Protection conferred by a live Salmonella Enteritidis vaccine against fowl typhoid in laying hens

Fowl typhoid is under control in poultry farms of developed countries, but it still endemically subsists in commercial laying hen farms of some countries. It has been demonstrated that Salmonella live vaccines can elicit cross-immunity against members of the same Kauffmann-White scheme serogroup. In this work, we explored the protection conferred by TAD Salmonella vac E, a live Salmonella enterica serovar Enteritidis vaccine, against fowl typhoid. Three groups of laying hens were vaccinated with different vaccination schedules starting on the first day of life, and afterwards were infected with 2 x 10(5) CFU of a virulent Salmonella Gallinarum strain, either at wk 28 or wk 52. Mortality, fecal shedding, and organ invasion of Salmonella Gallinarum were assessed. In this work we demonstrated that this Salmonella Enteritidis vaccine is able to cross-immunize against Salmonella Gallinarum. At wk 28, hens vaccinated with three oral doses or with two oral doses combined with one subcutaneous dose were protected by the vaccine. At wk 52, when hens were infected 36 wk after the final immunization, the vaccine was not able to confer protection. Thus, revaccination every 3 mo would be highly recommended. In countries where Salmonella Gallinarum subsists together with Salmonella Enteritidis, control programs should include vaccination of laying hens using safe attenuated Salmonella strains.     

Use of a live attenuated Salmonella typhimurium vaccine to protect hens against Salmonella enteritidis infection while undergoing molt

Previous studies demonstrated that Salmonella enteritidis infections in hens undergoing molt via feed withdrawal were more severe than in full fed hens. We conducted two trials to determine if immunizing specific-pathogen-free, Salmonella-culture-negative hens via aerosol exposure to MeganVacl, a commercially available attenuated Salmonella typhimurium vaccine, would reduce transmission of S. enteritidis from infected hens to uninfected but contact-exposed hens during a molt. In trial 1, one group of hens received two aerosol doses of vaccine 2 wk apart whereas a second group of hens remained nonvaccinated. In trial 2, the vaccinated group received only one dose of vaccine. Two weeks after the final immunization, feed was removed from all the hens, and on day 4, the center hen in rows of 11 hens received a dose of 3 x 10(5) (trial 1) or 1.3 x 10(6) (trial 2). Transmission to the unchallenged hens was followed 3, 10, 17, and 24 days later. Vaccination reduced the horizontal spread of S. enteritidis in vaccinated hens compared with their nonvaccinated counterparts, with vaccinated hens shedding significantly less S. enteritidis on day 10 postchallenge in trial 1 and on days 3, 10, 17, and 24 in trial 2. Recovery of S. enteritidis from ovaries was significantly reduced in the vaccinated hens in trial 1 and from livers/spleens, ovaries, and cecum in trial 2. These studies indicate that immunization of hens with a live S. typhimurium vaccine could help reduce S. enteritidis problems during a molt situation.     

Duration of immunity induced in chickens by an attenuated live Salmonella enteritidis vaccine and an inactivated Salmonella enteritidis/typhimurium vaccine

The aim of this study was to examine the duration of immunity of different vaccination schemes using the S. enteritidis live vaccine Gallivac Se and the S. enteritidis-S. typhimurium inactivated vaccine Gallimune Se+St. Three groups of Lohman Brown chickens were used. Group one was vaccinated three times orally with Gallivac Se at weeks one, seven and 13 of age. Group two was vaccinated twice orally with Gallivac Se in weeks one and seven and once i.m. with Gallimune Se+St in week 14 of age. A third group was not vaccinated and served as the control group. Eight randomly selected chickens from each of the three groups were challenged with a nalidixic acid resistant S. enteritidis PT4 strain in weeks 24, 51 and 71 of age and the same number of animals were challenged with a S. typhimurium DT 104 strain in weeks 26, 54 and 73 (75) of age.The chickens were euthanised seven days post challenge and the number of challenge strain organisms (log10 cfu) in the liver and on caecal mucosa was determined.The quantitative investigation of the challenge strain in the liver and caecal mucosa revealed a statistically significant (p < 0.05) lower challenge strain burden in the vaccinated groups compared with the non-vaccinated control group up to week 71 (73) of age. The protective effects were demonstrated for both challenge strains.     

