Replacement

It's the law that alternatives must be used. So, animal studies that continue today have no accepted replacement for them yet.

Replacing an animal experiment completely is not easy; nevertheless progress is being made. A good example of a replacement is the LAL test. There is a danger that an injection might cause fever or even death due to bacterial debris known as pyrogens. So injection liquids are checked for contamination. This used to be done with rabbits but the LAL test uses the blood of horseshoe crabs which clots if pyrogens are present. The crabs themselves can be returned to the water. This replacement tactic of using a lower species that is less likely to feel pain than mammals has been extended to yeasts, bacteria, and fungi. Another replacement is the Ames test. It uses bacteria to see if a chemical is like to damage DNA and possibly cause cancer.

Crabs are found mainly off the east coast of America. Their blood saves rabbits from tests [Mary Hollinger/NOAA].

In a test tube, a new chemical can lock onto its target, but what's likely to happen in real life remains uncertain. Animals used to be the only option when assessing whether a promising idea was worth developing further.

Nowadays, a number of artificial systems have been created to mimic aspects of what happens in life. They ensure flawed candidate medicines proceed no further and do not need to be given to animals. Scientists have taken the well-known kidney machine, used in hospitals all over the land to help patients cleanse their blood, and turned it into a laboratory device that tests new anti-viral medicines. The medicines are added to infected cells in the device to see if they are helping to fight the virus in question.

An artificial model of the lung has recently been created. This means that potential treatments for asthma do not have to be tested first of all in guinea pigs. The digestive system, too, has been partly recreated so that scientists can start to determine the best way for a new medicine to be administered (e.g. by tablet or capsule) without using animals.

Computer modelling is now well established. After many years studying the structure of molecules that make good medicines, it is possible to predict how our bodies are likely to alter and absorb new medicines. This again means that only the new chemicals with the best chance of becoming medicines need to be tested on animals, so the obvious failures can be weeded out with the computer beforehand.

Imaging technologies are routinely used in hospitals to confirm a diagnosis or check on a patient's progress. The same technologies are also used in animal studies. In the past, animals would have had to be put down in order to find out what was happening, now researchers can find out how a new medicine is being dealt with, for example, without killing the animal. So fewer animals are needed and the procedure is mild. This same approach has been used with the development of a new surgical technique. Instead of seeing how far a disease had progressed by putting down a number of the sheep in the study, imaging was used. Some 30% fewer animals were needed overall.

A new imaging technique, called transcranial magnetic stimulation, temporarily and safely disrupts the brain function of healthy human volunteers. Their ability to carry out various tasks is then assessed. This has replaced the use of monkeys in some comparable brain function studies.