Fine tuning ferrets’ pain control

One of the project’s ferrets in the thermal plantar test machine. Photo: Andrew Crookes.

There’s no room for assumptions in pain management — that principle has prompted a research team at the Western College of Veterinary Medicine (WCVM) to initiate a study investigating the efficacy of pain relief medications in ferrets. 

Ferrets are now considered the fourth most popular pet mammal, and veterinarians in the WCVM’s avian, exotic and wildlife medicine service regularly see the species in their practice. 

“[Ferrets] are the second most common species we see. We see rabbits the most and then ferrets are just after that,” says Dr. Isabelle Desprez, a small mammal medicine and surgery specialist at the WCVM. 

But despite their popularity, there’s still little scientific understanding of how medications such as opioids — drugs that are used to manage pain — affect ferrets. 

“I think [pain management comes] mainly from extrapolation … [we] started with cats and dogs and extrapolated from humans,” says WCVM veterinary anesthesiologist Dr. Barbara Ambros. 

“From species to species, you have different opiate receptors or a different distribution of opioid receptors in the brain and the central nervous system. That is why every species responds differently to different opioids.” 

For example, a particular opioid that causes sedation in one species may cause hyperactivity in another. Even animals within the same species may have dissimilar responses to opioids if the distribution or the number of opioid receptors in certain regions is different. 

As this trend of dubious extrapolation has continued with assumptions about non-traditional pets, veterinarians’ understanding of pain control in ferrets has remained limited, with few scientific studies aimed at the species’ response to opioid pain killers. 

Veterinarians currently treat pain in ferrets using pain medication protocols for cats — a practice that’s based on the questionable assumption that the two species have the same physiology. 

Desprez and Ambros are now investigating the effectiveness of that practice. 

“I cannot be quite sure that [how we are managing pain in] clinics at this point is still helpful to ferrets,” says Desprez. “So, [the aim of] this project is to try to assess, in a more scientific way, whether or not these drugs are indeed causing pain control in ferrets.” 

To measure the pain-relieving effects of the drugs, the researchers are using a thermal plantar test instrument that applies a heat stimulus to the ferret’s footpad. Since the animal will remain on the heat source longer if the drug is effective, the scientists can use the withdrawal times of the study’s participants to determine the effectiveness of the medication. 

“It actually doesn’t reflect the pain process … as pain is an emotional experience, and we don’t assess that in our research. We just assess the reflex … [as] it’s an unconscious response,” says Ambros, stressing that the pain inflicted during the study is transient with no long-lasting effects. “So, [the pain] didn’t get processed in the brain yet.” 

In fact, accurately measuring pain is very difficult. Since the researchers must inflict a reasonable and consistent amount of pain to elicit the similar type of response, they have to control each participant’s pain stimulus to achieve consistency. 

“The catch with that … [is] that pain is such an individual experience. So, there is also this dimension of pain that cannot be accounted for when we tried to do standardized studies,” Ambros explains. “[Our study] is very different from clinical pain, but this is a first step to get an idea about efficacy and duration of these drugs in ferrets.” 

Once their initial investigation is done, Desprez and Ambros plan to conduct a follow-up pharmacokinetic study using the same opioid medications. 

Their study’s results will establish a baseline for understanding pain control in ferrets, enabling veterinarians to provide sufficient and compassionate care. The WCVM’s research study is especially significant for ensuring the ferrets’ welfare since the mammal has become a common animal model for studying novel diseases such as the SARS-CoV-2 virus that causes COVID-19. 

“What is cool with this study is we are using ferrets for research, for the benefit of ferrets,” says Desprez. 

“These ferrets are not going to be sacrificed. These ferrets are being tested for the benefit of their own kind [to] start trying to improve the care of pet ferrets and animal research across the board, but we are not doing that because of a benefit to humans.” 

The WCVM’s Companion Animal Health Fund (CAHF) is providing financial support for this study. 

Andrew Crookes of Saskatoon, Sask., is a third-year veterinary student at the Western College of Veterinary Medicine (WCVM).


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