Investigating the introduction of porcine epidemic diarrhea virus into an Ohio swine operation

Abstract

Background: Porcine Epidemic Diarrhea virus (PEDV) is a highly transmissible coronavirus that causes a severe enteric disease that is particularly deadly for neonatal piglets. Since its introduction to the United States in 2013, PEDV has spread quickly across the country and has caused significant financial losses to pork producers. With no fully licensed vaccines currently available in the United States, prevention and control of PEDV disease is heavily reliant on biosecurity measures. Despite proven, effective biosecurity practices, multiple sites and production stages, within and across designated production flows in an Ohio swine operation broke with confirmed PEDV in January 2014, leading the producer and attending veterinarian to investigate the route of introduction.

Case presentation: On January 12, 2014, several sows within a production flow were noted with signs of enteric illness. Within a few days, illness had spread to most of the sows in the facility and was confirmed by RT-PCR to be PEDV. Within a short time period, confirmed disease was present on multiple sites within and across breeding and post weaning production flows of the operation and mortality approached 100% in neonatal piglets. After an epidemiologic investigation, an outsourced, pelleted piglet diet was identified for assessment, and a bioassay, where naïve piglets were fed the suspected feed pellets, was initiated to test the pellets for infectious PEDV.

Conclusions: The epidemiological investigation provided strong evidence for contaminated feed as the source of the outbreak. In addition, feed pellets collected from unopened bags at the affected sites tested positive for PEDV using RT-PCR. However, the bioassay study was not able to show infectivity when feeding the suspected feed pellets to a small number of naïve piglets. The results highlight the critical need for surveillance of feed and feed components to further define transmission avenues in an effort to limit the spread of PEDV throughout the U.S. swine industry.

Figure 1

A schematic representation of the pork production system with each of the four production flows represented in separate panels. Panels A, B, and C illustrate the three separate multi-site, farrow-to-finish production flows within the pork production system which are referred to as flows A, B, and C respectively. Weaned pigs from flow A are placed into wean-to-finish barns, whereas pigs from flows B and C are weaned into nursery facilities and later moved to finishing barns. Production flow D, as represented in Panel D, is a multiplier herd with a single breed-wean site. Weaned pigs from flow D are raised in gilt developer units or wean-to-finish barns. Production sites where porcine epidemic diarrhea virus (PEDV) was detected during the outbreak are shaded red and the date of PEDV detection is listed.