Vaccination of birds other than chickens and turkeys against avian influenza

Herbal Medicine Additives as Powerful Agents to Control and Prevent Avian Influenza Virus in Poultry – A Review

The complicated epidemiological situation of avian influenza viruses (AIV) caused by continuous emergence of new subtypes with failure of eradication, monitoring and vaccination strategies opens the door to alternative solutions to save the status quo and prevent new disasters for the poultry industry. Using of synthetic antiviral drugs such as neuraminidase and hemagglutinin inhibitors has been limited due to development of drug resistance and expensive commercial application. One of the most promising alternatives is herbal products and botanicals. This review presents a comprehensive and specialized view of in vivo studies of herbal plants in poultry species. Many herbal extracts as Nigella sativa oil, Astragalus, Cochinchina momordica and Sargassum pallidum polysaccharides proved very effective as adjuvants for AIV vaccines. Another beneficial role of herbs is enhancement of host response to vaccination with further better prevention of infection and easier control. For enumeration not inventory, this is best achieved with the use of virgin coconut oil, Echinacea purpurea, Ginseng stem-and-leaf saponins (GSLS), Astragalus polysaccharides (APS), Myrtus communis oil, Garlic powder, Turmeric, Thyme and Curcumin. This review aimed to evaluate most of the in vivo studies performed on poultry species as a step and a guide for scientists and field practitioners in establishment of new effective herbal-based drugs for prevention and control of AIV in poultry.

The response of mute swans (Cygnus olor, Gm. 1789) to vaccination against avian influenza with an inactivated H5N2 vaccine

Background

Recent epidemics of highly pathogenic avian influenza (HPAI) produced an unprecedented number of cases in mute swans (Cygnus olor) in European countries, which indicates that these birds are very sensitive to the H5N1 virus. The HPAI outbreaks stirred a debate on the controversial stamping-out policy in populations of protected bird species. After preventive vaccination had been approved in the European Union, several countries have introduced vaccination schemes to protect poultry, captive wild birds or exotic birds in zoos against HPAI. The aim of this study was to investigate the immune response of wild mute swans to immunization with an inactivated AI H5N2 vaccine approved for use in poultry. The serological responses of mute swans were assessed by comparison with racing pigeons (Columba livia), a species which is characterized by different susceptibility to infection with the H5N1 HPAI virus and plays a questionable role in the ecology of influenza (H5N1) viruses.

Results

Swans were vaccinated once or twice at an interval of 4 weeks. The humoral immune response was evaluated by hemagglutination inhibition (HI) and NP-ELISA. The lymphocyte blast transformation test was used to determine the cell-mediated immune response. Higher values of the geometric mean titer (GMT) and 100 % seroconversion (HI ≥32) were noted in double vaccinated swans (1448.2) than in single vaccinated swans (128.0) or in double vaccinated pigeons (215.3). Significant differences in HI titers were observed between swans and pigeons, but no variations in ELISA scores were noted after the booster dose. Immunization of swans had no effect on the proliferative activity of lymphocytes.

Conclusions

The inactivated H5N2 vaccine was safe and immunogenic for mute swans and pigeons. Vaccination may have practical implications for swans kept in zoos, wildlife parks or rehabilitation centers. However, challenge studies are needed to prove the efficacy of the H5N2 AI vaccine.

Challenges in Veterinary Vaccine Development and Immunization

In approaching the development of a veterinary vaccine, researchers must choose from a bewildering array of options that can be combined to enhance benefit. The choice and combination of options is not just driven by efficacy, but also consideration of the cost, practicality, and challenges faced in licensing the product. In this review we set out the different choices faced by veterinary vaccine developers, highlight some issues, and propose some pressing needs to be addressed.

H5-based DNA constructs derived from selected highly pathogenic H5N1 avian influenza virus induce high levels of humoral antibodies in Muscovy ducks against low pathogenic viruses

BACKGROUND

H5 low pathogenic avian influenza virus (LPAIV) infection in domestic ducks is a major problem in duck producing countries. Their silent circulation is an ongoing source of potential highly pathogenic or zoonotic emerging strains. To prevent such events, vaccination of domestic ducks might be attempted but remains challenging. Currently licensed vector vaccines derived from H5N1 HPAIV possess clade 0, clade 2.2 or clade 2.3.4 HA sequences: selection of the best HA candidate inducing the largest cross protection is a key issue. For this purpose, DNA immunization of specific pathogen free Muscovy ducks was performed using different synthetic codon optimized (opt) or native HA genes from H5N2 LPAIV and several H5N1 HPAIV clade 2.1, 2.2.1 and 2.3.4. Humoral cross-immunity was assessed 3 weeks after boost by hemagglutination inhibition (HI) and virus neutralization (VN) against three French H5 LPAIV antigens.

FINDINGS

Vaccination with LP H5N2 HA induced the highest VN antibody titre against the homologous antigen; however, the corresponding HI titre was lower and comparable to HI titres obtained after immunization with opt HA derived from clades 2.3.4 or 2.1. Compared to the other HPAIV-derived constructs, vaccination with clade 2.3.4 opt HA consistently induced the highest antibody titres in HI and VN, when tested against all three H5 LPAIV antigens and H5N2 LPAIV, respectively: differences in titres against this last strain were statistically significant.

CONCLUSION

The present study provides a standardized method to assess cross-immunity based on HA immunogenicity alone, and suggests that clade 2.3.4-derived recombinant vaccines might be the optimal candidates for further challenge testing to vaccinate domestic Muscovy ducks against H5 LPAIV.

