Submitted by dasko2 on Mon, 12/14/2020 - 09:41

The Veterinary Detective:
The Case of the Coughing Tiger


released December 16, 2020

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Dr. Mitek: Hi, I'm Dr. Ashley Mitek, a member of the faculty at the University of Illinois, College of Veterinary Medicine.  Over the next several weeks, we'll present a mini-series called "The Veterinary Detective". In each episode we discuss a case with a veterinary clinician who will walk us through the diagnostic process to help us understand how they apply clinical reasoning in their practice. 

As veterinarians, we examine our patients in person to develop a differential diagnosis list of possible causes.

But what happens when the patient is a rare Malaysian tiger located over 800 miles away? We’ll explore the unique challenges posed in a long-distance diagnosis in this episode we call “The Case of the Coughing Tiger".

Joining me is Dr. Karen Terio, chief of the Chicago-based, Zoo Pathology Program. It’s part of the Veterinary Diagnostic Laboratory at the College of Veterinary Medicine here at the University of Illinois.

Dr. Terio is a veterinary pathologist with expertise in zoo and wildlife and non-domestic species. She works with the Association of Zoos and Aquariums serving as a veterinary advisor for a number of different species including big cats.  

Now let’s go back to March, 2020 and join Dr. Terio.  She’s just received a phone call about a coughing tiger.

Dr. Terio:  I got involved in this case at the end of March. It was actually March 31st of 2020. And I was contacted by the Wildlife Conservation Society's Bronx Zoo. And so, in this case, the Zoo reached out to me on the 31st to ask about what they should be thinking about, and what types of things they should be doing for diagnostics on this individual tiger. This tiger had a history of a couple of days of coughing and of not eating very much.

And so, they were planning on immobilizing her the next day to collect samples. Obviously we’re limited in what samples we can collect from a live tiger who is awake.

Dr. Mitek: Wait – collect samples now?  But how do you create a differential list with such limited information.

Dr. Terio: We are very limited in what we have. We have what we can see. What is the animal doing? What are the overt clinical signs?

And you're right -- you know, normally, you might want to do the physical exam and get a history from the owner. We're mostly getting a history from the keepers, and we are looking at the animal, what can we actually physically see that the animal is doing or isn't doing. And then, looking at things like, have they eaten recently? All those sorts of things, and trying to pull it together. So, we're very limited in what information we have going into an immobilization and a procedure.

And so, your differential diagnoses list, you actually build beforehand, oftentimes. And so, you're looking at, what are all those possibilities of diseases, and what do you need to collect to be able to test for them?

And then, when you have the animal under anesthesia, it's a matter of trying to collect as much as possible to cover as broad a base as possible. Because the reality will be that we often will not even have those test results before we wake the animal up from anesthesia. And so, we need to really cast a broad net.

So, I've got, the information we have is: it's a cat that's coughing and hasn't been eating.

Dr. Mitek: And is coughing common in cats?

Dr. Terio: So, anybody who has domestic cats knows that they sneeze a lot, and that sometimes they don't eat for whatever reason. So, those are not particularly helpful. But coughing, like, true coughing, is kind of unusual for a cat. And so, that was in the back of everybody's mind, because a cough is not... like, they'll sneeze a lot, they'll have upper respiratory signs commonly, but not coughing.

And so, our differential diagnoses list included a lot of the common upper respiratory tract diseases of cats. Tigers are no different than a domestic cat, so, a herpes virus, a calicivirus, mycoplasma. Things like that are all on the list. All the common causes of upper respiratory tract infections are on the list.

Dr. Mitek: Now in order to move forward, we need to rewind a bit – back to the exact day Dr. Terio was contacted about the tiger.

Dr. Terio: But the other thing that happened that very day that also was important is that... so, this is end of March 2020. At this point, we know that we are all in lockdown. I'm working from home because of the COVID pandemic. And at this point in the pandemic, New York City was the epicenter. So, I knew that, and that was a bit of a concern in the back of my mind.

But what made it even more concerning is that that very day, there was an article that was published online as a preprint on a site called bioRxiv. And this is a site where scientists studying the novel SARS coronavirus were putting articles that they were submitting for publication so that the scientific community could see them before they were published. Because the publication process and the peer review process takes time, but this is a way for everybody to get information out as quickly as possible to other scientists so that we could learn from that.

So, on March 31, a publication was put on this site that showed that domestic cats could be infected by this coronavirus and could get pneumonia, they could get sick from this. So, all of a sudden, we started having conversations about, what does this mean for non-domestic cats?

