In this paper, we report the characterization of a genetically modified live-attenuated African swine fever virus (ASFV) field strain isolated from Vietnam. The isolate, ASFV-GUS-Vietnam, belongs to p72 genotype II, has six multi-gene family (MGF) genes deleted, and an Escherichia coli GusA gene (GUS) inserted. When six 6–8-week-old pigs were inoculated with ASFV-GUS-Vietnam oro-nasally (2 × 10⁵ TCID₅₀/pig), they developed viremia, mild fever, lethargy, and inappetence, and shed the virus in their oral and nasal secretions and feces. One of the pigs developed severe clinical signs and was euthanized 12 days post-infection, while the remaining five pigs recovered. When ASFV-GUS-Vietnam was inoculated intramuscularly (2 × 10³ TCID₅₀/pig) into four 6-8 weeks old pigs, they also developed viremia, mild fever, lethargy, inappetence, and shed the virus in their oral and nasal secretions and feces. Two contact pigs housed together with the four intramuscularly inoculated pigs, started to develop fever, viremia, loss of appetite, and lethargy 12 days post-contact, confirming horizontal transmission of ASFV-GUS-Vietnam. One of the contact pigs died of ASF on day 23 post-contact, while the other one recovered. The pigs that survived the exposure to ASFV-GUS-Vietnam via the mucosal or parenteral route were fully protected against the highly virulent ASFV Georgia 2007/1 challenge. This study showed that ASFV-GUS-Vietnam field isolate is able to induce complete protection in the majority of the pigs against highly virulent homologous ASFV challenge, but has the potential for horizontal transmission, and can be fatal in some animals. This study highlights the need for proper monitoring and surveillance when ASFV live-attenuated virus-based vaccines are used in the field for ASF control in endemic countries.

Senecavirus A (SVA) continues to cause vesicular lesions in swine in Canada and many regions worldwide. Since the vesicular lesions caused by SVA are similar to those caused by foot and mouth disease virus, swine vesicular disease virus and vesicular stomatitis virus, a foreign animal disease investigation must be initiated to rule out these diseases. SVA isolates from pigs displaying vesicular lesions in Canada from 2015 to 2023 were sequenced, and phylogeographic analysis was performed using the complete genome sequences. The results infer that SVA has spread between the United States and Canada several times. In addition, the results suggest that SVA spreads from different regions. SVA spread was inferred from Canada into Thailand, India and Mexico and inferred from the United States to Brazil, Columbia, Chile and China with ten separate introductions. Furthermore, recombination was observed in SVA genomes from Canada, the United States and China.

During the past 25 years, vesicular stomatitis virus (VSV) has produced multiple outbreaks in the US, resulting in the emergence of different viral lineages. Currently, very little is known about the pathogenesis of many of these lineages, thus limiting our understanding of the potential biological factors favoring each lineage in these outbreaks. In this study, we aimed to determine the potential phenotypic differences between two VSV Indiana (VSIV) serotype epidemic strains using a pig model. These strains are representative of the epidemic lineages that affected the US between 1997 and 1998 (IN98COE) and between 2019 and 2020 (IN0919WYB2), the latter responsible for one of the most extensive outbreaks in the US. Our initial genome analysis revealed the existence of 121 distinct mutations between both strains, including the presence of a 14-nucleotide insertion in the intergenic region between the G and L genes observed in IN0919WYB2. The levels of viral RNA in clinical samples between pigs infected with IN98COE or IN0919WYB2 were compared. Overall, higher and prolonged expression of viral RNA in pigs infected with IN98COE was observed. However, clinically, IN0919WYB2 was slightly more virulent than IN98COE, as well as more efficient at producing infection through contact transmission. Additionally, infectious virus was recovered from more samples when the pigs were infected with IN0919WYB2, as revealed by virus isolation in cell culture, indicating the increased ability of this virus to replicate in pigs. Sequence analyses conducted from isolates recovered from both experimental groups showed that IN0919WYB2 produced more variability during the infection, denoting the potential of this strain to evolve rapidly after a single infection–contact transmission event in pigs. Collectively, the results showed that epidemic strains of VSIV may represent disparate phenotypes in terms of virulence/transmissibility for livestock, a situation that may impact the intensity of an epidemic outbreak. This study also highlights the relevance of pathogenesis studies in pigs to characterize phenotypic differences in VSV strains affecting livestock in the field.

Diagnostic testing of foot-and-mouth disease virus (FMDV) currently utilizes reverse transcription quantitative PCR (RT-qPCR) to detect the presence of viral RNA and double antibody sandwich ELISAs (DAS-ELISAs) to determine viral serotype. Serotype identification is critical to support informed vaccine selection to combat outbreaks. While DAS-ELISAs are capable of serotype identification, the test suffers from low sensitivity and requires a viral isolate for successful detection. In this study, we developed FMDV-ONTAPS: an Oxford Nanopore Technologies Amplicon P1 Sequencing protocol involving reverse transcription-PCR to amplify P1 of the FMDV genome, and Nanopore sequencing of the amplicons to provide genetic data for serotype and subtype/topotype identification. FMDV isolates representing all seven serotypes were successfully sequenced with this method. Additionally, the protocol successfully provided serotype identification from a variety of specimen matrices obtained from experimentally infected animals that included milk, serum, oral and nasal swabs, tissue suspensions, vesicular fluid, and oral fluid. The limit of detection for FMDV cell culture isolates was comparable for both sequencing and RT-qPCR detection. RT-qPCR Cq values for clinical samples evaluated ranged from 8 to 28.21. Sequencing was successful for all samples except for a single tissue suspension sample (Cq of 28.21). Identification of FMDV serotype in clinical samples is critical for effective outbreak response, and Nanopore sequencing offers a timelier and more sensitive alternative to DAS-ELISAs.

During the past 25 years, vesicular stomatitis virus (VSV) has produced multiple epidemic outbreaks in the US, resulting in the emergence of different viral lineages. Currently, very little is known about the pathogenesis of many of these lineages, thus limiting our understanding of the potential biological factors favoring each lineage in these outbreaks. To determine the potential phenotypical differences between two VSV Indiana (VSIV) serotype epidemic strains using a pig model. These strains are representative of the epidemic lineages that affected the US between 1997-1998 (IN98COE) and 2019-2020 (IN0919WYB2), the latter responsible for one of the most extensive outbreaks in the US. Our initial genome analysis revealed the existence of 121 distinct mutations between both strains, including the presence of a 14-nucleotide insertion in the intergenic region between G and L genes observed in IN0919WYB2. The levels of viral RNA in clinical samples between pigs infected with IN98COE or IN0919WYB2 were compared. Overall, higher and prolonged expression of viral RNA in pigs infected with IN98COE was observed. However, clinically, IN0919WYB2 was slightly more virulent than IN98COE, as well as more efficient to produce infection through contact transmission. Additionally, infectious virus was recovered from more samples when pigs were infected with IN0919WYB2, as revealed by virus isolation in cell culture, indicating the increased ability of this virus to replicate in pigs. Sequence analyses conducted from isolates recovered from both experimental groups showed that IN0919WYB2 produced more variability during the infection, denoting the potential of this strain to evolve rapidly after a single infection-contact transmission event in pigs. Collectively, the results showed that epidemic strains of VSIV may represent disparate phenotypes in terms of virulence/transmissibility for livestock, a situation that may impact the intensity of an epidemic outbreak. This study also highlights the relevance of pathogenesis studies in pigs to characterize phenotypical differences of VSV strains affecting livestock in the field.