Michigan Reports More H5N1 Outbreaks in Dairy Herds, as Virus Appears in Domestic Cats

The Michigan Department of Agriculture reports three new H5N1 avian flu outbreaks in Clinton, Gratiot, and Ionia counties dairy herds.

Initial testing at Michigan State University's Veterinary Diagnostic Laboratory confirmed the presence of the virus, with samples now sent to the US Department of Agriculture (USDA) National Veterinary Services Laboratory (NVSL) for further verification.

Three new H5N1 avian flu outbreaks have been reported in Michigan dairy herds, affecting Clinton, Gratiot, and Ionia counties.

With these latest reports, Michigan has documented 18 H5N1 outbreaks across nine counties, the highest number for any state. As of May 16, the USDA reported a total of 51 dairy herd outbreaks in nine states, including recent cases in Michigan and Idaho.

H5N1 Found in Domestic Cats in South Dakota

In an unusual development, H5N1 has been detected in two domestic cats in South Dakota, as confirmed by a notification from US government officials to the World Organization for Animal Health (WOAH).

Notably, these cats were not from affected poultry or dairy farms, which marks a deviation from earlier cases where cats had consumed raw milk from infected cows. The two infected cats were from Campbell County, located on the northern border of South Dakota.

Although the WOAH report did not specify if these cats exhibited clinical symptoms, previous reports on H5N1 in cats have noted severe respiratory and neurological symptoms, often leading to fatal outcomes.

Since the Eurasian H5N1 strain was first identified in the United States in early 2022, the virus has sporadically appeared in mammals, particularly in wildlife species like bobcats and mountain lions known to prey on infected birds.

FDA Validates Pasteurization Process for H5N1

The FDA has announced further scientific studies to validate the effectiveness of pasteurization in neutralizing H5N1 in milk.

This research will involve testing with pasteurization equipment used in milk processing facilities. Preliminary inoculation tests on 297 retail milk samples with viral fragments showed no live virus, reinforcing the safety of pasteurized milk.

Additionally, the FDA is conducting tests on pooled raw milk before it undergoes commercial pasteurization, aiming to better understand virus levels in real-world conditions.

To support these efforts, the FDA has allocated $8 million to enhance the safety of the milk supply.

This funding will support studies validating pasteurization criteria, increase lab capacity, conduct surveillance at various stages of milk production, and train staff on biosecurity measures.

CDC Enhances Surveillance and Pandemic Risk Assessment

The CDC has outlined its response to the H5N1 outbreaks in dairy herds, including a plan to boost flu surveillance during the summer by increasing the number of flu specimens tested and subtyped at public health laboratories. This increased testing aims to maintain heightened surveillance levels despite the usual seasonal decline in influenza testing.

Moreover, the CDC has initiated a pandemic risk assessment for the H5N1 virus using its Influenza Risk Assessment Tool (IRAT).

This assessment evaluates 10 risk elements and can take several months to complete. The CDC's last IRAT assessment, conducted in July 2023, focused on the H5N1 strain responsible for an outbreak at a Spanish mink farm.

Though that strain scored higher on some risk measures, the overall threat was moderate.

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The CDC also monitors influenza A in wastewater, comparing current levels with those from the previous season. Locations in the "high" category trigger additional CDC outreach and intensified local surveillance. Recently, four sites were categorized as high risk: two in California (San Francisco/San Mateo and Sonoma), one in Kansas (Saline County), and one in Texas (Dallas). Despite these findings, no unusual flu indicators, including for H5N1, have been detected in people.

The ongoing H5N1 outbreaks in Michigan's dairy herds and the detection of the virus in domestic cats highlight the persistent and evolving challenges of managing avian influenza. The concerted efforts of the MDARD, FDA, and CDC demonstrate a robust response aimed at controlling the spread, ensuring the safety of food supplies, and protecting public health.

Disclaimer

The information provided in this article is intended for informational purposes only. It summarizes current developments and responses related to H5N1 avian influenza outbreaks in Michigan and related findings. Readers should consult official sources such as the Michigan Department of Agriculture and Rural Development (MDARD), the Food and Drug Administration (FDA), and the Centers for Disease Control and Prevention (CDC) for the most accurate and up-to-date information. The authors and publishers do not accept any liability for any loss or damage caused, directly or indirectly, by the use or reliance on this information.

Source: Cidrap