And then, I got the phone call from the zoo, explaining to me that they've got this cat, what do I think they need to have on the differential list? What samples do they need to think about collecting when they immobilize it the next day? And we had the discussion that we need to collect samples for coronavirus.

Dr. Mitek: At that point, I'm just curious, were you thinking COVID was, "Yes, it's definitely something we should consider, but very unlikely"? Or, based on the fact, you said it's unusual for the cats to be coughing, were you leaning more towards, "I am really worried this is COVID"?

Dr. Terio: A little of both, to be honest. It was, "We need to have this on the list, I think, to be able to be thorough and make sure that we're ruling everything out." But, you know, that would be weird. That would be unusual. But then, it was also, "Oh, no." Like, "We have a cat that's coughing, this is in New York City. Of course, this is probably what it's going to be." And I think there was a bit of dread in everybody's thought process that day.

Dr. Mitek: So, what did you guys end up doing?

Dr. Terio: So, the very next day, they immobilized-Nadia is the tiger's name. And they collected a whole series of samples. So, we collected samples from oropharyngeal swabs, we looked at serum, they did radiographs, they did pulmonary ultrasounds, they did a tracheal wash to try to get samples to look at that.

Dr. Mitek: You mentioned you had to anesthetize Nadia. Can you talk a little bit about, you had a patient who was sick with respiratory disease, and then you guys had to weigh the risk of anesthetizing this patient to get the samples? Can you talk a little bit about the anesthetic risk? And, were you worried about the anesthesia making her worse?

Dr. Terio: Anesthesia in general is a risk that you take. Even in a completely healthy animal for a spay, there's a risk within anesthesia. But it's a calculated risk. And everything becomes a risk analysis, and you look at that. In addition to Nadia, there were a couple of other cats that were also coughing at the time. And so, the decision was, she had the most severe clinical signs, so let's look at her, because we have the best chance of figuring out what's going on by looking at her case. And so, that was a decision. At that point, it's a group health concern. She was a Malayan tiger. She is a Malayan tiger. And there were also Amur tigers. And so, both Malayan and Amur tigers are incredibly endangered. There are like 200 Malayan tigers in the wild. I mean, we're talking very, very small numbers of these animals. So, highly endangered species. And so, while there's a risk for doing the anesthesia, the zoo clinicians, this is one of their areas of expertise. They're very good at this. And they have a lot of experience immobilizing animals. And so, they went into it knowing that it was a risk, but also knowing that they had the skills to be able to do this.

Dr. Mitek: So, you had the risk of anesthesia, the risk of losing a very endangered tiger, the human health risk of, if she does test positive, what does it mean for the people around her? And, I guess this uncertainty of, if she does have COVID, what's going to end up happening to her? How are we going to be able to treat it, since it's new? Has there ever been a case in your lifetime where you had so many high-risk factors going into it?

Dr. Terio: I'll answer that last one first -- it happens all the time in my world. [laughs] We have these conversations. Like, before they go to work on an animal -- it could be tiger, it could be a chimpanzee, or a gorilla, or a shark -- there's always times where we'll talk with clinicians -- I had one just yesterday afternoon on a completely different species, too -- we'll talk with clinicians about samples to collect ahead of time. So, we make sure that we're essentially covering and casting a very broad net, to make sure that we try to identify what might be going on. Because, again, we're taking a risk by doing the anesthesia, so let's learn as much as we possibly can.

As far as the concern about risk to others, there's a couple things that go into that. One is that the clinical zoo staff that work with the tiger, they all know how to use PPE, and they had full PPE on for this procedure, again, knowing that this was a concern.

The other piece of it is, Nadia is a tiger living in a zoo. She's not going anywhere. So, if we were concerned that she caught COVID, she had to catch it from a human, because she's not going on walkabouts in New York City. It had to be us bringing it to her. And this is a point with COVID generally, is that the risk is human-to-human transfer. That's your greatest risk. It's certainly possible that animals could be infected, but our risk is coming from humans.

Dr. Mitek: Nadia is anesthetized, and samples are collected at the zoo. What comes next?

