by A recent study published in the CDC’s Emerging Infectious Diseases journal has shed light on the impact of the highly pathogenic avian influenza (HPAI) A (H5N1) virus on non-domesticated terrestrial animals across the United States. The study, conducted between April 1 and July 21, 2022, characterized the pathophysiology of HPAI H5N1 infections in various wildlife species.
The HPAI A H5N1 virus, which belongs to the Eurasian lineage and 2.3.4.4b clade, has been spreading across Europe and the US since October 2021. The virus was first identified in the US in December 2021 and has since affected both domesticated animals and non-domestic birds. It continues to be active in non-domesticated bird reservoirs, leading to spillover and clinical disease in various animal species in European nations.
The study presented a series of cases that highlighted the pathophysiology of spontaneous HPAI H5N1 infections in terrestrial wild animals in the US. These cases coincided with elevated levels of highly pathogenic avian influenza viruses circulating among non-domesticated avian species during the summer and spring of 2022.
The researchers analyzed opportunistic specimens from unwell or dead wild animals that were sent to state-level wildlife authorities or veterinary laboratories for diagnosis. Clinical observations by wildlife and veterinary professionals, citizens, and rehabilitators were also included. Post-mortem examinations were conducted on all animals, except for two red foxes that only provided antemortem samples.
Various tests were performed on the specimens, including viral transfer mediums, tissue samples, and tissues preserved in formalin. The researchers used reverse transcription-polymerase chain reaction (RT-PCR) to target the conserved site of the influenza A virus matrix genes. Subtyping tests were also conducted to identify the H5 subtype of the virus.
The study identified HPAI in 67 non-domesticated animals across 10 US states between April and July 2022. The affected animals included red-colored foxes, striped skunks, raccoons, bobcats, Virginia opossums, coyotes, fishers, and gray foxes. The most common pathologies observed in infected animals were necrotizing meningoencephalitis, interstitial pneumonia, and cardiac necrosis. Sequencing revealed that these cases were a result of wild bird illnesses.
Most of the affected animals were juveniles, and there was no preference for either sex within the species. The study also found that multiple North American animals were vulnerable to HPAI H5N1 virus infections through infected wild bird consumption. The predominant clinical presentation of HPAI infections in wildlife is neurological symptoms.
The findings of this study highlight the expanding range of species vulnerable to the HPAI H5N1 virus in the US. It emphasizes the need to consider HPAI virus infection as a differential diagnosis in cases of neurologic illness in wild animals. The study provides valuable insights into the pathophysiology of HPAI infections in non-domesticated terrestrial animals and contributes to our understanding of the impact of avian influenza viruses on wildlife populations.
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- Source: Coherent Market Insights, Public sources, Desk research
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