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Seminar 787  

Seminar: 787
2 pm March 10, 2010
Speaker(s):Lee, Yen-Lin
Development of A Bovine Ephemeral Fever Live Vaccine Based on the YHL Strain
Bovine ephemeral fever (BEF) outbreaks occur once every 3-6 years in Taiwan. To improve the BEF vaccination program, we have tried to develop a live vaccine with the YHL virus strain that was isolated in Japan. In order to understand the growth rate and culture condition of infected HmLu-1 cells, a cell proliferation test was carried out, and the propagation curve of YHL virus was then established. The virus titer hit a peak of 
10TCID50/ml 2 days after virus inoculation into HmLu-1 monolayer cultures. In the safety test, the attenuated YHL virus didn’t cause any inoculated cattle fever or other adverse effects during the 14 days trial. After the safety of the attenuated YHL virus had been confirmed, an immune efficiency test of cattle followed. The calves boosted with a dose of NHRI BEF inactivated vaccine 3 weeks post YHL virus inoculation, produced a rapid neutralizing antibody response against BEFV. The antibody titers against BEFV reached a peak within 4 weeks post vaccination and then declined gradually. Furthermore, hyperimmune sera and a batch of lyophilized YHLV have been prepared. In the near future, we will continue to evaluate the quality, safety, efficacy and cell-mediated immune responses of YHLV live vaccine in cattle by both in vitro and in vivo tests.
Speaker(s):Tsai, Hsun-Hsun
A Survey on the Prevalence of Bovine Leukosis Serum Antibody in Taiwan
Enzootic bovine leukosis (EBL) is a disease inducing lymphosarcomas in cattle and is caused by the bovine leukaemia virus (BLV) - a kind of retrovirus. The EBL-infected cattle become persistently infectious and the reservoirs of this potent disease. The transmission of BLV may occur vertically through placenta, reproductive tracts and colostrum, or horizontally through blood and mlik that contains lymphocytes. The majority of infected cattle are asymptomatic; approximately 29% develop persistent lymphocytosis, and 0.1-10% develop lymphosarcomas. A recent study demonstrated that BLV-infected cows have lower mlik production and are susceptible to other diseases, such as mastitis, diarrhea and pneumonia, leading to increases in culling rates. In this study, a total of 2333 cattle sera from 77 dairy herds in 16 prefectures of Taiwan were collected in 2009. Results show that seropositive rates were 68.58% (1600/2333) using enzyme-linked immunosorbent assays (ELISA) and 63.78% (1488/2333) using agar gel immunodiffusion assays (AGID). The rates of herds with seropositive cattle were 96.10% (74/77). These figures clearly suggest that EBL is still widely distributed throughout Taiwan and that the seropositive rates are higher than a previous study (38.84%) in 2001.
Speaker(s):Hsieh , Cheng-Chu  Coordinator:Chang, Wei-Ming
Influence of Storage on Efficacy of Frozen Dried Lapinized Hog Cholera Seed Virus
As Classical Swine Fever can cause tremendous damage to the  animal husbandry industry in Taiwan, our institute developed a frozen dried lapinized hog cholera seed virus which has proven to be efficacious. However, in order to test whether the frozen dried lapinized hog cholera seed virus is still effective post-expiry, we randomly selected three batches of frozen dried lapinized hog cholera seed virus that had been carefully held for about 2.3 years in the storage unit of a quality control lab in our institute. The efficacy of these seed viruses was then tested through animal experiments with results indicating that seed virus stored under standard conditions are still effective even when it is 1.5 years past the expiration date.