[Transmissible gastroenteritis: vaccination of sows in contaminated environment using inactivated virus in oil emulsion].

An oil emulsion vaccine against TGE was prepared using a virus suspension produced in tissue culture and inactivated by formaline. Intramuscular vaccination trials were performed on sows in the field from two herds (167 sows) which had been infected by TGE virus more than one year previously. Considering qualities of immunity after natural infection, the objective of the work was to try to give a new impetus to immunity in such herds using vaccination as a booster. After two vaccine injections the serological pattern of the herd was modified: negative serological reaction disappeared, the proportion of highly positive serological reactions increased and higher homogeneity was observed in the distribution of levels of neutralizing antibody reactions. In contrast, using protection tests in piglets against virulent challenge, there was no evidence of significant differences between litters from vaccinated sows (86% of piglets were protected) and those of unvaccinated sows (89% of piglets were protected). Our results suggest that passive protection given to piglets by lactogenic immunity following natural infection could last all the economic life of the sow. The interest of the vaccination as a booster of mammary immune response and its epidemiological consequences are discussed.