Tag: summer

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.

Science page: Investigating PRRS summer outbreaks in the US

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 we are sharing an investigation into PRRS summer outbreaks by Dr. Juan Sanhueza and the MSHMP team.

Key Points

  • Each year approximately 3% of the sow farms have a PRRS outbreak during the summer.
  • The incidence of summer PRRS breaks has been constant over the last 9 years.
  • There are geographical areas with higher or lower risk of summer breaks.
prevalence of summer PRRS outbreaks per year
Figure 1. PRRS summer outbreak incidence per year between 2009 and 2017.

A summer outbreak was defined as a PRRS case that happened between June 21st and September 21st of the year. The mean incidence of PRRS summer outbreaks was 3.2% between 2009 and 2017, ranging between 1.6% and 4.4%. The trend was stable among the years. (Figure 1) Not all areas are equal against summer outbreaks. Indeed, the region of Southern Minnesota – Northern Iowa is more at risk of outbreaks than others like Southern Iowa or Eastern North Carolina. (Figure 2)

areas with higer lower PRRS risk in the summer
Figure 2. Geographical areas with higher (red) and lower (blue) PRRSV incidence risk

Biosecurity measures against PRRSV should therefore be a concern all year round for swine producers!