Submitted to: Avian Diseases
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/25/2003
Publication Date: 7/1/2003
Citation: HOLT, P.S., GAST, R.K., KELLY-AEHLE, S. USE OF A LIVE ATTENUATED SALMONELLA TYPHIMURIUM VACCINE TO PROTECT HENS AGAINST S. ENTERITIDIS INFECTION WHILE UNDERGOING MOLT. AVIAN DISEASES. 2003. 47:656-661. Interpretive Summary: Induced molting is an extremely important procedure for the table egg industry to achieve a second egg lay from aging layer flocks. It is estimated that over 70% of layer flocks are molted annually in the U.S., affecting more than 160 million hens. We had shown previously that this important industry tool could cause problems with Salmonella enteritidis (SE) infections so we examined methods to reduce this problem. One solution was to immunize hens prior to molt with a commercially available live Salmonella vaccine. Upon SE challenge, hens that had received this vaccine released less SE in their feces than nonvaccinated hens and there was also less SE found in livers, spleens, and ovaries. These results indicate that SE problems that may occur during molt can be minimized by prior vaccination of hens with a live Salmonella vaccine, enabling producers to retain this important management tool while ensuring the safety of eggs reaching the consuming public.
Technical Abstract: Previous studies demonstrated that Salmonella enteritidis (SE) infections in hens undergoing molt via feed withdrawal were more severe than in full fed hens. Two trials were conducted to determine whether immunizing hens with Megan®Vac1, a commercially-available attenuated S. typhimurium vaccine, would reduce transmission of SE from infected hens to noninfected but contact-exposed hens during a molt. In Trial 1, one group of hens received 2 doses of vaccine by coarse spray two weeks apart while a second group of hens remained nonvaccinated. In Trial 2, the vaccinated group received only one dose of vaccine. Two weeks following the final immunization, feed was removed from all the hens and on Day 4, the center hen in rows of 11 hens were challenged with SE and transmission to the nonchallenged hens was followed 3, 10, 17, and 24 days later. Vaccination reduced the horizontal spread of SE in vaccinated hens compared to their nonvaccinated counterparts, with vaccinated hens shedding significantly less SE on Day 10 post challenge in Trial 1, and Days 3, 10,17, and 24 in Expt, 2. Recovery of SE from ovaries was significantly reduced in the vaccinated hens in Trial 1, and from livers/spleens, ovaries, and ceca in Trial 2. These studies indicate that immunization of hens with a live S. typhimurium vaccine could help reduce SE problems during a molt situation.