Search results for: Tularemia

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.

Tularemia is a nasty bacterial disease. The bug that causes it, Francisella tularensis, is a category A bioterrorism agent (along with things like anthrax, botulism, plague, smallpox and Ebola virus). It’s classified as that because it’s highly transmissible and causes serious disease, so it’s something you definitely don’t want.

The bacterium circulates in the wild, most often associated with rabbits and rodents. Human infections are usually associated with exposure to these types of wild animals (including things like – gross as it is – running over a wild rabbit with a lawnmower and aerosolizing the bacterium). However, one complicating factor with this bug is that it can be spread a lot of different ways, including via tick and fly bites, water and minor contact with infected animals (e.g. just touching their skin).

Among domestic pets, cats are most commonly implicated in human infection, because cats with outdoor access tend to hunt species that harbor tularemia (fitting with the “it’s better off for cats to be indoors if they tolerate it” statement I made in my last post… that got lots of comments both for and against), and because they are fairly susceptible to infection when they get exposed. However, a variety of animals can harbor and transmit the bacterium.

Dogs are lower risk but not no risk, as a recent paper in Zoonoses and Public Health (Kwit et al. 2018) explains. They looked at US tularemia surveillance data from 2006-2016, and focused on the 24 cases that were deemed dog-associated. Whether those were all truly from dogs can’t be guaranteed, and it’s possible that some of the other cases were dog-associated but the link wasn’t investigated or identified.

Among the highlights:

  • Most cases were from Missouri, Colorado and Kansas, consistent with what we know about tularemia in general in the US.
  • Outcome was known for 20 of the affected people. Two died.
  • 50% of cases were thought to be from direct contact with dogs, including bites or scratches, but also contacts such “face snuggling” and licking
  • 33% of people were exposed from contact with carcasses brought home by their dogs.
  • 17% of cases were associated with ticks thought to have been brought in by dogs. Implicating dogs as a “source” of ticks in a household is tough, because if a dog is exposed to ticks, people in the same area have a similar risk of being exposed if they’re outside. The bigger risk might be an increased tendency to spend time in tick-infested areas when walking said dogs.
  • Not much dog-health information was reported. Four people had contact with “ill” dogs but it’s not clear how many dogs might have had tularemia vs been infected without signs of disease vs been contaminated by the bacterium but not infected (and been “ill” from something else entirely).
  • One dog was diagnosed with tularemia. That’s not too surprising since dogs tend not to get sick or at least not get very sick from tularemia (as opposed to cats), so it’s easy to miss a potential dog case.

The take-home messages are pretty straightforward. Tularemia is very rare and very low of my list of disease concerns when it comes to dogs. However, avoiding tularemia involves common sense practices that should help reduce a lot of other risks at the same time.

  • Reduce roaming of dogs, especially dogs that are able to or like to interact (e.g. chase, hunt) wildlife like rabbits.
  • If your dog brings back a carcass, handle it with care. Try to avoid touching it and, if you have to, wear gloves, then wash your hands after removing the gloves. Avoid contact with the dog’s mouth for a while (who knows how long… maybe a couple hours?) if it had a carcass in its mouth.
  • Reduce tick exposure as much as possible (for dogs and people).
  • Use tick preventives in dogs to reduce the risk of tickborne disease exposure. A variety of ticks can transmit F. tularensis, including the dog tick (Dermacentor variabilis), the wood tick (Dermacentor andersonii) and the Lone Star tick (Amblyomma americanum).
  • Mention rabbit and rodent exposure potential to your veterinarian if your dog gets sick.
  • Mention your dog ownership, your dog’s potential contact with wildlife, and any contact you have had with wildlife (dead or alive) to your physician if you get sick.

 

When it comes to handling microorganisms, there are 4 biosafety levels.

  • Biosafety level 1 (BSL-1) organisms are harmless.
  • BSL-2 organisms include most of the commonly encountered bugs, including things like E. coli, Salmonella and Staphylococcus aureus. They can cause serious disease but infections are often treatable and they can be handled safely with standard lab protocols.
  • BSL-3 organisms are a relatively small group of bad guys that require more extensive facilities and protocols to handle them. These include Coxiella burnetii (the cause of Q-fever) and Francisella tularensis, the cause of tularemia.
  • BSL-4 organisms are the really bad guys that require high level containment like you see in the movies. There are a limited number of BSL-4 facilities in the world and they deal with bugs like Ebola virus.

One of the BSL-3 pathogens I mentioned was a bug called Francisella tularensis, the bacterium that causes tularemia, which is also listed as a potential bioterrorism agent.  Tularemia is a very nasty disease. It’s uncommon but human infections occur sporadically in many regions, typically associated with wildlife exposure. It’s often associated with contact with rabbits, but the bacterium can be found in a wide range of animals (including insects) and in the environment.

