Avian Influenza: What Pet Owners and Veterinarians Need to Know

Commentary01/24/25 Laurie Hess, DVM, DABVP, The MSD Veterinary Manual

Avian Influenza: What Pet Owners and Veterinarians Need to Know

Authors:

David E. Swayne, DVM, PhD, DACVP, DACPV

Laurie Hess, DVM, Editor-in-Chief of the MSD Veterinary Manual and DABVP (Avian Practice)

Highly pathogenic avian influenza (HPAI) has made headlines following a surge of cases recently. Wild birds and poultry flocks have been significantly affected, as have dairy cows, goats, and pets, including cats, dogs, ferrets, and more. Humans have also been infected. Protecting animals and humans from this dangerous condition demands that veterinary professionals and the general public stay up to date on the latest outbreaks and understand key facts about the disease.

The Merck Veterinary Manual is committed to providing updated and reliable medical information concerning HPAI. The following Q&A will be updated with new and current information as it becomes available.

What is avian influenza?

Avian influenza is a viral infection that causes disease in domestic poultry and a wide range of other birds, with some viral strains sporadically causing illness in wild and domestic mammals and humans.

What is highly pathogenic avian influenza (HPAI)?

Highly pathogenic avian influenza (HPAI) viruses cause severe disease and high mortality in infected birds and poultry – specifically chickens and turkeys. Wild birds, especially waterfowl, are the primary carriers and transmitters of HPAI, typically with minimal clinical signs.

What should people know about the H5N1 strain?

Avian influenza viruses are defined by two types of surface proteins -- hemagglutinin or “H” proteins (typically H1 to H16), and neuraminidase or “N” proteins (N1 to N9). The current outbreak involves the H5N1 strain, with a hemagglutinin 5 protein and a neuraminidase 1 protein.

Why is this outbreak happening?

Virologists have been tracking HPAI viruses since the late 1950s. The vast majority of these viruses have been identified and eradicated quickly. One major exception is the Goose Guangdong virus, which was first detected in 1996 and is believed to be the precursor to the current dominant strain, which can infect chickens and turkeys, as well as a wide range of other wild and domestic bird species. This outbreak has also led to cases in mammals, including cattle, cats, and even humans. This virus is relatively unique among avian influenza strains, and it has mutated and changed, making it more broadly infecting to diverse wild bird and mammal species and more difficult to control.

According to the U.S. Centers for Disease Control and Prevention: “While the current public health risk is low, CDC is watching the situation carefully and working with states to monitor people with animal exposures.”

How is it transmitted to other birds?

Avian influenza spreads among birds or from birds to mammals through close contact with an infected bird or with aerosolized particles (such as respiratory tract secretions or dried fecal material) from an infected bird in places like open air markets, where birds are slaughtered. In other cases, contact can be less direct. For example, humans traveling between commercial or backyard farms can transmit the virus on their skin or clothes. In some instances, infected wild birds flying overhead spread the virus to susceptible backyard flocks on the ground below by defecating as they fly, dropping infected fecal material on or near these flocks, or landing and intermixing with the poultry.

How is it transmitted to dogs, cats, and other pets?

Avian influenza is most often transmitted to cats and dogs when the pet eats an infected carcass, such as a dead wild bird. There also have been cases of cats drinking raw milk from an infected cow or cats and dogs being fed infected raw chicken, turkey, or duck or commercial pet foods containing infected raw meat. Consequently, pet owners are being advised not to feed products containing raw meats of any kind to their animals.

How is it transmitted to humans?

Avian influenza spreads like other flu viruses. Most often, a person has the virus on their hands and then touches their nose or eyes. To date, transmission to humans has been primarily to individuals with increased risk of occupational exposure – people who work with bird populations or in dairy barns, etc. – or to immunosuppressed people who are particularly susceptible. There have been no documented cases of sustained human-to-human transmission.

What are the symptoms of HPAI in birds / dogs / cats?

The challenge, particularly among birds, is that some animals can be infected with HPAI without being significantly affected. In other words, you might not notice anything is wrong until the infected bird dies from the disease. This is particularly true for waterfowl like ducks and geese. However, some birds may show clinical signs of respiratory illness or abnormal neurological signs (such as twitching, seizures, abnormal body posture, etc.) and should be promptly separated from other birds and examined by a veterinarian, who can diagnose avian influenza by submitting samples for molecular detection of the virus to a National Animal Health Laboratory Network (NAHLN) veterinary diagnostic laboratory. Cats owners should monitor their pets for strange behaviors including malaise or respiratory issues.

How can pet owners and backyard farmers prevent the spread of HPAI?

Backyard farmers should practice strict biosecurity on their properties to prevent transmission of disease from other farms. This includes having all farm visitors walk through disinfecting footbaths and change clothing before entering the farm. This also means quarantining new birds and not intermingling your birds with other birds at fairs, shows, etc. Pet owners also should watch for unusual symptoms in their pets. Outdoor cats will be safer indoors, away from potentially infected wild birds, and dogs should be kept on a leash outside in case they come across a dead bird.

What precautions should veterinarians take in seeing animals that may have HPAI?

Veterinarians should take precautions to minimize their exposure to and spread of HPAI by wearing PPE such as gloves, N95 masks, shoe covers, protective eyewear, and disposable gowns. They should also isolate potentially infected animals as much as possible. Areas with potential exposure should be regularly disinfected. Suspected cases of HPAI must be reported immediately to the USDA and state animal health officials. Each state has specific guidelines for reporting, and veterinarians should contact their state veterinarian's office for guidance. Vets can also recommend effective biosecurity measures for backyard farmers and advise pet owners on how to keep their pets and their families safe.

Where should pet owners and the general public go for current information?

Where should veterinarians go for current information?