Inactivated Avian Influenza Vaccine Research Articles

Appraisal of Three Commercial Inactivated Avian Influenza Vaccines Efficacy Against Challenge with Egyptian Duck-Origin Clade 2.3.4.4b H5N8 in Commercial Broiler Chickens

Appraisal of Three Commercial Inactivated Avian Influenza Vaccines Efficacy Against Challenge with Egyptian Duck-Origin Clade 2.3.4.4b H5N8 in Commercial Broiler Chickens

Efficiency of natural oils as alternative adjuvants to mineral oils in inactivated avian influenza vaccine formulation

ABSTRACT 1. The effectiveness of inactivated vaccines depends on selecting the suitable adjuvant for vaccine formulation. The potency of vaccines with low antigen content can be improved with the appropriate adjuvant. This could allow production of more doses and lower the production cost. 2. This study evaluated the efficiency of vaccines prepared using oil extracted from natural sources including argan oil, almond oil, sesame seed oil, pumpkin oil, cactus oil and black seed oil as alternative adjuvants for improving the protection capacity of inactivated influenza virus vaccine as compared to commonly used mineral oils. 3. Each vaccine formulation was evaluated for stability, safety and immunogenicity in chickens, as well as for reducing the viral shedding after challenge infection. 4. The cactus, sesame and pumpkin seed oil-based vaccines were found to be potent and successfully induced the production of humoral immunity in vaccinated chickens.

Evaluation of inactivated vaccine's Antibody response to different H9N2 Vaccination programs with Hemagglutination Inhibition (HI) assay

Influenza is a significant poultry disease that can also affect humans, making it a zoonosis. The World Health Organization (WHO) and Contagious Diseases Organization (CDO) have increasingly focused on this disease in recent years. The isolation of influenza, particularly H5N1 and H9N2 subtypes, has dramatically increased, posing a global epidemic threat and causing deaths in various communities, as well as substantial losses in poultry. In response, using inactivated avian influenza vaccines has become common in controlling the disease. A comprehensive study was conducted in broiler farms in Iran to address the importance of influenza control through vaccination. The study involved 50,000 broiler chicks divided into seven groups with different vaccination programs. The groups were vaccinated at different ages and received varying vaccine doses. Serum samples were collected weekly and analyzed for antibody titers using hemagglutination inhibition (HI). The results showed that the groups vaccinated after seven days of age had a more consistent immune response and higher antibody titers than those vaccinated at a younger age or with only one dose. Early vaccination before seven days of age did not effectively stimulate the desired antibody response or achieve expected titers for the H9N2 influenza virus. Therefore, vaccinating older chicks improved immunity and flock protection more effectively. This study highlights the importance of vaccination strategies in controlling influenza in broiler farms. It provides valuable insights into the optimal timing and dosage of vaccines to enhance the immune response and protect against the H9N2 subtype. Implementing appropriate vaccination programs can contribute to mitigating the impact of influenza on poultry and reducing the risk of transmission to humans, ultimately safeguarding both animal and public health.

Using a Novel Nanoparticle as An Adjuvant for Inactivated Avian Influenza Vaccine

Using a Novel Nanoparticle as An Adjuvant for Inactivated Avian Influenza Vaccine

Discrepancies in the efficacy of H5 inactivated avian influenza vaccines in specific-pathogen-free chickens against challenge with the Egyptian H5N8 clade 2.3.4.4 Group B virus isolated in 2018.

