Investigation of suspected Newcastle disease (ND) outbreaks in Egypt uncovers a high virus velogenic ND virus burden in small-scale holdings and the presence of multiple pathogens

Abstract

Highly contagious Newcastle disease (ND) is associated with devastating outbreaks with highly variable clinical signs among gallinaceous birds. In this study we aimed to verify clinical ND suspicions in poultry holdings in Egypt suffering from respiratory distress and elevated mortality, comparing two groups of ND-vaccinated poultry holdings in three governorates. Besides testing for Newcastle disease virus (NDV), samples were screened for infectious bronchitis virus (IBV) and avian influenza virus (AIV) by RT-qPCR as well as by non-directed cell-culture approach on LMH-cells. Virulent NDV was confirmed only in group A (n = 16) comprising small-scale holdings. Phylogenetic analysis of the fusion protein gene of 11 NDVpositive samples obtained from this group assigned all viruses to genotype 2.VIIb and point to four different virus populations that were circulating at the same time in one governorate, indicating independent epidemiological events. In group B, comprising large commercial broiler farms (n = 10), virulent NDV was not present, although in six farms NDV vaccine-type virus (genotype 2.II) was detected. Besides, in both groups, co-infections by IBV (n = 10), AIV H9 (n = 3) and/or avian reovirus (ARV) (n = 5) and avian astrovirus (AastVs) (n = 1) could be identified. Taken together, the study confirmed clinical ND suspicion in small scale holdings, pointing to inefficient vaccination practices in this group A. However, it also highlighted that, even in an endemic situation like ND in Egypt, in cases of suspected ND vaccine failure, clinical ND suspicion has to be verified by pathotype-specific diagnostic tests. RESEARCH HIGHLIGHTS. Velogenic NDV circulates in small-scale poultry holdings in Egypt. . Viral transmission occurred among neighbouring farms and over long distances. . Co-infections with multiple pathogens were identified. . Pathotype specific diagnostic tests are essential to verify ND suspicions. ARTICLE HISTORY

Characterization and Genetic Analysis of Recent and Emergent Virulent Newcastle Disease Viruses in Egypt

“…On the other hand, NDV-infected flocks are customarily diagnosed based on clinical signs, gross lesions of freshly dead birds and partial molecular amplification of F gene (200-500 bp) using specific primers for the region flanking F0 precursor cleavage site (Moharam et al, 2019). However, this strategy was found to be insufficient for detecting immune escape variants that emerge from the continuous immune pressure of LaSota vaccines, which explains the reason for sequencing the complete F gene in this study.…”

“…Analysis of these antigenic epitopes in isolates from the current study and previously established isolates of different subgenotypes in Egypt showed that all these F neutralizing epitopes are highly conserved among our isolates, with one common amino acid substitution (K78R) detected. Interestingly, two old strains NDV-EG-35-2014 and NDV-KFR-B7-2012 showed an additional substitution at D170N; a recent isolate, found in both backyard birds and commercial vaccinated chickens (Moharam et al, 2019), showed a novel, uncommon amino acids substitution, V168I, that had not been previously detected (Table 2).…”

“…In the last decade, despite the intensive application of the NDV vaccination regiment, many velogenic NDV outbreaks have been recorded in different avian species such as chickens, ducks and pigeons (Ewies, Ali, Tamam, & Madbouly, 2017;Hussein et al, 2005;Mohamed, Kumar, Paldurai, & Samal, 2011;Radwan, Darwish, El-Sabagh, El-Sanousi, & Shalaby, 2013). Moreover, a recent study showed that velogenic NDV circulates in small-scale poultry holdings with the ability to transmit over long distances between farms (Moharam et al, 2019), which indicating a complex endemic situation for NDV in Egypt. Despite high levels of evolution and circulation of virulent NDV genotype VII.1.1 in Egypt (Orabi, Hussein, Saleh, El-Magd, & Munir, 2017), our previous study indicated that common NDV genotype II vaccine strains such as LaSota fully protected vaccinated chickens against clinical signs and mortalities but did not fully stop virus shedding post-challenge with velogenic NDV genotype VII.1.1 (Ali et al, 2019).…”

Monoclonal Antibodies Specific for the Hemagglutinin-Neuraminidase Protein Define Neutralizing Epitopes Specific for Newcastle Disease Virus Genotype 2.VII from Egypt.

“…MH899939; genotype VII.1.1) was isolated from an ND vaccinated layer ock in Egypt suffering respiratory distress. The virus was characterized as velogenic having an intracerebral pathogenicity index (ICPI) of 1.8 and belonged to genotype 2.VIIb [35]. Pigeon type paramyxovirus-1 (pigeon/Germany/R75/1998), genotype 2.VI, was derived from the repository of the ND reference laboratory (Acc.…”

Sequence analysis and pathogenicity of Avian Orthoavulavirus 1 strains isolated from poultry flocks during 2015–2019

“…The phylogenic analysis of AOAV-1 strains circulated in small-scale poultry holdings in Egyptian villages revealed them belonging to genotype VIIb. Also, the viral transmission occurred among neighboring farms over long distances, and co-infections with multiple pathogens were identified [ 14 , 15 ]. Circulating AOAV-1 in wild birds in borderline or frontier Egyptian provinces containing wetlands was recorded [ 16 ].…”