Delaware Department of

Disease Information

Animal Health Advisory: Unusual Dairy Cattle Morbidity Event

Black and white Holstein dairy cows drinking water from the water trough.In February 2024, an unknown disease affecting dairy cattle causing decreased lactation, low appetite, thickened colostrum-like milk, and other clinical signs was identified in Texas. Herds with these signs have tested positive for Highly Pathogenic Avian Influenza (HPAI) in individual cows and/or the milk. As of April 2, 2024, the United States Department of Agriculture (USDA) has confirmed additional cases in New Mexico, Kansas, Michigan, and Idaho of Highly Pathogenic Avian Influenza in dairy cattle.

While there have been no reported detections of HPAI in Delaware cattle, the Delaware Department of Agriculture is closely monitoring the situation. The State Veterinarian, Dr. Karen Lopez, DVM, has contacted the large animal veterinarians in Delaware who service cattle operations to ensure they know the clinical signs to look for.

There is no concern about the safety of the commercial milk supply because products are pasteurized before entering the market. A dairy may only send milk from healthy animals for processing; milk from impacted animals is being diverted or destroyed so that it does not enter the human food supply chain. Pasteurization has continually proven to inactivate bacteria and viruses, like influenza, in milk. The sale of raw milk and raw milk products for human consumption in Delaware is not legal, and pasteurization is required for any milk entering interstate commerce for human consumption.

Clinical Signs

Cattle owners should contact their veterinarians immediately if they notice the following clinical signs of illness:

• Decreased herd-level milk production
• Acute sudden drop in milk production
• Decreased feed consumption/appetite
• Thickened, discolored milk
• Abnormal bowel movements
• Lethargy, fever, and dehydration


Delaware farms are encouraged to continue practicing strict biosecurity. This includes:

• Keep visitors to a minimum. Only allow those caring for your herd to come in contact with the animals. Limit, monitor, and record any movement of people, vehicles, or animals on or off your farm using a log book.
• Wash your hands before and after working with your animals and equipment to reduce the chance of spreading infectious particles. Pay particular attention to mammary health, including good milking practices, such as disinfecting equipment and milking sick cattle separately or last before parlor cleaning.
• Isolate and quarantine new animals for 30 days before introducing them into an established herd.
• Test animals before necessary movements.
• Isolate sick cattle from the herd. Do not move sick or exposed animals off the farm.
• Starlings, songbirds, vultures, and other raptors can be carriers of avian influenza and not show signs of disease. Consider using bird deterrents to keep out of barns, feed, and calving areas.
• Limit non-production animal access to farm areas and implement measures to exclude domestic pets (e.g., cats) and wildlife from buildings.

If You Suspect Your Cattle Are Sick…

If cattle within your herd are showing signs of illness, please report these signs immediately to:

• Your local veterinarian,
• Delaware Department of Agriculture’s Poultry and Animal Health Section at (302) 698-4500 or email, or
• USDA Animal and Plant Health Inspection Service at 1-866-536-7593.


Control Orders

April 2, 2024 Delaware Control Order: Restricting Movement of Dairy Cattle into Delaware Due to the Unusual Dairy Cattle Morbidity Event


Resources for Producers

Secure Milk Supply

Influenza and Biosecurity: Not Just for the Birds (USDA-APHIS)

Manage Wildlife to Prevent Avian Influenza (USDA-APHIS)

Improving Biosecurity with Wildlife Management Practices: Preventing Access to Barns and Other Facilities (USDA-APHIS)

Improving Biosecurity with Wildlife Management Practices: Reducing Water Access (USDA-APHIS)

Improving Biosecurity with Wildlife Management Practices: Protecting Food Resources (USDA-APHIS)

Detection of HPAI in Dairy Herds: Frequently Asked Questions (USDA-APHIS, March 2024)

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