Detection of emerging bacterial diseases in Taiwan Litopenaeus vannamei
Yi-Ping Lu
Abstract
The bacteria that cause acute hepatopancreatic necrosis syndrome (AHPND) and necrotizing hepatopancreatic hepatitis (NHP), as listed by the World Organisation for Animal Health, can infect Litopenaeus vannamei. Other forms of vibriosis (including non-AHPND V. parahaemolyticus, V. harveyi, V. campbellii, V. vulnificus, V. alginolyticus), Streptococcus spp., Lactococcus garvieae, Aeromonas spp., Shewanella spp., and Photobacterium damselae subsp. damselae can also infect white shrimp and cause significant losses. Among these, translucent post-larvae disease (TPD), also known as highly lethal Vibrio disease (HLVD), and Photobacterium damselae subsp. damselae have emerged as major bacterial pathogens of Litopenaeus vannamei, attracting increasing attention following the outbreak of AHPND. After isolating bacteria from shrimp lesions, polymerase chain reaction (PCR) was used to detect 16S rRNA, PirA/PirB, Idh, toxR, and VHVP genes to establish methods for bacterial pathogen identification and pathogenicity analysis in white shrimp. These bacterial pathogens can cause infections from the late larval stage to adulthood. Infected shrimp exhibit clinical signs such as pronounced gill blackening, atrophy and necrosis of the hepatopancreas, and whitening of the posterior abdominal and tail muscles. These diseases are often associated with environmental stress factors, including high organic matter in the water, sudden changes in salinity and temperature, and physical stress from harvesting or pond relocation, all of which can weaken or injure shrimp and increase susceptibility to infection. In addition, pathogens may be transmitted horizontally from carrier broodstock to juvenile shrimp. Complex phenotypic traits, similar virulence gene profiles, and high genetic diversity are common features of bacterial pathogens isolated from diseased shrimp. Further whole-genome sequencing will be necessary to confirm the relationships between specific pathogenic genes and disease development.
Molecular epidemiology and pathogenicity study of Senecavirus A in swine
Cheng-Ju Pan
Abstract
Senecavirus A (SVA) is an emerging vesicular disease pathogen in swine, with clinical signs that closely resemble those caused by other vesicular viruses such as foot and mouth disease virus (FMDV) and swine vesicular disease virus (SVDV), making differential diagnosis based on clinical appearance challenging. In this study, we analyzed the full-length genome sequences and phylogenetic relationships of seven SVA isolates in Taiwan. The results revealed that these strains shared high sequence identity with contemporary strains from the United States and clustered within the same lineage in the phylogenetic tree. One of the SVA isolate from this study was further inoculated into 24-week-old pigs via oral-nasal route to evaluate its pathogenicity and immunological responses through clinical monitoring and sampling. During the experiment, oral and rectal swabs as well as serum samples were collected at regular intervals. All samples were tested using real-time reverse transcription PCR (RRT-PCR) and virus neutralization tests (VNT), respectively. Additionally, tissues from challenged sacrificed pigs were examined for viral distribution. All pigs in the group developed typical vesicular lesions, with viral RNA detectable in oral swabs up to 28 days post-infection (dpi). Neutralizing antibodies were maintained at high level through 56 dpi, and viral RNAs were widely distributed across various tissues. Overall, this study integrated molecular epidemiology and experimental infection models to systematically characterize the viral dynamics and host immune responses during the early and late phases of SVA infection in pigs. The findings provide a valuable foundation for future studies on SVA pathogenesis, transmission routes, and control strategies.
Implementation of the Asian Proficiency Testing for Rabies Diagnosis
Yu-Chia Chang
Abstract
In 2018, the Veterinary Research Institute (VRI), Ministry of Agriculture, Taiwan (R.O.C.) and the Nancy Laboratory for Rabies and Wildlife (Anses-Nancy, WOAH/WHO/EU reference laboratory for rabies), France jointly signed the WOAH Twinning Project for Rabies, which is implemented from 2018 to 2022. Within this collaborative framework, a Center of Laboratory Proficiency Test (PT) for Rabies Diagnosis within the Asian Network was established at VRI. This center provides rabies diagnosis proficiency test services to laboratories across Asia, addressing the regional demand for participation in PT to comply with ISO/IEC 17025 quality management standards, and also offers objective evaluations for the performance of regional diagnostic techniques. The first activity was successfully completed in 2022, with a total of 11 participating laboratories from 7 countries. The second proficiency testing activity is scheduled to be held in 2025.This report will introduce the background and ongoing activities of VRI in organizing the Asian Proficiency Testing for Rabies Diagnosis.