The effect of killed Salmonella enteritidis vaccine prior to induced molting on the shedding of s. enteritidis in laying hens

Effects of administering killed Salmonella enterica serovar enteritidis (SE) vaccines to laying hens prior to induced molting on egg production and on shedding of SE were investigated. Forty hens were vaccinated with one of two SE vaccines available commercially in the United States and Japan. Twenty-five days after vaccination, feed was withdrawn for 2 wk from 20 vaccinated plus 10 unvaccinated hens to induce molt. Four days after molt induction, all hens were challenged with a dose of 2.4 X 10(9) of SE. For the 25 days following administration of the SE bacterins, egg production in vaccinated hens showed approximately a 15% decrease. After molt induction, egg production in molted hens ceased and then returned to normal levels 8 or 9 wk postvaccination. Through the 3-mo experimental period, the decreases in numbers of eggs laid in the unvaccinated/molted group and two vaccinated/molted groups were 225 (26.2%), 245 (28.4%), and 274 (31.9%), respectively, compared with 860 in the unvaccinated/unmolted group. There was no significant difference in egg lay at the P < 0.05 level among the former three groups. Hens in the vaccinated/molted groups shed about two logs less SE than hens in the unvaccinated/molted group 3 14 days postchallenge (P < 0.05 or 0.01). These results indicate that vaccination prior to induced molting might be effective in preventing the exacerbation of SE problems within flocks in which the potential for SE contamination may exist.     

牛至油对成年蛋鸡生长性能和免疫功能的影响

本试验旨在研究不同水平的牛至油添加对蛋鸡生产性能及免疫功能的影响。选取30周龄海兰灰商品蛋鸡300只,随机分为5组(每组6个重复,每个重复10只):对照组饲喂基础饲粮,试验A、B和C组饲喂分别添加50,100和150mg/kg牛至油的试验饲粮,抗生素组饲喂添加100 mg/kg硫酸抗敌素的试验饲粮,试验期60d。结果表明:整个试验期各组间蛋鸡日采食量无显著差异(P>0.05),A和B组蛋鸡产蛋率显著高于对照组(P<0.05),料蛋比显著降低(P<0.05);A、B和C组蛋鸡血清中免疫球蛋白IgG含量比对照组有显著提高(P<0.05);试验30和60d,A组蛋鸡血清新城疫抗体滴度显著高于对照组(P<0.05);牛至油对蛋鸡脾脏指数无显著性影响(P>0.05);A组蛋鸡脾脏中的CD4+百分含量比对照组有所提高(P>0.05),CD8+百分含量显著低于对照组(P<0.05),而CD4~+/CD8~+显著升高(P<0.05);A组脾脏中IL-2和IL-4mRNA的表达量显著升高(P<0.05)。由此可见,饲粮添加牛至油能提高蛋鸡的生产性能和免疫功能,以50mg/kg牛至油为最适添加量。     

Cross-protection against Salmonella Typhimurium infection conferred by a live attenuated Salmonella Enteritidis vaccine

In this study, a genetically engineered live attenuated Salmonella Enteritidis (SE) vaccine was evaluated for its ability to protect against Salmonella Typhimurium (ST) infection in chickens. The birds were orally primed with the vaccine on the 1st day of life and given an oral booster at 5 wk of age. Control birds were orally inoculated with phosphate-buffered saline. Both groups of birds were orally challenged with a virulent ST strain at 9 wk of age. Compared with the control chickens, the vaccinated chickens had significantly higher levels of systemic IgG and mucosal IgA against specific ST antigens and a significantly greater lymphoproliferative response to ST antigens. The excretion of ST into the feces was significantly lower in the vaccinated group than in the control group on days 9 and 13 d after challenge. In addition, the vaccinated group had significantly fewer pronounced gross lesions in the liver and spleen and lower bacterial counts in the internal organs than the control group after challenge. These data indicate that genetically engineered live attenuated SE may induce humoral and cellular immune responses against ST antigens and may confer protection against virulent ST challenge.     

