Turkey Vaccine Research Articles

Vaccination of turkeys against Chlamydophila psittaci through optimised DNA formulation and administration

We have demonstrated that vaccination of turkeys with an unformulated DNA vaccine induces significant protection against Chlamydophila (Cp.) psittaci infections. Nevertheless, the immunogenicity of the DNA vaccine can still be improved by increasing translation and transfection efficiency. Therefore, the ompA codon was adapted to the codon usage in birds, resulting in pcDNA1/MOMPopt. To increase gene transfer, polyplexes of pcDNA1/MOMPopt–EGFP with different cationic polymers, such as linear and branched polyethyleneimine (lPEI and brPEI) and starburst PAMAM dendrimers, and lipoplexes with cationic DOTAP/DOPE liposomes were created. Transfection of lPEI and brPEI polyplexes with an N/P ratio of 8 resulted in the highest transfection efficiencies, but lPEI polyplexes were completely destroyed following nebulisation. Secondly, we examined the capacity of nebulised or intramuscularly (IM) administered brPEI-pcDNA1/MOMPopt to induce a significant protective immune response in SPF turkeys experimentally infected with 108 TCID50 of a virulent Cp. psittaci strain. Results were compared to IM administration of naked plasmid DNA and to results of non-vaccinated animals. Intramuscular administration of brPEI-pcDNA1/MOMPopt increased the immunogenicity of the Cp. psittaci DNA vaccine as compared to IM administration of pcDNA1/MOMPopt or aerosol delivery of brPEI-pcDNA1/MOMPopt. Improved immunogenicity was correlated with increased protection. Vaccinated groups were significantly protected against Cp. psittaci challenge.

Efficacy of Single Dose Recombinant Herpesvirus of Turkey Infectious Bursal Disease Virus (IBDV) Vaccination Against a Variant IBDV Strain

The use of viral vectors for transgenic expression of immunogenic proteins is a current trend in the poultry industry. The objective of this work was to assess the protection against the variant E of infectious bursal disease virus (IBDV), conferred by day-one vaccination with a commercial recombinant herpesvirus of turkey (HVT) vaccine (VAXXITEK) expressing the immunogenic viral protein 2 from a classical IBDV. In separate trials, 1-day-old specific-pathogen-free (SPF) or broiler chickens were vaccinated by the subcutaneous route and challenged with the variant E strain at 18 or 28 days of age. Bursa/body weight ratio and bursal histopathology were assessed as protection criteria. Protection was demonstrated at both challenge points, bursal indexes in vaccinated SPF and broiler groups were significantly higher than in the challenged controls. The commercial vaccine protected against bursal damage as indicated by significantly lower bursal lesion scores in the vaccinated birds. These experimental results indicate that a single dose of the recombinant HVT-IBDV confers protection against variant E challenge even though the VP2 expressed by the recombinant herpes virus belongs to a standard strain.

Estimated mortality and hospital admission due to rotavirus infection in the WHO European region

In 2006 two rotavirus vaccines were licensed for use in young children in Europe. This study aimed to estimate the mortality and hospital admissions due to rotavirus in children aged <5 years in the WHO European region using data from routine sources and published literature. We grouped 49/52 countries in the region by their World Bank Gross National Income (GNI) per capita. We obtained for children aged <5 years: populations, hospital discharges for diarrhoeal disease, estimated mortality rates and the percentage of deaths attributable to diarrhoeal disease, from WHO data sources or published literature, and combined them to estimate country-specific diarrhoeal disease mortality. Rotavirus-attributable percentages of hospital admissions due to diarrhoeal disease were obtained through a literature search, and an income-group median applied to countries in each GNI category. In the countries we studied in the WHO European region, rotavirus infection causes an estimated 6550 deaths (range 5671-8989) and 146 287 (range 38 374-1 039 843) hospital admissions each year in children aged <5 years. Hospital admission rates were similar across income groups (medians 2.0, 2.8, 4.2 and 1.9/1000 per year in low-, lower-middle-, upper-middle- and high-income countries, respectively). Seven countries, mostly in the low- and lower-middle-income groups, accounted for 93% of estimated deaths. Disease burden varied dramatically by income level in the European region. Rotavirus vaccination in Azerbaijan, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, Uzbekistan and Turkey could potentially prevent 80% of all regional rotavirus deaths. Data from low-income countries is still sparse, and improved disease burden studies are required to better inform regional vaccine policy.

