3Rs-Centre Utrecht Life Sciences

Faculteit Dierengeneeskunde

December 2017
Ferrets in the laboratory: opportunities for refinement

Ferrets are frequently used as an animal model, for example for influenza research. However, little was known about their behavior and needs. As a result, opportunities to refine the care and use of laboratory ferrets had not been identified and applied. Dr. Marsha Reijgwart studied the possibilities to enrich the ferrets’ environment, and also investigated how to recognize pain in these animals. On the 12th of December 2017, Reijgwart obtained a PhD degree with her dissertation entitled “Refinement of the care and use of laboratory ferrets”.

Ferrets are, amongst other purposes, used as a model to study the virulence, pathogenesis and transmission of influenza viruses. They are perceived as an appropriate model, since ferrets are sensitive to the same influenza strains as humans. They also show similar symptoms and disease progression to humans. Four years ago, Prof. dr. Coenraad Hendriksen, professor in alternatives to animal testing, was looking for a PhD candidate to investigate refinement possibilities for ferrets. Reijgwart was up for the job.

Enrichment in the home cage        
During her PhD study, Reijgwart first examined possibilities for enrichment. Reijgwart: “Most ferrets are neophilic animals, that show a high motivation to investigate their environment and might therefore easily get bored in a monotonous environment. Ferrets sleep a large portion of the day, but when they are awake, they need a lot of stimulation.” In a laboratory setting, this stimulation is not always provided and in these cases their behavioral needs are most likely not met. This has not only impact on the welfare of the animals, but also on the quality of the scientific results. To study the value of cage enrichment for ferrets, Reijgwart investigated how much energy they are willing to spend to gain access to different types of cage enrichment. Ferrets were given the opportunity to push open a weighted door that provided access to different cage enrichments. Using this paradigm, the enrichments for which the ferrets pushed the highest weights, the preferred enrichments, were determined. The ferrets were willing to push higher weights for access to a hammock, a water bowl and foraging toys than for balls or an empty space. The ferrets who received these preferred enrichments were less aggressive and played more with other ferrets than those who received no enrichment or enrichment that they pushed lower weights for, suggesting that providing ferrets with the preferred enrichments will improve their welfare. Reijgwart advices to provide ferrets in the lab with at least a hammock, a water bowl and foraging enrichment. “Practical applicability has been taken into account in the selection of the tested enrichments and these measures shouldn’t be too expensive,” says Reijgwart.

Ferrets with preferred enrichment

Get to know your animals  
In the second part of her research, Reijgwart examined whether ferrets change their facial expression when they are experiencing pain. By comparing photographs of the ferrets’ facial expressions before and after surgery, she identified 5 potential indicators of pain: orbital tightening, nose bulging, cheek bulging, ear changes and whisker retraction. With these indicators, she composed a grimace scale for ferrets. This type of scale is already used to recognize pain in other animal species, like mice[1]. Incorporating the grimace scale in a multifactorial pain assessment protocol can aid in the recognition of pain and therefore can improve analgesia of laboratory ferrets or a possible identification of a humane endpoint. According to Reijgwart, it is very important to take your time to get to know the animals you work with. Ferrets are not very expressive animals, so you need to know the normal behavior of each individual ferret to be able to timely recognize deviations in their behavior. Also, follow your instinct: continue to investigate if you suspect the animal being in pain, because chances are that you are probably right. The grimace scale will hopefully raise awareness on the relevance of these subtle changes in the assessment of the welfare of animals.”

Ferret with orbital tightening,           Dr. Marsha Reijgwart during her PhD defense
an indicator for pain assessment

Ultimately, Reijgwart wants to inspire researchers and animal caretakers to go the extra mile and do something extra for ferrets in the lab, as she expects that the results of her research have just scraped the surface.Anything you do for the ferrets will probably not be perceived as something extra, but rather something that is necessary for their wellbeing.”

If you are interested in reading the dissertation of Marsha Reijgwart, please contact the 3Rs-Centre ULS for a digital version.

[1] Leach, M. C., Klaus, K., Miller, A. L., Di Perrotolo, M. S., Sotocinal, S. G., & Flecknell, P. A. (2012). The assessment of post-vasectomy pain in mice using behaviour and the Mouse Grimace Scale. PloS one7(4), e35656.