J Vet Sci.  2020 Mar;21(2):e25. 10.4142/jvs.2020.21.e25.

A descriptive study of on-farm biosecurity and management practices during the incursion of porcine epidemic diarrhea into Canadian swine herds, 2014

• Perri AM
• Poljak Z
• Dewey C
• Harding JC
• O'Sullivan TL

• KMID: 2506186
• DOI: http://doi.org/10.4142/jvs.2020.21.e25

Abstract

Porcine epidemic diarrhea virus (PEDV) emerged into Canada in January 2014, primarily affecting sow herds. Subsequent epidemiological analyses suggested contaminated feed was the most likely transmission pathway. The primary objective of this study was to describe general biosecurity and management practices implemented in PEDV-positive sow herds and matched control herds at the time the virus emerged. The secondary objective was to determine if any of these general biosecurity and farm management practices were important in explaining PEDV infection status from January 22, 2014 to March 1, 2014. A case herd was defined as a swine herd with clinical signs and a positive test result for PEDV. A questionnaire was used to a gather 30-day history of herd management practices, animal movements on/off site, feed management practices, semen deliveries and biosecurity practices for case (n = 8) and control (n = 12) herds, primarily located in Ontario. Data was analyzed using descriptive statistics and random forests (RFs). Case herds were larger in size than control herds. Case herds had more animal movements and non-staff movements onto the site. Also, case herds had higher quantities of pigs delivered, feed deliveries and semen deliveries on-site. The biosecurity practices of case herds were considered more rigorous based on herd management, feed deliveries, transportation and truck driver practices than control herds. The RF model found that the most important variables for predicting herd status were related to herd size and feed management variables. Nonetheless, predictive accuracy of the final RF model was 72%.

Keyword

Swine; biosecurity; porcine epidemic diarrhea; random forests; Canada

Figure

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  Fig. 1. The distribution and mean minimal depth for the top variables for predicting porcine epidemic diarrhea virus during the incursion of the virus in Canadian swine herds, 2014. The vertical black line represents the mean minimal depth. The x-axis ranges from zero to 30 000 trees in which is the maximum any variable was used for splitting on X j. Variable HPU is the only variable that reaches the maximum number of trees. HPU, heat producing unit.

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  Fig. 2. Multi-importance plot using the accuracy decrease, Gini decrease and number of times as a root node to visually identify variables for predicting porcine epidemic diarrhea virus during the incursion of the virus in Canadian swine herds using random forests. The blue circles represent the top variables (most important) for predicting herd status (case versus control herd) and the black variables are the remaining variables using in the random forest model. HPU, heat producing unit.

Reference

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