PRRS incidence rate trends from 2015 to 2019 in the United States

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.

Key Points

  • Overall PRRS weekly incidence rate appear to have increased from 2015 to 2019, mostly due to the effect of a group of systems that joined the project after 2013.
  • PRRS weekly incidence rate has been decreasing slightly since 2015 in the cohort of the 13 systems that initiated the project.
  • The reasons for the apparent increase in the weekly incidence rate in a group of systems are largely unknown and should be further investigated.
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MSHMP Incidence Year 2018/2019 Annual Summary

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.

Today, we are sharing the 2018/2019 summary for the Morrison Swine Health Monitoring Program from the MSHMP team lead, Dr. Cesar Corzo and what his vision for the future is.

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PRRS incidence rate by status at break

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.

Key points

  • Current PRRS Chart 3 incidence risk by status does not take into account the time at risk farms contribute to each status.
  • Incidence rate takes into account the time a farm is at risk of disease.
  • Chart 3 will be replaced by a incidence rate chart that reflects more accurately the PRRS outbreak rate by status.
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Interpreting MSHMP chart 1 for PRRS and PED

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.

This week, the MSHMP team is sharing a quick reminder about chart 1 of the MSHMP report and how we can interpret it.

Continue reading “Interpreting MSHMP chart 1 for PRRS and PED”

NHF: PRRS is also a summer disease

Our latest collaboration with the National Hog Farmer was written by the Morrison Swine Health Monitoring Program team regarding the incidence of PRRS in the summer.

Although our understanding of disease and control methods has improved in recent years, we continue to learn new features of PRRSV epidemiology in part thanks to the Morrison Swine Health Monitoring Project. One of the most recent questions that we have addressed based on enquires from MSHMP participants is whether PRRS incidence during the summer was higher in recent years (i.e. 2016-17) compared to previous years (i.e. 2009-15). We know that PRRSV outbreaks tend to have a seasonal pattern and that they are more frequent during the fall and winter, but we know little about the breaks that happen in the summer and spring.

In order to dig into this question, we analyzed MSHMP data from 2009 to 2017 which included 1,329 outbreaks. Of these, 66% of the breaks occurred during fall and winter and 14% and 20% of the breaks occurred during summer and spring, respectively. Although there were fewer breaks in the spring and summer, the number of breaks in warmer seasons was still significant which represents an on-going frustration to producers because the “PRRSV season” is supposed to be over.

As part of the analysis we learned that between 3% and 6% of the herds break yearly during the summer and spring seasons, respectively. This represents approximately 83 herds out of the 917 reporting in the MSHMP database. If we estimate that the average sow farm has 3,000 sows, then almost a quarter of a million sows break yearly during these two seasons.

Remember, although the risk of PRRSV introduction is lower during the spring and summer, PRRSV breaks still happen, so biosecurity efforts should not be decreased. PRRSV is a sneaky virus so keep your biosecurity up, even in the summer.

All of our collaborations with the National Hog Farmer can be found here.