November 22, 2023
Ten ASF studies conducted in Vietnam completed
Ten field projects studying African swine fever (ASF) in Vietnam have been concluded and are helping inform the US pork industry's prevention and preparedness efforts, according to the Swine Health Information Center (SHIC).
In 2019, SHIC, with support from the National Pork Producers Council, received a grant from the US Department of Agriculture's Foreign Agricultural Service division to fund a multi-phase project including ASF field projects in Vietnam.
Results of the completed work are not only helping inform prevention and preparedness efforts for US pork producers and practitioners but they are also helping inform response and recovery efforts for the ASF epidemic in Vietnam.
"Among the grant-related efforts completed were sharing disease knowledge and strengthening veterinary services capacity for mitigating ASF impact on Vietnam and China, as well as on-the-farm field projects," said SHIC in a release. "Also, following a request from the Vietnamese Department of Animal Health, as a result of the introduction of the ASF vaccines, efforts were focused on supporting the DAH in the design and evaluation of the vaccination programme."
SHIC shares a brief update on the field projects that were ultimately planned, funded and completed through this effort:
- Potential of Rodents to be a Vector in the Transmission of African Swine Fever in Two Commercial Farms in Vietnam with Differing Biosecurity Levels: The two projects did not provide evidence that rodents are significant factors in the transmission of ASF virus between animals or farms;
- Using Standard Laboratory PCR Testing, and Comparing Available POC Technology, to Assess the Validity of Current ASF Test and Remove Practices in Commercial Swine Farms within Vietnam: Results showed tooth extraction did not eliminate ASF virus from sow farms and discovered ASF virus DNA was detected in blood from sows showing no clinical signs, as well as indicated POC tests had poor diagnostic performance;
- ASF Research Projects in Vietnam Examining the Use of Serum and Oral Fluid ELISAs: This unprecedented study showed there is no single best diagnostic approach for ASF virus surveillance and demonstrates that the combined use of the Tetracore qPCR and indirect ELISA tests and serum/oral fluid sampling increase efficiency of ASF disease surveillance;
- Determining the Pathways for ASF Introduction into Boar Studs and Risk of ASF Transmission via Semen Movements During an ASF Outbreak: The project used the experience with ASF in Vietnam to estimate the risk of ASF introduction into boar studs in the United States. The results varied from "negligible" due to water, as long as no surface water enters the facility to "low" from people, fomites and other entries as long as current biosecurity practices are strictly implemented;
- Time and Temperature Required for Complete Inactivation of African Swine Fever Virus: Heat treatment at 54oC and 63oC resulted in positive PCRs but negative viral isolation. However, after bioassay exposing pigs to ASFV-contaminated feces held at 54oC for 10 minutes, viral genomic DNA was detected in their blood at five days post-inoculation, indicating that ASF virus infectivity remained;
- Evaluate the Diagnostic Performance of Pen-side Tests for ASF Detection: The viral DNA PCR pen-side test had better performance than the viral antigen lateral flow test as it can detect infected pigs earlier and for a longer duration after infection;
- Field Evaluation of Oral Fluids as a Convenient, Aggregate Sample for Early Detection of African Swine Fever: Based on the overall field data, ASF virus DNA can be detected in oral fluids within 0-3 days of the initial detection of viremia in the pen. If the viral load in the pen is low, it may take up to three days to detect in oral fluids. This is consistent with the results from a previous study on experimentally inoculated animals under experimental conditions and further validates oral fluids as a reliable aggregate sample for screening swine herds for early detection of ASF;
- Identifying Pathways of Entry of ASF Virus onto Farms to Enhance Information for Improving Biosecurity in Vietnam: The top 10 shared risks for the spread of ASF in Vietnam included entry of water, feed trucks, replacement breeding animals, semen, visitors, tools (both for breeding replacements and cull animals) and livestock trailers (for both weaned pigs and replacement pigs) as well as pork and other food entering the premises.
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