Monday, August 30, 2010

Comparative medicine: what is a wallaby?

[ETA: this post was included in Grand Rounds Vol. 6 No. 49 — a conference in a tropical island resort. There are lots of great posts of a medical nature there.]

Last night my ex-roommate, now an intern, called me to say that she had a wallaby as a patient. I was enthused. “Wallaby! It is like a baby kangaroo! Is it really cute? You are so lucky. So what’s wrong with it?” It came in to the hospital with diarrhea, apparently, and feels pretty crappy.

This morning I have a lecture on cow diarrhea, and I thought, I wonder what’s wrong with that wallaby? I wonder if this morning’s lecture will give me any idea? Then I thought: What’s a wallaby?

There’s a popular t-shirt among vet students that says “Real doctors treat more than one species.” We learn about the common ones in vet school: dogs, cats, cows, horses. But we are (at least theoretically) responsible for any animal species except for one. What if something you’ve never seen before comes in the door? How do you start to approach that problem?

In our first year nutrition class, we learned how to deal with a related problem: feeding zoo animals. What do you feed a rhinoceros? Well, the lecturer said, what’s a rhinoceros? They are hind gut fermenters, like horses. So if you don’t have any idea what to feed it, feed it like you’d feed a horse. What’s a giraffe? It’s a cow (a foregut fermenter). What’s a tiger? (You can probably manage that one on your own.) You’re not going to do a perfect job of constructing a diet if this is all the information you have, but in a pinch, it can be a good start.

But that’s nutrition. Can you take the same approach in medicine? The medical problems that we see in different kinds of animals seem to mostly be affected by two things: the animal’s basic anatomy, and how we use the animal. Pets (dogs, horses) have congenital problems (hip dysplasia); they have problems associated with old age (heart disease, kidney disease, cancer); they have trauma (hit by car, athletic injuries). Animals with complicated guts (horses, cows) have gut diseases (colic in horses, all sorts of things in cows). Horses have problems with their legs and feet. Food animals have more herd health issues, associated with management problems (poor husbandry) or infections (lots of animals living in close quarters).

So when a general practitioner encounters an animal like a wallaby, one place to start is to ask: What is a wallaby? This one was a pet, so I might put it into the same framework as a dog, expecting diseases of old age rather than diseases of poor herd management.

Of course, this is only a rough place to start. Even the species we know well have very different medical issues. For example, cats have notoriously ineffective livers when it comes to processing medications; acetominophen can kill a cat. That’s an important species difference to know. A general practitioner really should not be seeing something like a wallaby; an animal like that should go to an exotics practitioner. (This one was presumably a patient of the exotics department, but the ER department was keeping an eye on it over the weekend.) But even the exotics practitioner is going to be lacking a lot of information, and may need to engage in some informed guesswork.

The species differences that we have to learn in school make veterinary education a somewhat overwhelming process. But on the flip side, veterinarians have the opportunity to see medicine from a very different perspective from human doctors. Treat multiple species? Veterinarians treat multiple phyla.


  1. Do american vets get any information about opossums? That would seem to be the closest familiar relative to the wallaby.

  2. Good question! So there are two ways you learn about something in school: in classes, and in clinical rotations. I don't know about other schools, but looking at my Zoological Medicine course, the closest thing to opossums seems to be the two hour "carnivores" lecture (and I am not sure they'll be in that, as they are obviously not members of Carnivora). I haven't had that lecture yet, though, so who knows. My guess is if they're in that lecture, they will be covered for five minutes or less, so let's just say that the answer to that part of your question is "no."

    Then there is the clinical rotation part. My school is the only American vet school to require a two-week wildlife rotation. I may well see possums on that. If I do it during the spring, I will certainly see orphaned baby possums (I already worked with them as a wildlife clinic volunteer, actually). In an adult possum in the clinic, I would almost certainly be dealing with some form of trauma. The way you handle trauma in wild animals is in some ways similar to pets (bones get fixed similarly) and in some ways different (different goals, different ways of handling an animal that doesn't like to be touched, much more likely to opt to euthanize, etc). So the answer to that part of your question is "for most schools, no; for my school, possibly, but very little."

  3. Isn't is 'wallaby', not 'wallby'?

  4. It is! I guess it is especially hard to know what a wallby is, huh? Typo edited. Thanks for pointing that out.

  5. Well the Wallabies are playing the All Blacks after they play the Springboks this weekend. So it's no wonder the poor thing is shitting itself.


  6. I'll pass that diagnostic suggestion on to the hospital in question :)