Tularemia in muskrats: Long Point, Ontario (that’s in Canada)

For a Brantford kid, Port Dover on the glimmering shores of Lake Erie was the closest beach; but for the full Lake Erie experience, we would drive a little further west to Long Point.

My friend Scott Weese, who is apparently treating the lock-down like I do, by writing more because ya don’t have to waste time at stupid meetings or commuting, writes in his Worms and Germs Blog that a recent report from the Canadian Wildlife Health Cooperative (CWHC) describes an outbreak of tularemia in muskrats in Long Point, Ontario. Tularemia is a potentially nasty disease caused by the bacterium Francisella tularensis. While not many people have contact with muskrats or live in Long Point, it’s still noteworthy.

 The investigation was initiated following a report of at least 35 sick or dead muskrats in the area. Necropsies were done on some of the rodents, and they were found to have enlarged lymph nodes and lesions in their spleens and livers. Testing at the National Microbiology Laboratory identified Francisella tularensis.  This was done at the national lab because F. tularensis is a containment level 3 pathogen requiring enhanced biosafety practices – so it’s not a bacterium which regular labs handle.

This isn’t a new finding, since we know this bacterium is present in Ontario, but it’s rare. Francisella tularensis is sporadically found in various animals and rarely in people (there’s been one reported human case in Ontario so far in 2020). It’s a reportable disease in animals and people because of the potential severity of infection, and because it’s a potential bioterrorism agent.

Back to the muskrats… tularemia is a rare finding in wildlife. That doesn’t mean it doesn’t cause disease, since sporadic disease in wildlife rarely gets investigated. It’s most commonly associated with rabbits, and human and domestic animal infections can be associated with rabbit or rodent contact. The fact that this occurred as an outbreak with a significant number of animals affected over a short period of time is interesting, and it’s also concerning from human and animal health standpoints. The bacterium can be spread in a variety of ways, including direct contact, inhalation (e.g. running over an infected animal with a lawnmower and aerosolizing the bug and then breathing it in… gross but true) and via some insects (e.g. ticks, deer flies).

Tularemia avoidance measures are pretty basic:

Avoid contact with wildlife, live or dead.

People handling dead wildlife, especially those handling them closely such as trappers, should use good routine hygiene and infection control practices.

Avoid ticks. For pets, that involves use of a good tick preventive. For the rest of us, well… we don’t have a chewable tick preventive but we can do other things to reduce the risk of tick exposure, including (and most importantly) doing “tick checks” if you’ve been outside in an area where ticks are likely to be lurking.

Keep your pets under control, especially if they are prone to chasing wildlife or snacking on dead animals (also gross but true).

The CWHC warning is pretty similar to my comments: “During an outbreak situation, it is presumed that bacterial levels would be higher in the surrounding environment, so caution is warranted for anyone who is traversing through the area or wading into the water in the Crown Marsh area of Long Point. There is also a danger to off-leash dogs as they can become infected and develop similar symptoms to humans, especially if they consume infected meat. It is recommended that dogs are kept on leash and monitored closely while in this area. It is recommended that people do not handle wildlife found dead unless they are wearing protective gloves (or a similar protective barrier) to prevent direct contact of the animal with the skin. Anyone who handles dead wildlife (even while wearing the appropriate protective gear) should wash their hands thoroughly to minimize the chances of exposure.”

A related topic that applies to animals and people is talking to healthcare providers about travel. The risk for various diseases differs geographically. A disease might not be on a physician’s or veterinarian’s list of considerations if they don’t know about travel. So, physicians and veterinarians need to query travel history, and everyone needs to remember that travel means going somewhere else, regardless where it is (even if they haven’t left the province).

Here’s a scenario that highlights that:

Me: Have you traveled with your dog lately?

Owner: No.

Me: Do you have a cottage?

Owner: Yes, it’s a beautiful place a couple of hours from here. We go there every weekend in the summer.

Me: So, you travel with your dog every weekend in the summer?

Owner: Well, that’s not travel, it’s going to the cottage.

Me: Ok, now let’s talk about the different things I need to consider now that I know your dog travels.

That’s not an unusual situation. Understanding where people and animals have been is important when thinking about infectious disease risks. Veterinarians and owners need to clearly communicate to identify potential problems.