I’m focusing on antimicrobials this week since it’s World Antimicrobial Awareness Week, but this is a timely topic and there’s an antimicrobial twist.

A couple of recent reports about a canine pneumovirus outbreak in a shelter in Tacoma WA and a separate outbreak of canine pneumovirus in a shelter in Las Vegas NV have, predictably, launched more concern about this virus (and some over-reaction).

The antimicrobial stewardship (or lack thereof) aspect is highlighted by a quote from shelter personnel in one of those reports: “We’re really treating it symptomatically by throwing antibiotics at it, that’s all we’ve essentially come up with.”

Throwing antibiotics at it.  For a viral outbreak.

Sometimes we need antibiotics during respiratory disease outbreaks to treat secondary bacterial infections in certain dogs, but antibiotics are massively overused in dogs with (often mild) upper respiratory tract infections, in both shelters and the community at large. Our ISCAID antimicrobial use guidelines for treatment of respiratory tract disease in dogs and cats are getting a bit dated (2017), but still highlight the considerations for antibiotic use in respiratory disease – and the overall limited need for such use.

Outbreaks like these are important reminders of the need for good routine infection control, prompt response to disease incidents, and effective communication.

They should also be a reminder to think about how we use antibiotics in respiratory disease in dogs and cats. I understand why antibiotics are “thrown” at outbreaks… they’re stressful situations, and there’s often pressure to just “DO SOMETHING!!!” However, from the standpoint of both effectiveness and antimicrobial stewardship (paraphrasing the immortal words of Winnie the Pooh), sometimes doing nothing is the best something.

Back to the pneumovirus outbreaks:

Since I’m lazy, I’ll cut-and-paste from a post about a canine pneumovirus outbreak in another shelter from earlier in the year, as not much has changed since then.

I always talk about pneumovirus when I list potential causes of infectious respiratory disease in dogs, but usually with the disclaimer “I don’t really know how important it is.” Studies that have looked at different dog populations have reported finding canine pneumovirus in 1-15% of dogs with respiratory disease, but most often in less than 5%. Rates of 0-6.1% have been reported in healthy dogs. Finding the virus in healthy dogs doesn’t mean it can’t cause disease, it just makes it harder to determine if it’s relevant in sick dogs.

Studies looking at antibodies against penumovirus in dogs (an indication of previous infection) have found high rates in healthy dogs, often over 50%. Dogs often develop antibodies to the virus after being admitted to a shelter. This suggests that this virus is circulating widely in the dog population and probably not causing much disease, or at least not much serious disease. When dogs mix in congregate settings like shelters, the risk of infection goes up.

My guess is that this virus does cause some disease, but likely usually just mild upper respiratory tract infections, with exposure being common when younger dogs start mixing. Once they’ve been infected, dogs are probably low risk for getting sick later in life. Shelters are high risk for exposure because of the number and variety of dogs in close quarters.  Dogs that haven’t been previously infected would be susceptible, and that could lead to an outbreak with what I’d expect to be relatively mild disease.

So, do these recent reports indicate that things are changing, since we’ve had a couple new reports of outbreaks in shelters?

Probably not. Most likely, this virus has been a cause of outbreaks like this before and we just couldn’t put a name to it. With advances in testing, we can identify things we missed before. Most likely, we’re just picking up the sporadic outbreaks of typically mild disease that pneumovirus has probably been causing for some time.

That doesn’t mean we should ignore it. We need to use good infection control practices to reduce disease and outbreaks in shelters. However, at the same time, we need to take care not to over-react to disease or to “new” things that might not actually be very new.