Combination of competitive exclusion and immunization with an attenuated live Salmonella vaccine strain in chickens

To use the advantages of both the competitive exclusion (CE) technique and immunization with a live Salmonella vaccine, the combination of these methods was studied. Specific-pathogen-free chickens were pretreated by combined or single administration of a CE culture and a commercial live Salmonella typhimurium vaccine on days 1 and 2 of life and challenged with Salmonella typhimurium on day 3 to study the exclusion effect by both the CE preparation and the Salmonella vaccine. The exclusion effect by the CE culture combined with the immunologic effect by the live vaccine was studied after challenge of the birds on day 43 of age. The number of challenge organisms in ceca was used to evaluate the efficacy of the pretreatment. The protective exclusion effect of the CE culture was substantial in very young chicks and still detectable in 6-wk-old birds. The attenuated Salmonella typhimurium vaccine produced only an initially occurring exclusion effect. Because the exclusion effect of the CE culture was considerably stronger than the exclusion effect of the attenuated Salmonella typhimurium vaccine, the combination of both did not result in an additive protective effect. In order to exploit the exclusion potential between Salmonella strains and to attain an additive exclusion effect by a CE culture and a vaccine strain, live Salmonella vaccines are needed that are sufficiently attenuated without affecting genes essential for colonization exclusion of other Salmonella organisms. In 6-wk-old birds, the exclusion effect by the CE culture combined with the immunologic effect by the live Salmonella vaccine resulted in a degree of protection considerably beyond that generated by the exclusive use of the two methods. The administration of the live Salmonella vaccine strain prior to or simultaneously with the CE culture revealed the best protective effect because such combinations ensure an adequate persistence of the vaccine strain as prerequisite for the expression of an exclusion effect in very young chicks and the development of a strong immune response affording protection in older birds.     

Comparison of a live attenuated Salmonella Enteritidis vaccine candidate secreting Escherichia coli heat-labile enterotoxin B subunit with a commercial vaccine for efficacy of protection against internal egg contamination by Salmonella in hens

This study compared a new live attenuated Salmonella Enteritidis vaccine candidate secreting Escherichia coli heat-labile enterotoxin B subunit (SE-LTB) with a commercial Salmonella Enteritidis (SE) vaccine for efficacy of protection against SE infection in laying hens. Chickens were divided into 3 groups of 20 each. Group A chickens were inoculated orally with phosphate-buffered saline and served as controls, group B chickens were inoculated orally with the vaccine candidate, and group C chickens were inoculated intramuscularly with a commercial vaccine, the primary inoculation in groups B and C being at 10 wk of age and the booster at 16 wk. Groups B and C showed significantly higher titers of plasma immunoglobulin G, intestinal secretory immunoglobulin A, and egg yolk immunoglobulin Y antibodies compared with the control group, and both vaccinated groups showed a significantly elevated cellular immune response. After virulent challenge, group B had significantly lower production of thin-shelled and/or malformed eggs and a significantly lower rate of SE contamination of eggs compared with the control group. Furthermore, the challenge strain was detected significantly less in all of the examined organs of group B compared with the control group. Group C had lower gross lesion scores only in the spleen and had lower bacterial counts only in the spleen, ceca, and ovary. These findings indicate that vaccination with the SE-LTB vaccine candidate can efficiently reduce internal egg and internal organ contamination by Salmonella and has advantages over the commercial vaccine.     

Serological detection of experimental Salmonella enteritidis infections in laying hens

The antibody response of laying hens to experimental Salmonella enteritidis infection was evaluated in microagglutination, tube agglutination, and rapid whole-blood plate agglutination assays. Hens of three different ages were infected by either oral inoculation or horizontal contact transmission. Blood was collected at weekly intervals, and the presence of specific antibodies was assessed by reaction with antigens prepared from strains of S. enteritidis and S. pullorum. The sensitivity of detection of infected hens did not vary significantly between the assays, as all three tests effectively identified most exposed hens as seropositive. Within each test, however, variation was observed in the detection sensitivity when different antigens were used. The microagglutination titers of serum samples were determined by serial dilution. Antibody titers peaked at 1 to 2 weeks postinoculation and declined steadily, although most birds were still identified as seropositive at 10 weeks postinoculation. The mean microtest titers obtained with S. enteritidis antigens were higher than with an S. pullorum antigen, indicating greater test sensitivity. However, use of the S. pullorum antigen resulted in fewer false positives when sera from uninfected control hens were tested. The titers of contact-exposed hens peaked later and at lower values than did those of inoculated hens, but these two groups of hens had similar antibody titers after the third week postinoculation.     