Cloned Histomonas meleagridis passaged in vitro resulted in reduced pathogenicity and is capable of protecting turkeys from histomonosis

Histomonas meleagridis is a flagellated protozoan parasite and the aetiological agent of histomonosis (histomoniasis or blackhead disease), a severe disease in poultry with very limited options for treatment. In the present investigation an inactivated vaccine, based on destroyed parasites and administered by intramuscular injection, failed to induce an efficient protection against a severe challenge. By cloacal infection of 14-day-old turkeys with cloned protozoa passaged in vitro for 95, 215 or 295 times, respectively, severe attenuation could be demonstrated as none of the infected birds died. Following infection with one of the higher passages, the birds resisted the challenge with virulent parasites. Using this approach no mortality due to histomonosis could be recorded in all of the 42 birds subjected to vaccination, either through direct infection or kept as in-contact birds, whereas all of the control animals died. Pathological lesions in the liver and caeca were only noticed in a few birds. The absence of parasitic DNA in the liver of vaccinated birds confirmed the effect of vaccination. For the first time vaccination of turkeys is reported to induce a solid protection against a severe challenge, both based on a clonal culture of Histomonas meleagridis.

Expression of cytokine genes following pre- and post-hatch immunization of chickens with herpesvirus of turkeys

Induction of immune response as characterised by expression of cytokine genes in the spleen following immunization of pre- and post-hatch chickens with herpesvirus of turkeys (HVT) vaccine was studied. The pattern of expression of IFN-gamma and IL-10 genes in pre-hatch immunized chickens was different from that observed in post-hatch HVT immunized chickens. This expression pattern of cytokine genes was associated with significantly higher HVT transcripts in pre-hatch immunized chickens than in post-hatch immunized chickens. In conclusion, HVT immunization in chickens, irrespective of the age of immunization, stimulates host response characterised by the expression of cytokine genes, such as IFN-gamma and IL-10 in the spleen. However, the age of immunization appears to influence the temporal pattern of IFN-gamma and IL-10 expression as well as replication of HVT.

Molecular evaluation of responses to vaccination and challenge by Marek's disease viruses

A real-time quantitative polymerase chain reaction was utilized to study the in vivo replication of Marek's disease vaccine viruses and of virulent oncogenic strains. In the first of four experiments, the growth of the herpes virus of turkeys (HVT) vaccine was detectable in various organs of infected chicken embryos, with the highest viral loads being present in the spleen. No evidence was obtained for replication of serotype-1 Marek's disease viruses in embryos. In the second experiment, viral loads were measured in several organs of chickens after administration of the Rispens and HVT vaccines immediately after hatching. Lowest levels were noted for the Rispens strain after 1 to 8 weeks. By contrast, HVT vaccine grew well in all tested organs, with the highest loads being present in the spleen. Highest loads were observed in unvaccinated birds after challenge with the highly virulent strain MPF57 at day 8, especially in lymphoid organs. A positive relationship was observed between viral load and clinical signs, including tumour formation. In a third study, viral loads were measured in the organs of chickens administered the Rispens vaccine on the day of hatch and challenged at day 8 with MPF57. High levels of clinical protection were afforded against MPF57 by the Rispens vaccine but, in confirmation of earlier findings, sterilizing immunity was not induced. In a fourth study, two experiments were conducted—in which viral loads were measured after challenge of chickens vaccinated with HVT in ovo or at day 1 after hatching. Similar protection was achieved in birds vaccinated in ovo on embryonic days 11 and 17, although protection was slightly, but not significantly, lower than for birds vaccinated at day 1.

