Labrador retriever in a field

I have Labrador Retrievers, so I’m well versed in dealing with the implications of what my dogs have been eating (Labs being prone to considering just about anything fair game for ingestion). Owning such a pair of environmental vacuums, the question of whether dogs might be at risk of H5N1 avian flu exposure from bird feces or other things in the great outdoors has a personal spin.

It’s a really common question these days, and we don’t have a really solid answer, and it’s a very hard thing to study. In natural settings, teasing out environmental exposure from direct bird-to-bird or bird-to-other-animal exposure is tough. We rarely have situations where we can clearly say “this individual was exposed to this and only this type of environment, and then did (or did not) get infected.” There’s also a species susceptibility component. Environmental transmission of H5N1 influenza to birds is likely very different from environmental transmission to mammals because of the lower susceptibility of mammals. Even within mammals, there’s likely a lot of variation in susceptibility of different species, and types / level of exposures they’re likely to have.

So is there cause for concern regarding exposure of dogs (and other mammals) to H5N1 flu from bird feces in the environment?

Yes, to some degree. Environmental exposure has been identified as a risk factor for human H5N1 infection in the past, but that’s usually from contact with very high risk environments like infected farms or markets, or where people live with poultry (e.g. in the household). More recently, environmental exposure was deemed to be the most plausible source of infection with H5N1 influenza in a person in Chile.

So, there’s a plausible risk of environmental exposure to this virus, but it’s hard to extrapolate those reports to common casual outdoor exposure to bird feces or other sources. We also have to remember that these are rare incidents during an outbreak where millions of birds have been infected, and have been shedding a vast amount of flu virus into the environment.

What types of environments are of greatest concern?

The more infected birds in a particular area, the greater the risk the virus will be present in the environment. That’s pretty obvious. One infected bird can shed a little bit of virus, ten thousand infected birds can shed a whole lot more. But the risk doesn’t depend solely on the amount of virus expelled by birds; it also depends on things like how well the virus survives in the environment, and how people or other animals are exposed.

Does the H5N1 influenza virus survive long in the environment?

Yes and no. Fortunately, flu viruses don’t usually survive well outside the body. If it’s dry and sunny, the virus will die pretty quickly (typically within hours). But, if the virus is in a nice protected environment, it can survive for longer periods of time (potentially days or weeks).

Can a dog get H5N1 influenza from eating bird poop?

Potentially. It would have to be fairly fresh poop from an infected bird, with enough of a viral load to cause infection (but we don’t know how much of a load that is for a dog). I’d say the risk is pretty limited in most situations. However, if a dog is “grazing” in an area with a lot of infected birds and a lot of bird poop, there’s going to be some risk.

Can a person or dog get infected from virus on someone’s shoes if they walk where infected birds have been?

This is getting into the “theoretically possible but extremely unlikely” area. It’s not impossible but there are bigger things to worry about. That said, if there are lots of birds in an area and flu is active, it’s wise to stay away (and not just to keep your shoes clean).

Overall, I’d say the risk of H5N1 influenza infection in dogs from normal activities like walking in a park is low. It’s not zero, but it’s low enough that people shouldn’t panic. Like most things, it’s a matter of balancing costs and benefits of preventive measures. A bit of common sense goes a long way:

  • Stay away from areas with lots of birds.
  • Be more restrictive about outdoor activities when flu is active in birds in the area.
  • Avoid direct dog-to-bird contact (including both live and dead birds).
  • Avoid situations where direct dog-to-bird contact is more likely to happen (e.g. lots of territorial or habituated geese, like in many public parks).
  • Avoid areas with obvious accumulations of bird poop.

And the most important measure:

  • Keep dogs away from sick or dead birds.