Molecular Survey of Respiratory and Immunosuppressive Pathogens Associated with Low Pathogenic Avian Influenza H9N2 Subtype and Virulent Newcastle Disease Viruses in Commercial Chicken Flocks

Mapping Genetic Markers Associated with Antigenicity and Host Range in H9N2 Influenza A Viruses Infecting Poultry in Pakistan

The aim of the current study was to map the genetic diversity in the haemagglutinin (HA) glycoprotein of influenza A viruses (IAVs) of the H9N2 subtype. Twenty-five H9N2 IAVs were isolated from broiler chickens from March to July 2019. The HA gene was amplified, and phylogenetic analysis was performed to determine the evolutionary relationship. Important antigenic amino acid residues of HA attributed to immune escape and zoonotic potential were compared among H9N2 IAVs. Phylogenetic analysis revealed that sublineage B2 under the G1 lineage in Pakistan was found to be diversified, and newly sequenced H9N2 isolates were nested into two clades (A and B). Mutations linked to the antigenic variation and potential immune escape were observed as G72E (1/25, 4%), A180T (3/25, 12%), and A180V (1/25, 4%). A twofold significant reduction (P < 0.01) in log2 hemagglutination inhibition titers was observed with H9N2 IAV naturally harboring amino acid V180 instead of A180 in HA protein. Moreover, in the last 20 years, complete substitution at residues (T127D, D135N, and L150N) and partial substitution at residues (72, 74, 131, 148, 180, 183, 188, 216, 217, and 249, mature H9 HA numbering) associated with changes in antigenicity were observed. The presence of L216 in all H9N2 IAV isolates and T/V180 in four isolates in the receptor-binding site reveals the potential of these viruses to cross the species barrier to infect human or mammals. The current study observed the circulation of antigenically diverse H9N2 IAV variants that possess potential mutations that can escape the host immune system.

Metagenomic characterization reveals virus coinfections associated with Newcastle disease virus among poultry in Kenya

Newcastle disease (ND) is an endemic viral disease affecting poultry and causing massive economic losses. This cross-sectional purposive study detected coinfections that are associated with the Newcastle disease virus among poultry from selected regions in Kenya. Cloacal (n = 599) and oral-pharyngeal (n = 435) swab samples were collected and pooled into 17 and 15 samples, respectively. A total of 17,034,948 and 7,751,974 paired-end reads with an average of 200 nucleotides were generated from the cloacal and oral-pharyngeal swab samples, respectively. Analysis of the de novo assembled contigs identified 177 and 18 cloacal and oral-pharyngeal contigs, respectively with hits to viral sequences, as determined by BLASTx and BLASTn analyses. Several known and unknown representatives of Coronaviridae, Picobirnaviridae, Reoviridae, Retroviridae, and unclassified Deltavirus were identified in the cloacal swab samples. However, no Newcastle disease virus (family Paramyxoviridae) was detected in the cloacal swabs, although they were detected in the oropharyngeal swabs of chickens sampled in Nairobi, Busia, and Trans Nzoia. Additionally, sequences representative of Paramyxoviridae, Coronaviridae, and Retroviridae were identified in the oral-pharyngeal swab samples. Infectious bronchitis virus and rotavirus were chickens' most prevalent coinfections associated with the Newcastle disease virus. The detection of these coinfections suggests that these viruses are significant threats to the control of Newcastle disease as the Newcastle disease virus vaccines are known to fail because of these coinfections. Therefore, this study provides important information that will help improve disease diagnosis and vaccine development for coinfections associated with the Newcastle disease virus.

Molecular detection of respiratory avian mycoplasmosis associated bacterial and viral concurrent infections in the poultry flocks

Respiratory tract infections are of serious concern to the poultry industry. The present study was aimed to delineate the extent of respiratory avian mycoplasmosis associated bacterial and viral concurrent infections in the poultry flocks. A total of 146 poultry flocks of Haryana and Rajasthan, India, suspected for chronic respiratory disease (CRD) were screened for avian mycoplasmas, Newcastle disease virus (NDV), infectious bronchitis virus (IBV), and avian pathogenic Escherichia coli (APEC) by conventional polymerase chain reaction (PCR) assays. A total of 49.31% (72/146) flocks were found positive for Mycoplasma infection. Of the Mycoplasma-positive flocks, 80.55% (58/72) represented pathogenic avian mycoplasmas (MG and/or MS), while 19.44% (14/72) flocks were positive for commensal avian mycoplasmas (other than MG and MS). A correlation was deduced between avian mycoplasmosis and bacterial and/or viral co-infections. The results revealed that 17.24% (10/58) flocks had only avian mycoplasmosis infection. However, in the remaining flocks, the avian mycoplasmosis was associated either with APEC infection [17.24% (10/58)], IBV infection [43.10% (25/58)], or both APEC and IBV infections [22.41% (13/58)], respectively. Further epidemiological studies on respiratory avian mycoplasmosis associated concurrent infections with other pathogens are recommended to assess circulating strains, risk factors, and economic losses.

Predominance of low pathogenic avian influenza virus H9N2 in the respiratory co-infections in broilers in Tunisia: a longitudinal field study, 2018-2020

Respiratory diseases are a health and economic concern for poultry production worldwide. Given global economic exchanges and migratory bird flyways, respiratory viruses are likely to emerge continuously in new territories. The primary aim of this study was to investigate the major pathogens involved in respiratory disease in Tunisian broiler poultry and their epidemiology. Between 2018 and 2020, broilers farms in northeastern Tunisia were monitored, and 39 clinically diseased flocks were sampled. Samples were screened for five viral and three bacterial respiratory pathogens using a panel of real-time PCR assays. The reemergence of H9N2 low pathogenic avian influenza virus (LPAIV) in commercial poultry was reported, and the Northern and Western African GI lineage strain was typed. The infectious bronchitis virus (IBV) GI-23 lineage and the avian metapneumovirus (aMPV) subtype B also were detected for the first time in broilers in Tunisia. H9N2 LPAIV was the most detected pathogen in the flocks tested, but rarely alone, as 15 of the 16 H9N2 positive flocks were co-infected. Except for infectious laryngotracheitis virus (ILTV), all of the targeted pathogens were detected, and in 61% of the respiratory disease cases, a combination of pathogens was identified. The major combinations were H9N2 + aMPV (8/39) and H9N2 + IBV (6/39), showing the high contribution of H9N2 LPAIV to the multifactorial respiratory diseases. This field survey provided evidence of the emergence of new respiratory viruses and the complexity of respiratory disease in Tunisia. A comprehensive and continuous surveillance strategy therefore is needed to better control respiratory pathogens in Tunisia.