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Seminar 875  
Date:2017-07-20
Update:2017-11-07

  

Seminar:  875  

1

Speaker(s)

Wei-Yu Lin

Topic

Production of a live freeze-dried lapinized vaccine against Classical Swine Fever (Hog Cholera)

Abstract

Classical swine fever (CSF) is a highly contagious disease affecting swine. The responsible infectious agent is a virus of the genus Pestivirus in the family Flaviviridae. The main routes of infection are through the mucous membranes (oral, nose, etc.) And CSF is one of the most important swine virus diseases in Taiwan, with symptoms ranging from fever, anorexia, diarrhea, death, and possibly neurological ones. With its highly contagious and fatal nature, CSF poses serious threats to the hog industry and causes huge economic losses to hog farmers. The freeze-dried lapinized hog cholera seed virus was introduced from the Philippines by Dr. Robert C.T. Lee. Cultivated in continuous subculture in rabbits for over 800 generations, it has become a highly attenuated swine fever virus called lapinized Philippine Coronel-China (LPC-china) strain. Since the implementation of the LPC vaccine in Taiwan during the past 47 years, the incidence of swine fever has decreased from an incidence level of 8.13% to below 0.02%, indicating that the vaccine can effectively control this disease. In its use the past 50 years in Taiwan, over 2,700 batches of LPC strain vaccine has been produced. The vaccine is now commonly used in pig farms and has received high appreciated by hog farmers. In 2016 alone, AHRI produced 3,107,560 doses of the LPC-China strain live vaccine which has greatly enhanced the prevention of hog cholera in Taiwan. At present many countries are committed to eradicate hog cholera, and similarly for the Taiwanese hog industry the eradication of this very important disease affecting swine production remains paramount.

2

Speaker(s)

Yen-Lin Lee

Topic

Development of an oil emulsion vaccine against bovine ephemeral fever

Abstract

Bovine ephemeral fever (BEF) is an arthropod-borne disease caused by members of the family Rhabdovirus. In Taiwan, the first outbreak of BEF occurred in 1967 and since then, the disease tends to occur every two to six years. This febrile disease has caused serious economic damage to the dairy and cattle industry by reducing milk production and raising cull rates. Although the conventional aluminum –containing (Al-gel) vaccines are safe and induce a quick immune response, the elevated serum neutralizing (SN) antibodies do not last long enough to provide effective protection for the cattle herd. To reduce the financial losses caused by this disease, the aim of this study was to develop an oil-based, inactivated vaccine. After the safety and efficiency tests of eight kinds of adjuvants were conducted on mice, we selected four potential adjuvants (T, C, S and G) for further studies on rabbits and cattle. A total of seventeen rabbits were divided into four test groups, one positive control group (A), and one negative control group (B). Body temperatures and inoculation regions were normal in all groups after three immunizations. The top three geometric mean titers of SN antibodies calculated after two shots of basic immunization were T, G, and C (in descending order), and they were all above 469.5. The order then changed to G, C, and T after the third immunization, and the average titers all reached 886.3titers. In group G, the SN titers were ≥1024 at week twenty-four after the third immunization. Immunity had been conferred for at least six months. In addition, similar results were seen in cattle trials. A total of twenty-four cattle were divided into six groups, as in rabbit trials, and body temperatures and inoculation regions were again normal in all groups after three immunizations. The top three geometric mean titers of SN antibodies calculated after two shots of basic immunization were G, S, and T, and they were all above 90.6 units (or titers or IU/mL?).The order then changed to G, T, and S after the third immunization, and during this period the average titers all reached 703.5 units. In group G, the SN titers were ≥256 at week twenty-four after the third immunization. Again, immunity had been conferred for at least six months. In conclusion, we chose the G adjuvant as the adjuvant with the most potential for future field trials. We will then confirm its safety, and its ability to induce SN antibodies for long-term immunity. This adjuvant may serve as a replacement of the current Al-gel in BEF inactivated vaccines used in Taiwan, and the new vaccine should provide better protection for the herd against BEF viral infection.