Protection of laying hens against Salmonella Enteritidis by immunization with type 1 fimbriae

Eighteen chickens were immunized subcutaneously with purified type 1 fimbriae from Salmonella enterica serotype Enteritidis at 18 and 21 weeks of age. Evidence of IgG and IgA responses was found in the eggs and in the sera of the immunized hens. Three weeks later, immunized and non-immunized chickens (n=18) were challenged intravenously with 2x10(7) live Salmonella enterica serotype Enteritidis. There was no significant difference in the numbers of eggs laid by immunized and non-immunized birds. The percentage of Salmonella contaminated eggs was significantly higher in the non-immunized group than in the immunized group due to a higher percentage of contamination of the externally disinfected egg shells. There were no statistical differences in the percentages of contaminated yolks and egg whites between control and immunized birds. No differences in the number of colonizing bacteria could be found in the spleen nor in the liver between the immunized and the control groups throughout the experiment. Salmonella was cleared from the ovary of the immunized birds in the second week p.i., in contrast to the control birds where Salmonella was isolated till the third week after infection. Oviducts were significantly more infected in the control group than in the immunized group. Salmonella was cleared from the oviducts at 3 weeks p.i. in the immunized hens but not in the control hens. In conclusion, we demonstrated that the immunization of laying hens with type 1 fimbriae reduced the number of contaminated eggs and reduced the colonization of the reproductive organs.