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


METHODS
Randomized controlled longitudinal study.


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


METHODS
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-gamma-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
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.
Vashisht
Kapil
K
MPI Research, 54943 N Main St, Mattawan, MI 49071, USA.
Erlandson
Keith R
KR
Firkins
Lawrence D
LD
Zuckermann
Federico A
FA
Goldberg
Tony L
TL
D000222:Adaptation, Physiological / Q000276:immunology; D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D000914:Antibodies, Viral / Q000097:blood*; D004781:Environmental Exposure; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000662:veterinary; D005260:Female; D008137:Longitudinal Studies; D009500:Neutralization Tests / Q000379:methods / Q000662:veterinary; D019318:Porcine Reproductive and Respiratory Syndrome / Q000517:prevention & control / Q000635:transmission*; D019316:Porcine respiratory and reproductive syndrome virus / Q000276:immunology*; D011897:Random Allocation; D013552:Swine / Q000254:growth & development; D014611:Vaccination / Q000662:veterinary*; D015430:Weight Gain
D000914:Antibodies, Viral