The Swine Health Information Center, in collaboration with the American Association of Swine Veterinarians, hosted a webinar on influenza A viruses on Friday, April 19, 2024. The goal of the webinar was to understand the threat HPAI H5N1 poses to domestic livestock species and to inform producers of actions that can be taken to prevent infection on-farm. This article includes an overview of the clinical presentation and epidemiology of the multi-state dairy herd outbreak and a review of biosecurity considerations for swine farms to mitigate risks of HPAI H5N1. A separate article addresses global influenza surveillance and research outcomes for HPAI H5N1 experimental infection in swine. The webinar garnered high interest with 1341 registrants and 921 joining the webinar live from 30 countries.
The webinar recording is available here.
Dr. Jamie Jonker, chief science officer with the National Milk Producers Federation, shared information on the diagnosis of HPAI H5N1 in domestic livestock. The first confirmation of H5N1 in a dairy herd was in Texas on March 25, 2024. As of the date of the webinar, 29 herds in eight states had confirmed HPAI H5N1 detections including Texas, New Mexico, Kansas, Idaho, South Dakota, Michigan, Ohio, and North Carolina. As of May 1, 36 herds in nine states confirmed HPAI H5N1 detection.
Affected dairy cows are typically multiparous in production at over 150 days in milk. About 10% of this population are affected in impacted herds with no mortality. Affected cows exhibit decreased activity with a drop in rumination and decline in feed intake. Milk yield drops with a change in milk consistency to a thicker, often yellowish to brown color resembling colostrum. Flakes can periodically be observed in milk which are most often associated with mastitis. Severely affected cows have all quarters impacted while others have just one or two quarters affected. There is a widespread increase in milk conductivity, also a typical indicator of mastitis. Affected herds take just four to six days to reach peak incidence, then clinical signs taper off at 10 to 12 days. However, it takes around 45 days for full herd recovery. Affected cows are managed symptomatically as there are no current treatments or vaccines approved for use in dairy cattle.
Dr. Jonker pointed to migratory birds as the likely source of HPAI H5N1 infection in dairy cows as well as subsequent animal movements. He also shared information about commercial poultry herds in the vicinity of impacted dairies being diagnosed with HPAI since March 25, including one egg layer in the Texas panhandle and three egg layers in Michigan. Research on virus transmission is needed to understand areas of risk and to identify potential management and mitigation steps. Additional research needs include understanding the long-term health and production implications for infected mature lactating dairy cattle and characterizing the impact in young-stock and dry cows.
Due to the HPAI outbreaks in dairy herds, a new emphasis is being placed on biosecurity on dairy farms to reduce the risk of introduction and infection. Dr. Jonker described the challenges of dairy farms’ typically open design and areas of concern for disease introduction. USDA, American Association of Bovine Practitioners, National Milk Producers Federation, FARM, and Secure Milk Supply are all providing guidance and resources to dairy farms in these biosecurity efforts. Human workers can also be at risk of infection, with upper respiratory protection (eyes, nose and mouth mucosa) being important after a dairy caretaker presented with symptoms of conjunctivitis after exposure. The CDC is providing additional guidance for animal caretaker protection to prevent potential exposure.
Dr. Derald Holtkamp of Iowa State University shared perspectives on what the HPAI H5N1situation means for biosecurity on swine farms. While these outbreaks do not signal novel biosecurity hazards for swine farms, it can change the prioritization of hazards to be addressed relative to wildlife. Dr. Holtkamp talked about the biosecurity hazards posed by wild birds and other animals inside and around swine barns, compost facilities, storage sheds, and other facilities including the perimeter buffer areas.
Water, food, and shelter including trees/windbreaks can act as attractants for wild birds. To implement control measures, attractants should be removed or protected from wild bird access. This includes cleaning up spilled feed daily, eliminating bird nesting and roosting sites, controlling rodents, removing wild animal habitats, using bird netting to prevent access inside swine barns, repairing curtains where needed, and draining ponds. Biosecurity control measures to eliminate nests and roosting sites near air inlets and entry points into swine farms is especially important. Harassment of birds to deter contact is also possible through lasers and loud noises. The potential use of lethal control measures for birds should always be carefully considered with assistance from the USDA Wildlife Services before being implemented. Contaminated feed sources are another area of concern. Ingredient sources, including DDGs, feed storage facilities and feed mill biosecurity all need to be assessed for potential biosecurity hazards. In some cases, bovine-derived feed ingredients are used in swine rations including whey, milk replacers, dairy by-products, and raw milk potentially fed to show pigs. To address these factors, Dr. Holtkamp recommends an audit of ingredient sources, storage, and off-site processing. Bird-proofing and rodent control in these feed manufacturing and storage facilities are necessary.
Surface water used as a source of drinking water for pigs is another biosecurity hazard. Surface water control measures included avoidance or water treatment with chlorine, acidifiers, iodine or peroxide. Proximity to nearby poultry and dairy farms and the related operational connections of third-party service providers (equipment repairs, supply deliveries, etc.) raise additional concerns for biosecurity hazards.
Dr. Holtkamp shared information regarding the SHIC-funded Standardized Outbreak Investigation Program. This consistent approach to identify, assess, and prioritize biosecurity hazards can be used to conduct outbreak investigations or to proactively conduct a biosecurity hazard analysis. To request access to this free tool, send an email to soip@iastate.edu. Influenza A viruses are constantly evolving and pose a risk to domestic livestock species. To address and mitigate the impact of emerging influenza strains for producers, SHIC and AASV collaborated to provide this influenza A virus webinar with the latest information on influenza in domestic livestock species. Prevention efforts should focus on actions to reduce biosecurity risks including the use of outbreak investigation tools to identify and prioritize biosecurity hazards at the farm. Understanding the status of influenza in US pig populations through targeted surveillance provides information on virus evolution, distribution and support of diagnostic tests and vaccines. Influenza viruses present a challenge for swine health and production and tools exist to reduce the impact this disease can have on pork producers. 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 mniederwerder@swinehealth.org or Dr. Lisa Becton at lbecton@swinehealth.org.