Dog nose B&WThis latest flu strain probably isn’t as big a deal as some other influenza viruses found in dogs, but it demonstrates that it’s important to monitor influenza in different species and look for changes.

A paper published ahead of print in Emerging Infections Diseases (Lin et al, Dec 2015) describes an H6N1 influenza virus in dogs in Taiwan. This strain of influenza A has been widespread in chickens in Taiwan for decades, and rarely have infections with this type been found in mammals (which is a good thing). This study involved collection of samples from pet dogs presented to a University teaching hospital as well as from free-roaming rural dogs. Blood samples were tested for the presence of antibodies against influenza. Nasal swabs were also collected from dogs presented to the teaching hospital with signs of respiratory disease, to look for the virus itself.

  • Antibodies against flu virus were identified in 3/281 (1.1%) pet dogs and 6/193 (3.1%) strays. Antibodies against H6N1 were confirmed in one of these animals.
  • More interesting was results of testing for the virus itself. Influenza virus was detected by PCR (a test that looks for genetic material from the virus) in 4/185 (2.1%) dogs. All of these dogs had nasal discharge or cough. Three were young (<6 months of age). Three were also what I’d consider higher-risk: two were strays adopted from the streets and one was adopted from a shelter.
  • Virus culture was attempted and influenza virus was grown from one sample, a 4-month-old puppy that also had distemper.
  • Interestingly, serial blood samples did not detect any antibodies against the virus in this dog. Maybe that’s because the pup was too sick to respond to the infection, but it shows that infection may occur in the absence of detectable antibodies (the test that is often used for surveillance studies).
  • When the genetic sequence of the cultured virus was assessed, it was confirmed as H6N1, and 99% similar to H6N1 from chickens in Taiwan. That’s not surprising at this was likely a spillover event from chickens or other birds into the dog.

Fortunately, this H6N1 influenza strain (currently) poses little risk to people. The fact that it can infect dogs, and maybe cause disease (that wasn’t really confirmed, as the dogs could have had some other respiratory disease) does raise some concern.

This study should be yet another reminder of the unpredictable nature of influenza and the need to include domestic animals, including dogs and cats, in influenza surveillance.