Background and Aim:Highly pathogenic avian influenza H5N8 virus of clade 2.3.4.4 was newly emerged to Egypt and firstly detected in carcasses of wild birds in November 2016. This study assessed the protection efficacy and virus shedding reduction of three different inactivated avian influenza (AI) H5 (H5N1, H5N2, and H5N3) commercial vaccines against challenge with two newly emerging highly pathogenic AI virus H5N8 Egyptian isolates in specific-pathogen-free (SPF) chicks.Materials and Methods:10-day-old SPF chicks (n=260) were divided into 20 groups (n=13). Groups 1-5 were vaccinated through the subcutaneous route (S/C) with 0.5 mL of H5N1 vaccine, Groups 6-10 were vaccinated (S/C) with 0.5 mL of H5N2 vaccine, and Groups 11-15 were vaccinated (S/C) with 0.5 mL of H5N3 vaccine. Positive control groups (16-19) were challenged at 25 and 31 days old (2 and 3 weeks post-vaccination [PV]) using H5N8 clade 2.3.4.4 A/duck/Egypt/F13666A/2017(H5N8) and H5N8 clade 2.3.4.4 A/chicken/Egypt/18FL6/2018(H5N8). Group 20 was left non-vaccinated as a control. All vaccinated groups were divided and challenged with both viruses at 25 and 31 days of age. The viral challenge dose was 0.1 mL of 106 EID50/0.1 mL titer/chick, and it was administered oronasally. All chicks were kept in isolators for 14 days after each challenge. Sera samples were collected weekly and at 2 weeks post-challenge (PC) to detect a humoral immune response. PC mortalities were recorded daily for 10 days to calculate the protection percentages. Tracheal swabs were collected from the challenged chicks in different groups at 3, 5, 7, and 10 days PC. Kidneys and spleens were collected at 3, 5, 7, and 10 days PC and kept in formalin for histopathological examination to assess lesions and severity scores. Tracheal swabs were inoculated in 10-day-old SPF embryonated chicken eggs for virus titration and to calculate shedding levels.Results:All studied vaccines displayed 70-100% protection within 10 days PC. Hemagglutination inhibition results from sera samples revealed antibody titers ranging from 0.6 to 5.4 log2 starting at 1-week PV with the highest titers at 4 weeks PV. Challenged SPF chickens exhibited a notable reduction in virus shedding, with an average of 1.5-2 log10, compared to control birds. Various histopathological lesions with different scores were detected.Conclusion:Our findings suggest that the inadequate virus shedding reduction and protection efficacy of studied vaccines were variable and that the type of vaccine to be used under field conditions should be reconsidered. Study of the variability between the Egyptian old emerged AI (AIV) 2017 H5N8 strains and the new emerging AIV 2018 H5N8 is required to achieve optimal protection and limit the current economic losses.

Antibody Response of an H9 Subtype Avian Influenza Poultry Vaccine on Three Kinds of Wild Birds in Shanghai Zoo.

A semiannual immunization with a commercial inactivated H9 subtype avian influenza virus (AIV) vaccine developed for poultry has been used to prevent and control the avian influenza (AI) infections among captured wild birds in Shanghai Zoo. However, the overall safety and effectiveness of the poultry vaccine for housed birds in the zoo remain unclear. To verify the safety and efficacy of the commercial inactivated H9 AI vaccine on zoo birds and to explore a more reasonable and effective immunization procedure, 48 zoo birds, including 11 Oriental white storks, 25 peafowl, and 12 silver pheasants, were administered the AI vaccine developed for poultry use. Then, the clinical signs of the immunized birds were observed for 2 weeks, and the antibodies against H9 AI were determined via the hemagglutination inhibition test. Results showed that no harmful effects related to the vaccination were observed, and the antibody titers of the Oriental white stork, peafowl, and silver pheasants were all higher than 7 log 2 at 21 days, 30 days, 60 days, 120 days, and 180 days postimmunization. For further study, the H9 AIV titers of 11 peafowls and 6 Oriental storks, which were raised in the nursing ground, were continuously monitored for 15 months. All of their antibody titers were above the national standards of China (5 log 2; GB/T18936-2003), even at 12 months and 15 months postimmunization. We concluded that the commercial inactivated H9 AI vaccine used at the present time in Shanghai Zoo can induce high and prolonged immune responses in vaccinated birds.

H7N9 Influenza Virus in China.

In early 2013, human infections caused by a novel H7N9 avian influenza virus (AIV) were first reported in China; these infections caused severe disease and death. The virus was initially low pathogenic to poultry, enabling it to spread widely in different provinces, especially in live poultry markets. Importantly, the H7N9 low pathogenic AIVs (LPAIVs) evolved into highly pathogenic AIVs (HPAIVs) in the beginning of 2017, causing a greater threat to human health and devastating losses to the poultry industry. Fortunately, nationwide vaccination of chickens with an H5/H7 bivalent inactivated avian influenza vaccine since September 2017 has successfully controlled H7N9 avian influenza infections in poultry and, importantly, has also prevented human infections. In this review, we summarize the biological properties of the H7N9 viruses, specifically their genetic evolution, adaptation, pathogenesis, receptor binding, transmission, drug resistance, and antigenic variation, as well as the prevention and control measures. The information obtained from investigating and managing the H7N9 viruses could improve our ability to understand other novel AIVs and formulate effective measures to control their threat to humans and animals.

