Spatiotemporal patterns and risks of herd breakdowns in pigs with postweaning multisystemic wasting syndrome

Area of Science:

• Veterinary Epidemiology
• Swine Health Management
• Disease Ecology

Background:

• Postweaning multisystemic wasting syndrome (PMWS) is a significant disease affecting pig herds.
• Identifying epidemiological risk factors is crucial for effective disease control and prevention strategies.

Purpose of the Study:

• To investigate epidemiological risk factors associated with herd breakdowns due to PMWS in British pig farms.
• To develop survival models for PMWS outbreaks based on different case definitions and time periods.

Main Methods:

• Retrospective cohort study of 116 British pig farms.
• Utilized three case definitions for PMWS, including farmer-reported status, laboratory confirmation, and porcine circovirus type 2 detection.
• Employed multivariable Cox proportional hazard models to analyze time to breakdown, considering factors like herd size, gilt sourcing, and proximity to other farms.

Main Results:

• Farms with 600 or more breeding sows had a higher risk of PMWS breakdowns across all definitions.
• Purchasing replacement gilts and proximity to other pig farms were associated with increased risk, particularly before and during the 2001 Foot-and-Mouth Disease outbreak.
• From October 2001 onwards, proximity to an infected farm (<5 miles) became a significant risk factor.

Conclusions:

• Herd size, biosecurity practices (visitor protocols, gilt sourcing), and farm proximity are key factors influencing PMWS outbreak risk.
• The study highlights the dynamic nature of PMWS risk factors, influenced by disease outbreaks like FMD.
• Findings underscore the importance of robust biosecurity and strategic farm management to mitigate PMWS in commercial pig production.