks may be infected through eggs for some ND virus strain but

there is no clear evidence of the role of flies in mechanical transmission of the infective ND virus

(Anon, 2013).

Three major panzootics of ND have been recorded and it is present in all continents except

Antarctica (Alexander, 2003). Spradbrow (1999) described Epizootic and Enzootic ND in village

chickens as non-self-limiting event that can smolder for several months and even years in a

typical village housing one or two thousand birds. Epizootics occur when virus is introduced into

a susceptible population with spectacular outbreaks and high mortalities which may cover whole

villages or area within a short time and this form comes most readily to notice. Enzootic ND

occurs when the virus transmits slowly in partially immune population such that there are few

susceptible birds to maintain an outbreak and the occasional birds that die do not come to

veterinary and public attention. These occur in commercial chickens in Nigeria (Ezeokoli et al.,

1984; Echeonwu et al., 1993). The role of exotic and wild birds in the epizootics of ND is not

well understood; however, it is assumed that they play a critical role in the dissemination of virus

1