Farm connections confirmed transmission link in H5N1 spread

By Lorraine Stevenson-Hall

Animal movement, shared vehicles and workers who move between farms are recognized transmission links for spread of H5N1 among dairy herds, according to a USDA report.¹ H5N1 has now affected 139 dairy farms in 12 US states, and most recently, four poultry workers in Colorado recently contracted bird flu, bringing the total of U.S. human cases to nine.²

Over 50% of farms affected had shared trucks and trailers prior to the onset of clinical signs.

The USDA data was collected from 54% of the premises confirmed positive as of June 8, 2024 and shows that of farms affected, over 50% shared trucks and trailers prior to the onset of clinical signs. On top of that, over 50% of the farms that shared vehicles did not clean them prior to use.

Shared personnel between dairy farms is also identified as a transmission link on over 20% of farms with clinical signs. Another recognized transmission link is animal movement with more than 20% of farms receiving cattle within 30 days of clinical signs and more than 60% of farms continuing to move animals off the farm after onset of these signs.

Farm networks are more connected than we think, and people and vehicle movements between farms are likely a bigger risk for animal disease transmission than we realize. The USDA data confirms this.

The US swine sector is keeping a close eye on the situation. Pork industry partners are monitoring developments of the disease and how the dairy industry is responding. Stakeholders have been meeting at least weekly to discuss potential implications and possible response,” says Marisa Rotolo, veterinary epidemiologist, director of swine health, National Pork Board.

If needed, the pork industry could launch an effective response and is armed with extensive knowledge and experience in managing and monitoring flu. “We have multiple programs that can be quickly deployed should H5N1 be detected in swine,” Rotolo observed.

Meanwhile, the World Organization for Animal Health (WOAH) says that Germany has recently reported an outbreak of highly pathogenic H7N5 bird flu on a farm near the border with the Netherlands. The outbreak was detected on June 29^th and confirmed on July 2^nd, killing 6,000 out of a flock of 90,879 birds.³

This is a different strain than H5N1 that decimated poultry flocks in 2021 and 2022. In fact, it is the first outbreak anywhere of H7N5 on WOAH’s public records on global animal disease outbreaks, which goes back to 2005.

New disease strains and the connected nature of our farm networks point to the need for innovative biosecurity solutions like Farm Health Guardian. Learn more: farmhealthguardian.com.