Canine flu, vaccine shortages wreak havoc on shelters across the Midwest

Shelter dogs across the Midwest are experiencing a highly contagious form of influenza called H3N2, a related but separate strain of virus to the avian influenza strain H5N1 currently wreaking havoc on wild birds, which recently jumped species to infect marine mammals.

“It’s never like COVID-19 was, which infected the whole country, the whole world at the same time,” said veterinarian Dr. Ann Hohenhaus, who is double board-certified — in oncology and internal medicine — at the Schwarzman Animal Medical Center in New York. “Flu will have little pockets of influenza in a population of dogs, in New York, or Chicago. Hotspots can get started with dogs who travel. A hotspot might travel ten blocks or ten states depending on where people are taking dogs.”

H5N1, or bird flu, can also infect dogs, such as one dog in Ontario, Canada that died in April after contact with a wild goose, Canada’s Food Inspection Agency (CFIA) confirmed.

“We’ve heard about bird flu for years now, so it is really confusing,” said Minnesota Board of Animal Health veterinarian Dr. Veronica Bartsch. “And one of the strains of canine flu did originally come from birds.”

Previously, there was no vaccine for the current H5N1 strain of avian flu. On May 16, U.S. Department of Agriculture officials granted emergency use of a trial bird flu vaccine for critically endangered California condors only.

For H3N2, a few types of vaccine are available, yet difficult to get. Most are backordered from manufacturers—Merck Animal Health and Zoetis—and have been for months, causing delays in community immunity.

“The current, intermittent backorder situation for Vanguard CIV is due mainly to the fact that the other manufacturer of CIV vaccine has been on extended backorder, leaving Zoetis as the only manufacturer of CIV vaccine for the entire U.S.,” said Lauren Dorsch, Head of Petcare Brand Communications for Zoetis, about its vaccine.

In a statement to TCR, Dorsch referred to Merck Animal Health as the other manufacturer of H3N2 vaccines.

“We understand the challenges that our Nobivac supply disruptions have caused our customers,” said Laurel Mundth, a spokesperson for Merck Animal Health.  “As veterinary professionals know, making vaccines is a complex and rigorous process. We are diligently working towards resolving the supply challenges for our Nobivac vaccines. However, at this time, we do not have a specific date to share when we will be back to full capacity.”

In April, three Animal Humane Society shelters in Minnesota shut down intakes and adoptions due to an outbreak. Five dogs were euthanized after testing positive for dog flu at centers in Woodbury, Coon Rapids and Golden Valley. Two hundred dogs went under a 30-day quarantine and received medication to treat symptoms.

The Backstory on H3N2 and the Current Outbreak

“In Minnesota, we haven’t had a case [before this spring] of canine influenza since 2018,” said Dr. Bartsch. “It’s been pretty quiet. We’ve been lucky.”

Dr. Bartsch said in the southern U.S., particularly Texas, Oklahoma, and some other southern states have dealt with increased case incidents since last fall. It’s considered endemic in the southern U.S. and parts of the east coast.

“Some of that we think is due to crowding or high populations of dogs in animal shelters or just living close together in dense urban areas,” she said.

Dr. Graham Brayshaw, Director of Veterinary Medicine for the Animal Humane Society in Minnesota said Chicago, experienced a large outbreak in 2017. “The virus didn’t go completely underground after that, but just the way it behaves and how dogs interact in the community, you might get some nose-to-nose contact, but there definitely is not as much canine exposure to each other as you would see with human exposure,” he said.

The H3N2 strain isn’t the first dog flu to be seen in the U.S. Many viruses from the genus Alpha-influenzavirus, family Orthomyxoviridae, first originate in birds then mutate to infect mammals and end up in a particular host species. H3N2 is only the second to be maintained in dogs.

“The H3N2 canine influenza, that’s the one that mutated and changed and adapted to dogs, it also however, adapted to cats,” said Dr. Bartsch, “And so while we don’t tend to see it spread as rapidly or as aggressively in cats, we do know they can pick up the disease from infected dogs.”

The first, “H3N8 canine influenza virus seems to have jumped ‘whole’ from horses to dogs in North America, probably in the late 1990s or early 2000s,” according to a 2022 Iowa State University College of Veterinary Medicine report.

