We can't do without just yet

A visit to Leiden's test animals

Photo by Marc de Haan‘Rats are better for some studies, because they’re bigger and their physiology is more like humans’.

Jan-Bas Prins is in charge of some five thousand test animals at Leiden University Medical Centre. “Like a farmer, you should look after them.”

In Leiden University Medical Centre’s animal testing centre, a researcher, wearing a mouth cap, hairnet and yellow coat, bends over a white mouse.

The tiny creature lies, anaesthetised, on its back on the table with its legs expanded while the researcher injects something into its brain, all in aid of Huntingdon research. “We’re trying to cure it.”

The plastic cages next to the researcher contain a number of mice playing with each other. After the injection, the sedated mouse is kept separate, Jan-Bas Prins explains, so the creature can come round without being disturbed by its fellow mice.

Prins recently held his inaugural lecture to celebrate his appointment as the new Professor of Laboratory Animal Science; he’s been the head of Leiden’s animal testing centre for fifteen years now. He is also a member of a government advisory body on animal testing. It’s the Dutch ambition to lead the way in science that’s free of animal testing and Prins helped write a recommendation on the issue in 2016.

In theory, the centre is closed to the public, but Prins is willing to show Mare around. He’s noticed that many people imagine that all sorts of horrors occur at animal testing centres. “Like in the awful pictures from the fifties and sixties, but when they visit this place, they realise that things are much, much better.”

Visitors must wear an overcoat and cover their hair with a paper hat. Anyone working with the animals, picking them up, must wear a mouth cap and gloves too. Just to make sure, Prins asks where the note pad Mare brought has been before.

The different rooms are all sealed off from each other to limit the risk of spreading bacteria. The departments are classified by what Prins calls “containment levels”, which are related to the risk to humans. For instance, there is a bio-hazard area: “That’s where people work with material that’s also dangerous to humans. We’re talking Ebola, at its most contagious. We don’t have that level in the Netherlands, but we do have the next level down, with SARS and TB.”

The animals, in their isolated plastic cages on racks against the wall, are quiet. The light is dimmed, because the mice should not be subjected to bright light. However, most of them hardly seem to take notice when a brighter work light is switched on for a moment.

Filtered air flows into the cages through pipes. The food is treated with x-rays to kill bacteria and other dirt from the outside world that could affect the animals.

Prins explains: “It’s important to enhance the cages. They’d be terribly bored with just bedding so we give them nesting material, tubes and wooden blocks. Sometimes they have a wheel, but we’re a bit wary about that: if one mouse runs more often than another, it might produce physiological differences.”

A single, black mouse is completely bald. “That’s a spontaneous mutation that comes from the white variety. We have bred a black mouse line, which produces a faulty immune system. We use them for transplant experiments.”

He estimates that LUMC has twelve to fifteen hundred animals at the moment. Most of them are mice but there are some rats. “It’s easier to manipulate rats’ genes. Rats are better for some studies, because they’re bigger and their physiology is more like humans’.

These rats are only used for breeding descendents in which heart cells are grown. “I was a ‘mouse person’”, admits Prins, while the mothers sniff at the bars on their cages. “But rats are truly lovely animals – more alert and more responsive to humans.”

His Laboratory Animal Science Chair is new to Leiden and comes at a politically sensitive time: the European Union wants to reduce animal testing as much as possible and is tightening the legislation.

According to Prins, a phasing-out plan is “quite drastic”. He believes that most people agree with banning animal testing, but in reality, things are more complicated. “We want to be one hundred per cent certain that alternatives work at least as well as animal testing. There’s room for improvement, but we need to change the rules on testing the safety of substances too and that will take time.”

He agrees that it’s still a tricky subject. “On a moral level, I say: get rid of animal testing, but many people think I’m weird because I’ve been the head of the animal testing centre for fifteen years. But the same goes for everyone. We’re in a position that lets us take the moral high ground, but we don’t always do as we say.

“I can’t say I don’t approve of animal testing. Without it, we wouldn’t be where we are today: what about insulin, for example? But we do need to take a critical look at how we use animals – every day. They shouldn’t be taken for granted.”

As a student, Prins experimented on animals. “Back then, I believed it caused significant distress. We made the animals diabetic by destroying their insulin-producing cells, then I collected the eggs. It was upsetting. I talked to my supervisor about it, but he just said: ‘that’s how we do it’. There weren’t any ethical checks; they were only introduced in 1996. The checks prescribe an official weighing-up model: will the expected results outweigh the expected distress?

As from 1996, researchers require the consent of the national Central Authority for Scientific Procedures on Animals. Their research proposals must include an estimate of the extent of suffering, following European guidelines.

Prins lists them: “Non-recovery – an awful term for ‘terminal’ –, mild, moderate and serious.”MRI scans and minor injections are classified as “slight suffering”. Serious suffering could be drastic surgery: LUMC does heart surgery, for instance. Forced swimming sessions that tire the creatures out, electric shocks or high doses of chemotherapy are classified as “serious suffering”. However, LUMC does not do those kinds of experiments, according to the professor.

Compared to pets, the animals’ care is governed by much stricter rules. Test animals must not be put in a cage alone, unless it is essential for the experiment, the cage should be large enough and not too brightly lit. Rabbits – there are none at LUMC right now, must never be kept on their own and their cages must have at least two storeys. “By law, those cages you see in people’s gardens are prohibited here.”

If you want to conduct the experiments properly, you need to be sure all the animals are the same. The genetic foundations and habitat must be identical. “The microbiological quality is very important too. We don’t want any bacteria or parasites because they reduce an animal’s suitability for studies. If you buy a mouse from a pet shop, nine times out of ten, it’s got a norovirus, pinworm or other kind of subclinical infection.”

Logically, LUMC has its own breeding department where only staff are allowed. But even then, some animals are not suitable because not all mouse babies have all the desired genetic traits. A number of animals from the “breeding surplus” are used for training researchers. Prins explains: “If we can’t use them for anything, we kill them before they are weaned.”

The killing is also done according to standard procedures. “If they’re very tiny, we cut their heads off on dry ice to prevent pain. Another method is hypothermia: we put them in vapours produced by dry ice and they die quickly because they don’t have any fur. Adult animals are sometimes beheaded but only if we need samples we can’t obtain if we use anaesthetics. Otherwise, they are given an overdose or we fill the cage with a CO2 mix. That knocks them out fast.”

Prins explains: “I’ve realised that I’m still aware of how the animals are doing, even after all these years. If you lose that, you need to stop. The same applies to doctors if you don’t care about your patients any more, you should give it up. Compare it to good farmers: they care about their animals. The same goes for researchers.”

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