Development of a rapid biological assay for determination of potency of Newcastle disease vaccine (strain I-2) |
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| Authors: | P N Wambura J Meers P Spradbrow |
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| Institution: | (1) School of Veterinary Science, Faculty of Natural Resources, Agriculture and Veterinary Science, University of Queensland, Brisbane, Australia |
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| Abstract: | A rapid biological assay based on incubation time has been developed for determination of the potency of Newcastle disease
virus strain I-2 vaccine. It is based on the observation that the interval between inoculation and the first detection of
haemagglutinin (HA) depends on the titre of the vaccine inoculated. Chicken embryonated eggs were inoculated with different
titres (109, 106 and 103 EID50/0.1 ml) of vaccine and incubated for 24 h. At hourly intervals, 5 eggs from each vaccine titre were tested for the presence
of HA. The results showed that the HA activity was detected from 5, 11 and 15 h after inoculation with vaccine doses of 109, 106 and 103 EID50, respectively. On the basis of these results it is suggested that if there is no HA detected from 5 to 11 h after inoculation
of eggs with the vaccine virus, the vaccine should not be used to vaccinate chickens as it might have an infectivity titre
of less than 106 EID50/0.1 ml, which is equivalent to the recommended single chicken dose. It is concluded that measuring the time between inoculation
of the vaccine virus and the onset of HA activity might provide an estimate of the titre of the vaccine within 24 h. |
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| Keywords: | Biological assay Chickens Newcastle disease Potency Strain I-2 Vaccine |
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