Dr. Terio: So, what happened next is a flurry of events. They FedEx-ed the biological samples to both Illinois' Veterinary Diagnostic Lab and to Cornell. And we had them send them to the diagnostic lab. I work with the Zoological Pathology program. We're actually based up in Chicago. But, I had them send them down to the VDL because Dr. Leyi Wang, who's a virologist in the VDL, is an expert on animal coronaviruses, and he had an assay for this coronavirus. And so, we knew that he was the one who needed to do the testing. So, samples got sent to him. He ran what is called a quantitative PCR, reverse transcription PCR. So, it's a PCR that can detect viral RNA within a sample. And so, he ran that assay. At the same time, the same process is going on at Cornell.

Dr. Mitek: Samples have been collected and provided to two diagnostic labs. Now all that’s left is to wait.

Dr. Terio: My phone rang. Dr. Fredrickson, who is the director of the Veterinary Diagnostic Lab, contacted me.

Dr. Mitek: Dr. Terio just mentioned a couple of important terms related to public health. First, the OIE is the World Organization for Animal Health. Among its goals is to control epizootic diseases to prevent their spread. A reportable disease is a disease considered to be of great animal or public health importance, in this case COVID-19. Because it is a reportable disease, the results produced by each lab were considered presumptive positive because those results would need to be confirmed by the USDA here in the U.S. The USDA provides diagnostic testing at the National Veterinary Services Laboratories (or NVSL). One of those labs is located in Ames, Iowa.

Dr. Terio: Illinois is literally physically closer to NVSL than Cornell is. So, Dr. Fredrickson drove the sample to NVSL to get the confirmation. So, that next day, which was a Saturday now, we were all sort of starting to get pieces in place. Because we knew that NVSL would be required to report this, which means that it would be public knowledge.

Dr. Mitek: But now that the diagnosis had been confirmed, how do you treat Nadia? COVID-19 was a brand new disease both for cats and humans.

Dr. Terio: I immediately called the Zoo. And, you know, there's silence then at that moment. And I think we all knew this was a possibility. But then you start to think through, what does this mean?

We had no way of treating Nadia for this disease. So, it was simply supportive care. That was all that we could provide her. And so, the Zoo knew that already. And so then, from the perspective of the individual animal health, it's a matter of, can we support her? And we're keeping our fingers crossed that she gets better. Having a tiger on a ventilator for a week in an intensive care situation is not particularly practical.

That was one of the concerns in the back of, I think, everybody's head. We were seeing how human cases were progressing, and we were crossing our fingers and toes that she would not progress to that. And so, just hoping that the supportive care that we were able to give her was going to help.

Dr. Terio: And then, there is the bigger concerns of, now, what does this mean? We knew what it meant in the zoo world with regards to the big cats.

Zoos had already had great apes on their radar, because great apes and humans share a lot of respiratory diseases already. We already were concerned about protecting great apes in zoological collections from getting infected. And so, there were already procedures that got put in place. And so, what I started working on was adapting procedures for working with big cats in a way to minimize transmission from human caretakers to the cats. How can we minimize that transmission?

So, making sure that you're wearing a mask around the cats. Remember, this is March. Mask mandates were not universal. And so, what we were doing was saying that if you are working with big cats, you have to be wearing a mask. You need to be wearing a cloth mask or a surgical mask. We weren't recommending N95 masks, but what we were saying was that you need to be wearing some form of a mask.

We also started to recommend things like, again, frequent hand washing, but also increasing your physical distance from the cats. Obviously, we're not in with the cats. These are dangerous animals, you're not in with them. But there are times when keepers will do training with cats. And so, they will be within a six-foot radius of them during those procedures. And so, the discussion was, do we put a halt to that for now? Do we pause that at this point, because there's too great a risk of us transmitting the virus to the cats?

And so, those were sort of all the discussions. And again, because in our world, we're so used to doing risk analysis, that's what it came down to. We said, "These are our recommendations. These are things that you need to look at at your individual facility, how you manage your cats, and think about how you need to employ additional levels of PPE, how you need to put into place procedures for working with the cats, and think critically about how you are training your cats and how you're working with them, for both your health and their health." Again, our main concern was us transmitting the virus to them.

Dr. Mitek: But there was another concern. What about the risk of spreading the disease from a cat to a person?

Dr. Terio: But we also then had a concern, if at big cat were to get sick, could they replicate the virus? Could the virus then be shed in respiratory secretions? And could you then get infected? Right? So, could it spill back to humans? And that was a big concern. If you think about-I'm going to give an example of a lion. A lion's roar can be heard miles away. I don't think six feet is going to be enough if a lion with COVID is roaring. Right? So, those are all the things that we started to think through.

