Competitive replication kinetics and pathogenicity in pigs co-infected with historical and newly invading classical swine fever viruses
Chia-Yi Chang
Abstract
Classical swine fever (CSF), also known as hog cholera, is caused by classical swine fever virus (CSFV) and is an economically important and highly contagious disease affecting pigs. Analysis of the E2 and NS5B sequences from CSFVs that were isolated from field outbreaks in Taiwan showed that the viruses could be divided into different genotypes. The historical subgroup (genotype 3.4) in Taiwan seems to have been endemic before the 1920s. The exotic subgroup (genotype 2.1) was first isolated in 1994 and further sporadic outbreaks of this subgroup has subsequently occurred. Analysis also showed that, during the these more recent outbreaks, the CSFV population has shifted from genotype 3.4-dominant to 2.1-dominant after 1996. To understand the mechanisms of viral population shifts in the field, viruses belong togenotype 2.1 and 3.4 have been analyzed in depth both in vitro and in vivo to compare viral replication rates and pathogenicity between these two genotype viruses. Inoculation of the viruses into cells (in vivo) demonstrated that the CSFV genotype 2.1 has a higher S/C (secreted/intracellular) ratio than genotype 3.4, indicating that genotype 2.1 is secreted efficiently into the supernatant. In pigs challenged with the CSFV genotypes 2.1 and 3.4, genotype 2.1 was detected earlier and the viral titer was higher than genotype 3.4, indicating that genotype 2.1 replicated more efficiently in pigs. These findings will be useful to further understand the characteristics of CSFV and will be helpful for the control of CSFV.
Mass production of a freeze-dried lapinized hog cholera live vaccine
Chyi-Sing, Hwang
Abstract
Hog Cholera also known as Classical Swine Fever (CSF), is a highly contagious and lethal disease caused by the Classical Swine Fever Virus (CSFV), and affecting industrial hog operations. Clinical signs vary dependent on different virus strains, with symptoms presenting as insignificant, chronic or acute (sometimes with 100% mortality) and thereby potentially causing large economic losses. CSFV is a RNA virus belonging to the genus Pestivirus in the family Flaviviridae, and can induce fever, diarrhea and internal organ hemorrhage. AHRI produced 2,151,340 doses of Lapinized Hog Cholera vaccine in 2017, and an average of 467 doses were obtained per rabbit. In order to increase production capacity, AHRI had bought a new freeze-dryer in December, 2017. The capacity for freeze-dried vials in this machine is ~38% higher than the previously used machine and we estimate that the production yield can be increased up to 80,000 doses. Currently, we are testing various freeze-drying conditions in order to improve manufacturing efficiency.
Reports on the OIE Twinning Program workshop: Recent status and control of koi herpesvirus in Southern-east Asia as well as a visit to the Wisconsin Veterinary Diagnostic Laboratory
Chieh-Hao Wu
Abstract
We recently participated in a workshop in Bali, Indonesia from August 25-28, 2017 held by the OIE Twinning Program on the topic of koi herpesvirus disease (KHVD) in Southeast Asia, and as preparation for setting up our own international reference laboratory. We briefly reported on the recent status of KHV in Taiwan. Mainly, this project was aimed to prepare for an international reference laboratory for KHV. The main sessions for discussion included the results of the Japan-Indonesia Twinning Program during the past three years, as well as of the resultant KHV quarantine and control strategies in Indonesia. Furthermore, we visited the Wisconsin Veterinary Diagnostic Laboratory (USA) from September 3 to 9, 2017, in order to more fully understand the diagnostic techniques for aquatic animal disease. By learning the diagnostic and practical operation of this veterinary diagnostic laboratory along with the related operational (management and quality control) practices, we will be able to strengthen Taiwanese diagnostic laboratories for aquatic animal diseases.