Science Page: Investigating the role of the environment and the lactating sow in PRRSV infections during an outbreak (Part 1)

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, Dr. Carles Vilalta and Dr. Juan Sanhueza in collaboration with Dr. Montse Torremorell discuss the sensitivity and specificity of sampling the farrowing environment and lactating sows at processing to detect PRRSV in an infected farm.

Key Points:

  • Lactating sows and the farrowing environment can be sources of PRRS virus
  • Sampling the farrowing environment and the udder skin of lactating sows can be used to monitor for PRRSV although the sensitivity is lower than that of serum samples.
  • The farrowing environment and the lactating sow may serve as a source of infection for PRRSV.

Sampling started 2 weeks after a PRRSV outbreak was reported in a sow farm. Sampling was conducted from 10 litters every 3 weeks for a total of 24 weeks. Samples were collected at processing (~ 3 days of age) and included: surface wipes of farrowing crates, surface wipes of the udder skin of lactating sows, blood samples from all piglets within the selected litters.

PRRS sampling in the environment and on the sows.gif
Scatter plot of the individual RT-PCR Ct values in serum (all piglets) compared with those from surfaces (A) and udder skin (B).

PRRSV was detected in the farrowing crate environment and on the skin of the lactating sow at processing. The surface and udder skin wipes were less sensitive at detecting PRRSV than serum PCR at processing. However, in this study all pigs in the litter were bled which is not the standard practice in the field.

The results show that the environment and the lactating sow may serve as a source of
infection for PRRSV, indicating a need to further understand their roles to establish herd level stability.

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