2012 Annual Report
1a.Objectives (from AD-416):
This cooperative research project focuses on the study of the pathogenicity of Foot-and-Mouth Disease Virus (FMDV) Korean isolates, A/ROK/2010 and O/ROK/2010 in pigs and cattle. Specific objectives are: 1. Conduct a time-course study of FMD infection in pigs and cattle; including direct transmission, 2. Obtain and catalog quality pictures of lesions and reference stocks of research material; serum and tissues.
1b.Approach (from AD-416):
NVRQS will provide FMDV A/ROK/2010 and O/ROK/2010 from pigs and cattle, as well as conduct epidemiological analysis and conduct genomic sequencing of viral isolates. ARS, PIADC will conduct FMDV pathogenicity studies on swine and cattle; inclusive of time-course study and histopathological evaluation and sample collection. NVRQS scientists will be trained to conduct research on FMDV pathogenesis using methology developed by ARS, PIADC scientists. Data generated will help to develop and upgrade current diagnostic assays for the detection of FMD circulating in south east Asia.
Two different strains of serotype A and O have been introduced into the Republic of Korea (ROK) in 2010. Both of them had been spreading in East Asia since 2009 and a great threat to the countries in that region. During the outbreaks of FMD in 2010 Korea, in case of serotype A, all the affected animals were ruminants. The strain of serotype O has spread to pigs and cattle. From these facts, we need to examine and compare the pathogenesis of both strains in different species, pigs and cattle in a controlled environment. In addition, there is a need to develop and upgrade current diagnostic assays for the detection of FMDV strains emerging recently, the samples collected during the time course study and at the end of the study will be used effectively.
During FY 2012 fifteen different isolates were provided by NVQRS to ARS, PIADC for analysis. Using LF Bovine Kidney Cells (LFBK-av6), virus titers were performed by plaque assay. In vivo experiments using the NVRQS isolates included; 1. Preparation of bovine high titer stocks . Two cattle were inoculated by intradermal inoculation (IDL) with infectious doses of FMDV serotype O. Vesicular tissue was harvested and used to prepare “FMDV/O/Korea/2010, Plum Island Bovine passage 1, High Titer Stock” (FMDV/O/SKR2010 PI BovP1). 2. Preparation of swine titer stocks. Due to low titers of the original swine derived isolate (FMDV O, NVRQS07, 1011_01V), the bovine isolate (FMDV O, NVRQS10, 1012_49V) was used instead. To adapt it to swine, four pigs were inoculated by ID inoculation. At 48 and 72 hours post inoculation vesicular fluid was collected from all pigs and pooled to prepare “FMDV/O/Korea/2010, Plum Island Swine passage 1, High Titer Stock” (FMDV/O/SKR2010 PI PorP1). 3. Determine cattle pathogenesis, cattle-to-pig transmission, and cattle-to-cattle transmission with FMDV Serotype O, Korea 2010 (FMDV O, NVRQS10, 1012_49V). Two steers were IDL inoculated with FMDV/O/SKR2010 PI BovP1 and 24 hours later 4 cows were added for 24 hours to be in direct contact with the direct inoculated cows. Once contact cows were removed, 4 pigs were added for direct contact for 24 hours, and then removed. Direct inoculated animals were followed for 7 days. Contact animals were followed for 35 days. 4. Determine swine pathogenesis by direct inoculation. Swine that were inoculated with FMDV O, NVRQS10, 1012_49V with the purpose of generating a porcine high titer stock, and were followed after vesicular fluid was collected to obtain preliminary data regarding pathogenicity of this strain in swine. Samples were collected from all experiments and analyzed using rRT-PCR . The results indicated that the FMDV isolate serotype O that caused cattle and swine FMD in Republic of Korea in 2010 was used to study direct- and contact-inoculation in swine and cattle. So far, after direct inoculation, both species showed typical FMD. After contact inoculation, with cattle as donors, both species have also shown typical FMD.
Major accomplishments include: FMDV O/Korea 2010 strain was amplified in pigs and cattle to generate virus for future experiments. The cattle derived virus was successfully utilized to show cattle-to-cattle and cattle-to-swine transmission. In addition, pictures of clinical signs were obtained and reference materials were collected. In addition, Collaborating scientist from the Foot-and-Mouth Disease Division, Animal, Plant and Fisheries Quarantine and Inspection Agency, MIFAFF, Republic of Korea visited ARS, PIADC on November 7 through 11, 2011. During that visit, he presented a seminar to PIADC staff and met with ARS collaborators to discuss the project.
ARS, PIADC provided NVQRS with LF Bovine Kidney Cells (LFBK) for the purpose of diagnostics and research on FMDV. No peer-reviewed publications have been produced to date from this ongoing work.