Highest priority needs for prevention and preparedness of H5N1 infections in the swine industry included
The recent emergence of H5N1 Influenza A clade 2.3.4.4b in dairy animals, coupled with persistent outbreaks in commercial poultry, poses a significant threat to the US swine industry. To summarize the current understanding of H5N1 risk to pigs as well as identify knowledge gaps, the Swine Health Information Center funded a literature review conducted by Dr. Montse Torremorell and colleagues at the University of Minnesota College of Veterinary Medicine. The goal of the literature review completed October 17, 2024, was to help identify highest priority research needs for H5N1 risk to the swine industry, assist in the process of influenza prevention and response planning for pork producers, and provide a summary of the clinical presentation of H5N1 in livestock compared to other known influenza strains.
Given the transmission of H5N1 infection to novel species including livestock, the potential risk of H5 infections in humans, and the epidemiological connections between swine, dairy, and poultry, it is imperative to fully understand the risks to pigs. Developing science-based strategies to prevent H5N1 introduction into swine populations and to contain outbreaks, should they occur, is equally critical.
Read the literature review in full with references here. The following headings highlight topics covered in the review:
H5N1 has caused significant losses in the US poultry industry and has more recently affected the US domestic dairy industry, with infections leading to reduced milk production, changes in milk quality, and occasional respiratory clinical signs. While experimental studies have shown pigs can be infected with H5N1, the specific impact of the 2.3.4.4b clade on pigs remains unknown. The potential for severe consequences to the US pork industry as well as human health is significant.
Experimental infections in pigs have shown variable results, with some studies indicating mild infections and others showing more severe disease. Several factors, such as viral genotype, animal species from which the strain was isolated, and immune status, can influence the severity of H5N1 infections in pigs. Questions surrounding the differences between H5N1 and endemic swine influenza viruses H1 and H3 remain, such as if current protocols for diagnostic surveillance and management of endemic swine influenza can be utilized for H5N1 control and elimination if introduced into commercial swine herds. Direct contact, indirect transmission through fomites, and aerosol transmission are potential routes of H5N1 spread. Enhanced surveillance, improved biosecurity measures, and vaccination strategies are crucial for considering how to best prevent and rapidly control a potential H5N1 infection in pigs.
Results of the literature review confirm studies are needed to assess the clinical signs, viral shedding, and transmission dynamics of H5N1 2.3.4.4b in pigs. Monitoring of pig populations, particularly those with outdoor access or exposure to poultry and dairy cattle, is essential to identify potential H5N1 infections. Literature review authors report research on the survival of H5N1 in various environments, including farm settings and outdoor habitats, is important. Additionally, studies should evaluate whether pre-existing immunity to other influenza viruses or H5N1 vaccines can provide protection against the 2.3.4.4b clade in pigs. For the research needed, validation of diagnostic tests for H5N1 in pigs is necessary to ensure accurate and timely detection.
Addressing these knowledge gaps and implementing effective control measures is crucial to protect the swine industry and public health.
The Swine Health Information Center, launched in 2015 with Pork Checkoff funding, protects and enhances the health of the US swine herd by minimizing the impact of emerging disease threats through preparedness, coordinated communications, global disease monitoring, analysis of swine health data, and targeted research investments. As a conduit of information and research, SHIC encourages sharing of its publications and research. Forward, reprint, and quote SHIC material freely. For more information, visit http://www.swinehealth.org or contact Dr. Megan Niederwerder at [email protected] or Dr. Lisa Becton at [email protected].
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