A genetically engineered prime-boost vaccination strategy for oculonasal delivery with poly( d,l-lactic- co-glycolic acid) microparticles against infection of turkeys with avian Metapneumovirus

In this study we demonstrated the use of an oculonasally delivered poly( d,l-lactic- co-glycolic acid) microparticle (PLGA-MP)-based and genetically engineered vaccination strategy in the avian system. An avian Metapneumovirus (aMPV) fusion (F) protein-encoding plasmid vaccine and the corresponding recombinant protein vaccine were produced and bound to or encapsulated by PLGA-MP, respectively. The PLGA-MP as the controlled release system was shown in vitro to not induce any cytopathic effects and to efficiently deliver the F protein-based aMPV-vaccines to avian cells for further processing. Vaccination of turkeys was carried out by priming with an MP-bound F protein-encoding plasmid vaccine and a booster-vaccination with an MP-encapsulated recombinant F protein. Besides the prime-boost F-specific vaccinated birds, negative control birds inoculated with a mock-MP prime-boost regimen as well as non-vaccinated birds and live vaccinated positive control birds were included in the study. The MP-based immunization of turkeys via the oculonasal route induced systemic humoral immune reactions as well as local and systemic cellular immune reactions, and had no adverse effects on the upper respiratory tract. The F protein-specific prime-boost strategy induced partial protection. After challenge the F protein-specific MP-vaccinated birds showed less clinical signs and histopathological lesions than control birds of mock MP-vaccinated and non-vaccinated groups did. The vaccination improved viral clearance and induced accumulation of local and systemic CD4+ T cells when compared to the mock MP-vaccination. It also induced systemic aMPV-neutralizing antibodies. The comparison of mock- and F protein-specific MP-vaccinated birds to non-vaccinated control birds suggests that aMPV-specific effects as well as adjuvant effects mediated by MP may have contributed to the overall protective effect.

Rubella Seroprevalence among Women of Childbearing Age Residing in a Rural Region: Is There a Need for Rubella Vaccination in Turkey?

Rubella Seroprevalence among Women of Childbearing Age Residing in a Rural Region: Is There a Need for Rubella Vaccination in Turkey?

Safety and Efficacy of the Mycoplasma synoviae MS-H Vaccine in Turkeys

The live, attenuated, temperature-sensitive Mycoplasma synoviae (MS) vaccine strain MS-H is used to control virulent MS infection in commercial chicken flocks. However, the safety of this vaccine and its potential to prevent disease in turkeys have not been investigated. In this study, MS-H was shown to colonize the upper respiratory system and to induce an antibody response in turkeys but, even at the maximum release dose, was not found to cause air sac, joint, or tracheal lesions typical of wild-type MS infection. Histopathologic examinations of the vaccinated turkeys after exposure to a virulent MS challenge revealed that administration of the vaccine by aerosol, but not eye drop, at the dose recommended for chickens protected the birds against microscopic lesions and colonization of the virulent MS in trachea. It is concluded that MS-H vaccine is safe for use in turkeys and, when used as aerosol at the dose recommended for commercial chickens, can protect turkeys against tracheal lesions caused by a wild-type MS strain.

Onset of immunity following in ovo delivery of avian metapneumovirus vaccines

Avian metapneumovirus (aMPV) is an important cause of disease in chickens and turkeys. As infection can occur early in life and spread of the virus throughout a flock is rapid, an early onset of immunity post-vaccination would be advantageous. We have studied the serological immune response and the onset of protective immunity of an aMPV vaccine delivered to chickens via the in ovo route compared to oculonasal delivery at day old. A 1000-fold lower dose delivered in ovo to chicken specific pathogen free (SPF) embryos, than vaccination at day old, provided a significantly higher antibody response. In the presence of maternally derived antibody (MDA), there was no significant difference in antibody response between the vaccination routes. However, the onset of immunity (OOI) for the vaccine delivered to MDA positive chicken embryos was 5 days post-hatch in comparison to 8 days post-hatch for the same dose of vaccine given at day old indicating that chicks would be protected against disease earlier in the field if vaccinated by the in ovo route. In further experiments the OOI for a turkey vaccine delivered to MDA positive turkey embryos was shown to be 8 days post-hatch.