Persistence of immunity in commercial egg-laying hens following vaccination with a killed H6N2 avian influenza vaccine

The California poultry industry experienced an outbreak of H6N2 avian influenza beginning in February 2000. The initial infections were detected in three commercial egg-laying flocks and a single noncommercial backyard flock but later spread to new premises. The vaccination of pullet flocks with a commercially prepared, killed autogenous vaccine prior to their placements on farms with infected or previously infected flocks was used as a part of the eradication programs for some multiage, commercial egg production farms. The purpose of this study was to follow three vaccinated flocks on two commercial farms to track the immune responses to vaccination. The antibody-mediated responses of the three flocks followed in this study were markedly different. One flock achieved 100% seroconversion at 12.5 wk of age, but by 32 wk of age, all of the hens were seronegative by agar gel immunodiffusion (AGID). In contrast, at 32 wk of age, flocks from the other farm (flocks 2A and 2B) were 95% and 72% seropositive by AGID, respectively. Of the differences that were identified between the vaccination protocols on the two farms, the distinction that could explain the level of disparity between responses is the delivery of the second dose of vaccine with a bacterin on the first farm, which may have interfered with the persistence of immunity in this flock. Hens from flocks 2A and 2B were experimentally challenged at 25 wk of age with H6N2 avian influenza virus. Hens from flock 2A did not transmit virus to naive contact-exposed hens, but hens from flock 2B did. At 34 wk of age, hens from flock 2A were again challenged and naive contact-exposed hens were infected in this second trial. These challenge experiments served to demonstrate that despite detectable antibody responses in flocks 2A and 2B, the birds were protected from infection for less than 21 wk after the second vaccination.     

牛磺酸对老龄蛋鸡体内抗氧化作用影响的研究

试验选用504只59周龄海兰褐蛋鸡,随机分为7组,每组3个重复,每个重复24羽。预试期1周,正试期又分为60～64周和64～68周两阶段,在各组鸡饲粮中分别添加0、0.005%、0.01%、0.02%、0.04%、0.08%、0.16%的牛磺酸,研究牛磺酸对蛋鸡抗氧化能力的影响,并初步探讨其影响机制。研究结果表明:(1)试验前期0.005%、0.16%水平牛磺酸添加组蛋鸡全血谷胱甘肽过氧化物酶(GSH-Px)活性显著升高(P<0.05),且0.16%组在试验后期全血GSH-Px活性也显著升高(P<0.05);添加牛磺酸64周龄蛋鸡血清超氧化物歧化酶(SOD)活性没有升高,68周龄SOD活性升高,并且0.08%组酶活极显著升高(P<0.01)。(2)添加牛磺酸可以显著降低蛋鸡心、脑脂褐质含量(P<0.05),其中0.005%添加效果最好。另外,日粮中添加牛磺酸降低了试验后期蛋鸡血清丙二醛含量,其中0.005%、0.02%、0.04%、0.08%组差异显著(P<0.05)。总体上以添加0.005%水平牛磺酸提高蛋鸡抗氧化能力的效果最佳。     

槲皮素对蛋黄卵磷脂含量的影响

试验将29周龄海赛蛋鸡240只随机分4组,每组6个重复,每个重复10只鸡,对照组饲喂基础饲粮,试验组在基础饲粮基础上分别添加0.02%、0.04%和0.06%槲皮素,预试期1周,试验共8周。旨在研究饲粮中添加槲皮素对蛋黄卵磷脂含量的影响。结果表明,与对照组相比,0.04%槲皮素组蛋黄卵磷脂与粗脂肪含量分别显著提高19.86%和5.81%(P<0.05);0.02%槲皮素组血清游离脂肪酸(FFA)含量显著升高(P<0.05);0.04%槲皮素组血清极低密度脂蛋白胆固醇(VLDL-C)、载脂蛋白B(apo-B)、载脂蛋白A1(apo-A1)含量均显著升高(P<0.05);0.04%槲皮素组血清雌二醇(E2)、胰岛素(INS)含量与0.02%槲皮素组胰岛素(INS)含量均显著升高(P<0.05)。由此可见,一定剂量槲皮素能通过改善蛋鸡内分泌活动,提高血脂水平来提高蛋黄卵磷脂含量。     

槲皮素对蛋鸡胆固醇代谢的影响

采用单因素试验设计,选体重和产蛋率相近的29周龄蛋鸡240只,随机分为4组,每组6个重复,每重复10只鸡。在玉米-豆粕型饲粮基础上添加0、0.02%、0.04%和0.06%槲皮素,进行8周的饲养试验。研究槲皮素对蛋鸡的血脂、鸡蛋胆固醇和甘油三酯、肝脏胆固醇和甘油三酯、血清雌激素和胰岛素的影响。结果表明,与对照组相比,0.04%槲皮素可显著降低血清甘油三酯含量(P<0.05);0.02%、0.04%槲皮素极显著降低蛋黄胆固醇含量(P<0.01),三个剂量槲皮素均可显著降低肝脏胆固醇含量(P<0.05),但对肝脏和蛋黄甘油三酯含量无显著影响(P>0.05);0.04%槲皮素可显著提高血清胰岛素和雌二醇含量(P<0.05)。由此可见,一定剂量槲皮素能降低鸡蛋中胆固醇含量,最适添加量为0.04%。     

