There was certainly hope but there were also many questions, uncertainties and doubts, and because of that, a very significant extra investment was made to know and understand the potentialities of this new product. Scientific work inside as well as outside the company, in collaboration with independent research centers, was designed, organized and conducted. The information obtained regarding the vaccine induced immunity and tangible protection results far exceeded our expectations.
Vectormune® ND is a recombinant HVT vector vaccine, in which genome the “F” gene of a genotype I NDV has been inserted. The HVT strain used (FC 126), its origin, the low number of passages applied, the “F” insert, the insertion site, the promoter selected to ensure the expression of the F gene, the terminal sequence, etc... are all key elements explaining the uniqueness and outstanding features of this vaccine. Most of these features have been patented and belong to Ceva Animal Health. Vectormune® ND is actually unique and cannot be confused with other rHVT-ND vaccines.
The “F” (for “fusion”) protein is the epitope present on the surface of NDV, allowing it to attach and penetrate target cells. It is, at the same time, a key factor of virulence of the virus, as well as a key protective antigen. One can easily understand that if immunity is built up against “F”, then NDV would have much more difficulties to infect cells and create damage, which is probably explaining the incredibly high efficacy of Vectormune® ND. Vaccinated chickens are not only chicken’s body limited increase protected against clinical and economical consequences of infection: the replication of NDV inside the is also hampered as indicated by a reduction of the shedding of the challenge virus as well as a more in antibody titers following infection.
The HVT strain used to carry and express the “F” gene is known for decades as a very safe and very stable virus, used worldwide to vaccinate chickens against Marek’s disease. The particular strain and passage level used for the construction of Vectormune® ND replicates actively in the chicken and this may explain why protection against ND appears so quickly.
Duration of immunity
Duration of immunity is probably the most impressive feature of this vaccine.
Following a single injection of Vectormune® ND at day of hatch, layers are totally protected against clinical signs, mortality and drop in egg production until, at least, 72 weeks of age (Palya et al., 2012c). This cannot be compared to any existing ND vaccination conventional program where a minimum of 2 to 4 killed and 5 to 8 live vaccinations would be necessary to achieve acceptable (but not comparable) level of protection.
Since protection with Vectormune® ND requires replication of the HVT vector and this generally takes some days, the first 3 weeks of life are gradually covered by Vectormune® ND. For this reason, in ND endemic countries, the vaccination strategy with Vectormune® ND requires ensuring early protection by application of a live attenuated ND vaccine by spray on the first day of age in the hatchery. In order to avoid damages to the trachea, which are detrimental to both growth and the integrity of the respiratory tract, it is strongly recommended to use a vaccine based on an apathogenic enterotropic NDV strain, like the Phy.LMV.42 NDV strain present in Cevac® Vitapest L (ND only) or Cevac® Vitabron L (combination of ND + IB).
In countries where ND is only an epizootic risk, it is advisable to remove any live ND vaccine from the program. The combination of a reliable ND passive immunity together with Vectormune® ND induced active immunity will ensure a very significant level of protection. By removing the use of any live ND vaccine in chicken flocks, this innovative approach helps to improve the overall respiratory health, which could in turn result in less antibiotic medication and lower rates of airsacculitis at the processing plant.
Following several years of investigation with Vectormune® ND, we believe that this vaccine is more a revolution than a simple evolution.
Vectormune® ND has been changing the approach of Newcastle disease prevention in the field and is being considered as a strong tool towards the long term control of this important poultry disease.
Spectrum of protection
Vectormune® ND is provided with a broad spectrum of efficacy.
Perfect protection has been demonstrated against challenges conducted with high doses of various NDV strains, belonging to diverse genotypes, including genotype II (Texas GB strain, B1B1 strain), genotype IV (Herts 33 strain), genotype V (Mexican Chimalhuacan strain), and genotype VII (several isolates).