Vector Newcastle Vaccine Usage in Latin America

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Abstract

Newcastle disease (ND) has been a tremendous burden for the worldwide poultry industry for many decades since its first two diagnosis in 1926 (Java island, Indonesia) and 1927 (Newcastle-upon-Tyne, England). And according to the World Organization for Animal Health (OIE;  HYPERLINK «http://www.oie.int/» \t «_blank» www.oie.int) only 16 countries around the world have never reported velogenic Newcastle Disease. Velogenic ND is caused by specified viruses of the avian paramyxovirus type (APMV-I only) of the family Paramyxoviridae. Mortality in unprotected or semi-protected broiler flocks may range from 30-90%.

The ND epidemiological situation in Latin America is quite variable since there are several countries presenting an endemic status for velogenic ND (e.g., Venezuela, Mexico, Colombia, Peru and Bolivia) while others have their modern poultry industry free of velogenic ND (e.g., Brazil, Argentina, Chile and Uruguay). However, the countries’ officially certification as free of velogenic ND applies only to the ND monitored industrial poultry production systems as detection of velogenic ND virus (NDV) is not rarely done in backyard poultry and wild birds in those ND free countries. Therefore, vaccination of modern poultry against ND is most the times a requirement.

Prevention and/or control of velogenic ND in Latin America rely heavily, as in many other countries worldwide, upon the use of conventional live and inactivated vaccines plus a well-planned and implemented biosecurity program. The main disadvantages of conventional ND vaccines are: 1. neutralizing effect of maternal antibody (MAb) levels on the vaccines’ antigens; 2. quality of application and 3. post-vaccination reactions.

In the last 3-4 years a new vaccine technology for prevention and/or control of ND has been introduced in Latin America and in many other areas around the world. It’s a molecular biology derived technology product defined as vector vaccine. This recent vector vaccine development against velogenic ND is a turkey herpesvirus-based recombinant vaccine (rHVT) expressing a key protective antigen (F glycoprotein) of the ND virus (Vectormune® ND® - Ceva Animal Health - Lenexa, KS, USA). A series of field and controlled trials on commercial broilers with the vectorrHVT ND vaccine, applied either in ovo or subcutaneously at day 1, have been carried out in some Latin American countries during the last 2.5 years. These trials involved basically three different epidemiological areas (field challenge from velogenic ND): 1) endemic high challenge area (Mexico); 2) endemic medium to low challenge area (Peru); and 3) ND free area (Brazil).

In all areas the vector vaccine was able to induce significant protection against the circulating NDV both field velogenic and vaccine lentogenic strains. Vaccinated broilers taken from the farm and challenged in isolation showed not only complete protection against mortality but also a quite significant reduction in challenge virus excretion when compared to broilers vaccinated with conventional vaccines. The detected reduction in virus excretion may have significant impact on the epidemiology of the disease as it’s expected that field challenge will decrease with time as less field velogenic viruses will be maintained in the environment. Field post-vaccination reactions were either much less evident in broilers vaccinated with the vector vaccine plus a live conventional vaccine or completely eliminated when the vector vaccine was applied alone. This induced lower normal mortality and allowed the broilers to better express their genetic potential for growth and meat production and thus generating a higher financial income to the farmers.

In conclusion, the vector rHVT ND vaccine proved itself quite safe and effective in all three ND epidemiological situations.

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