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Newcastle Disease: Knowing the Virus Better to Make the Best Control Decisions. Part I
Newcastle disease (ND) is considered one of the most important infectious diseases of poultry because velogenic strains of the virus can cause outbreaks with high morbidity, mortality and restriction of international trade.
This causes significant economic losses to the poultry industry. This is why the disease is included in the list of notifiable diseases to the World Organization for Animal Health (Miller and Koch, 2020).
Newcastle disease is prevented by biosecurity and vaccination, and even though several types of effective live and inactivated vaccines are applied, ND continues to be a problem in many countries around the world.
THE CAUSAL AGENT
The International Committee on Viral Taxonomy database classifies the virus as family Paramyxoviridae, subfamily Avulavirinae, the latter distributed in three genera:
Orthoavulavirus.
Metaavulavirus.
Paravulavirus.
Avian paramyxoviruses have been isolated from different avian species, and are classified into 21 serotypes by serological tests and phylogenetic analysis (WOAH, 2021).
Newcastle disease is caused by virulent strains of Avian Paramyxovirus type 1 (APMV-1), species Avian Orthoavulavirus type -1 (OAV-1).
Newcastle disease virus (NDV) has a single-stranded, unsegmented, negative-sense RNA genome measuring 15,186 nucleotides (Alexander, 2003).
The virion has a lipid bilayer envelope derived from the plasma membrane of the host cell (Mast y Demeestere, 2009).
The virus genome is composed of six genes in 3’-NP-P-M-F-HN-L-5’ order, encoding seven viral proteins:
Nucleoprotein (NP),
Phosphoprotein (P),
Matrix protein (M),
Fusion protein (F),
Hemagglutinin-neuraminidase (HN) and
RNA polymerase, called the large polymerase (L).
RNA editing of the P protein produces an additional protein, the V protein, with anti-interferon activity, which allows the virus to counteract the innate host cell response (Miller and Koch, 2020) (Figure 1).
Figure 1. Schematic representation of the ND virus genome and its proteins
The main biological property of the virus is to agglutinate red blood cells of birds, amphibians and reptiles, due to the action of the HN protein on the sialic acid receptors on the surface of red blood cells.
Viral hemagglutination (HA) allows the determination of viral presence in viral cultures and allantoic fluid of chicken embryos (Miller and Koch, 20...
