Dairy farms emerge as vulnerable link in controlling avian influenza outbreak, research reveals

USA – As avian influenza spreads across U.S. dairy farms, research reveals that dairy operations are becoming a significant obstacle to containing the outbreak.

According to David Suarez, laboratory director at the National Poultry Research Center, limited data sharing and biosecurity lapses have hindered efforts to curb the virus.

More than 250 dairy farms across 14 states have tested positive for avian influenza. However, Suarez believes this figure grossly underestimates the true number of infections.

“There’s a lot of disease going on out there where there is no sampling,” he said during the National Meeting on Poultry Health, Processing, and Live Production on October 2.

Avian influenza research is crucial for understanding how the virus spreads and operates in new host species, but scientists face a challenge with dairy cows.

Studying the virus in cows under controlled lab conditions is difficult, and many infected farms have denied researchers access for follow-up studies.

Risky practices contributing to virus spread

Several risky behaviors by dairy farms have contributed to the virus’s spread. Suarez highlighted the sharing of unclean equipment between farms and employees working across multiple farms as major concerns.

The most significant risk factor, however, is the movement of cattle between farms. Over 40% of infected farms continued to ship cattle even after clinical signs of illness were present.

“For us as poultry people, that’s just something that’s inconceivable,” Suarez remarked.

Unlike in poultry, where avian influenza is controlled by culling entire farms, dairy farms have managed infections with movement restrictions.

Culling large dairy herds is logistically challenging, and the U.S. Department of Agriculture (USDA) lacks the regulations to compensate farmers for culled cows.

Instead, the USDA has implemented mandatory testing for interstate movement of lactating dairy cows since April.

Despite the testing requirement, avian influenza continues to spread among dairy herds. There are concerns that farmers are circumventing regulations.

“There’s a rumor in the field that dairy farmers are being very sneaky about moving some of these cattle,” Suarez said.

Limited participation in testing programs

The USDA also introduced a bulk milk testing program that allows farms to move cows without testing each group.

However, participation in the program remains limited. Only 60 herds are enrolled nationwide, half of them in Michigan.

Shawn Jasper, New Hampshire’s Agriculture Commissioner, recently noted that farmers are hesitant to test their herds because they fear cooperatives may cut them off if avian influenza is detected in their milk.

While the virus has mostly affected cows, farm cats have died after drinking untreated milk from infected cows, and some dairies have brought in feral cats to control rodent populations.

Infected dairy farms have also reported sick or dead wild birds, likely infected by the farm’s high viral load.

One of the most alarming findings is the significant amount of the virus found in cows’ mammary glands, far exceeding the virus levels produced by poultry at their infection peak.

This can result in decreased milk production and poor milk quality, although federal authorities maintain that pasteurization eliminates any food safety risks.

The presence of avian influenza in dairy cattle has raised concerns about its potential adaptation to humans.

While most human cases in the U.S. have been mild, all but one were linked to infected dairy or poultry farms.

Researchers are still trying to determine how the virus infects cows and whether it poses a growing threat to human health.

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