A Pigeon-Derived Sub-Genotype XXI.1.2 Newcastle Disease Virus from Bangladesh Induces High Mortality in Chickens

Abstract

Newcastle disease virus (NDV) is a significant pathogen of poultry; however, variants also affect other species, including pigeons. While NDV is endemic in Bangladesh, and poultry isolates have been recently characterized, information about viruses infecting pigeons is limited. Worldwide, pigeon-derived isolates are commonly of low to moderate virulence for chickens. Here, we studied a pigeon-derived NDV isolated in Bangladesh in 2010. To molecularly characterize the isolate, we sequenced its complete fusion gene and performed a comprehensive phylogenetic analysis. We further studied the biological properties of the virus by estimating mean death time (MDT) and by experimentally infecting 5-week-old naïve Sonali chickens. The studied virus clustered in sub-genotype XXI.1.2 with NDV from pigeons from Pakistan isolated during 2014–2018. Deduced amino acid sequence analysis showed a polybasic fusion protein cleavage site motif, typical for virulent NDV. The performed in vivo pathogenicity testing showed a MDT of 40.8 h, and along with previously established intracerebral pathogenicity index of 1.51, these indicated a velogenic pathotype for chickens, which is not typical for pigeon-derived viruses. The experimental infection of chickens resulted in marked neurological signs and high mortality starting at 7 days post infection (dpi). Mild congestion in the thymus and necrosis in the spleen were observed at an advanced stage of infection. Microscopically, lymphoid depletion in the thymus, spleen, and bursa of Fabricius were found at 5 dpi, which progressed to severe in the following days. Mild to moderate proliferation of glial cells was noticed in the brain starting at 2 dpi, which gradually progressed with time, leading to focal nodular aggregation. This study reports the velogenic nature for domestic chickens of a pigeon-derived NDV isolate of sub-genotype XXI.1.2. Our findings show that not all pigeon-derived viruses are of low virulence for chickens and highlight the importance of biologically evaluating the pathogenicity of NDV isolated from pigeons.

Detection of Avian Orthoavulavirus-1 genotypes VI.2.1 and VII.1.1 with neuro-viscerotropic tropism in some backyard pigeons (Columbidae) in Eastern Saudi Arabia

“…It is speculated that PPMV1 evolved from the chicken AOAV1 ( 3 ) and became adapted to columbiform ( 16 ). While circulating in the pigeon population, PPMV1 adaptation and virulence increase for pigeons and decrease for chickens ( 42 ). Beside columbiform and chickens, PPMV1 may infect many other wild birds and gallinaceous species ( 43 , 44 ).…”

“…After a few passages in chickens, PPMV1 eventually acquires some mutations that increase its adaptation and virulence in chickens, possibly by increasing its replication efficiency ( 48 ). However, some PPMV1 isolates were readily virulent for chickens (ICPI=1.51) with no need for prior adaptation ( 42 ). Variable ICPI scores were reported for pigeon derived PPMV1.…”

Pros and Cons on Use of Live Viral Vaccines in Commercial Chicken Flocks

“…Class II includes 21 genotypes (I –XXI) of NDV viruses evolved over time with further subgrouping into sublineages within genotypes that are responsible for the periodic panzootics in both domestic poultry and wild birds worldwide (7). Lentogenic and mesogenic pathotypes are found in Genotypes I–III and velogenic pathotypes in Genotypes IV–VIII (6,8). Genotype XI was isolated from chickens in Madagascar between 2008 and 2011 and evidenced common ancestry with viruses of Genotype IV.…”

A Booster with a Genotype-Matched Inactivated Newcastle Disease Virus (NDV) Vaccine Candidate Provides Better Protection against a Virulent Genotype XIII.2 Virus

“…Vaccination against ND is routinely practiced in commercial poultry farming across the world. Despite widespread vaccination, commercial poultry farms in Bangladesh often encounter ND [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ].…”

“…Primary vaccination is performed with a live vaccine based on a lentogenic strain (LaSota, B1, or F strain), while for booster vaccination, either a lentogenic live vaccine, a lentogenic killed vaccine, or, less frequently, a mesogenic live vaccine (Mukteswar strain) is used. Still, a high prevalence of ND outbreaks is being reported in Bangladesh [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 45 ]. Among different factors, genotypic mismatches between the circulating viruses and vaccine strains could potentially contribute to vaccine failure in the field [ 33 , 35 ].…”