Science Page: Investigating the role of the environment and the lactating sow in PRRSV infections during an outbreak (Part 2)

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 part 2 of the report on the role of the environment and the lactating sow in PRRSV outbreak. You may find part 1 of the report here.

Key Points:

  • PRRS virus can be detected in the environment of the farrowing house (surfaces and air) and on the udder skin of lactating sows. However, PRRSV detection in the environment decreases as time after an outbreak increases.
  • PRRSV was not detected in the environment after 4 months of an outbreak
  • Role of environmental PRRSV in the transmission of the disease is still unknown.

In this study, udder and surface wipes as well as particle deposition wipes were collected both at processing and at weaning, starting 2 weeks after the PRRSV outbreak.

PRRS sampling udder wipes surface wipes particle deposition

Results showed that PRRSV was detected at processing up to 14 weeks after the outbreak in surfaces and udder skin of lactating sows. At weaning, PRRSV was detected up to 17 weeks post-outbreak using udder skin wipes. The number of positive samples decreased over time and the Ct values of the positive samples increased over time indicating a decrease in infection load overtime. Detection of airborne particle deposition positive samples followed a similar pattern to those of the crate surfaces and udder wipes. Virus could be isolated and sequenced from all sample types.

Udder skin and environment may play a role in the transmission and maintenance of PRRSV in piglets in breeding herds; however further research is needed to validate this observation.

 

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.