|DIMITROV, KIRIL - Consultant|
Submitted to: Veterinary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2016
Publication Date: 7/1/2017
Publication URL: http://handle.nal.usda.gov/10113/5734383
Citation: Dimitrov, K.M., Afonso, C.L., Yu, Q., Miller, P.J. 2017. Newcastle disease vaccines- a solved problem or a continuous challenge? Veterinary Microbiology. 206:126-136. https://doi.org/10.1016/j.vetmic.2016.12.019.
Interpretive Summary: Most of the Newcastle disease vaccines administered to poultry today are killed and live vaccines made with Newcastle disease virus (NDV) strains isolated from the United States in the 1950s. These traditional vaccines are able to prevent chickens from getting sick and dying when the vaccines are administered correctly to healthy birds who are able to develop a good immune response before being exposed to the challenge virus. However, none of them are able to prevent the virulent challenge virus from infecting the vaccinated bird or prevent the vaccinated bird from shedding that challenge virus in saliva and feces even though the bird does not look sick. New scientific techniques have allowed scientists to manipulate and create new vaccines made with recombinant viruses. These vaccines can use viruses other than NDV, like fowlpox virus or herpes virus of turkeys that are able to have a part of the NDV genome inside of them. These vectored vaccines have the advantage of not causing respiratory disease that can sometimes be seen with live NDV vaccines. Other scientists have manipulated the NDV genome itself so that the virus is similar or homologous to the challenge NDV strain, but changed so that it does not cause disease. The benefits of these recombinant NDV (rNDV) vaccines are that they are able to decrease the amount of challenge virus shed from vaccinated birds that are infected more than the traditional ND vaccines. This review summarizes the historical and current situation with ND and NDV strains and reviews the types of ND vaccines available today.
Technical Abstract: Newcastle disease (ND) has been defined by the World Organization for Animal Health as infection of poultry with virulent strains of Newcastle disease virus (NDV). Lesions affecting the neurological, gastrointestinal, respiratory, and reproductive systems are most often observed. The control of ND must include strict biosecurity that prevents virulent NDV from contacting poultry, and also proper administration of efficacious vaccines. When administered correctly to healthy birds, ND vaccines formulated with NDV of low virulence or viral-vectored vaccines that express the NDV fusion protein are able to prevent clinical disease and mortality in chickens upon infection with virulent NDV. Live and inactivated vaccines have been widely used since the 1950’s. Recombinant and antigenically matched vaccines have been adopted recently in some countries, and many other vaccine approaches have been only evaluated experimentally. Despite decades of research and development towards formulation of an optimal ND vaccine, improvements are still needed. Impediments to prevent outbreaks include uneven vaccine application when using mass administration techniques in larger commercial settings, the difficulties associated with vaccinating free-roaming, multi-age birds of village flocks, and difficulties maintaining the cold chain to preserve the thermo-labile antigens in the vaccines. Incomplete or improper immunization often results in the disease and death of poultry after infection with virulent NDV. Another cause of decreased vaccine efficacy is the existence of antibodies (including maternal) in birds, which can neutralize the vaccine and thereby reduce the effectiveness of ND vaccines. In this review, a historical perspective, summary of the current situation for ND and NDV strains, and a review of traditional and experimental ND vaccines are presented.