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Since i%Z the try of making an attenuated Newcastle disease virus through duck ernbyo-ssa,ge has keen performed and the psexation of the wet type vaccine with the virus studied. The primarily results were already descriked at the first report in l9. In this study, the results on fre-dryig the attenuati virus and further ssage by cell culture are summarixed here under:
1.Among the various media used in the dried vaccine preparation studied has ten found that both 25% yeast extract,and the mixture i.e. 50% yeast extract mixed with 30% skimmilk or normal cattle serum and 50% glurx6e apiaRy mixd,showed ketter efkts but skimmilk or normal cattle serum singly used gave much harmful effazt on the viabilityof the virus.
2.The trial vaccine prepared with 50% yeast exixact maintsined good effect after 4 months preserved at rcom temperature (28 to 302)and 10 months in refrigerator of 4- 8? even dep freear of k-i 8? at the authers’ last test.
3.In coparative study of diluents, these were no remarkable differences in potency when the dried samples were reconstitutl and dilutei respettively with 0.85% saline, 5% glucose and Hanln solution They were still effect after 8 hours preserved at rcom temperature.
4.The TCI) value of the attnual stain to duck emlxyo tissue ailture cell showed 10 almcGt as high as that of to 12-day-old duck enhyos. The protect value of the attenuateivirusto3 month-oldchicbenshowedl0andchicks inocula1with10 TCID could prot against the newcastle disease virulent virus.
5.HI antibcdies obined maternally, may gradually disappear at 3-4 weks after hatchingantheperioi lastisems to keclc€elyrelatedtothedegxeofits original titers. Therefore the optimum age of chicks for vaccination with the vaccine should ke at 4 web or okier.
6.As to theHI antibodies, if the vaccination with the attenuated virus to chicks having 1:320 HI titer or higher, it usually decreases and 1 :lm or lowest increases. Therefore the time of revaccination should ke done at 4 months after the first vaccination after it Hlantibodytiterhas kendroperlto 1:1or1ower.
7.The primary passage-virus to swine ticles showed very little po€t-vaccinal reactions but good potency to chickens. The attenuated virus could also propagate in cattle kidney cells and maintained as long as % days only by changing the media every 10 days at the author last test, lie outline of this paper was read kefore the 19 Annual Meting of the Taiwan Asscciation of Animal Huskendry and Veterinary Medicine,
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