Recently, people in Bell and Coryell counties in Texas (between Dallas and San Antonio) were warned about the potential for tularemia exposure from wild hogs, since 15-50% of tested feral hogs in those areas had evidence of current of past infection. While evidence of past infection (the presence of antibodies against the bacterium in their blood) does not mean that they are actively infectious, it indicates that the bacterium is circulating in the area and that hogs are being exposed. If a hog was actively infected, it could be a source of human infection if there was direct contact (i.e. hunting and butchering).

Because of the potential risk of exposure, the following recommendations have been made:

  • Always wear rubber gloves and eye protection when dressing (i.e. skinning & gutting) wild game.
  • Ensure that game meats are handled carefully and thoroughly cooked.
  • Use insect repellent to keep ticks, biting flies and other insects at bay.
  • Look for rabbit nests in tall grasses before mowing. (As unusual as it sounds, running over rabbits with a lawnmower has been associated with development of tularemia).

The risk of tularemia is pretty low, but it’s a very serious disease and you don’t want it. Using these basic precautions should help reduce the risk.

Tularemia has been diagnosed in five dogs and cats in Sioux Falls, South Dakota. At least one of the pets has died. Tularemia, sometimes referred to as "rabbit fever" is caused by the bacterium Francisella tularensis. Infections occur throughout much of the Northern Hemisphere but are much more common in certain regions, such as the central US. This bacterium has received a lot more attention over the past decade because of its potential use as a bioterrorism agent, but infections have been occurring in people and pets for a long time. In North America, the cottontail rabbit, wild hares and some rodents are the main reservoirs. People and other animals get infected through close contact with infected animals (e.g. rabbit hunting) or through bites from blood-feeding insects. 

There was no mention of human cases in the recent report from South Dakota. One of the implications of identifying this disease in pets is that whatever infected the pet could also be a risk for people. If the pets were infected by contact with wild animals, people with similar contact with wild animals could also be exposed. If there is no chance the animals had contact with infected wildlife, then insect-transmission is most likely, and the same could happen to human members of the household (or elsewhere in the area). Therefore, diagnosis of tularemia in a person or pet should put both veterinarians and physicians on the lookout for further cases in all species.

Transmission of tularemia from infected pets to humans is also a concern. This has been reported in numerous instances, most often with cats. There are published reports of transmission from dogs to humans, but these are less convincing than the numerous cat-to-human reports. There’s also a report of tularemia transmission from a hamster to a child. The overall risk of transmission is probably low, but tularemia can be spread from pets to people by scratches, bites, and perhaps regular close contact.

You can reduce the risk of your pet being exposed to tularemia by:

  • Keeping pets indoors as much as possible. Cats should stay indoors. Dogs should not have uncontrolled outdoor access.
  • Dogs should not be allowed to hunt rabbits in areas where tularemia is endemic.
  • Animals that venture outside should be checked regularly for ticks and a preventive medicine program for ticks should be in place.
  • Routine measures to reduce bites and scratches from dogs and cats should be taken.

A case of pneumonic tularemia was recently reported in New York City.

Tularemia is a disease caused by the bacterium Francisella tularensis.  It causes different signs of illness depending on how the bacteria enter the body.  If the bacteria are inhaled, it tends to cause pneumonia (pneumonic tularemia).  If the bacteria get in through a break in the skin, infection may cause the local lymph nodes (glands) to become very swollen, and in some cases the skin itself may become infected resulting in the formation of large sores (ulcers).  Infection can also cause sores in the mouth and diarrhea.  The earliest, most common signs are things like fever, headache, chills, sore muscles, and sore throat which often come on very abruptly.  The infection can be treated with antibiotics, but it is important to see a doctor and start treatment as soon as possible.

Tularemia is also sometimes called "rabbit fever," because the bacteria are often carried by animals such as rabbits and hares.  Rodents (including beavers, rats, mice, squirrels etc.) can also carry F. tularensis, and occasionally so can cats and dogs.  Some biting insects like deerflies and certain species of ticks can carry the bacteria and transmit it when they bite.  Francisella tularensis can also survive in water and soil for a long time.  People can become infected by being bitten by an infected insect, handling an infected animal (dead or alive), or coming into contact with feces from an infected animal.  Occasionally a person may inhale the bacteria if it is in the air, as may happen with disturbed, dusty, contaminated soil.

More information on tularemia can be found on the CDC’s tularemia website.

Things you can do to avoid tularemia:
Avoid touching or handling wildlife (dead or alive), especially rabbits and rodents.
Don’t let your pet touch or eat dead animals.
Always wash your hands if you have been working outside in the dirt/soil.
Wear insect repellent containing DEET (visit the Health Canada website for more safety tips) 
Make sure you only wash food with and drink water that has been properly treated.

One of the reasons tularemia is such a big deal is it is very infectious – as few a ten bacteria can be enough to make even a healthy person sick!  But it is still quite uncommon in North America – about 100-200 cases are reported in people in the USA every year.  Between 2002-2004 there were 34 cases reported in Canada, most of which occurred in Quebec and in adults.  However, infection can be fatal in a very small number of cases, especially if proper treatment is not given as soon as possible.