Epidemic field strains of Newcastle disease virus (NDV) originating from the Far East were allowed to spread in groups of twice vaccinated chickens after a challenge by the contact route and swabs taken daily from the mouth were titrated by plaque assay. SPF and broiler chickens were vaccinated at 2 weeks of age and in the hatchery, respectively. First vaccination was performed with a lentogenic vaccine strain by the oronasal route, which was followed by a second vaccination with another lentogenic vaccine given oronasally or the mesogenic vaccine H injected into the wing-web or an inactivated vaccine given intramuscularly. At the 2nd vaccination hemagglutination inhibition (HI) titres rose to a level averaging in 1:64. The inactivated vaccine elicited a booster level (HI 1:256 or higher) in SPF chickens. 3 and 4 weeks after the 2nd immunization, SPF and broiler chickens were challenged with a South-Korean and an Indonesian virus, respectively. 80% of SPF chickens and 100% of broilers shed virus for a period of 3 and 4 days, respectively, irrespective of the fart, if chickens received one or two vaccinations (Table 1 and 2). All parameters of broilers showed less anti-infection protection which can be attributed to the fact, that at the time of 1st vaccination maternal antibodies were as high as 1:128 or more. The level of excretion of the challenge virus was 10-100 times less in immunized than in control birds but the dynamics of excretion was similar in the different groups of vaccines (Figure 2). Clinical signs were insignificant and transient, therefore body weights were used to record health condition. Weight gain curves of the different groups (Figure 1) show an apparently normal development of chickens. The total number of days with arrest of weight gain in the different groups are shown in Table 1 and 2.
|Translated title of the contribution||Examination of field virus excretion in chickens vaccinated against Newcastle disease. 2. Excretion of two recent NDV strains from chickens vaccinated twice by different routes|
|Number of pages||9|
|Journal||Magyar Allatorvosok Lapja|
|Publication status||Published - Dec 1 2005|
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