A dog transported from Oklahoma to a Minnesota shelter brought the H3N2 virus with it. Some shelter dogs in Minnesota are brought from “areas of low resources to areas of high resources” to receive vet care and be adopted into homes, said Dr. Bartsch. For the infected dog, “They were doing their normal transport, their normal precautions, and found out a week and a half later the shelter in Oklahoma had confirmed cases of canine influenza.”

Canine flu has been studied for years and is often grouped in several respiratory diseases commonly referred to “kennel cough.”

“There’s 20-plus different agents that can cause it,” said Dr. Brayshaw about kennel cough. But to call H3N2 “kennel cough” undermines its severity. Kennel cough is often seen as a mild to moderate inconvenience—an inevitable part of the equation when a dog-owner adopts from a shelter.

“They get pretty profoundly sick,” said Dr. Brayshaw. “They are coughing everywhere and feel really crummy for a full week. Green, nasty nasal discharge is common.”

And it can be occasionally fatal. Most dogs that die from infection also develop bronchitis or pneumonia.

“In the shelter itself, once the virus is started to spread, it really spreads very quickly. In an animal shelter, there is a percentage of respiratory disease that is considered normal. Whenever you have groups of dogs in a confined space together, you are going to get respiratory disease, just like kids in schools,” said Dr. Bartsch.

“We have seen some community spread, and we are suspicious that it did come from the shelter outbreak. In the couple of weeks in between when the initial infected dog was transported up, and where the outbreak became evident and then put under quarantine, they were conducting business as usual. They were doing adoptions, training classes, people were coming in and out of the shelters, and so from there we started to see the community spread.”

So far, Dr. Bartsch said as of May 12, there are 20 confirmed cases in community dogs, dogs owned by people in the Twin Cities. “This is probably the tip of the iceberg for dogs that are truly sick with this disease. The 20 confirmed cases we have right now probably represent 100 dogs that are sick.”

“This is probably the tip of the iceberg for dogs that are truly sick with this disease. The 20 confirmed cases we have right now probably represent 100 dogs that are sick.”

“Peak viral shed”

One of the largest preventative measures to protect against further spread is testing for H3N2, said Dr. Bartsch.

However, it can be difficult to test due to the cost for dog-owners. It also can be difficult to get a confirmed positive on a test.

“It’s a lot like COVID testing in people, you really have to hit that peak viral shed, to get that positive,” said Dr. Bartsch.

Dogs at high-risk for canine flu include dogs that visit doggie daycares, dog parks, grooming salons, or are frequently around a lot of other dogs. They should be taken to a veterinarian as soon as symptoms occur.

Because many of the Animal Humane Society’s shelter dogs survived the disease and now have antibodies, vaccinating the shelter populations isn’t as necessary as getting it to high-risk community dogs, and the shelter’s incoming dogs. For dog owners, the first shot of a two-dose regimen including a booster is between $20 and $40.

Still, many veterinarians across the country are waiting for their supply while most types are backordered by the manufacturers “indefinitely,” said Dr. Bartsch, due to supply chain issues.

“Although we have been ramping up, the other manufacturer has been completely out of stock since June of 2022, resulting in Zoetis attempting to cover 100% of the CIV vaccine market in a very short time period, in relation to the long lead times involved with the supply of biologicals,” said Dorsch about Zoetis’s supply of H3N2 vaccines.

“They were pushed back until the end of the month, or early June,” said Dr. Brayshaw of the Minnesota shelters obtaining a type of canine flu vaccine. The idea of getting a good background immunity where every dog is vaccinated, like COVID-19 in humans, isn’t possible.

“We don’t have enough vaccines to even hope in doing that. That’s probably half a million dogs in the Twin Cities area, and you need to booster this, and I definitely don’t have access to a million vaccines. I’m hoping to get 50 or 100.”

Risk to people?

“Influenza viruses love to mutate, love to infect new species. The general progression is less severe and more contagious.”

“This [mutating] is part and parcel for what flu viruses do,” said AMC’s Dr. Hohenhaus.

The Animal Humane Society’s shelter dogs finished their 30-day quarantine on May 12 and adoptions are now open.