Candida auris in dogs
Candida auris is an emerging threat that we need to pay attention to. This fungus causes disease almost exclusively in immunocompromised people, with infections most often acquired in hospital. While infections are rare, it’s a bit problem because mortality rates tend to be very high (20-60%), it can cause outbreaks in healthcare facilities, it can live on the skin of healthy people, antifungal resistance is common and routine disinfectants don’t always work very well.
That’s a perfect combination for a nasty hospital-associated infection, and when something is a problem in hospitals, we have to consider whether that will spill into the community. Since infections are most often in highly compromised patients the community risk is probably low, but since it’s an emerging disease, we need to pay attention.
Here’s a map of US human cases from the CDC.
As I often say, when we see a new disease threat in people, we need to look at animals too. Not to blame, not to freak people out, but to understand. Most often, an animal side is completely ignored or there’s overreach and unnecessary blame an animal source. A logical middle ground is needed, where we look and try to understand, addressing a potential problem proactively and without panic or sensationalism.
What do we know about C. auris and animals?
Very little so far.
A study of dogs in India reported detection of C. auris in the ear (3/87) or skin (1/87) dogs (Yadav et al 2023) . It’s a bit hard to follow the results of that paper and not all the infections are described well but one of those dogs had chronic skin and ear infections, and had been previously treated with antibiotics and antifungals. C. auris was identified on two samples from that dog taken a month apart, which is important as we need to understand whether animals can be long-term carriers, short-term carriers or are largely resistant to infection (and if positive, are just contaminated transiently).
Another study from the US found C. auris from the oral swab of one of 251 dogs from an animals shelter in Kansas (White et al 2024). It was a 2yr old Lab cross that had recently been surrendered. When they looked at the genetic makeup of C. auris, it was the same clade (group) as C. auris isolates that have been found in people in a couple places in the US, including Chicago.
The isolate was resistant to fluconazole, amphotericin B and terbinafine, but susceptible to voriconazole, itraconazole and caspofungin. So, it was resistant to some common antifungals but not others, but that degree of resistance is still a concern since we have limited antifungal options.
Where did the dog get infected?
It’s hard to say. It could have been acquired in the shelter or before it was surrendered. No one at its previous home was immunocompromised and the dog didn’t visit human hospitals, the two first things I’d look at. No shelter workers were known to have been infected (but people weren’t tested). The dog hadn’t traveled, had no previous medical issues and had not been treated with antifungals. No other dogs in the shelter were positive, including the littermate that she was surrendered with. She was subsequently adopted and 2 years later, neither she nor the other dog in her new household were positive. (Why was she only tested 2 years later? Probably because the C. auris aspect was a secondary result from a main study and it took that time for the side-work to be done, plus the confirmatory testing).
When we’re thinking about C. auris (or other emerging diseases) in animals, we’re looking at two main areas.
- One is the zoonotic component…can animals be a source of infection for people? That’s an important area, obviously.
- Sometimes, the 2nd component is overlooked….can it cause disease in animals? Sometimes the animal health component is overlooked.
(Actually, we should probably add in a 1b component….can animals be infected by people? While it’s usually overlooked, we have ample precedent of infectious diseases emerging in human healthcare and spilling over into animals, particularly companion animals (e.g. MRSA, various other multidrug resistant bacteria)).
While it’s rare, it’s clear that dogs can be infected, at least temporarily. It’s fair to expect that that applies to other species too.
So, that leads to the big question….can infected animals infect people?
- Who knows.
- Probably.
It’s logical to assume that an infected dog could infect a susceptible person just like an infected person could infect another susceptible person. Fortunately, this organism tends to infect highly compromised people and most dogs don’t much contact with those individuals. The risk would be greatest when a dog had direct contact with an infected person then contact with another high risk person (or, if the first infected person was successfully treated and lived with the dog, there’d be a question about whether the dog could be a source of re-infection).
What about hospital visitation dogs?
This is a unique group that I’ve worked with on and off. We know that these dogs are at increased risk of picking up various infectious agents during visitation (e.g. MRSA acquisition rates can be really high….transient but high). So, a similar situation could be considered with C. auris. Fortunately, the risk of exposure is going to be much lower than with many other hospital-associated pathogens since C. auris is still very rare. However, this should be yet another reminder of the need to run visitation program well (some guidelines are here) and to take efforts to reduce the risk of exposure of dogs during visitation.
When MRSA first emerged in dogs, we tended to see it most in healthcare personnel’s pets and dogs that visited hospitals. Visitation dogs are at the forefront of exposure to various things that concentrate in human healthcare facilities, and if we’re going to see an animal spreading C. auris, this is a prime way for that to occur.
So, we need to think about potential human-animal and animal-human aspects of C. auris and use basic infection prevention and control measures to reduce the risk. We shouldn’t over react since we have no evidence of a problem, but we also shouldn’t wait for definitive proof before taking reasonable precautions.