Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 12/20/2013
Publication Date: N/A
Technical Abstract: Vaccination of poultry has been used for decades and is a common practice in integrated poultry production. However, the decision to use vaccination for protection against avian influenza (AI) is typically dependent on several factors including pathotype, type of birds and eradication strategies. The recent outbreaks in poultry of AI H7N3 in Mexico and H7N9 in China underscore the need for continued research in vaccine countermeasures as part of an eradication effort. However, these two outbreaks contrast the use for vaccines as one involves infection of commercial egg-laying birds (H7N3) and the other is primarily found in live bird markets (H7N9) but with human health implications. In June of 2012, an outbreak of highly pathogenic avian influenza (HPAI) H7N3 was reported in egg-laying hens in Jalisco, Mexico. Since that time the virus has spread to many surrounding States and new outbreaks continue to be reported with millions of birds depopulated. Vaccine trials were performed to determine protective efficacy of an inactivated H7 vaccine. In the first set of experiments, a Mexican-lineage low pathogenic AI (LPAI) H7N3 was applied to 2 week-old chickens. When challenged, vaccinated birds demonstrated 100 % protection. In a second experiment, 26 week-old egg-laying hens were vaccinated and challenged against the HPAI virus. All vaccinated birds reduced shedding of virus compared to sham vaccinated birds. Vaccinated birds were also protected against drops in egg production. These results demonstrate the LPAI vaccine isolate can provide protection against the HPAI H7N3 virus. In March of 2013, the first cases of H7N9 were reported in humans and shortly thereafter the virus was isolated from pigeon and poultry in live bird markets. The genetic composition of these H7N9 viruses appears to be solely of avian origin, although of low pathogenicity (LP). Although few isolations of these viruses have been demonstrated on poultry farms, the correlation between live bird market shut downs and reduced human infections in China underscores a linkage between poultry and humans. In response to the outbreak, vaccine efficacy trials were recently performed to determine if inactivated H7N9 vaccine could increase resistance of birds to clinical disease and shedding of virus. A homologous H7N9 vaccine was formulated into an inactivated emulsion and injected at various doses into 3 week old SPF birds. Birds were challenged at 6 weeks of age with 108 EID50 per bird delivered via intranasal route. Sham vaccinated birds demonstrated 10 % mortality and reduction in weight gain. In contrast vaccinated groups demonstrated improved weight gain compared to sham vaccinated birds. Taken together, these results indicate that the homologous vaccine can provide protection to poultry against this recent LPAI H7N9 virus.