INCREASED LITTER SURVIVAL RATES, REDUCED CLINICAL ILLNESS AND BETTER LACTOGENIC IMMUNITY AGAINST TGEV IN GILTS THAT WERE PRIMED AS NEONATES WITH PORCINE RESPIRATORY CORONAVIRUS (PRCV)

Authors: Wesley, Ronald; Lager, Kelly

Submitted to: Veterinary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/21/2003
Publication Date: 9/1/2003
Citation: Wesley, R.D., Lager, K.M. Increased litter survival rates, reduced clinical illness and better lactogenic immunity against TGEV in gilts that were primed as neonates with porcine respiratory coronavirus (PRCV). Veterinary Microbiology. 95(3):175-186.

Interpretive Summary: Transmissible gastroenteritis (TGE) is an economically important disease of swine worldwide. It has been estimated to cost U.S. swine producers about 100 million dollars annually due to death and poor growth of infected pigs. To control this disease, maternal antibodies from colostrum and post-colostral milk of immune sows are crucial to provide protection for suckling piglets. In this study we show that immunity and immunological memory against TGE were induced in 4-day-old female piglets by exposure to a respiratory coronavirus vaccine. By providing a TGE virus booster exposure to these primed pigs when they were pregnant, higher levels of protective maternal antibodies were produced and passively transferred to their offspring resulting in less illness and higher survival rates. This vaccination scheme, alternating a respiratory coronavirus exposure in very young pigs with an enteric virus exposure late in gestation, can be used by swine producers to protect against severe TGE outbreaks.

Technical Abstract: Establishing immunological memory in female piglets at a young age with PRCV was effective in inducing a secondary immune response to a limiting dose of TGEV given orally 2 to 3 weeks prior to farrowing. Subsequently, because of passive antibody transfer, the offspring of these primed gilts were more efficient in surviving a lethal TGEV challenge. An average survival rate of 89% occurred in 6 litters of piglets from primed gilts that were boosted with 2.8 x 10**6 plaque forming units (PFU) of TGEV whereas 76% of the piglets survived in 3 litters that suckled primed gilts boosted with 3.0 x 10**5 PFU of TGEV. Non-primed gilts given identical prefarrowing doses of TGEV had litter survival rates of 63% and 55% respectively. Moreover, both groups of litters from primed gilts suffered less clinical illness (as measured by the extent of weight loss post-challenge) than control litters. Priming of the piglets as neonates and boosting the pregnant gilts produced an anamnestic systemic immune response and correspondingly higher milk titers in the primed gilts compared to control animals. Thus, priming piglets with PRCV was beneficial in providing resistance to TGEV and could be incorporated into a vaccine strategy that yields better protection against TGEV.