From the Montana Department of Livestock:

Update Regarding the Detection of H5N1 Highly Pathogenic Avian Influenza (HPAI) in Dairy Cattle - Montana Department of Livestock (MDOL)

1. The virus isolated from cattle is the same strain as the H5N1 circulating in wild birds.

2. Affected cattle appear to have a high viral load in mammary tissue and milk.

   1. Because of HPAI is a potential zoonotic disease, there is specific concern for individuals who work around affected animals, in particular those individuals involved in the milking process.

   2. Center for Disease Control (CDC) has provided interim recommendations [cdc.gov] for keeping people safe following the detection of the H5N1 virus in a human with conjunctivitis in Texas. Additional information on managing the risk to people can be found here [cdc.gov]. 

3. The high viral load appears to be responsible for lateral, specifically mechanical, transmission from cattle to cattle or cattle to poultry (contaminated milking equipment, hands, or other contamination of the environment)

4. States have experienced clinical cases that appear to be associated with the movement of asymptomatic animals.  

   1. USDA has issued a Federal Order with requirements for dairy cattle moving across state lines. Loosely, these include a negative test for lactating animals, a health certificate, and official identification.

   2. If you are purchasing or selling animals across state lines, please work with your local veterinarian to ensure compliance and to protect your herd in the case of new introductions.

5. Biosecurity is paramount to prevent the spread of this virus.

   1. While biosecurity should always be a consideration, additional emphasis should be placed on biosecurity on premises with multiple species present.

   2. Because of the severe consequences of the HPAI virus in poultry, biosecurity should focus on movement and workflows to minimize the risk of spread from cattle to poultry.

   3. Because of the ability of influenza viruses to reassort, consideration should also be given to prevent spread to swine. 

6. Clinical signs that should prompt reporting in dairy cattle include rapid declines in feed intake or milk production, viscous mammary secretions that are like colostrum, fecal abnormalities (either diarrhea or tacky feces), dehydration, and fever.

7. As of Tuesday 4/30/2024, detections in cattle have been confirmed in 34 herds in 9 states. United States Department of Agriculture (USDA) has a dedicated webpage [aphis.usda.gov] with additional information. As of yet, there has been no detection in Montana.

8. While the current focus is on dairy cattle specifically, HPAI has been detected in other mammalian species, primarily mesocarnivores (skunks, fox, bears, and domestic cats) and recently in goats on a Minnesota premises. The affected goats in Minnesota shared feed and water sources with a poultry flock that was affected with HPAI. Because of this, biosecurity and monitoring for clinical illness is important for all species. If you have lactating small ruminants that are exhibiting similar clinical signs, please contact your local veterinarian.