High pathogenicity avian #influenza in #pinniped #conservation

 

Abstract

Since 2020, H5Nx high pathogenicity avian influenza viruses (HPAIVs) have caused widespread disruptions not only to global agriculture and trade but also to the health of free-ranging wildlife. Pinnipeds have experienced greater mortality from H5Nx HPAIV than any other mammalian taxa. Emergent virus strains, persisting over long time periods and vast geographic distances, have repeatedly triggered large-scale mortality events in pinniped populations. Of particular concern is the spread of H5Nx HPAIV to the Southern Hemisphere—including the emergence of a marine mammal-adapted clade in South America and detections in the sub-Antarctic and Antarctic—and to other remote locations such as the Hawaiian Islands. These developments elevate concern for the world’s endangered, isolated and endemic pinnipeds. While managing HPAIV in any animal population is a formidable task, working with free-ranging marine mammals poses unique challenges. In this review and perspective piece, we attempt to synthesize complexities at this intersection. We describe lessons learned from HPAIV investigations in marine wildlife, highlight gaps in knowledge and capacity, and discuss the incorporation of outbreak risk assessment and countermeasures into pinniped conservation. Finally, we propose ways in which pinnipeds—and marine wildlife broadly—could be better integrated into existing systems for HPAIV intelligence, control and prevention.

This article is part of the theme issue ‘Managing infectious marine diseases in wild populations’.

Source: 

Link: https://royalsocietypublishing.org/rstb/article/381/1945/20240320/480666/High-pathogenicity-avian-influenza-in-pinniped

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#Pathobiology of Highly Pathogenic Avian #Influenza A #H5N1 Clade 2.3.4.4b Virus from #Pinnipeds on Tyuleniy Island in the Sea of #Okhotsk, #Russia

 

Abstract

Highly pathogenic avian influenza (HPAI) A(H5N1) clade 2.3.4.4b has recently emerged as a major threat to wildlife, agriculture, and public health due to its expanding host range and the increasing frequency of spillover into mammals. In July–August 2023, the mass death of over 3500 northern fur seals (Callorhinus ursinus) and at least one Steller sea lion (Eumetopias jubatus) was recorded on Tyuleniy Island in the Sea of Okhotsk, Russia. Two HPAI A(H5N1) viruses were isolated from fur seal carcasses and designated A/Northern_fur_seal/Russia_Tyuleniy/74/2023 and A/Northern_fur_seal/Russia_Tyuleniy/75/2023. Both viruses exhibited high pathogenicity in chickens (IVPI 2.7–3.0) and mice (MLD50 1.9–2.5 log10EID50/mL), with distinct differences in disease progression, histopathology, and organ tropism. Experimental infection of mice revealed that strain A/74/2023 induced more severe pulmonary and neurological lesions than A/75/2023. Whole-genome sequencing and phylogenetic analysis demonstrated close relatedness to HPAI H5N1 strains circulating in the Russian Far East and Japan from 2022 to 2023, with several mutations associated with mammalian adaptation, including NP-N319K and, in one isolate, PB2-E627K. According to our findings, northern fur seals (Callorhinus ursinus) on Tyuleniy Island acted as spillover hosts for the highly pathogenic avian influenza (HPAI) H5N1 virus of clade 2.3.4.4b. Furthermore, the high population density of fur seals and the extensive mortality observed during the outbreak highlight these animals’ potential role as another vessel for the evolution of avian influenza viruses. This study represents the first documented case of HPAI H5N1 in pinnipeds in the North Pacific region and supports previous reports indicating that pinnipeds, including northern fur seals, are highly susceptible to HPAI H5N1 clade 2.3.4.4b viruses.

Source: 

Link: https://www.mdpi.com/1999-4915/18/1/51

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#Transmission, Pathological and Clinical Manifestations of Highly Pathogenic Avian #Influenza A Virus in #Mammals with Emphasis on #H5N1 Clade 2.3.4.4b

 

