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Doggie Flu in Los Angeles... Are we next?

Here's a Sept 16, 2021 news report about a new respiratory infection outbreak in dogs from the H2N2 Influenza Virus.

Click on the image to watch the video

Influenza Viruses

Since 1999, canine H3 influenza A viruses (CIVs) have caused many thousands or millions of respiratory infections in dogs in the United States. While no human infections with CIVs have been reported to date, these viruses could pose a zoonotic risk. Read on to see how the flu virus jumped from horses to dogs, and another strain that jumped from birds to dogs. Are humans next?

Influenza viruses are enveloped viruses with segmented single-stranded RNA genomes that belong to the family Orthomyxoviridae. Currently two strains, H3N8 and H3N2 are spreading across the US, but another flu bug, H3N1, which can infect humans has been found in Southern California dogs. A respiratory outbreak in dogs in a boarding kennel was reported in the southern half of Los Angeles County this week. The initial report estimated that 30-40 dogs showed respiratory signs at the facility, starting in mid-to-late July. Clinical signs reported include coughing, nasal discharge, and dyspnea. The death of one dog is being investigated as potentially being part of the outbreak. As of this report, no human illnesses have been reported. Two cats in the facility also had respiratory signs, but they have not been confirmed to be related to the outbreak. Preliminary PCR testing and sequencing results on 3 dogs, reported yesterday, identified the likely cause as Influenza A, subtype H1N1. Further analysis is underway.

This virus is different than the canine influenza subtypes H3N2 and H3N8 which have caused outbreaks in dogs in Los Angeles County and the elsewhere in the United States before.

Here's the skinny on the early h3n2 and h3n8 serotypes:

In the USA, canine influenza virus (CIV) H3N8 jumped from horses to dogs, emerging in racing greyhounds in Florida in 2003 and 2004, where it caused hemorrhagic pneumonia and a high mortality. Serologic evidence of infection in the greyhound dog population dates back to 1999. Infections spread slowly and were subsequently reported in racing greyhounds and non-greyhounds in at least 38 US states. However, this strain of canine flu virus was self-limiting, and appeared to be dying out. That's why I wasn't ready to market the vaccine to my patients.

In its place is the more virulent and deadly H3N2. Researchers identified the avian-origin H3N2 canine influenza virus five years ago circulating in farmed dogs in Guangdong, China. In March 2015 this new H3N2 strain appeared in Chicago when humane organizations bought Korean dogs destined for the meat market and imported them into the US.

In the United States, inactivated, parenteral vaccines are available for reduction of disease caused by H3N8 and H3N2 CIV and viral shedding. These vaccines do help to prevent severe clinical signs of illness but do not prevent infection of a dog or shedding of influenza virus. Their use has been recommended for dogs that may contact other dogs in regions where CIV is endemic. CIV is shed in the incubation period by infected animals who are not showing the clinical signs. Sources are dog parks, day care, groomers etc and it can be spread indirectly through fomites, owners, clothing, environment. Affected dogs should be kept away from others for 4 weeks.

Protection is not complete until at least 7-10 days AFTER the SECOND immunization. Therefore, owners should plan ahead to begin to vaccinate at risk dogs at least 3 weeks prior to entering a potential exposure situation. Yearly revaccination is recommended for at risk dogs. There is no cross protection from vaccination against H3N8 against H3N2 and vice versa. Therefore, vaccination against both strains is required to protect against both.

The initial vaccine may be given as early as 6 weeks of age. Because CIV vaccines are inactivated, two initial doses are required 3–4 weeks apart, and maximum immunity does not occur until 1 week after the second dose.

Here's a true horror story I found on the Veterinary Information Network (VIN)

At Christmastime, Jessica Mantoani opened her home in San Carlos, California, to a beautiful golden retriever from South Korea in need of a foster family.