Relationship between Marek's disease virus load in peripheral blood lymphocytes at various stages of infection and clinical Marek's disease in broiler chickens

Vaccination with herpesvirus of turkey (HVT) vaccine provides protection against clinical Marek's disease (MD) but does not preclude infection with wild-type MD virus (MDV). The quantity of MDV detected in circulating lymphocytes during the early period after infection may be a useful predictor of subsequent clinical MD later in the life. A study was designed to quantify MDV and HVT copy number in peripheral blood lymphocytes (PBL) using real-time polymerase chain reaction between days 5 and 35 post-challenge and to relate this to subsequent development of gross MD lesions. Female commercial broiler chickens were vaccinated with HVT or were sham-vaccinated at hatch, then challenged with MDV strain MPF-57 at day 2 post-vaccination and reared in positive-pressure isolators up to 56 days post-challenge, when all survivors were euthanized. All dead and euthanized chickens were examined post mortem for gross MD lesions. Birds were scored for MD lesions and mortality. MDV and HVT genome copy numbers were determined for each PBL sample. There was an increase in HVT load in PBL between days 7 and 37 post-vaccination, with marked increases between days 7 and 16 and again between days 30 and 37. There was a steady increase in MDV load to 35 days post-challenge. The mean MDV copy number (log(10)) was greater in chickens subsequently exhibiting gross MD lesions (5.05 +/- 0.21) than in those that did not (2.88 +/- 0.223), with the largest difference at 14 and 21 days post-challenge (P < 0.001). Quantification of MDV during early infection is therefore a potential tool for monitoring MD in broiler flocks.

Immunity against tetanus and effect of vaccination in Turkey

The immune status against tetanus in relation to vaccination was investigated among healthy populations in 3 selected provinces in Turkey (n=2094). In-house ELISA supplemented with the particle agglutination test was performed for this purpose. An exact correlation was found between vaccination status and immunity against tetanus. The immunity was high among children and sharply decreased with age among adults. The primary vaccination for children increased the immunity, reaching a geometric mean titer (GMT) of 6.2 IU/ml at the fourth dose. There was a reduction of immunity during the next y, followed by an increase with a booster injection at primary school age. Among adolescents and adults, the GMTs after the last vaccination fell off exponentially with a slope of -0.068 log10 IU/ml per y. Extrapolation of the regression line predicted that the minimum protective level (> or =0.01 IU/ml) would be maintained for approximately 30 y on average after the last vaccination. Diyarbakir, 1 of the selected provinces, had lower immunity than the other 2 provinces with poor immunization. Adult females tended to show slightly higher GMTs than males, probably due to the neonatal tetanus elimination program. Reinforcement of immunization against tetanus for adults is recommended.

Invoices and farmer interviews for vaccine-exposure measurement in turkey-broiler production

Exposure measurement in pharmaco-epidemiological studies can be based on various sources that do not always concur. However, reliability is an important criterion when selecting the method used to assess exposure and interpreting the results obtained. An analysis based on invoices might be more informative and more accurate to assess vaccines exposure (yes/no) in turkey broiler production than a questionnaire administered to farmers, which is nevertheless more feasible and less time-consuming. We compared the two methods to assess vaccination exposure in 239 turkey broiler flocks reared in 129 farms in 2000–2001. The agreement (crude agreement and kappa) was calculated, and association between discrepancy and farm and flock characteristics was investigated. Marek's-disease vaccine, Newcastle-disease vaccine, turkey haemorrhagic-enteritis vaccine and turkey-rhinotracheitis vaccine exposures were reported on the questionnaire for 2.1, 27.6, 93.0, and 98.3% of flocks, respectively, and for 2.1, 29.3, 89.4, and 86.6%, of invoices for the flocks studied, respectively. A discrepancy was observed in 24.9% of flocks. A discrepancy was observed more frequently in specialised farms without any other animal production (OR = 3.6; CI = 1.5, 8.9) and when the farmer did not know whether vaccination had been performed in the hatchery (OR = 7.1; CI = 2.6, 19.7).

Fowlpox virus infection causes a lymphoproliferative response in chickens.

While attenuated fowlpox virus (FPV) strains are widely used for vaccination of chickens and turkeys for prevention of fowlpox, recombinant FPV expressing various foreign genes have been evaluated for their ability to offer protection against various diseases in poultry as well as mammals. Little is known regarding the cell-mediated immune responses to FPV infection. In this study, immune response in chickens infected with a virulent and a vaccine strain of FPV were compared by a lymphoproliferation assay. Interestingly, a lymphoproliferative response was seen during 2-4 weeks post-infection irrespective of the FPV strain used in this study. Analyses of the buffy coat cultures with (35)S-methionine pulse labeling revealed an elevated protein of approximately 48-50 kDa in the culture supernatants. Furthermore, those supernatants could stimulate naive, non-adherent cells of the buffy coat cultures, in a dose dependant manner, suggestive of stimulatory cytokines. FPV, a complex virus presumably stimulates a variety of cytokines in vivo causing a proliferative cellular response. Knowledge of those cytokines or a better understanding of the proliferative responses is pivotal in evaluation of FPV vaccines and in the design of FPV-based recombinant vaccines.

