Abstract
BackgroundNewcastle disease is still a serious disease of poultry especially in backyard free-range production systems despite the availability of cross protective vaccines. Healthy-looking poultry from live bird markets have been suspected as a major source of disease spread although limited studies have been conducted to ascertain the presence of the virulent strains in the markets and to understand how they are related to outbreak strains.MethodsThis study evaluated the occurrence of Newcastle disease virus in samples collected from poultry in live bird markets across Uganda. The isolates were pathoyped using standard methods (mean death time (MDT), intracelebral pathogenicity index (ICPI), and sequencing of the fusion protein cleavage site motif) and also phylogenetically analysed after sequencing of the full fusion and hemagglutin-neuraminidase genes. The isolates were classified into genotypes and subgenotypes based on the full fusion protein gene classification system and compared with other strains in the region and world-wide.ResultsVirulent avian paramyxovirus type I (APMV-1) (Newcastle disease virus) was isolated in healthy-looking poultry in live bird markets. The viruses belonged to a new subgenotype, Vd, in genotype V, and clustered together with Tanzania and Kenya strains. They harbored low genetic diversity.ConclusionThe occurrence of virulent AMPV-1 strains in live bird markets may serve as sources of Newcastle disease outbreaks in non-commercial farms.
Highlights
Newcastle disease is still a serious disease of poultry especially in backyard free-range production systems despite the availability of cross protective vaccines
Newcastle disease is a highly contagious disease affecting chickens and other poultry species and wild birds. It devastates unvaccinated flocks in periodic outbreaks resulting in up to 70-100% mortality, which is a big loss to the households. It is caused by RNA viruses of the Avian Paramyxovirus type 1 (APMV-1), [1]
The purpose of this study was to assess the occurrence of Newcastle disease virus (NDV) pathotypes in live bird markets across Uganda and to determine their genetic diversity and relatedness using the new NDV nomenclature
Summary
Newcastle disease is still a serious disease of poultry especially in backyard free-range production systems despite the availability of cross protective vaccines. Newcastle disease is a highly contagious disease affecting chickens and other poultry species and wild birds. It devastates unvaccinated flocks in periodic outbreaks resulting in up to 70-100% mortality, which is a big loss to the households. It is caused by RNA viruses of the Avian Paramyxovirus type 1 (APMV-1), (synonym: Newcastle disease virus, NDV) [1]. Most research has focused mainly on basic epidemiology especially during ND outbreaks in poultry and it is believed ND in village chickens is attributed to birds that are shedding virus during and after incubation or post vaccination [2,3]. Markets may serve as a source of Newcastle disease infection and contribute to its spread as infected birds not showing clinical signs are sold before they come down with the disease
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