We always look for replacement research methods

Arjan Stegeman
Arjan Stegeman

Arjan Stegeman is a veterinary epidemiologist and Professor of Farm Animal Health at the Faculty of Veterinary Medicine, Utrecht University. He is part of the Covid-19 Outbreak Management Team Zoonoses. In this interview he gives his view on animal experiments and the possibilities of animal-free innovations, also in light of the corona crisis.

What is the importance of animal research in combating Covid-19?

Animal experiments play an important role in the research that enables the fight against the virus. Just think about the development of vaccines, which we hope will get us out of the crisis soon. To do this, we need to understand pathogenesis: how the disease originates and how to build resistance to it.

Traditionally, the ferret is used often for research into respiratory disease in humans. However, this animal is not comparable to humans in all aspects relevant to Covid-19. In ferrets, an infection usually remains in the upper respiratory tract. It does not lead to pneumonia.

The Syrian hamster shows a clinical picture that is more comparable to the human situation, and also a similar transmission of the virus from individual to individual. That is why this animal is widely used for animal experiments, also because the effect of Covid-19 on physical fitness in vaccinated and unvaccinated animals can be compared easily. Everyone is familiar with the running wheels that are used for hamsters. These running wheels allow you to objectively measure the effort that an animal can exhibit.

How are you yourself involved in animal research for Covid-19?

So far, I have been involved mainly in the research of Covid-19 in mink, dogs and cats. The infection  originated from animals possibly at a Chinese market. From there, the virus spread from human to human. From that moment on the virus no longer needed animals to spread, but it is still relevant to know which animals can function as “reservoir” of the virus, animals in which the virus can maintain itself, so that it could reappear after it has been extinguished in humans.

Also, one does not want “two-host systems” to emerge. The reproduction ratio, which expresses the extent to which individuals infect each other, is calculated on the basis of infections between people. If animal species can also be hosts, you have to combine the reproduction numbers in your calculations. So then the R-factor is actually higher than you think based on your calculations on the basis of humans only. Suppose you have tested positive and you go into quarantine, but you infect your cat, which goes drinking from a neighbor's milk saucer. In that way, it could bring the infection to their house.

We think something similar has happened in the mink industry. Pretty quickly, a ban on moving mink between farms became effective, but it was probably the employees who transferred the virus from farm to farm. The number of infected mink farms increased because the virus had two “hosts”: mink and humans.

How big a role do pets play?

As far as cats and dogs are concerned, we collaborate with Wageningen University, Wageningen Research and the Erasmus University Medical Center. We look at pets in infected households, at animals in shelters and at stray cat populations. If you gain insight into what is going on with these animals, you can base measures on that knowledge. For example, people who have tested positive should keep their pets indoors.

We have made agreements with the public health authority that they ask people who have tested positive whether they have dogs or cats, and whether they would like to cooperate in testing their animals. We then go to these people’s homes with a special van and take a blood sample and a throat sample, which we then test for Covid-19. Because the animal has to be fixated and a needle sting is unpleasant, it is legally seen as an animal experiment, for which a permit was granted. However, it is no more unpleasant than it is for humans.

To what extent is there animal-free Covid-19 research?

The binding between the receptor of the human or animal cell and the virus via the now familiar “spikes” protruding from the protein is also studied in cell cultures. But there is debate about how well you can study the infection process in them. For example, one such study seemed to indicate that minks have little susceptibility to infection, but we now know that was incorrect. They actually turn out to be highly susceptible. In other words, it is sometimes difficult to draw conclusions from in vitro based research, also about the effectiveness of a vaccine, for example. You can look at how antibodies in a cell culture can inhibit the growth of the virus, but that often turns out to be still a too limited way of predicting the vaccine efficacy in humans.

How else do you apply the 3Rs in your work: Replacement, Reduction and Refinement?

We always look very carefully for replacement research methods. Take as an example research on intestinal health of chickens. For that research, a PhD student is investigating the possibilities of making organoids with chicken intestinal cells, a kind of mini-intestines that work the same as real intestines in several aspects. Those kinds of techniques don't make all animal experiments unnecessary, but they do allow for the initial selection of what is worth investigating further with animals. That saves a lot of laboratory animals.

In our group we also use mathematical models to describe infection processes. With these models, you can simulate experiments on the computer and calculate the best possible design of the animal experiments. On this basis you can determine the optimum number of animals, so that you don't use too many animals, but neither too few animals to draw reliable conclusions. Because the latter would be even worse: then your animal experiments are completely useless.

We work via three pillars: animal experiments, mathematical models and field observations. By field observations I mean, for example, the pet research I mentioned earlier, but also working with farms, which we do more and more. There, for example, we are investigating whether we could do more measurements using sensors: sound recordings, camera images and scent systems. We are now at the stage where we want to compare such systems with measurements done in the blood, amongst others. This means that we still need to do animal tests – taking blood samples – to be able to measure the predictive value of the sensors against the measured blood values. But if it turns out that the predictive value is high, we can eventually do without the blood samples and do this kind of research without animal experiments.

And Refinement?

Refinement is focused at improving the welfare of the laboratory animals. We do this mainly by making the experimental procedures as animal-friendly as possible and, for example, by designing animal-friendly housing. We are doing our best to make it as comfortable as possible for the animals we use. In that respect, the current close cooperation with fellow researchers in the field of animal welfare is perfect.

Utrecht University is working hard on the transition to animal-free innovation. What is your view on this?

As you can see, we as a faculty of Veterinary Medicine are working hard on deminishing the number of animal experiments. But I don’t envision a completely laboratory-animal-free country of the Netherlands in the near future. I also think it is important to distinguish between animal experiments for human benefit and animal experiments for the benefit of animals. Think of a Covid-19 vaccine. We find it very normal to test that on thousands of human volunteers, just to make sure it is effective and safe. Whether you can do that is determined by a recognized Medical Research Ethical Committee. And the volunteers make their own judgment on top of that.

Vaccines or drugs for animals also reach this stage at some point: you want to test them on the animals for which they are intended. According to the law, these tests are animal experiments. The ethical review process is more or less the same as for research on humans. The animal species itself benefits from these animal tests. But you cannot ask animals whether they are willing to participate voluntarily. The animal is not competent; it cannot make this assessment on its own. You have to recognize this difference when you talk about a transition to animal-free science. To improve the health of our animals using vaccines or drugs, animal experiments will be needed.

How do you envision the future of your research field in relation to animal experiments?

Ideally, I would like to see that the link between in vitro models and field observations that are not animal experiments keeps improving, which would reduce animal use immensely. However, development in that direction is hampered by privacy rules and competitive sensitivity. The financial value of data is recognized increasingly. Companies are getting bigger and so are the interests. When we collaborate with livestock companies, it is increasingly difficult to share their data. That sometimes gets in the way of open science. With that caveat in mind, I do see things moving in the right direction. I want to add the necessary nuance to the debate on animal experiments, but nevertheless it is wise to reduce or even eliminate animal experiments wherever possible.