Field Efficacy In broiler Chickens In Latin America Of VHVT-013, A Marek’s HVT Vector Vaccine Expressing VP2 On Infectious Bursal Disease Virus

Fernandez R., Rojo F., Garcia H., Sanchez P., Martinez H., Menendez A., Ruiz H., Jaramillo C., Icochea E., Guzman J., Gonzales R., Reyna P., Davila E., Gutierrez H., Talavera B., Pereira J., Oliveira C., Lemiere S | Merial Avian Science Review | 2008


Infectious Bursal Disease (IBD) and Marek’s disease (MD) are the main viral diseases that affect the chicken immune system. Gumboro virus, or Infectious Bursal Disease virus (IBDV), is a double-stranded RNA Birnavirus that destroys immature B-lymphocytes in the bursa of Fabricius. Very virulent strains of IBDV (vvIBDV) can induce severe immunosuppression and up to 50% mortality. Since the mid-1980’s, vvIBDV has spread in an explosive manner to nearly all continents. It is necessary to establish protection as early as possible for commercial chickens, which are usually infected early in life. Current vaccines that are used in field conditions are not entirely efficacious against different virus strains present on the field where the IBD virus can mutate rapidly and cannot overcome easily maternally derived antibodies. The vaccine for Marek’s disease, caused gallid herpesvirus 2 (GaHV-2), was introduced in 1970. vHVT-013 used to formulate a live frozen vaccine against IBDV and Marek’s Disease, uses a classical Marek’s vaccine vectorized turkey Herpesvirus (HVT) expressing the protective antigen (VP2) of IBDV. VHVT-013 based frozen vaccine has been approved in the EU, USA and Latin American countries, based on experimental safety and efficacy data, for use on one-day old chicks and in ovo. The field efficacy of vHVT-013 vaccine has been studied for the first time with trials in Latin America in broiler chicken flocks where classical, vvIBD and variant strains have been reported.