An Outbreak of Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) in a German Boar Stud: A Retrospective Analysis of PRRSV Shedding in Boar Semen.

Simple Summary: In this retrospective and longitudinal field study, PRRSV was detected in fresh boar semen using PCR. The aim of the study was to reconstruct the duration and shedding profiles of PRRSV in semen using field data. The detection of PRRSV in semen proved to be difficult due to low virus concentrations and the presence of inhibitors that affect PCR accuracy. Shedding patterns were highly variable, with some boars shedding the virus intermittently, continuously, or not at all over a period of weeks to months. Regular monitoring of the boars included testing of serum and semen samples, with PRRSV often detected earlier in blood than in semen. The study demonstrates the importance of combining PCR and antibody testing to improve detection accuracy and timing. In addition, the results suggest that enhanced biosecurity measures such as air purification systems and strict hygiene protocols are crucial for controlling the spread of PRRSV in boar studs. Comprehensive surveillance and early detection are necessary to minimize PRRSV transmission, maintain boar health, and prevent further outbreaks. The porcine reproductive and respiratory syndrome virus (PRRSV) causes high economical costs due to reduced productivity and losses in pig production. The virus can infect sow herds through various routes. One possible risk factor is the transmission of PRRSV through artificial insemination with infected boar semen. For these reasons, conventional boar studs should be closely monitored to detect an outbreak of PRRSV at an early stage. In the presented retrospective study, 2184 fresh semen samples from 336 boars were investigated (RT-qPCR) after an accidental PRRSV introduction to the herd. Hence, the different shedding profiles of PRRSV via semen resulted in 42.2% where no virus was detected, 2.0% intermittent shedding, and 8.4% permanent shedding. The duration of viral shedding varies from 2 days to 83 days post outbreak (on average 33 days). A significant impact of breed on PRRSV shedding duration could not be shown. Also, the distribution of the shedding profile does not follow a consistent mode, indicating that not every boar is shedding the virus via semen. [ABSTRACT FROM AUTHOR]