Abstract
Newcastle disease (ND) is one of the most important avian diseases with considerable threat to the productivity of poultry all over the world. The disease is associated with severe respiratory, gastrointestinal, and neurological lesions in chicken leading to high mortality and several other production related losses. The aetiology of the disease is an avian paramyxovirus type-1 or Newcastle disease virus (NDV), whose isolates are serologically grouped into a single serotype but genetically classified into a total of 19 genotypes, owing to the continuous emergence and evolution of the virus. In Nigeria, molecular characterization of NDV is generally very scanty and majorly focuses on the amplification of the partial F gene for genotype assignment. However, with the introduction of the most objective NDV genotyping criteria which utilize complete fusion protein coding sequences in phylogenetic taxonomy, the enormous genetic diversity of the virus in Nigeria became very conspicuous. In this review, we examine the current ecological distribution of various NDV genotypes in Nigeria based on the available complete fusion protein nucleotide sequences (1662 bp) in the NCBI database. We then discuss the challenges of ND control as a result of the wide genetic distance between the currently circulating NDV isolates and the commonest vaccines used to combat the disease in the country. Finally, we suggest future directions in the war against the economically devastating ND in Nigeria.
Highlights
Poultry production is globally threatened by a highly devastating disease of birds called Newcastle disease (ND)
This pandemic was quickly placed under control with the available ND vaccines, the third pandemic still occurred around the early 1980s among the racing pigeons [5, 6]
Since it is an established fact that ND vaccines are more effective in reducing virus shedding when the vaccine strains are genetically closer to the challenge strain [57, 97], the evolutionary distance between the vaccine strains and the circulating field strain represents an important factor in effective disease control, since it explains the continuous occurrence of ND outbreaks despite the extensive poultry vaccination programs in the country
Summary
Poultry production is globally threatened by a highly devastating disease of birds called Newcastle disease (ND). In the late 1960s, the second pandemic of the disease occurred with an incredibly high speed, taking only four years to spread throughout the world, probably due to extensive commercialization of poultry production and the improvement of air transport systems which facilitated the exchange of exotic birds into new areas [4]. This pandemic was quickly placed under control with the available ND vaccines, the third pandemic still occurred around the early 1980s among the racing pigeons [5, 6]. In this review, we analyze the current ecological distribution of NDV genotypes in various parts of Nigeria and discuss the implication of the genotype mismatch between the circulating field strains and the vaccine strains to ND control in the country
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