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Abstract
October 2016, Vol. 77, No. 10, Pages 1108-1113

Evaluation of the minimum infectious dose of porcine epidemic diarrhea virus in virus-inoculated feed

Loni L. Schumacher, DVM; Jason C. Woodworth, PhD; Cassandra K. Jones, PhD; Qi Chen, MS, DVM; Jianqiang Zhang, PhD; Phillip C. Gauger, DVM, PhD; Charles R. Stark, PhD; Rodger G. Main, DVM, PhD; Richard A. Hesse, PhD; Mike D. Tokach, PhD; Steve S. Dritz, DVM, PhD
Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, College of Agriculture, Kansas State University, Manhattan, KS 66506. (Schumacher, Hesse, Dritz); Department of Animal Sciences and Industry, College of Agriculture, Kansas State University, Manhattan, KS 66506. (Woodworth, Tokach); Department of Grain Science and Industry, College of Agriculture, Kansas State University, Manhattan, KS 66506. (Jones, Stark); Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011. (Chen, Zhang, Gauger, Main)
Address correspondence to Dr. Schumacher ().

OBJECTIVE To determine the minimum infectious dose of porcine epidemic diarrhea virus (PEDV) in virus-inoculated feed.

ANIMALS 30 crossbred 10-day-old pigs.

PROCEDURES Tissue culture PEDV was diluted to form 8 serial 10-fold dilutions. An aliquot of stock virus (5.6 × 105 TCID50/mL) and each serial PEDV dilution were mixed into 4.5-kg batches of feed to create 9 PEDV-inoculated feed doses; 1 virus-negative dose of culture medium in feed was also created. Pigs were challenge exposed via oral administration of PEDV-inoculated feed, and fecal swab specimens were collected. All pigs were euthanized 7 days after challenge exposure; fresh tissues were collected and used for PCR assay, histologic examination, and immunohistochemical analysis.

RESULTS The PCR cycle threshold (Ct) decreased by approximately 10 when PEDV was added to feed, compared with results for equivalent PEDV diluted in tissue culture medium. Pigs became infected with PEDV when challenge exposed with the 4 highest concentrations (lowest concentration to cause infection, 5.6 × 101 TCID50/g; Ct = 27 in tissue culture medium and 37 in feed).

CONCLUSIONS AND CLINICAL RELEVANCE In this study, PEDV in feed with detectable Ct values of 27 to 37 was infective. The Ct was 37 for the lowest infective PEDV dose in feed, which may be above the limit of detection established for PEDV PCR assays used by some diagnostic laboratories. Overall, results indicated 5.6 × 101 TCID50/g was the minimum PEDV dose in feed that can lead to infection in 10-day-old pigs under the conditions of this study.


CITING ARTICLES
Jordan T. Gebhardt DVM, PhD; Steve S. Dritz DVM, PhD; Cassandra K. Jones PhD; Jason C. Woodworth PhD and Chad B. Paulk PhD. (2021) Lessons learned from preliminary monitoring for African swine fever virus in a region of ongoing transmission. Journal of the American Veterinary Medical Association 258:1, 35-38.
Online publication date: 14-Dec-2020.
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Authors:
Loni L. Schumacher
Jason C. Woodworth
Cassandra K. Jones
Qi Chen
Jianqiang Zhang
Phillip C. Gauger
Charles R. Stark
Rodger G. Main
Richard A. Hesse
Mike D. Tokach
Steve S. Dritz

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