As sled dogs race, they’re working muscles, expending energy and, of course, occasionally relieving themselves. They’re the living, breathing, barking engines that power their own bodies and that of their mushers’ across miles and miles of snow and ice.
All that mammalian movement often draws applause from watchful spectators, but it’s also earning attention from scientists at Cornell University who are looking into the role of genetics in a muscle condition that sometimes stops sled dogs in their tracks.
Tapping into the bundles of biological information in the animal athletes, though, requires enough hands and the right tools.
“They just shipped these from Cornell University,” said Dr. Christina Hansen, arching forward from a chair in her office at the University of Alaska Fairbanks (UAF). She straightened up, holding some styrofoam, then repeated the motion as she unboxed a recently-arrived sampling kit.
Eventually, she pulled out a plastic package containing a large swab and a tube with a splash of blue liquid inside.
“And these are what I’ve most been waiting for,” she said. “These are the swabs – because, I’m not a geneticist, so when I do DNA work I just use whole blood. Geneticists want perfect DNA, like with no damage to it and no breaks in it, and these swabs should do that,” she said.
Hansen is an assistant professor of veterinary physiology at UAF. She’s also the former head vet for the Yukon Quest and held that post for the Copper Basin 300 this year.
As she emptied the box, her desktop started piling up with more tubes and vials, more strips and swabs.
It’s the scientific paraphernalia that veterinarians at multiple races will be equipped with this mushing season to collect urine, saliva and blood samples from dogs that experience rhabdomyolysis while on the trail. When possible, the vets will gather samples from those dogs’ relatives, as well.
The condition is also referred to as rhabdo or sled dog myopathy, and it occurs when muscle fibers release the protein myoglobin into the bloodstream after strenuous exercise.
“If we identify a dog with it – first of all, regardless of the study, that dog, we don’t let them run anymore. They’re done with the race. They get dropped. It’s a pretty serious condition,” Hansen said.
Once myoglobin reaches places in the body it’s not supposed to go, a slew of complications can follow, with kidney failure among them. Symptoms first show in sled dogs as fatigue and soreness, but coffee-colored urine is the tell-tale sign.
Rhabdo was a major culprit behind sled dog deaths in the 1980s and 1990s, but that's not so much the case anymore, according to Dr. Karolynn Ellis, a researcher at Cornell.
A 2008 study published in the Journal of the American Veterinary Medical Association assessed the necropsies of 23 sled dogs who died in the Iditarod between 1994 and 2006, finding that 2 of them were attributable to sled dog myopathy.
The condition does still affect teams today, however, leading mushers to drop dogs during races for the sake of their health.
So, why bother with blood, spit and pee of rhabdo-affected dogs this year?
“[The condition] is pretty poorly understood, which is what makes it interesting from an exercise physiology standpoint,” said Ellis.
She’s the lead veterinarian on the study, working alongside Cornell associate professor of animal science Dr. Heather Huson. Ellis said their team is hunting for clues in the DNA that suggest whether dogs’ genetic profiles hint at their susceptibility to rhabdo.
And their effort seems to be gaining traction.
“From many different races, people have contacted us already asking for sampling supplies and things like that,” she said.
Similar conditions have a genetic component for humans and horses, according to Ellis, but scientists currently aren’t sure if ancestral cues for rhabdo exist in dogs. In October, that question cropped up at a conference for the International Sled Dog Veterinary Association in Sweden.
“And so that’s basically what kind of sprung everything into trying to get everybody motivated to see if we can find an answer,” she said.
Were those genetic links to exist, parsing them out could help kennels avoid genetic predispositions for rhabdo in future generations.
“If we can do that, then maybe we can say, ‘Hey, don’t breed this dog with this dog. You might be more prone to having this disease process affect you and your kennel,’” Ellis said.
From her office at UAF, a big part of Hansen’s role is to dole out the kits to a handful of Alaskan race vets. Sampling already happened during the Copper Basin 300, and the Kobuk 440, Two Rivers 200, T-Dog 200 and Yukon Quest Alaska will add to the mix. The Su Dog 300 also planned to participate, but organizers recently cancelled that race.
That kit distribution will land Dr. Mercedes Pinto with her share of the gear. Pinto is this year’s head vet for the Quest, and she said she’s more than willing to chip in with the sampling, helping lay the foundation on which the Cornell researchers’ analysis will build.
“I’m just excited that someone is looking into this,” she said.
There are still plenty of questions when it comes to rhabdo, according to Pinto, leaving room for this study to offer new and useful answers.
“We know that when animals are really stressed – like if the temperatures are much warmer or colder than usual – they’re more likely to experience it. And we know that it tends to happen around 200 or 300 miles into a race cycle. But we don’t know a whole lot more about it,” she said.
The Cornell researchers also plan to rack up DNA-containing dog fluids from the Lower 48, and maybe loop in some races from Scandinavian countries as part of the study.
Even with the international scope, though, gathering enough samples likely won’t be a quick job. The scientists want at least a couple dozen to analyze before drawing conclusions, and that could take a couple years, said Hansen, the UAF professor and Copper Basin 300 head vet.
“Over all veterinary medicine, it’s super rare. Like, your average vet who works in a small animal practice would probably never see one of these [cases]. It’s relatively common in sled dogs, but still not very common,” she said. “I mean, in the whole Copper Basin, we had one.”
But the slow-going isn’t necessarily a bad thing. Fewer samples translates to fewer sled dogs suffering from the condition – and, after all, seeing lower rates of rhabdo is kind of the point.