HPAI Genotype Commonly Found in Birds Discovered in Dairy Cattle for the First Time

Key Takeaways

A highly pathogenic avian influenza genotype D1.1 has been confirmed in dairy cattle for the first time.
The virus likely originated from wild birds, marking a concerning cross-species transmission.
The USDA initiated a testing strategy to monitor milk for the virus following its spread from Texas cattle to other states.

First Recorded Transmission of Avian Influenza Genotype in Dairy Cattle

The U.S. Department of Agriculture (USDA) has reported the first confirmed case of a highly pathogenic avian influenza, genotype D1.1, in dairy cattle. This finding represents a significant development in understanding the transmission of this virus, as it was previously identified only in wild birds. The USDA’s Animal and Plant Health Inspection Service noted that D1.1 has been the prevalent genotype across North American flyways during the past fall and winter seasons.

The confirmation occurred in a herd of dairy cattle in Nevada, the announcement being made on Wednesday. According to Fred Gingrich, executive director of the American Association of Bovine Practitioners, this is the first documented instance of cows contracting the virus directly from wild birds, highlighting a concerning shift that had not been identified previously. Initially, the virus was likely transmitted to cattle from birds early last year, but the presence of D1.1 indicates a more direct spillover event.

Gingrich pointed out that while a different genotype, B3.13, had been detected in prior cases among dairy cattle, this new evidence of interspecies transmission complicates efforts to control the spread of the virus. The difficulty of preventing contact between wild birds and cattle on dairies adds to the concern surrounding this discovery.

Further analysis revealed that the virus began spreading within the national dairy herd after a shipment of cattle from Texas took place in early 2024. The USDA’s epidemiological study indicated that a significant spillover event likely occurred in December 2023, with the initial transmission from wild birds to dairy cattle happening in the Texas panhandle. This event has led to the subsequent spread of the virus across eight additional states.

Detection of the genotype in the Nevada dairy herd was accomplished through silo testing as part of the USDA’s National Milk Testing Strategy, launched in response to the virus’s increasing prevalence. Nevada is among the 28 states that have committed to this effort, aiming to monitor and safeguard dairy health effectively.

As the situation evolves, the implications of this genotype’s presence in dairy cattle could impact agricultural practices and animal health policies. The USDA’s findings will likely influence future monitoring strategies and highlight the need for heightened biosecurity measures in dairy operations to mitigate potential outbreaks linked to avian influenza. Stakeholders in the dairy industry are advised to remain vigilant in monitoring their herds and implementing strategies to limit interactions with wild birds, as this recent discovery underscores the interconnected nature of wildlife health and agricultural biosecurity.

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