POULTRY Congress of the WVPA 4-8 September 2023 -Verona (Italy)
Protective efficacy with a novel recombinant vaccine r-HVT-ND-H9 against H9N2 infections and other respiratory pathogens in Lebanese and Jordanian broiler productions.
A.Cherfane 2, S. Alam 1, C. Cazaban 2, M.S. Sandikli 2, B. Le Tallec 2.
Ceva Animal Health, LLC NEGU, Lebanon. 2Ceva Animal Health Corporate, France
Introduction
Avian influenza H9N2 usually causes mild disease or asymptomatic infection in SPF birds;
however, it is considered as a great threat to poultry industry due to mixed infections with other pathogens.
Diagnostic investigations of severe respiratory problems revealed that co-infection of H9N2 with other respiratory pathogens (e.g., IBV, NDV, Mycoplasma, ORT, E. coli …) known as “Mutual conspiracy” indicate that most of these factors are synergistic and potentate themselves in infected flocks: H9N2 complicated with other pathogens (IBV, NDV…)
and contributing environmental factors (e.g., poor ventilation, high environmental temperature), the trachea are embolized by fibrinous mucus, leading to severe respiratory disease that can cause mortality up to 50-60% in broilers..
Newflend ND-H9®is a novel recombinant vaccine (r-HVT-ND-H9), using a turkey herpes virus (HVT) as a vector to express a dual insert the hemagglutinin (HA) gene from H9N2 LPAI strain and the Fusion (F) gene for Newcastle).
It is expected to provide a strong level of protection against Newcastle disease and H9N2 challenges due to the broad and strong cell-mediated and humoral immunity it can induce..
The positive impact on the general health status, the cumulative mortality, and losses due to secondary infections needed further investigations. That was the objective of this work: By implementing in Lebanon and Jordan large scale field trials in Broilers flocks vaccinated with Newflend ND-H9®, we evaluated the specific protection of H9 disease, the occurrence and consequences of the co-infections and secondary infections and at the end impact of the vaccination on the overall performances of these broiler productions
Materials and Methods
Diagnostic investigations were conducted to address severe respiratory problems associated with co-infections in avian populations. These investigations aimed to identify the presence of various pathogens and environmental factors contributing to the phenomenon known as “Mutual Conspiracy.”
The investigation involved thorough clinical assessments, sample collection, and laboratory analysis
The concept of “Mutual Conspiracy” involves the synergistic interaction of multiple respiratory pathogens and environmental stressors in avian flocks.
The presence of avian influenza H9N2 alongside pathogens such as infectious bronchitis virus (IBV), Newcastle disease virus (NDV), Mycoplasma, Ornithobacterium rhinotracheale (ORT), and Escherichia coli (E. coli) contributes to the severity of respiratory diseases.
Environmental factors, such as poor ventilation and high temperatures, are recorded to check their impact on the co-infection situation.
Results
Results showed almost systematically a circulation of H9N2 and IBV. Besides them, a significant prevalence of the other pathogens (Mycoplasma, ORT, E coli…) were recorded.
The average percentage of prevalence of H9 in the kidney of birds vaccinated with Newflend is lower by 30% than for the flocks vaccinated with an inactivated ND/H9 vaccine suggesting than only the cell mediated immunity induced by the recombinant vaccine can block or decrease the systemic dissemination of the virus from the trachea to the cecal tonsils then to the kidney.
Interestingly, flocks vaccinated with Newflend ND-H9®are more resistant to secondary infections as MG and MS than the houses vaccinated with Killed ND/H9.
This finding substantiates our hypothesis that by decreasing the amount of H9 virus shed, losses due to secondary or coinfections are minimized
Conclusion
As a conclusion, the vaccination with this recombinant r-HVT ND-H9 has significantly impacted the overall performances positively
Reducing significantly the amount of virus shed and the cumulative mortality of challenged commercial broiler flocks by direct effect of
H9N2 infections. It is impacting positively also by mitigating the losses, controlling the risks of co-infections and bacterial secondary infections.