Cold adapted avian pneumovirus for use as live, attenuated vaccine in turkeys

We report the development of a cold adapted strain of avian pneumovirus (APV) and its evaluation as a live vaccine candidate in 2-week-old turkey poults. A US isolate of APV (APV/MN/turkey/1-a/97) was serially passaged in Vero cells for 41 passages and then adapted to grow at sub-optimal temperatures by growing successively at 35, 33 and 31 °C for eight passages at each temperature. The virus thus adapted to grow at 31 °C was used as a candidate vaccine. The birds were vaccinated with two different doses of cold adapted virus and challenged with virulent virus 2 weeks after vaccination. No clinical signs were observed post-vaccination. Upon challenge, no clinical signs were seen in vaccinated birds but severe clinical signs were seen in non-vaccinated, challenged birds. The signs included unilateral or bilateral mucoid nasal discharge, watery eyes and swelling of infraorbital sinuses. The antibody levels in vaccinated birds were not very high. None of the vaccinated birds were found to shed virus after challenge in their choanal secretions whereas all of the non-vaccinated, challenged birds shed the virus. The absence of clinical signs and virus shedding in vaccinated birds as compared to that in non-vaccinated birds suggests that the cold adapted strain of APV is a viable candidate for use as a live, attenuated vaccine in turkeys.

Reduced Efficacy of Hemorrhagic Enteritis Virus Vaccine in Turkeys Exposed to Avian Pneumovirus

Avian pneumovirus (APV) is an immunosuppressive respiratory pathogen of turkeys. We examined the effect of APV infection on the vaccine efficacy of hemorrhagic enteritis virus (HEV) vaccines. APV was inoculated in 2-wk-old turkeys. Two or four days later, an attenuated HEV vaccine (HEVp30) or marble spleen disease virus (MSDV) vaccine were administered. Virulent HEV challenge was given 19 days after HEV vaccination. APV exposure compromised the ability of HEVp30 and MSDV to protect turkeys against virulent HEV. The protective index values were as follows: MSDV (100%) versus APV + MSDV (0%) (P < 0.05); HEVp30 (60%) versus APV + HEVp30 (30%) (P < 0.05) (Experiment I) and HEVp30 (56%) versus APV + HEVp30 (20%) (P < 0.05) (Experiment II). These data indicated that APV reduced the efficacy of HEV vaccines in turkeys.

Vaccination of Turkeys with an Avian Pneumovirus Isolate from the United States

Four-week-old poults obtained from avian pneumovirus (APV) antibody-free parents were vaccinated with different serial 10-fold dilutions of cell culture-propagated APV vaccine. The birds were vaccinated with 50 microl into each conjunctival space and nostril (total of 200 microl). Each poult of each group was vaccinated in groups that received doses of 4 x 10(4), 4 x 10(3), 4 x 10(2), 4 x 10(1), or 4 x 10(0) 50% tissue culture infective dose (TCID50) of APV vaccine, respectively. Respiratory signs were seen between 3 and 12 days postvaccination (PV) in the poults that were vaccinated with 4 x 10(4), 4 x 10(3), and 4 x 10(2) TCID50, respectively. In these groups, APV was detected from swabs collected at 5 days PV and seroconversion was detected at 2 wk PV. The groups that were originally vaccinated with 4 x 10(1) and 4 x 10(0) TCID50 developed mild clinical signs after vaccination, but neither virus nor antibody was detected PV. At 2 wk PV (6 wk of age), birds from each group, along with five unvaccinated controls, were challenged with APV. Upon challenge, the 4 x 10(4) and 4 x 10(3) TCID50 groups were protected against development of clinical signs and were resistant to reinfection. The group previously vaccinated with 4 x 10(2) TCID50 developed clinical signs after challenge that were considerably milder than those seen in the groups that had previously been vaccinated with lower doses or no virus. Even though 4 x 10(2) TCID50 vaccine dose administered by intranasal ocular route resulted in infection, incomplete protection resulted with this pivotal dose. Upon challenge, the 4 x 10(1) and 4 x 10(0) TCID50 groups exhibited milder disease signs than those seen in the challenged unvaccinated controls. In these groups, APV was detected in preparations of swabs collected at 5 days postchallenge (PC) and seroconversion was detected at 2 wk PC. These results indicate that the dose of APV vaccine that causes protection is higher than that required to produce infection.

