Background and Aims: The incidence of vvIBDV in Croatia by 1995 seems to be a consequence of the global spread and resulted in up to 60% and 20% mortality of layers and broilers, respectively. Vaccination of parent stock with a live vaccine and revaccination with an inactivated vaccine at point of lay in order to ensure transfer of maternal antibodies (MN-Abs) to progeny, was proposed as a prophylactic measure. For this purpose an inactivated vaccine, adjuvanted by a multiple water-in-oil-in-water emulsion (WOWE) of low viscosity, was designed. IBDV-WOWE vaccine was tested in order to determine its ability to elicit a level of specific Abs in parents which should result in improved progeny protection. Methods: Winterfield 2512 strain of IBDV, inactivated with 0.1% v/v formalin, was prepared in WOWE. WOWE characterised low content of mineral oil (30% v/v), high aqueous/oil ratio (2/1), low relative viscosity (h = 3.45) and high hydrophile-liophile balance (HLB = 9.35). It contained 3.3% w/v of both aqueous- (Tween 80) and oil-phase surfactants (Aralcel 83). Flocks of 4500 light ISA Brown SSL layers and 2400 heavy Hybro breeders, aged 10 days, were vaccinated in field conditions by a live IBDV vaccine (Gumbokal, Pliva, Zagreb, Croatia) in drinking water. At the age of 19 and 18 weeks light and heavy pullets, respectively, were both divided in three equal groups and i.m. vaccinated with 1.0, 0.5 or 0.25 ml vaccine/bird. Serological response was monitored during whole laying period. Eggs, collected 31 weeks after vaccination of dams, were hatched. Sera from 3- and 10-day-old hatched chickens were analysed for the presence of MN-Abs. Results and Conclusions: WOWE contributes to the stability, low viscosity and injectability of IBDV vaccine without side effects. Serological responses (ELISA-titers) in both light and heavy breeders were directly related to the doses of the vaccine administered. A single vaccination generated high and long-lasting humoral immunity and no additional vaccinations were required during laying period. The vaccination with IBDV-WOWE vaccine did not influence on egg production. The levels of specific Abs in egg yolks were at least twice higher than those in the sera of vaccinated dams. Anti-IBDV antibodies were transferred to progeny. ELISA-titer of MN-Abs in sera of 3-day-old offspring was about 2800 and declined till the 10th day of life.

Temeljne medicinske znanosti,Veterinarska medicina