Success factors for avian influenza vaccine use in poultry and potential impact at the wild bird-agricultural interface

Thirty-two epizootics of high pathogenicity avian influenza (HPAI) have been reported in poultry and other birds since 1959. The ongoing H5N1 HPAI epizootic that began in 1996 has also spilled over to infect wild birds. Traditional stamping-out programs in poultry have resulted in eradication of most HPAI epizootics. However, vaccination of poultry was added as a control tool in 1995 and has been used during five epizootics. Over 113 billion doses of AI vaccine have been used in poultry from 2002 to 2010 as oil-emulsified, inactivated whole AIV vaccines (95.5%) and live vectored vaccines (4.5%). Over 99% of the vaccine has been used in the four H5N1 HPAI enzootic countries: China including Hong Kong (91%), Egypt (4.7%), Indonesia (2.3%), and Vietnam (1.4%) where vaccination programs have been nationwide and routine to all poultry. Ten other countries used vaccine in poultry in a focused, risk-based manner but this accounted for less than 1% of the vaccine used. Most vaccine "failures" have resulted from problems in the vaccination process; i.e., failure to adequately administer the vaccine to at-risk poultry resulting in lack of population immunity, while fewer failures have resulted from antigenic drift of field viruses away from the vaccine viruses. It is currently not feasible to vaccinate wild birds against H5N1 HPAI, but naturally occurring infections with H5 low pathogenicity avian influenza viruses may generate cross-protective immunity against H5N1 HPAI. The most feasible method to prevent and control H5N1 HPAI in wild birds is through control of the disease in poultry with use of vaccine to reduce environmental burden of H5N1 HPAIV, and eventual eradication of the virus in domestic poultry, especially in domestic ducks which are raised in enzootic countries on range or in other outdoor systems having contact with wild aquatic and periurban terrestrial birds.

Prime-boost vaccination with recombinant H5-fowlpox and Newcastle disease virus vectors affords lasting protection in SPF Muscovy ducks against highly pathogenic H5N1 influenza virus

Vaccination protocols were evaluated in one-day old Muscovy ducklings, using an experimental Newcastle disease recombinant vaccine (vNDV-H5) encoding an optimized synthetic haemagglutinin gene from a clade 2.2.1 H5N1 highly pathogenic (HP) avian influenza virus (AIV), either as a single administration or as a boost following a prime inoculation with a fowlpox vectored vaccine (vFP89) encoding a different H5 HP haemagglutinin from an Irish H5N8 strain. These vaccination schemes did not induce detectable levels of serum antibodies in HI test using a clade 2.2.1 H5N1 antigen, and only induced H5 ELISA positive response in less than 10% of vaccinated ducks. However, following challenge against a clade 2.2.1 HPAIV, both protocols afforded full clinical protection at six weeks of age, and full protection against mortality at nine weeks. Only the prime-boost vaccination (vFP89+vNDV-H5) was still fully protecting Muscovy ducks against disease and mortality at 12 weeks of age. Reduction of oropharyngeal shedding levels was also constantly observed from the onset of the follow-up at 2.5 or three days post-infection in vaccinated ducks compared to unvaccinated controls, and was significantly more important for vFP89+vNDV-H5 vaccination than for vNDV-H5 alone. Although the latter vaccine is shown immunogenic in one-day old Muscovy ducks, the present work is original in demonstrating the high efficacy of the successive administration of two different vector vaccines encoding two different H5 in inducing lasting protection (at least similar to the one induced by an inactivated reassortant vaccine, Re-5). In addition, such a prime-boost schedule allows implementation of a DIVA strategy (to differentiate vaccinated from infected ducks) contrary to Re-5, involves easy practice on the field (with injection at the hatchery and mass vaccination later on), and should avoid eventual interference with NDV maternally derived antibodies. Last, the HA insert could be updated according to the epidemiological situation.

Insight into alternative approaches for control of avian influenza in poultry, with emphasis on highly pathogenic H5N1

Highly pathogenic avian influenza virus (HPAIV) of subtype H5N1 causes a devastating disease in poultry but when it accidentally infects humans it can cause death. Therefore, decrease the incidence of H5N1 in humans needs to focus on prevention and control of poultry infections. Conventional control strategies in poultry based on surveillance, stamping out, movement restriction and enforcement of biosecurity measures did not prevent the virus spreading, particularly in developing countries. Several challenges limit efficiency of the vaccines to prevent outbreaks of HPAIV H5N1 in endemic countries. Alternative and complementary approaches to reduce the current burden of H5N1 epidemics in poultry should be encouraged. The use of antiviral chemotherapy and natural compounds, avian-cytokines, RNA interference, genetic breeding and/or development of transgenic poultry warrant further evaluation as integrated intervention strategies for control of HPAIV H5N1 in poultry.

Antiviral efficacy of oseltamivir against avian influenza virus in avian species

Avian influenza is one of the most contagious viral diseases in bird species and, increasingly, interspecies transmission to mammalian species has been reported. Prevention and eradication of avian influenza virus (AIV) infection in birds may require vaccines as part of a comprehensive program including biosecurity, culling, diagnostics, and surveillance. However, for valuable bird species in zoos, novel eradication strategies are needed, including antiviral treatments. The present study evaluated the anti-influenza efficacy of the potent neuraminidase inhibitor oseltamivir in avian species using the orders Galliformes (chickens) and Anseriformes (ducks). Viral replication of low pathogenic AIV was significantly reduced in the chicken model and completely reduced in the duck model. Anti-influenza drug administration to valuable bird species with an appropriate extrapolation approach could be useful for control of AIV in combination with active surveillance and vaccination strategies. Further, evaluation of oseltamivir against highly pathogenic avian influenza (HPAI) using avian models would be needed to optimize the oseltamivir application guideline for HPAI control.