Serological response to vaccination against Aujeszky’s disease with a needle-free injector

Aujeszky’s disease or pseudorabies is still present in Italy. One of the major tools to control and eradicate the disease is the systematic vaccination of swine with gEdeleted modified live vaccines. Needle-free injection of vaccines prevents residual needle fragments and associated meat defects from the injection site. AKIPOR® 6.3 (Merial, Lyon, France) is a freezed dried modified live vaccine (gE-deleted Bartha strain) with an oily adjuvant against Aujeszky’s disease. This study aimed to compare the serological response to different vaccination programs either combining the recommended intra-muscular (IM) administration route of AKIPOR® 6.3 to intra-dermal (ID) vaccine administration using a needle-free injection device or combining only ID vaccine administrations. Materials and Methods The trial was conducted in a 400-sow multi-site farrowto- finish operation known to be gE-negative and raising fatteners for Parma ham until 270-300 days of age. The vaccination program against Aujeszky’s disease in force on the farm includes a two-shot primo-immunization at 70 and 90 days of age in the pre-fattening period followed by a booster injection at 180 days of age in the fattening period. A total of 36 pigs divided in 3 groups of 12 pigs was vaccinated against Aujeszky’s disease according to the treatment groups. Vaccine IM administrations were performed under a 2.0- mL dose following reconstitution according to the manufacturer recommendations (i.e. mixing 100 mL O/W adjuvant mixed with a 50-dose freezed-dried virus pellet). Intra-dermal administrations were performed using a needle-free injection device (VALERY® device, equipped with a nose-piece adapted for 0.2 mL ID injection, Giordano Poultry-Plast, Caraglio, Italy) under a 0.2-mL dose prepared by mixing 10 mL O/W adjuvant mixed with 50-dose freezed-dried virus powder. Serum samples were collected from each pig before primo-immunization, one month later and one month following booster injection. Routine gE and gB ELISA assays were conducted at IZSLER (Brescia, Italy). No adverse event was observed following vaccine administration whatever the vaccination protocol. No seroconversion against gE protein did occur thus confirming the absence of viral circulation in the pigs in the conditions of the study. In this context, a clear seroconversion against gB protein following primoimmunization was evidenced following each vaccination protocol with no difference evidenced between groups (Kurskall-Wallis test, p>0.27). A clear increase in gB antibody titer was also observed following the ID booster whatever the vaccination protocol applied for the primo-immunization. The vaccination programs against Aujeszky’s disease tested in this study included 2 to 3 ID injections with AKIPOR 6.3 at an adjusted dose in 0.2 mL O/W adjuvant and appeared to be similarly potent to elicit a satisfying serological response. These findings corroborate previous results obtained in similar conditions where only the booster injection was administrated intra-dermally.