Protection afforded by avian influenza vaccination programmes consisting of a novel RNA particle and an inactivated avian influenza vaccine against a highly pathogenic avian influenza virus challenge in layer chickens up to 18 weeks post-vaccination

ABSTRACTThe efficacies of an oil adjuvanted-inactivated reverse genetics-derived H5 avian influenza virus (AIV) vaccine and an alphavirus replicon RNA particle (RP) AIV vaccine were evaluated in commercial Leghorn chickens. Challenge utilized A/turkey/MN/12582/2015, an isolate representing the U.S. H5N2 Clade 2.3.4.4 responsible for the 2015 highly pathogenic avian influenza (HPAI) epornitic in commercial poultry the United States. As part of a long-term, 36-week study, chickens were challenged at seven weeks of age after receiving a single vaccination, at 18 weeks of age following a vaccine prime-single boost, and at 36 weeks of age after a prime- double-boost. All vaccine programmes reduced virus oropharyngeal and cloacal shedding and mortality compared to the non-vaccinated control birds; however, chickens receiving at least one administration of the RP vaccine generally had diminished viral shedding especially from the cloacal swabbings. A detectable serum antibody response and protection were observed through 18 weeks post-vaccination. Our data suggest that, in conjunction with a comprehensive eradication, enhanced biosecurity and controlled marketing plan, vaccination programmes of commercial layer chickens with novel RP vaccines may represent an important tool for preventing HPAI-related mortalities and decreasing viral load during a catastrophic influenza outbreak.RESEARCH HIGHLIGHTSImmunization of poultry following a vaccination schedule consisting of inactivated and RNA particle vaccines offered significant protection against lethal disease following HPAIV challenge.Virus shedding was significantly (P < 0.05) reduced in chickens vaccinated with either inactivated and/or recombinant vaccines.Serum antibody titres were not a reliable indicator of protection.An inactivated vaccine containing 384 HAU of the homologous antigen was unable to induce complete protection.

FIELD APPLICATION FOR EXPERIMENTAL INACTIVATED MULTI-VALENT P. multocida AND AVIAN INFLUENZA (H9N2) VACCINE IN POULTRY

Fowl cholera (FC) and Avian Influenza (AI) are two of the major economically important respiratory and septicaemic disease of poultry in Egypt and allover the world. A field trails was conducted to evaluate the immunogenicity of an experimentally multivalent inactivated Fowl cholera (P. multocida) and Avian Influenza (H9N2) vaccine. The In this study a combined inactivated Montanide ISA fowl cholera and AI vaccine was prepared then the immunization potency and protective efficacy were evaluated through experimental application on different poultry breeds including broiler breeder, broiler and turkey flocks.The peak of humeral immune response against P. multocida as measured by ELISA was at the 5th week post vaccination and at 3rd week post boostering all over the used poultry flocks. At the same time, AI immune response as measured by HI reached the peak at the 6th week post vaccination and at 2nd week post boostering. Regarding the challenge test, the protection levels were 76.6, 70 and 80% and 90, 86.6 and 93.3% against P. multocida while protection levels were 83.3, 80 and 86.6% and 93.3, 90 and 96.6% against AI virus after challenge with the used virulent strains post single and booster dose respectively. In conclusion the combined prepared fowl cholera and AI vaccine succeeded in eliciting protective antibody titres and full protection against both fowl cholera and AI diseases.Key words: Pasteurella multocida; AI; vaccine; ELISA; PHA; HI; challenge test

Preparation and immunological evaluation of inactivated avian influenza virus vaccine encapsulated in chitosan nanoparticles

