Veterinarian emphasizes early detection and reporting of bird flu 

Highly pathogenic avian influenza continues to pose a significant threat to the poultry industry. Since the outbreak began in 2022, the United States has recorded approximately 2,300 detections in domestic poultry, affecting 211 million birds, according to Dr. Eryn McGrath, DVM, assistant state veterinarian with the Colorado Department of Agriculture’s Animal Health Division. 

McGrath spoke during a Colorado Egg Producers webinar and provided an update on the disease and outlined biosecurity measures poultry producers can use to reduce the risk of infection. 

Highly pathogenic avian influenza, commonly known as bird flu, is a zoonotic disease, meaning it can spread from animals to people. The virus circulates in wild bird populations, which serve as reservoir species, and can spread to domestic poultry, wild and domestic mammals, dairy cattle and humans. 

“Highly pathogenic avian influenza is capable of causing really severe disease, particularly in our domestic poultry populations, where it can cause up to 100% morbidity and mortality,” McGrath said. 

Colorado has recorded 56 detections affecting more than 11 million birds since the beginning of the outbreak. Eight premises tested positive during the year covered by McGrath’s presentation, including a commercial egg-laying facility where more than 1.3 million birds were depopulated. 

Spread to other species 

The virus also has affected other animal populations in Colorado, including domestic cats, captive big cats and numerous wildlife species. McGrath highlighted the unusual spread of avian influenza into dairy cattle in 2024. The first detection in dairy cattle occurred in Texas in March of that year. Since then, more than 1,200 dairy premises in 21 states have been affected. 

Colorado experienced widespread dairy herd infections during the initial 2024 outbreak, with approximately 75% of the state’s dairies affected. Another detection was recently confirmed in a Colorado dairy herd on Oct. 23, according to McGrath. The infection was identified through routine bulk tank milk surveillance testing and was confirmed by the National Veterinary Services Laboratories. 

The detection involved the B3.13 genotype, which McGrath said has primarily been associated with dairy-to-dairy transmission through animal or equipment movement. 

Following the detection, Colorado’s status under the U.S. Department of Agriculture’s National Milk Testing Strategy changed from unaffected to affected. The change reinstated testing requirements for lactating dairy cattle moving interstate. 

The state also increased bulk tank milk surveillance from monthly to weekly testing for a minimum of four weeks, with plans to reevaluate the schedule based on additional detections. 

“The transmission to multiple species doesn’t appear to be changing,” McGrath said. 

Although the dairy outbreak has drawn attention, McGrath emphasized the importance of continued vigilance among poultry producers. The virus remains prevalent in wild bird populations and continues to move among multiple species. 

Biosecurity and early reporting 

McGrath said biosecurity practices should be tailored to individual facilities, but several measures are important across poultry operations. 

Producers should limit visitors and ensure anyone entering poultry areas follows established biosecurity protocols. Workers and visitors should wash their hands before and after handling birds, change clothing before entering and leaving poultry areas and use dedicated clothing or disposable outer garments. 

Changing footwear, using disposable boot covers or providing disinfectant foot baths also can help reduce the risk of introducing the virus. 

Equipment and tools should be cleaned and disinfected before being moved between facilities or even between barns on the same property. Producers also should take steps to limit poultry exposure to wild birds and other wildlife. 

Establishing a relationship with a veterinarian before a disease concern develops is another important part of preparedness, McGrath said. Veterinarians can help producers develop biosecurity plans and provide a point of contact if illness occurs. 

Proper disposal of dead animals and animal waste also is important. Early detection and reporting are critical to limiting the spread of the virus. 

Poultry producers should monitor their flocks for signs of illness, particularly unusual mortality events. Reports of sick or dead wild birds and mammals also are important because the virus can affect multiple species.  

“By rule, anyone with knowledge or even just suspicion of HPAI must report that to our office immediately,” she added. 

McGrath also discussed the importance of protecting people who work around potentially infected animals. She said a dairy farm worker in Washington state died from complications associated with avian influenza, underscoring the need for appropriate personal protective equipment, symptom monitoring and prompt reporting. 

Early medical attention is important for people who may have been exposed, she said, noting that antiviral treatment is most effective when started early in the course of illness. 

Resources for producers 

Several resources are available to help poultry producers assess and improve their biosecurity practices. 

The USDA’s Defend the Flock program provides information and guidance for poultry operations. The Colorado Department of Agriculture also offers a Biosecurity 101 webpage with general recommendations and links to additional resources. 

For backyard flock owners and smaller poultry operations, McGrath recommended the Small Flocks Collaborative website, healthybirds.info. The resource provides biosecurity information, flock care recommendations and general disease guidance. 

Commercial poultry producers also can participate in USDA’s free Biosecurity Incentive Focused Assessment program. State-certified assessors evaluate an operation’s biosecurity practices and recommend improvements. USDA provides financial assistance to help producers implement recommended changes. 

“Right now, the tools we have at hand are continued surveillance, enhancing biosecurity, and just focusing on our preparedness efforts,” she said. “Unfortunately, this doesn’t seem to be going anywhere. At least not anytime soon.” 

Lacey Vilhauer can be reached at 620-227-1871 or [email protected].