Detection of foot-and-mouth disease virus in semen of infected cattle bulls

未知. Foot-and-mouth disease is a highly contagious disease of all cloven hoofed animals caused by FMD virus (FMDV) and is mainly transmitted by contact, aerosols and fomites. Reports of FMDV dissemination in the cattle population via frozen semen straw are scanty, but virus may spread to susceptible population through artificial breeding programme. FMD carrier or recovered animals may secrete virus in semen without manifesting clinical symptoms that is why biological security of semen used for artificial insemination should be ensured by regular screening for FMDV. However, routine FMD diagnostic methods such as virus isolation and immunoassays have low sensitivity for detection of FMDV in the semen. Hence the study was undertaken to optimize a multiplex PCR assay for rapid screening of FMDV in cattle bull semen. Different RNA extraction procedures from semen were modified and evaluated for in vitro amplification of FMDV target gene. Analytical sensitivity of optimized mPCR assay was determined by experimental spiking of FMDV in semen samples. Detection limit of the optimized RNA procedure for mPCR amplification was determined to 0.5 TCID50/ml in FMDV serotypes O, A and Asia1. The optimized mPCR assay was used for screening of a cattle bull farm having recent history of FMD outbreak. Clinically infected animals were found positive for the amplification of FMDV gene in semen samples collected after more than 5 months of infections but not after 8 months post infection.