This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.
In today’s Science Page we bring you a summary of research on tonsil oral scrubbing done by Peng Li, Isadora Machado, Thomas Petznick, Emily Pratt, Jinnan Xiao, Chris Sievers, Paul Yeske, Swami Jayaraman, Daniel C. A. Moraes, Guilherme Cezar, Mafalda Mil-Homens, Hao Tong, Kelly Will, Darwin Reicks, Jason Kelly, Onyekachukwu H. Osemeke, Gustavo S. Silva and Daniel C. L. Linhares.
Highlights: At around 90 days post-LVI and herd closure,
- Sow TOSc had significantly higher PRRSV positivity than their respective neonatal tongue fluids, dead piglet serum, and live piglet’s blood swab pools.
- Sows testing PCR-positive on TOSC had ~25% probability of PRRSV-positive litter. Conversely, those testing PCR-negative on TOSC had ~90% probability of producing PRRSV-negative offspring.
Background: This study aimed to describe PRRSV RNA detection by RT-rtPCR among different sample types from sows (before and after farrowing) and respective litters and determine the probability of PRRSV-positive piglets based on PCR results of gestating sow TOSC samples.
Materials and Methods: At three months post-live virus inoculation (LVI), 555 sows were sampled by Tonsil-oral-scrubbing (TOSc) 2 weeks pre-farrowing and tested for PRRSV RNA. From these, 59 PRRSV-positive sows, and 88 PRRSV-negative sows matched by parity were conveniently selected. TOSc from sows, blood swabs from live piglets, and tongue fluids (TF) plus serum from stillborn and dead piglets 12 hours within birth were collected individually from all study litters within 12 hours post-farrowing and tested for PRRSV RNA detection by RT-rtPCR.
Results: Pre-farrow TOSc had significantly higher PRRSV positivity (34.3%) than TF (10.9%), dead piglet serum (4.7%) and blood swab pools (8.0%), while dead piglet serum had significantly lower median Ct values (20.3) than all other sample types. The probability of TOSC-positive pre-farrow sows and post-farrow TOSc to produce PRRSV-positive “live litter” were ~ 25% (22.8% and 30.2%, respectively). However, the probability of PRRSV-negative sows on pre-farrow TOSc and post-farrow TOSc to produce negative “live litter” were ~90% (87.2% and 89.0%, respectively). PRRSV positive litter had 3.6 more neonatal loss (including mummies) than negative litters, while having similar total born.
Conclusions and implications:
TOSc had significantly higher PRRSV positivity, suggesting the role of positive sows and potential opportunities for interventions such as test segregation or removal of sows based on their PRRSV status to achieve stability sooner. Dead piglet serum had lower Ct values than all other sample types, highlighting the need to handle them in a bio-secure manner to avoid PRRSV transmission to live pigs.
The full paper can be found at: 10.3390/vetsci12020150