VACCINATION OF CHICKENS WITH STRAIN CVL30, A GENETICALLY DEFINED SALMONELLA-ENTERITIDIS AROA LIVE ORAL VACCINE CANDIDATE

Newly hatched chicks were vaccinated orally with a genetically defined Salmonella enteritidis aroA candidate, strain CVL30. In chickens immu nized with 10(5) or 10(9) CFU and challenged by the intravenous route with 10(8) CFU of S. enteritidis 109 Nal(r) at 8 weeks old, there were similar reductions in colonization of the spleens, livers, and ceca o f vaccinees compared with unvaccinated controls. Two groups of newly h atched female chicks were vaccinated orally with 10(9) CFU of strain C VL30, and one group was revaccinated intramuscularly with 10(9) CFU at 16 weeks old, When challenged intravenously with S. enteritidis 109 N al(r) at 23 weeks old, there was a reduction in the colonization of sp leens, livers, ovaries, and ceca compared with unvaccinated controls. Inclusion of the intramuscular booster gave increased protection to th e ovary, although the vaccine strain was isolated on one occasion from a batch of eggs laid at 20 weeks old. In chickens immunized with 10(9 ) CFU of strain CVL30 and challenged orally with 10(9) CFU of S. enter itidis 109 Nal(r), there was a reduction in intestinal shedding bf the challenge strain from vaccinees compared with unvaccinated controls. Circulating immunoglobulin G antibodies to lipopolysaccharide (LPS) we re detected in unvaccinated controls within 7 to 10 days of oral chall enge. In contrast, circulating immunoglobulin G antibodies to LPS in v accinees were not altered by the oral challenge, which suggested that vaccination reduced or prevented invasion by the challenge strain from the gut or multiplication of the challenge strain in the tissues. New ly hatched chicks were vaccinated orally with ca. 10(9) CFU of strain CVL30, and 1 day later, the vaccinees and unvaccinated controls were c hallenged orally with 10(5) or 10(9) CFU of S. enteritidis 109 Nal(r). Colonization of the ceca and invasion from the gut by the S., enterit idis challenge strain nas reduced in the vaccinees up to 5 days postch allenge compared with controls. In a second trial, vaccinees and contr ol were challenged orally with 10(7) or 10(9) CFU of S. typhimurium 23 91 Nal(r) in contrast to the challenge with S. enteritidis, colonizati on of the ceca and invasion by the S. typhimurium strain were not grea tly reduced.