Efficacy maximization of inactivated avian influenza vaccine using safe adjuvants was investigated. Chitosan nanoparticles were prepared by ionic gelation method with average size of 150 nm and their Zeta potential was 11.5 mV. After encapsulation of avian influenza vaccine, the average size was 397 nm and Zeta potential was 4.29 mV. The highest HI antibody titer results were shown in chicken group vaccinated with inactivated avian influenza virus AIV-chitosan followed by the group vaccinated with inactivated AIV-chitosan nanoparticles then the group vaccinated with oil inactivated AIV vaccine, on using chicken antigen at 2 weeks post second vaccination. Upon using duck antigen, the highest HI antibody titers were shown in chicken group vaccinated with inactivated AIV oil emulsion vaccine followed by chicken group vaccinated with AIV-chitosan nanoparticles then the group vaccinated with AIV–chitosan. Chicken in the group vaccinated with AIV-chitosan nanoparticles induced the best results of lymphocyte proliferation assay. The results of phagocytic activity percentage and phagocytic index of AIV-chitosan nanoparticles and AIV–chitosan groups at 3 days post first vaccination were increased significantly in comparison with other groups, whereas at 14 days post first vaccination, group vaccinated with AIV-chitosan nanoparticles showed significant increase in phagocytic activity percentage and phagocytic index.

H5N1 influenza vaccine induces a less robust neutralizing antibody response than seasonal trivalent and H7N9 influenza vaccines

Conventional inactivated avian influenza vaccines have performed poorly in past vaccine trials, leading to the hypothesis that they are less immunogenic than seasonal influenza vaccines. We tested this hypothesis by comparing the immunogenicity of the H5N1 and H7N9 vaccines (avian influenza vaccines) to a seasonal trivalent inactivated influenza vaccine in naïve ferrets, administered with or without the adjuvants MF59 or AS03. Vaccine immunogenicity was assessed by measuring neutralizing antibody titers against hemagglutinin and neuraminidase and by hemagglutinin -specific IgG levels. Two doses of unadjuvanted vaccines induced low or no HA-specific IgG responses and hemagglutination-inhibiting titers. Adjuvanted vaccines induced comparable IgG-titers, but poorer neutralizing antibody titers for the H5 vaccine. All adjuvanted vaccines elicited detectable anti- neuraminidase -antibodies with the exception of the H5N1 vaccine, likely due to the low amounts of neuraminidase in the vaccine. Overall, the H5N1 vaccine had poorer capacity to induce neutralizing antibodies, but not HA-specific IgG, compared to H7N9 or trivalent inactivated influenza vaccine.

H9 subtype influenza vaccine in MDCK single‐cell suspension culture with stable expression of TMPRSS2: Generation and efficacy evaluation

Vaccination is the most effective way to protect chickens from avian influenza pandemics. Mammalian cells, especially MDCK cells, are being investigated as a good alternative to the embryonated chicken eggs for avian influenza vaccine production. In this work, we developed a new MDCK cell line, which has two main features: single‐cell suspension growth and stable expression of human TMPRSS2 protein (transmembrane protease serine S1 member 2) anchored on cells membrane, named MDCK‐Sus‐TMPRSS2. Reverse‐transcription polymerase chain reaction, western blot analysis and indirect immunofluorescence assay were employed to detect the expression of TMPRSS2 in the MDCK‐Sus‐TMPRSS2 cells. Then, H9 subtype avian influenza virus, NJ02/01 strain, was adapted in MDCK‐Sus‐TMPRSS2 cells with serial blind passages and propagated in stirred bioreactor with 9.5 log2/25 μL hemagglutination titers for inactivated avian influenza vaccine production without addition of exogenous trypsin. The MDCK‐Sus‐TMPRSS2 cell‐derived H9 subtype avian influenza vaccine could induce high titers of hemagglutiniton inhibition antibodies in specific pathogen‐free chickens and protect chickens against heterologous H9 subtype influenza virus challenge, showing lower virus shedding rate and sickness rate than in the egg‐derived vaccines group. High titers of H9 subtype‐specific antibodies above 6 log2 were maintained for 6 months in commercial chickens vaccinated by the MDCK‐Sus‐TMPRSS2 cells derived H9 subtype avian influenza vaccine and there were no negative effects on body weight increase in these chickens. Taken together, the results of this work revealed that MDCK‐Sus‐TMPRSS2 cell line could be a promising and safe substitute for embryonated chicken eggs as a host cell line for H9 subtype avian influenza virus propagation.

