Pathological investigation of high pathogenicity avian influenza H5N8 in captive houbara bustards (Chlamydotis undulata), the United Arab Emirates 2020.

At the end of 2020, an outbreak of HPAI H5N8 was registered in captive African houbara bustards (Chlamydotis undulata) in the United Arab Emirates. In order to better understand the pathobiology of this viral infection in bustards, a comprehensive pathological characterization was performed. A total of six birds were selected for necropsy, histopathology, immunohistochemistry, RNAscope in situ hybridization and RT-qPCR and nanopore sequencing on formalin-fixed and paraffin-embedded (FFPE) tissue blocks. Gross lesions included mottled and/or hemorrhagic pancreas, spleen and liver and fibrinous deposits on air sacs and intestine. Necrotizing pancreatitis, splenitis and concurrent vasculitis, hepatitis and fibrino-heterophilic peritonitis were identified, microscopically. Viral antigens (nucleoprotein) and RNAs (matrix gene) were both detected within necro-inflammatory foci, parenchymal cells, stromal cells and endothelial cells of affected organs, including the myenteric plexus. Molecular analysis of FFPE blocks successfully detected HPAI H5N8, further confirming its involvement in the lesions observed. In conclusion, HPAI H5N8 in African houbara bustards results in hyperacute/acute forms exhibiting marked pantropism, endotheliotropism and neurotropism. In addition, our findings support the use of FFPE tissues for molecular studies of poorly characterized pathogens in exotic and endangered species, when availability of samples is limited.

Exposure to and Circulation of Avian Influenza and Newcastle Disease Viruses in Peridomestic Wild Birds in the United Arab Emirates.

Avian influenza and Newcastle disease viruses (AIV, NDV) are major pathogens of captive and wild birds worldwide. Wetlands and their associated bird communities, especially waterfowl and shorebirds, are known to play a central role in the epidemiology of these diseases as maintenance hosts. However, these viruses also circulate in places where these ecosystems and communities are uncommon, suggesting the involvement of other taxa in their epidemiological cycles. In the arid region of Abu Dhabi of the United Arab Emirates (UAE), both viruses are regularly detected, and represent a threat for local poultry and for the Houbara Bustard (Chlamydotis macqueenii) conservation breeding programs. To assess the presence, transmission, and maintenance of these viruses in such environments, 4,521 individuals from six resident and peridomestic wild bird species were sampled in the vicinity of two Houbara Bustard conservation breeding centers, and tested for AIV and NDV using real-time reverse transcriptase PCR and an enzyme-linked immunosorbent assay. A limited exposure to AIV was reflected in a virus prevalence below 0.4% and a serologic prevalence of 0.6%, and a moderate circulation of NDV was indicated by a virus prevalence of 0.9% and a serologic prevalence of 18.9% in the targeted peridomestic wild birds, suggesting different epidemiological roles for each taxa. Thus, some peridomestic species could actively participate in the epidemiological cycle of NDV in arid environments such as the UAE, challenging the conceptual epidemiologic framework centered on the involvement of waterfowl and shorebirds.