Species

Although most experiments are carried out in mice and rats, biomedical research uses a wide variety of species.

In safety testing, regulators require information from both a rodent and a non-rodent species. The non-rodent is often the dog. However, the dog may not be suitable for the particular medicine being tested. Perhaps because its metabolism is quite different to human for the specific biological reactions that will take place. In this case, another species is chosen. Sometimes this can be a monkey. Safety testing is the reason why three quarters of procedures using monkeys are carried out.

Safety testing in animals does not "prove" a medicine is not going to have side effects in patients. It simply gives the scientists, doctors and regulators confidence that testing can now move to people. Even clinical trials in patients will not find every side effect, every time.

Other animals are often chosen because they can replicate an aspect of a human disease. For example, ferrets vomit like humans and were used when medicines to combat the nausea caused by cancer chemotherapy were being developed. Watanabe rabbits have a genetic defect exactly the same as some people with high cholesterol. Armadillos have been used to study leprosy because the bacteria which cause leprosy prefer lower temperatures. That is why they attack the extremities of humans. The armadillo has a lower temperature than many other mammals.

Apart from modelling some aspect of disease, different species are chosen because they offer specific scientific insights. For example, zebra fish have transparent embryos which helps enormously with developmental biology. Squid have very large nerve cells which made it easier to take measurements.

Finally there can be very pragmatic reasons. Fruit flies have a short life cycle, are easy to breed and produce many offspring. That made them perfect for geneticists.