Effects of dietary boron supplementation on laying hens

1. The effects of dietary boron on egg production and on the ultimate shear force, stress, and fracture energy of the tibia, femur, humerus, and radius from White Leghorn laying hens were investigated.

2. The shear force, stress, and fracture energy of the bones were not affected by increasing dietary concentrations of boron.

3. Egg production, food consumption and body weight were suppressed at a dietary boron concentration of 400 mg/kg.

4. Boron concentrations increased significantly in all tissue samples tested in birds given 400 mg/kg dietary boron.     

Salmonella in Belgian laying hens: an identification of risk factors

Since the 1980s, the prevalence of Salmonella in Belgian poultry layers and broilers has greatly fluctuated with a rise observed in 2003 and a significant decrease in 2005. In order to alleviate the risk at egg consumer level, it is crucial to understand the factors which influence the contamination and the spread of Salmonella in laying hens. To study such determinants we explored the Belgian data from the 2005 baseline study on the prevalence of Salmonella in laying flocks of Gallus gallus in the European Union. The response variables corresponded to presence or absence of Salmonella from dust and faecal samples taken from the environment of a Belgian layer flock. The explanatory variables included: region of Belgium, sampling time (month the flock was sampled), production type (cage or barn and free range), Salmonella vaccination status, flock age and flock size. Analyses of these data were performed using a bivariate logistic regression model assuming independence between the two responses and bivariate generalized estimating equations model, which incorporates the correlation between the two responses on the same flock. The main risk factor that was identified was rearing flocks in cages compared to barns and free-range systems. The results also showed a significant higher risk for Salmonella for a 1 week increase in flocks’ age as well as with a unit increase in the size of the flock.     

Effects of temperature and stabilizer on the viability of a live attenuated avian metapneumovirus vaccine

A commercial live attenuated, freeze-dried avian metapneumovirus vaccine, Pneumomune, was assessed for its viability at three different temperatures (5.6 C, 21 C, and 37 C). No significant reduction in virus titer was observed when the vaccine was stored at 5.6 C for a period of 24 hr. However, reductions in virus titer of 1 log10 and 2 log10 were observed after 24 hr at 21 C and 37 C, respectively. Batch-to-batch variation in virus reduction was also observed. The addition of a dye or a vaccine stabilizer to the vaccine preparation did not have any deleterious effect on the survival of vaccine virus.     

Prevalence and antimicrobial resistance of Salmonella isolates in Moroccan laying hens farms

Increasing emergence of salmonellosis presents a threat to the effective control of foodborne disease in humans. The purpose of this study was to evaluate the prevalence of drug susceptibility and molecular characteristics of non-typhoidal Salmonella (NTS) isolated from laying hens (LH) in 3 Moroccan regions, Rabat-Salé-Zemmour-Zaër (RSZZ), Souss-Massa-Drâa (SMD), and the grand Casablanca (GC). A total of 351 samples were collected from 30 consumer egg laying houses at the end of the egg laying period from April to July 2011. Sixty-four out of these 351 examined samples were contaminated by Salmonella. The Salmonella isolated strains were then serotyped and tested for drug susceptibility and analyzed by polymerase chain reaction (PCR) for the presence of the invasion-associated genes invA and spvC and nalidixic acid resistance-associated qnr gene. The prevalence of NTS infection in LH was estimated to be 73.3%. Seven Salmonella enterica serovars were identified: Enteritidis (37.5%), Kentucky (31.2%), Infantis (10.9%), Typhimurium (6.2%), Thompson (6.2%), Agona (4.6%), and Amsterdam (3.1%). Drug susceptibility testing showed that 65.6% of Salmonella were resistant to at least one antibiotic and 25% were resistant to ciprofloxacin. All isolates were positive for the invasion gene invA and 28% of them were positive for the virulence gene spvC. All nalidixic acid-resistant S. Enteritidis isolates were negative for qnr plasmid genes. Our findings clearly suggest the necessity to establish an NTS monitoring and control program for LH in Morocco.