Immunopotentiators Improve the Efficacy of Oil-Emulsion-Inactivated Avian Influenza Vaccine in Chickens, Ducks and Geese.

Combination of CVCVA5 adjuvant and commercial avian influenza (AI) vaccine has been previously demonstrated to provide good protection against different AI viruses in chickens. In this study, we further investigated the protective immunity of CVCVA5-adjuvanted oil-emulsion inactivated AI vaccine in chickens, ducks and geese. Compared to the commercial H5 inactivated vaccine, the H5-CVCVA5 vaccine induced significantly higher titers of hemaglutinin inhibitory antibodies in three lines of broiler chickens and ducks, elongated the antibody persistence periods in geese, elevated the levels of cross serum neutralization antibody against different clade and subclade H5 AI viruses in chicken embryos. High levels of mucosal antibody were detected in chickens injected with the H5 or H9-CVCA5 vaccine. Furthermore, cellular immune response was markedly improved in terms of increasing the serum levels of cytokine interferon-γ and interleukine 4, promoting proliferation of splenocytes and upregulating cytotoxicity activity in both H5- and H9-CVCVA5 vaccinated chickens. Together, these results provide evidence that AI vaccines supplemented with CVCVA5 adjuvant is a promising approach for overcoming the limitation of vaccine strain specificity of protection.

Immunogenicity and efficacy of fowlpox-vectored and inactivated avian influenza vaccines alone or in a prime-boost schedule in chickens with maternal antibodies

Inactivated and fowlpox virus (FP)-vectored vaccines have been used to control H5 avian influenza (AI) in poultry. In H5 AI endemic countries, breeder flocks are vaccinated and therefore, maternally-derived antibodies (MDA) are transferred to their progeny. Results of three immunogenicity and one efficacy studies performed in birds with or without MDA indicated that the immunogenicity of an inactivated vaccine based on a H5N9 AI isolate (inH5N9) was severely impaired in chicks hatched from inH5N9-vaccinated breeders. This MDA interference was lower when breeders received only one administration of the same vaccine and could be overcome by priming the chicks at day-of-age with a live recombinant FP-vectored vaccine with H5 avian influenza gene insert (FP-AI). The interference of anti-FP MDA was of lower intensity than the interference of anti-AI MDA. The highest interference observed on the prime-boost immunogenicity was in chicks hatched from breeders vaccinated with the same prime-boost scheme. The level of protection against an antigenic variant H5N1 highly pathogenic AI isolate from Indonesia against which the FP-AI or inH5N9 alone was poorly protective could be circumvented by the prime-boost regimen in birds with either FP or AI MDA. Thus, the immunogenicity of vaccines in young chicks with MDA depends on the vaccination scheme and the type of vaccine used in their parent flocks. The heterologous prime-boost in birds with MDA may at least partially overcome MDA interference on inactivated vaccine.

Immunogenicity and efficacy of fowlpox-vectored and inactivated avian influenza vaccines alone or in a prime-boost schedule in chickens with maternal antibodies

Inactivated and fowlpox virus (FP)-vectored vaccines have been used to control H5 avian influenza (AI) in poultry. In H5 AI endemic countries, breeder flocks are vaccinated and therefore, maternally-derived antibodies (MDA) are transferred to their progeny. Results of three immunogenicity and one efficacy studies performed in birds with or without MDA indicated that the immunogenicity of an inactivated vaccine based on a H5N9 AI isolate (inH5N9) was severely impaired in chicks hatched from inH5N9-vaccinated breeders. This MDA interference was lower when breeders received only one administration of the same vaccine and could be overcome by priming the chicks at day-of-age with a live recombinant FP-vectored vaccine with H5 avian influenza gene insert (FP-AI). The interference of anti-FP MDA was of lower intensity than the interference of anti-AI MDA. The highest interference observed on the prime-boost immunogenicity was in chicks hatched from breeders vaccinated with the same prime-boost scheme. The level of protection against an antigenic variant H5N1 highly pathogenic AI isolate from Indonesia against which the FP-AI or inH5N9 alone was poorly protective could be circumvented by the prime-boost regimen in birds with either FP or AI MDA. Thus, the immunogenicity of vaccines in young chicks with MDA depends on the vaccination scheme and the type of vaccine used in their parent flocks. The heterologous prime-boost in birds with MDA may at least partially overcome MDA interference on inactivated vaccine.

