Science Page: Making epidemiological sense out of large datasets of PRRS sequences

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 epidemiological report regarding a large PRRS sequence dataset from Dr. Igor Paploski in the VanderWaal research group.

Key points:

  • Occurrence of PRRS lineages is not equal in different years, systems or production types
  • Occurrence of specific PRRS lineages is associated with movement of animals
  • Continuous surveillance for PRRS occurrence is important in understanding its determinants and might be able to provide insights that can
    help on its prevention

By utilizing a dataset of 1901 PRRS sequences provided by the Morrison Swine Health Monitoring Project (MSHMP) participants over 3 recent years, the spatiotemporal patterns in the occurrence of different lineages of PRRSV was described and the extent to which the network of pig movement between farms determines the occurrence of PRRS from similar lineages was investigated.

PRRS lineages occurred at different frequencies across geographically overlapping production systems. Preliminary analysis showed that the relative frequency in which specific lineages occur increase while others are decrease over time. The rate at which these changes occur appears to be system-specific. Some lineages were also more common in farms of specific production types (i.e. sow farm or nurseries). As expected, farms that were connected via pig movements were more likely to share the same lineages than expected by chance across all years.

These findings suggest that system-specific characteristics partially drive PRRS occurrence over time and across farms of different production types. Our results also
indicate that animal movement between farms is a driver of PRRS occurrence, strengthening this hypothesis of viral transmission.

Additional research is needed to quantify risks and develop mitigation measures related to animal movement.

Large PRRS sequencing dataset

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