Mantoani recalls feeling proud that her local rescue organization, Doggie Protective Services, aimed to save animals from Korea’s dog-meat trade by bringing them to the United States. Having volunteered for years with the nonprofit, Mantoani's main concern was whether the foster dog would blend well with the three beloved canines she had at home. That wasn't a problem. "The dog was friendly, had a lot of energy," Mantoani said. But another, more serious, issue arose. "[W]e noticed about two days after he arrived that he was coughing and would spit up white, goopy stuff onto the floor," she recounted. Mantoani guessed it was a mild case of kennel cough. "It didn’t seem to bother him; he had no other real symptoms," she said.

Mantoani contacted the rescue group, which took the dog to be treated for an upper respiratory infection and returned him to her home. Then Mantoani's younger dog, Sheldon, stopped eating, started coughing and became lethargic. Her two elderly Jack Russell terriers, Bailey and Tildon, also became ill — gravely so.

On New Year’s Day, 11-year-old Tildon began vomiting and having seizures. After a harrowing trip to the SAGE Centers for Veterinary Specialty & Emergency Care in Redwood City, the dog perished.

Mantoani later learned that the golden carried H3N2, a virulent, potentially deadly strain of canine influenza that public-health experts say is being spread to the U.S. from infected dogs imported from foreign countries.

Sheldon eventually beat the virus. Bailey almost didn't. "My daughter was sleeping next to the dog, praying over her and playing 'Hallelujah’ on repeat," Mantoani recalled. "... The next morning, Bailey was sitting up. This dog has nine lives. She still has a lingering cough, but the fact that she's living is a miracle."

Doggie Protective Services eventually reimbursed Mantoani the $3,500 she spent on veterinary care for her three dogs. The organization still partners with a Korean exporter of animals. "It is our strong belief that because we have the resources and the ability to save highly adoptable dogs from certain death, that we should do so," the website reads. "It doesn't matter if the dogs in need are in the Bay Area, LA, or as far away as Korea. Our philosophy is simple: If there is a need, and we can and want to assist, then we will."

Is canine influenza virus transmissible from dogs to humans or other animals?

There is no evidence that either strain of canine influenza is zoonotic, as this usually requires a substantial antigenic shift. Thus, while the potential exists (as is evidenced by the cross-over of species from equine to canine, or the recent experience with avian influenza), there is no current concern. H3N2 CIV can infect cats, but the incidence appears to be low. The greatest concern is likely the potential for dogs to act as ‘mixing vessels’, because they can rarely be infected with human influenza viruses. If they are concurrently infected with CIV and human influenza, there is potential for recombination of those viruses into a new viral strain. This is unlikely but possible.

I manage a kennel/veterinary clinic/animal shelter/dog day care center. How do I keep canine influenza out of my facility, and if it does enter my facility, what should I do?

Vaccines for both canine influenza H3N8 and H3N2 exist. Dogs at risk for exposure to contagious canine respiratory diseases should also receive vaccination against the other respiratory pathogens. This may allow clinicians to help rule out diseases such as "kennel cough" (Bordetellosis, Parainfluenza) in a coughing dog. Dogs that are scheduled for boarding should be vaccinated against "kennel cough" 2 weeks prior to boarding. Dogs admitted to shelters should be vaccinated on admission.

Canine influenza is easily killed by most disinfectants (quaternary ammonium compounds, accelerated hydrogen peroxide, bleach solutions), and does not survive well outside the host. Good clinic practice, involving regular disinfecting of cages, kennels, feeding utensils, etc., and regular hand-washing by personnel is advised.

Clients should be interrogated about boarding/kenneling history, vaccination status, or any relevant clinical signs. Any dog with clinical signs should be quarantined, avoiding the waiting area/common areas as much as possible.

Dogs in a Chicago shelter demonstrated prolonged intermittent shedding of the H3N2 strain during the 2015 outbreak, suggesting that vigilance is required even if things appear to be settling in the event of an outbreak.

I suggest that you get the flu shot for your pet if he/she goes to public places like doggie parks, or regularly sees other dogs.

Call my office at (805) 239-1206.


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