Protection against H7N3 high pathogenicity avian influenza in chickens immunized with a recombinant fowlpox and an inactivated avian influenza vaccines

Beginning on June 2012, an H7N3 highly pathogenic avian influenza (HPAI) epizootic was reported in the State of Jalisco (Mexico), with some 22.4 million chickens that died, were slaughtered on affected farms or were preemptively culled on neighboring farms. In the current study, layer chickens were vaccinated with a recombinant fowlpox virus vaccine containing a low pathogenic AI (LPAI) H7 gene insert (rFPV-H7-AIV) and an inactivated oil-emulsified H7N3 AIV vaccine, and subsequently challenged against the Jalisco H7N3 HPAIV. All vaccine combinations provided similar and significant protection against mortality, morbidity, and shedding of challenge virus from the respiratory and gastrointestinal tracts. Serological data also suggested analogous protection from HPAIV among immunized birds. Control of the recent Jalisco AIV infection could be achieved by using various combinations of the two vaccines tested. Even though a single dose of rFPV-H7-AIV vaccine at 1-day-of-age would be the most pragmatic option, optimal protection may require a second dose of vaccine administered in the field.

Impact of Vaccines and Vaccination on Global Control of Avian Influenza

There are 30 recorded epizootics of H5 or H7 high pathogenicity avian influenza (HPAI) from 1959 to early 2012. The largest of these epizootics, affecting more birds and countries than the other 29 epizootics combined, has been the H5N1 HPAI, which began in Guangdong China in 1996, and has killed or resulted in culling of over 250 million poultry and/or wild birds in 63 countries. Most countries have used stamping-out programs in poultry to eradicate H5N1 HPAI. However, 15 affected countries have utilized vaccination as a part of the control strategy. Greater than 113 billion doses were used from 2002 to 2010. Five countries have utilized nationwide routine vaccination programs, which account for 99% of vaccine used: 1) China (90.9%), 2) Egypt (4.6%), 3) Indonesia (2.3%), 4) Vietnam (1.4%), and 5) Hong Kong Special Administrative Region (< 0.01%). Mongolia, Kazakhstan, France, The Netherlands, Cote d'Ivoire, Sudan, North Korea, Israel, Russia, and Pakistan used < 1% of the avian influenza (AI) vaccine, and the AI vaccine was targeted to either preventive or emergency vaccination programs. Inactivated AI vaccines have accounted for 95.5% of vaccine used, and live recombinant virus vaccines have accounted for 4.5% of vaccine used. The latter are primarily recombinant Newcastle disease vectored vaccine with H5 influenza gene insert. China, Indonesia, Egypt, and Vietnam implemented vaccination after H5N1 HPAI became enzootic in domestic poultry. Bangladesh and eastern India have enzootic H5N1 HPAI and have not used vaccination in their control programs. Clinical disease and mortality have been prevented in chickens, human cases have been reduced, and rural livelihoods and food security have been maintained by using vaccines during HPAI outbreaks. However, field outbreaks have occurred in vaccinating countries, primarily because of inadequate coverage in the target species, but vaccine failures have occurred following antigenic drift in field viruses within China, Egypt, Indonesia, Hong Kong, and Vietnam. The primary strategy for HPAI and H5/H7 low pathogenicity notifiable avian influenza control will continue to be immediate eradication using a four-component strategy: 1) education, 2) biosecurity, 3) rapid diagnostics and surveillance, and 4) elimination of infected poultry. Under some circumstances, vaccination can be added as an additional tool within a wider control strategy when immediate eradication is not feasible, which will maintain livelihoods and food security, and control clinical disease until a primary strategy can be developed and implemented to achieve eradication.