Embryo vaccination of turkeys against Newcastle disease infection with recombinant fowlpox virus constructs containing interferons as adjuvants

Recombinant fowlpox viruses (rFPV) expressing the fusion and hemagglutinin-neuraminidase glycoproteins of Newcastle disease virus (NDV) as well as chicken type I interferon (IFN) or type II IFN were used to vaccinate specific pathogen-free (SPF) turkeys in ovo. No significant changes in the hatchability, survival rate, performance and weight gain were observed after vaccination with the rFPV vaccines in comparison to diluent-inoculated embryos. The rFPV-NDV-IFN-II construct induced the onset of anti-NDV antibody production in SPF birds at one week post hatch, one week earlier than other vaccine constructs. Three to five weeks post hatch, the turkeys were challenged with the neurotropic velogenic NDV strain Texas GB (NDV-GB-Tx). The rFPV-NDV-IFN-II construct was the most protective vaccine against NDV. rFPV vaccines significantly ( p<0.05) suppressed the mitogenic response of peripheral blood leukocytes in vaccinated turkeys in comparison to placebo inoculated controls at 25 days post vaccination. Birds vaccinated with rFPV-NDV-IFN-I construct did not have an inhibition in the mitogenic response.

Vaccination of turkeys in the wattles (dewlap) with turkey meningo-encephalitis live vaccine and Pasteurella multocida killed-in-oil vaccine

Vaccination of turkeys via the wattle has been introduced as a novel route of vaccination using attenuated live viral turkey meningo-encephalitis (TME) and killed-in-oil bacterial (Pasteurella multocida) vaccines. The efficacy of the immunization was evaluated by the haemagglutination-inhibition test for TME and by challenge for TME and P. multocida. Immunization via the wattle route was comparable or better as compared with the conventional routes, intramuscular and subcutaneous, for P. multocida and TME, respectively. These results were obtained by wattle vaccination administered either by injection, punching with a needle as used for fowl pox vaccination or by topical application. The advantages of wattle vaccination are: no local untoward reactions (P. multocida), which might frequently occur in the muscles following improper subcutaneous mass vaccination, less time and labour consuming, and less stress for the turkeys. It is suggested to test the wattle route of vaccination with other viral and bacterial vaccines in turkeys and other avian species.

Rubella seroprevalence in an unvaccinated population in Izmir: recommendations for rubella vaccination in Turkey.

The European Advisory Group on the Expanded Program on Immunization of WHO has recommended that by 2010 or earlier congenital rubella should be well-controlled or eliminated in all countries in Europe. Debate on the introduction of rubella vaccine into national immunization schedules continues to occur, and data on rubella and congenital rubella syndrome in Turkey are insufficient. To determine age-specific rubella seroprevalence in the 1- to 29-year-old unvaccinated population in Izmir, Turkey. A total of 600 unvaccinated persons 1 to 29 years old were selected for the study with cluster sampling in Izmir, Turkey. The information on sociodemographic characteristics and disease history was gathered for each participant, and in 580 of them rubella-specific IgG antibodies were assayed quantitatively by the micro-enzyme immunoassay. Of the 580 participants tested for rubella antibodies, 135 (23.3%) were seronegative. The proportions of susceptible individuals were 61.7, 29.5, 12.4, 10.3 and 8.4% in the age groups of 1 to 4, 5 to 9, 10 to 14, 15 to 19 and 20 to 29 years, respectively. Of the young women 15 to 19 years of age, 13.5% were susceptible to rubella infection. Because a substantial proportion of women in their childbearing years are susceptible to rubella, immunization efforts should be directed at infants or prepubertal children.