Abstract

Highly pathogenic avian influenza A virus (HPAIV) H5N1, clade 2.3.4.4b, has emerged as a significant zoonotic threat. H5N1 is widely circulating in wild birds, and an increasing number of spillover events have been observed in a wide range of mammalian species. These cases are primarily reported in countries on the European and American continents. This review describes the likely transmission routes, lesions, and clinical manifestations of HPAIV H5N1 clade 2.3.4.4b in naturally infected mammals, with a focus on the involvement of the central nervous system (CNS). In the analysis, pathological findings were categorized by organ system and host species, which were further divided into terrestrial mammals, marine mammals, and dairy cattle. The most frequently reported clinical manifestations were neurological and respiratory signs in marine mammals and neurological signs and lethargy in terrestrial mammals. Macroscopic and histological lesions were commonly found in the CNS and lungs of terrestrial and marine mammals, while dairy cattle showed mainly gastrointestinal and mammary gland involvement. Immunohistochemistry and reverse transcriptase real-time PCR analyses confirmed high viral loads in brain tissues, indicating a neurological tropism of H5N1 clade 2.3.4.4b. Routes of CNS invasion remain uncertain, though both hematogenous and olfactory nerve pathways are discussed. Recent evidence suggests mammal-to-mammal and vertical transmission, raising concerns for the zoonotic and pandemic potential of this virus. In conclusion, the findings emphasize an urgent need for enhanced surveillance to effectively disclose changes in viral pathogenicity and transmissibility among mammalian hosts.

Source: 

Link: https://www.mdpi.com/1999-4915/17/12/1548

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Cross-species and #mammal-to-mammal #transmission of clade 2.3.4.4b highly pathogenic avian #influenza A #H5N1 with #PB2 adaptations

Abstract

Highly pathogenic H5N1 avian influenza viruses (HPAIV) belonging to lineage 2.3.4.4b emerged in Chile in December 2022, leading to mass mortality events in wild birds, poultry, and marine mammals and one human case. We detected HPAIV in 7,33% (714/9745) of cases between December 2022–April 2023 and sequenced 177 H5N1 virus genomes from poultry, marine mammals, a human, and wild birds spanning >3800 km of Chilean coastline. Chilean viruses were closely related to Peru’s H5N1 outbreak, consistent with north-to-south spread down the Pacific coastline. One human virus and nine marine mammal viruses in Chile had the rare PB2 D701N mammalian-adaptation mutation and clustered phylogenetically despite being sampled 5 weeks and hundreds of kilometers apart. These viruses shared additional genetic signatures, including another mammalian PB2 adaptation (Q591K, n = 6), synonymous mutations, and minor variants. Several mutations were detected months later in sealions in the Atlantic coast, indicating that the pinniped outbreaks on the west and east coasts of South America are genetically linked. These data support sustained mammal-to-mammal transmission of HPAIV in marine mammals over thousands of kilometers of Chile’s Pacific coastline, which subsequently continued through the Atlantic coastline.

Source: Nature Communications, https://www.nature.com/articles/s41467-025-57338-z

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#Pathology of #Influenza A (#H5N1) #infection in #pinnipeds reveals novel tissue #tropism and vertical #transmission.

Abstract

In 2023, an unprecedented outbreak of highly pathogenic avian influenza (HPAI) H5N1 resulted in the death of thousands of pinnipeds along the Argentinean coast, raising concerns about its ecological and epidemiological impact. Here, we present clinical, pathological, and molecular findings associated with HPAI H5N1 infection in pinnipeds from Chubut, Argentina. Necropsies were conducted on three South American Sea Lions (SASLs) (Otaria flavescens) and one Southern Elephant Seal (SES) (Mirounga leonina), followed by histopathological, immunohistochemical and RT-sqPCR analyses. Neurological clinical signs were observed in two SASLs, with one also exhibiting respiratory distress. Neuropathological findings included lymphoneutrophilic meningoencephalomyelitis and choroiditis, neuronal necrosis, gliosis, hemorrhages, and perivascular cuffing. Viral antigen was localized in neurons, glial cells, choroid plexus epithelial cells, ependymal cells, and the neuropil. Systemic manifestations included HPAI-related necrotizing myocarditis in the elephant seal and placental necrosis in a sea lion, with fetal tissues testing positive for HPAIV. Pulmonary lesions were minimal, limited to bronchial glands in one individual. RT-sqPCR confirmed HPAI H5 in all tested animals. Our findings highlight the neurotropism of HPAI H5N1 in pinnipeds, and expand the known systemic effects of the virus, revealing new tissue tropism and vertical transmission.

Source: BioRxIV, https://www.biorxiv.org/content/10.1101/2025.02.07.636856v1

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