Adjuvanticity of epimedium polysaccharide-propolis flavone on inactivated vaccines against AI and ND virus

The purpose of this research was to compare the activities of different dose of epimedium polysaccharide-propolis flavone adjuvant (EPA). The inactivated avian influenza (AI) and Newcastle disease (ND) vaccine containing three doses of EPA were prepared. In AI vaccine vaccination experiment, 300 14-day-old chickens were randomly divided into 6 groups and inoculated with three EPA-AI vaccines taking oil adjuvant (OA), non-adjuvant (NA) vaccines and physiological saline as controls, repeated at 28-day-old. The lymphocyte proliferation and serum antibody titer were determined. In ND vaccine vaccination experiment, 300 14-day-old chickens were grouped, treated with three EPA-ND vaccines, and determined same to AI vaccine vaccination experiment; at 42-day-old the chickens were challenged with NDV. On D15 after challenged, the immune protective effect was observed. The results showed that EPA could significantly promote lymphocyte proliferation and enhance serum antibody titer against AI and ND, and reduce the morbidity of chickens challenged with NDV after vaccinated with ND vaccine, especially the effect of medium dose was better than that of non-adjuvant and oil adjuvant. These results indicated that EPA could enhance the immune effect of inactivated AI vaccine and ND vaccine and would be expected as a new-type adjuvant.

Assessment of national strategies for control of high-pathogenicity avian influenza and lowpathogenicity notifiable avian influenza in poultry, with emphasis on vaccines and vaccination

Twenty-nine distinct epizootics of high-pathogenicity avian influenza (HPAI) have occurred since 1959. The H5N1 HPAI panzootic affecting Asia, Africa and Eastern Europe has been the largest among these, affecting poultry and/or wild birds in 63 countries. A stamping-out programme achieved eradication in 24 of these epizootics (and is close to achieving eradication in the current H5N2 epizootic in South African ostriches), but vaccination was added to the control programmes in four epizootics when stamping out alone was not effective. During the 2002 to 2010 period, more than 113 billion doses of avian influenza (AI) vaccine were used in at-risk national poultry populations of over 131 billion birds. At two to three doses per bird for the 15 vaccinating countries, the average national vaccination coverage rate was 41.9% and the global AI vaccine coverage rate was 10.9% for all poultry. The highest national coverage rate was nearly 100% for poultry in Hong Kong and the lowest national coverage was less than 0.01% for poultry in Israel and The Netherlands. Inactivated AI vaccines accounted for 95.5% and live recombinant virus vaccines for 4.5% of the vaccines used. Most of these vaccines were used in the H5N1 HPAI panzootic, with more than 99% employed in the People's Republic of China, Egypt, Indonesia and Vietnam. Implementation of vaccination in these four countries occurred after H5N1 HPAI became enzootic in domestic poultry and vaccination did not result in the enzootic infections. Vaccine usage prevented clinical disease and mortality in chickens, and maintained rural livelihoods and food security during HPAI outbreaks. Low-pathogenicity notifiable avian influenza (LPNAI) became reportable to the World Organisation for Animal Health in 2006 because some H5 and H7 low-pathogenicity avian influenza (LPAI) viruses have the potential to mutate to HPAI viruses. Fewer outbreaks of LPNAI have been reported than of HPAI and only six countries used vaccine in control programmes, accounting for 8.1% of the total H5/H7 AI vaccine usage, as compared to 91.9% of the vaccine used against HPAI. Of the six countries that have used vaccine to control LPNAI, Mexico, Guatemala, El Salvador and Italy have been the biggest users. In countries with enzootic HPAI and LPNAI, development and implementation of exit strategies has been difficult.

Enhancement of humoral immune responses to inactivated Newcastle disease and avian influenza vaccines by oral administration of ginseng stem-and-leaf saponins in chickens

Newcastle disease (ND) and avian influenza (AI) are common in the poultry industry. The objective of this study was to evaluate the effect of oral administration of ginseng stem-and-leaf saponins (GSLS) on the humoral immune responses of chickens to inactivated ND and AI vaccines. In experiment 1, oral administration of GSLS at a dose of 5 mg/kg of BW for 7 d on the immune response in chickens intramuscularly injected with inactivated ND vaccine was evaluated. Results showed that GSLS significantly increased the antibody level against ND in the serum of chickens. In experiment 2, the same regimen of GSLS was administered to chickens inoculated with inactivated AI vaccines, and an enhanced serum antibody response to AI vaccination was also observed. Considering the safety of GSLS, because no adverse effect was found throughout the experiments, GSLS may be a promising oral adjuvant to improve immunization in poultry.