Avian Flu Diary: OKC Animal Shelters Closed Due To Severe Canine Flu Outbreak

#17,390

Up until 20 years ago, dogs (and cats) were believed to be fairly immune to influenza A infection, but the emergence of H5N1 in Southeast Asia quickly proved that both large and domestic cats were susceptible (see HPAI H5: Catch As Cats Can).

Meanwhile, halfway around the world at a racetrack in Miami, Florida - another influenza spillover - this time from horses (Equine H3N8) - was beginning to spread among greyhounds (see 2008 EID Journal article Influenza A Virus (H3N8) in Dogs with Respiratory Disease, Florida).

Three years later (2007), a second canine flu virus emerged - this time evolved from an avian H3N2 virus - and began to spread in Asia. (see Transmission of Avian Influenza Virus (H3N2) to Dogs). Analysis showed that the HA and NA genes of the A/canine/Korea/01/2007 (H3N2) isolate were closely related to those identified in 2003 from chickens and doves in South Korea.

Three years later, researchers in South Korea demonstrated that this Canine H3N2 virus could also infect cats (see Korea: Interspecies Transmission of Canine H3N2).

Canine H3N2 entered the United States, and began spreading widely in 2015 (see Midwest Canine Influenza Outbreak Due To `New’ Korean H3N2 Virus). Since then it has co-circulated with canine H3N8 in dogs, sparking outbreaks in dozens of states.

Although it differs genetically from both the equine and avian H3N2 viruses, H3N2 was enough of a public health concern that the CDC ordered a risk analysis in March of 2016 (see PDF report).

While the risks of human infection were viewed as low, canine H3N2 was added to the CDC's IRAT List of zoonotic flu viruses with pandemic potential in the summer of 2017.

H3N2: [A/canine/Illinois/12191/2015]

The H3N2 canine influenza virus is an avian flu virus that adapted to infect dogs. This virus is different from human seasonal H3N2 viruses. Canine influenza A H3N2 virus was first detected in dogs in South Korea in 2007 and has since been reported in China and Thailand. It was first detected in dogs in the United States in April 2015. H3N2 canine influenza has reportedly infected some cats as well as dogs. There have been no reports of human cases.

Summary: The average summary risk score for the virus to achieve sustained human-to-human transmission was low risk (less than 4). The average summary risk score for the virus to significantly impact public health if it were to achieve sustained human-to-human transmission was in the low risk range (less than 4).

While there are no known instances of human infection with canine H3N2 or H3N8, these viruses continue to evolve, and their presence in dogs today is proof they can expand their host range.

All of which brings us to reports out of Oklahoma City, OK where their local animal welfare department has been under siege for more than a week by an influx of severe respiratory disease in dogs. On March 30th, they posted the following notice on their Facebook page.

As of yesterday morning, some test results have been received, prompting the following announcement on their website.

Animal Shelter infection - situation update April 5
Post Date:04/05/2023 7:31 AM

Background

On March 29, the Oklahoma City Animal Shelter closed for at least a week to identify and contain a contagious upper respiratory infection that spread to 130 dogs. This is the first time in more than 24 years the shelter has closed due to a disease outbreak.

Situation Update

On the day the shelter closed (March 29), the OKC Animal Shelter staff pulled samples from 10% of their ill dog population, which was 14 samples.

Eight of the samples tested positive for the following:
Streptococcus zooepidemicus (strep zoo)
H3N2 Influenza
Influenza A (Canine Flu).
Every shelter dog is being treated with a round of amoxicillin and doxycycline, which are antibiotics. To date, five dogs have died because of the infections.

Shelter staff is working with the shelter’s veterinary team as well as an outside national organization to form a plan to move forward. More information will be provided when the plan is in place.

The shelter will remain closed until further notice.

People who find a lost pet are advised to provide the pet with temporary housing and look for the owner through lost animal reports on okc.gov/animalwelfare, Facebook, Nextdoor and Craigslist.

Both of these canine flu viruses (H3N2 and H3N8) have continued to evolve, spread, and reassort with other viruses, raising concerns that dogs could serve as a `mixing vessel' for influenza (see Study: Dogs As Potential `Mixing Vessels’ For Influenza), much in the way that pigs are viewed today.

As companion animals, dogs (and cats) are uniquely positioned to serve as a conduit for novel flu viruses to jump to humans. In late 2016 when we saw an avian H7N2 virus sweep through hundreds of cats housed at multiple New York Animal shelters - which also infected at least two people.

While the public health threat from these canine viruses is believed quite low, six months ago we looked at a preprint by Chinese scientists who warned on the continued evolution of canine H3N2, which they said appears to be moving towards becoming a more `humanized' virus.

They cautioned:

Here, we carried out a systematic and comparative identification of the biological characteristics of H3N2 canine influenza viruses (CIVs) isolated in the worldwide over 10 years.

We found that during the adaptation of H3N2 CIVs to dogs, H3N2 CIVs became to recognize the human-like SAα2,6-Gal receptor, gradually increased HA acid stability and replication ability in human airway epithelial cells, and acquired a 100% transmission rate via respiratory droplet in ferret model, which were essential hallmarks of being adapted to humans.

We also identified that the frequency of substitutions related to human adaptation has gradually increased in H3N2 CIVs, and determined four cumulative molecular changes responsible for the increased airborne transmission ability in ferrets.

Our results suggested that canine may serve as an intermediate for the adaptation of avian influenza virus to human. Continuous surveillance coordinated with risk assessment for CIVs is necessary

While canine H3N2 and H3N8 are admittedly both pretty far down our zoonotic worry list, influenza viruses are highly unpredictable, and so they deserve our attention. For some recent studies on canine influenza, you may wish to revisit: