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At NAVS, we often discuss how the differences between humans and other animal species make translating data from animal experiments to people problematic.

So how do scientists continue to justify their use of animal models—and in particular, specific animal species such as mice, rats and pigs—in their experiments? Researchers in the Netherlands aimed to answer this question and published their findings in ALTEX.

The study’s authors examined research project applications issued in the Netherlands from 2017-2019, looking for the scientists’ justifications for using particular animal models in their studies. They examined 110 different research project applications and identified 125 animal models that were used in experiments, including animals such as mice, rats, guinea pigs, sheep and pigs, among others.

The most common justification for using a particular animal model was simply that the model was available (79%). The second most common reason for using an animal model was because the scientist conducting the study had expertise in using the model or access to expertise via collaborators (62%). The model showing a similar disease pathology or symptoms compared to humans accounted for 59% of usage.

The authors concluded that “in all project applications, it remained unclear whether the selected animal model was the model with the highest likelihood of predicting the clinical outcome. A clear justification and scientific discussion on ‘why’ and based on ‘what’ specific animal models or outcomes are chosen was often absent, suggesting the applicants selected their animal models based on a ‘trust me’ (tradition) rather than a ‘show me’ approach.”

Project applications were also examined for descriptions regarding how the “3 R’s” principle— replacement, reduction and refinement—was implemented, but the study’s authors found that the applicants justified these measures with general, unspecific phrasing, making it difficult to determine whether they actually followed the European Union Directive to demonstrate that the 3 R’s principle was considered and implemented when possible.

While the study’s authors concluded their paper by suggesting steps that can be taken to “improve the value of animal models in drug development,” we at NAVS have a different take on the matter.

Studies such as this remind us that the scientific community feels justified in using animal models without having a solid scientific reason to do so. However, this continued investment in flawed animal studies wastes time, resources and animal lives.

Just because the research community has historically relied on animal experiments does not mean they must continue to do so.

Rather than continuing the status quo of using animal models, we know that the better approach is to invest resources into human-relevant research, as NAVS does through the International Foundation for Ethical Research. This investment in smarter, more humane science will not only spare animal suffering but will also pay much higher dividends in terms of progress in human health.

Source: Veening-Griffioen, D. H. et al. “Tradition, not science, is the basis of animal model selection in translational and applied research,” ALTEX, 38(1), 2021.