And we're still learning about this disease. We're not even a year in. We're still learning. And at that time, in March, we knew very, very little about what our true risks were going to be, what was going to happen with animals. There had been a few reports of possible infections in dogs and cats. And this was the very first confirmed infection in the U.S. And so, we were trying to make a lot of educated guesses.

Dr. Mitek: But the actual risk of cat to human transmission is extremely low, even with house cats. There are no documented cases of cats passing the virus to people.

Dr. Terio: I think it's simply to do with contact. In a zoo setting, the tiger's human contacts are predominantly their animal caretakers, their keepers. So, they have very limited contacts with people.

Same thing with your domestic cat, right? Your domestic cat's primary human contacts are you and your family. They're not out and about in the neighborhood. They're not particularly social that way, right? And so, the chances are that you as a human have already been exposed to whoever gave the infection to the cat. It's much more likely that you've already been exposed to that human being than you're going to get it from the cat.

Dr. Mitek: And what became of Nadia?

Dr. Terio: The good news is, and this is a happy story, is that they've all recovered. And they all recovered with just supportive care. We didn't have to do any more interventions. They ended up having very mild infections.

One of the things that we found out through this whole process was, first off, cats will cough up the virus and then swallow it. And so, we found that that we could identify the presence of the virus in fecal samples. So, we were able to go in and test all the other cats in the building that Nadia lived in, as well as a group of lions that lived in a different building that were also showing some clinical signs. And so, we were able to test all of them, and we found that that they were all positive, including cats that had absolutely no clinical signs. So, it seems that, at least in this group of cats, that it really parallels a lot of what we see in humans, where there are a number of cats that are asymptomatically infected. They're infected, they have no clinical signs, but they're infected, they're able to replicate the virus, and they shed the virus. And so, we were able to do that. They were able to do some of the molecular epidemiology, where they sequenced the virus out of the cats, and then the human health professionals looked at keeper staff and risks. And we were able to prove that the tigers had a strain that was identical to a strain that was in one of the keepers as well. So, again, showing that that's the likely source of transmission.

We don't blame anybody at this point, because nobody prior to March 31st had cats even on their radar as a susceptible species. And so, we weren't necessarily worried, so we hadn’t been taking those precautions at the time.

Dr. Mitek: This is a great case about a very important, timely topic that's COVID-related. And I've got one last question for you, which is, in your early days as a veterinarian, what did you tend to get wrong? What mistakes did you make in working up a case when you just got out of vet school?

Dr. Terio: Thinking about this question, it has less to do with clinical medicine and more to do with, what I got wrong was communication-related. I learned early on that bad communication makes things much worse, and good communication can make all the difference. The fact that I was even called in the first place to be involved in this cat is because I had a good, collaborative relationship with the clinical vets there and they knew that they could talk to me, they knew that I would keep the information that they were telling me in confidence, and that we could have an open conversation about this. I think that earlier in my career, I might have been brasher than I am now. I've definitely learned that the art of communication is really key. And I encourage all the students to work on that.

And it's kind of on different levels. There's one, the communication with colleagues and peers, where you're communicating about a case, and you never want to come across as sounding as if, "Well, you idiot, you didn't think of this." And not that you would ever say it, but to have that be the tone that comes across. And then the other thing is learning how to communicate complex issues to other stakeholders. And those other stakeholders, they could be an owner of a pet who may have no medical background whatsoever. And in my world, it's being able to effectively communicate with keeper staff, but also zoo directors. And so, a variety of different people who may be very good at what they do, but they don't have this specific expertise, and trying to discuss things and talk in terms of a risk analysis and complex ideas, but in a way that everybody feels that they have a voice, and they feel that their voice is being heard and is valued. That's a really a key piece that I think I didn't do as well earlier in my career, and it's something I've worked really hard on, and I think it's one of the reasons I've been as successful as I've been now later in my career. And it's provided opportunities like being involved in this case.

Dr. Mitek: And that’s the case. Our thanks go out to Dr. Karen Terio for joining us to share this interesting case and story. During this pandemic there’s been plenty of discussion of zoonosis, the transmission of disease from animal to human. But this case probably resulted in reverse, human to animal disease transmission, also know as anthroponosis.

And thanks to all of you for joining us. Please subscribe and tell your friends about the show. It's available on iTunes or the podcatcher of your choice.

One last thing. In addition to this podcast we offer a wide range of learning opportunities for veterinary students and veterinarians. You can learn more about those by visiting

I’m Dr. Ashley Mitek, your veterinary detective.

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