Vaccines for Dog Flu May Offer Cross-Protection, Maybe


The dog flu epidemic in the Chicago area turns out to be caused a canine influenza flu virus (CIV) strain never before seen in the U.S. It’s a strain that for nine years has been seen in China and South Korea.

There are several questions being asked by dog owners, and first and foremost – will the current vaccine for dog flu be effective against this novel CIV strain, called influenza A H3N2.

“At this time, we do not know if the vaccines for dog flu will be helpful,” says Dr. Jill Lopez, senior Specialist Drug Safety at Merck Animal Health.  “Testing is taking place to see if our vaccine would offer cross protection and we should know something more when that is completed.” This process could take weeks, or months -no one knows.

While the dog flu appears rampant around them, the Dog Spot in Downers Grove has not had a single coughing dog. Is it a coincidence that the facility mandates that all dogs entering are vaccinated for CIV?

“It’s anecdotal evidence to be sure, but reports such as this lead me to be optimistic that the vaccine can cross protect,” Lopez adds.  “While we do not know if our Nobivac Canine Influenza H3N8 vaccine provides protection against H3N2, we do know that none of the 140 dogs that tested positive for dog flu had been vaccinated for dog flu prior to their illness.   This leads me to be optimistic that the vaccine may cross protect.” .

Other veterinarians aren’t so sure.

“While it’s still an H3 virus (the strain impacting Chicago now from Asia), it  is antigenically different from  the H3N8 virus strain so it is likely to be seen differently by the immune system,” says Dr. Amy Glaser, director of molecular diagnostic center at the animal health diagnosis Center at College of Veterinary Medicine, Cornell University. Still, Glaser strongly recommends the CIV for all social dogs, particularly those living in urban areas.

Lopez told me that when researchers first began to look at the bug carefully, it just didn’t appear to like the H3N8 virus which Merck Animal Health has long been dealing, following the launch of their Nobivac Canine Flu vaccine in 2009.  That original dog flu virus, known as H3N8 was first identified in Florida in 2004. There have been sporadic outbreaks around the country since then, including one in Chicago, in 2008. Aside from looking different under a microscope, it appeared that more dogs were getting sicker than typically seen in H3N8 infections, often more profoundly ill, and spreading faster than H3N8 ever did.

A press release issued today from Merck animal health: The diagnosis was accelerated by Merck Animal Health’s collection of samples from sick dogs from veterinarians in the Chicago area, as well as resources the company committed to the effort. During a three week period, more than 130 dogs tested positive for canine influenza virus.

“This is the first time this strain of canine influenza virus has been found in North America, so there’s a lot we don’t yet know about it,” said Edwin Dubovi, Ph.D., professor of virology and director virology laboratory at the Animal Health Diagnostic Center, College of Veterinary Medicine, Cornell University. “Veterinary professionals are advised that diagnostic testing of samples from sick pets can be done using a broadly targeted influenza A matric reserve transcriptase-polymerase chain reaction assay (RT-PCR). The canine-specific influenza A H3N8 RT-PCR in use in several laboratories will not detect this virus. We are developing a H3N2-specific serologic assay and are continuing to work with Merck Animal Health to test serum samples from sick dogs, both of which will provide us with valuable information about emerging disease.”

Lopez told me, “Chicago’s response has overall been amazing, veterinarians have readily shared information and have been proactive about warning the public. What’s more the media there has been great.”

Lopez also credited this blog which she says herself and colleagues read “religiously.”

Lopez echoes her colleagues who suggest limiting socialization is the best guaranteed protection right now. Chicago Park District continues to strongly discourage dogs from using the park district Dog Friendly Areas, a decision supported by the Chicago Veterinary Medical Association. The same is true for dog daycare, boarding, dog training classes, even visiting pet stores with dogs.

The good news is that via good luck or precautions taken, based on anecdotal reports – for the first time in weeks, many clinics are reporting fewer cases of the dog flu. Though that is difficult to discern at this moment.

Note the early onset symptoms are the same for either flu virus strain in dogs:

  • Coughing
  • Lethargy
  • Lack of Appetite
  • Nasal Discharge
  • Trouble Breathing

Any time you observe a change in your pets behavior, or any of the above symptoms, contact your veterinarian.

Cornell Press Release regarding canine influenza virus.

Also, there’s more information available at