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Evaluation of contact exposure as a method for acclimatizing growing pigs to porcine reproductive and respiratory syndrome virus

Kapil Vashisht BVSc & AH, PhD1, Keith R. Erlandson DVM, MS2, Lawrence D. Firkins DVM, MS, MBA3, Federico A. Zuckermann DVM, PhD4, and Tony L. Goldberg PhD, DVM5
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  • 1 MPI Research, 54943 N Main St, Mattawan, MI 49071
  • | 2 Carthage Veterinary Service Ltd, 34 W Main St, Carthage, IL 62321
  • | 3 Department of Pathobiology, College of Veterinary Medicine, University of Illinois, Urbana, IL 61802
  • | 4 Department of Pathobiology, College of Veterinary Medicine, University of Illinois, Urbana, IL 61802
  • | 5 Department of Pathobiology, College of Veterinary Medicine, University of Illinois, Urbana, IL 61802

Abstract

Objective—To determine whether 6.5-week-old gilts that have not previously been exposed to porcine reproductive and respiratory syndrome (PRRS) virus can be acclimatized to an endemic strain of the virus by commingling with age-matched gilts inoculated with the endemic PRRS virus strain and whether 10.5-week-old gilts can be acclimatized by commingling with age-matched inoculated or contact-exposed animals.

Design—Randomized controlled longitudinal study.

Animals—80 gilts seronegative for PRRS on a farm in the Midwestern United States with a history of PRRS.

Procedures—20 gilts were inoculated with the endemic PRRS virus strain at 6.5 weeks of age (group 1) and were commingled with 20 gilts that were not inoculated (group 2). Four weeks later, the remaining 40 gilts (group 3) were commingled with gilts in groups 1 and 2. Presence of viral RNA in the tonsils, seroconversion rate, serum neutralizing antibody titers, interferon-γ-mediated cellular immunity, and reproductive outcomes were analyzed.

Results—Acclimatization of PRRS virus-naïve pigs was achieved by means of contact exposure at both 6.5 and 10.5 weeks of age. No differences were observed among the 3 groups with respect to development of anti-PRRS virus-specific immune responses or reproductive outcomes.

Conclusions and Clinical Relevance—Results suggested that contact exposure of 6.5- to 10.5-week-old pigs that had not previously been exposed to PRRS virus to pigs inoculated with endemic PRRS virus may be an efficient acclimatization strategy for controlling outbreaks on commercial farms on which PRRS is endemic.

Contributor Notes

Supported by the USDA Cooperative State Research, Education, and Extension Service (grant No. 2003-02374).

Presented in part as a poster at the International PRRS Symposium, Chicago, December 2006.

The authors thank Drs. Robert J. Husmann, Gabriela Calzada-Nova, and Mauricio Villamar for laboratory assistance and Dr. Hsin-Yi Weng for assistance with statistical analyses.

Address correspondence to Dr. Vashisht.