UNDER THE MICROSCOPE:Technology has greatly reduced the need for animal experimentation but it is still a crucial research tool, writes William Reville
THE ISSUE OF whether science should experiment on animals is in the news again. Many people, including many scientists, have mixed feelings about using animals in research and awkward ethical questions arise, but enormous advances in biological and biomedical research have resulted from experimentation on animals.
Ethical questions include: Is it ethical to allow human and animal diseases to continue for which cures could be found through painless research on animals? Is it ethical to perform painful experiments on animals where these experiments lead to cures for human disease or to new and better treatments? And is it ethical to experiment on animals when new treatments resulting from these experiments might not occur for many years, if ever?
Surveys show that most people condone painless research on animals that produce treatments and cures for human disease. But a minority think that such research should be carried out on consenting humans, not on animals. However, most people would not condone research on humans, believing that humans deserve higher moral consideration than animals.
Some anti-vivisectionists condemn biomedical animal research on the grounds that animals are so different from humans that any results obtained cannot be successfully extrapolated to humans. This argument is wrong. Animals contract many of the same diseases as humans. For example, humans and dogs have 65 infectious diseases in common. The figure for cattle is 50, 42 for pigs, 35 for horses and 26 for fowl. We are susceptible to many of the same parasites, viruses and bacteria as animals and some of these can be transmitted between animals and people, eg rabies and malaria. Many non-infectious chronic human diseases, such as epilepsy, also afflict other species.
We all know today that micro-organisms (germs) can invade the body and cause disease. The "germ theory" of disease led to the development of antibiotics to fight these micro-organisms and vaccines to render people immune to them. It could not have arisen without animal research.
Towards the end of the 19th century, Robert Koch (1843-1910) established that specific diseases are caused by specific germs. He saw rod-shaped bacteria in the blood of cows that had died from anthrax and guessed that they caused anthrax. When Koch injected mice with this blood, they also developed anthrax. Koch, Pasteur and others also identified the germs causing diphtheria, rabies and the plague. This allowed scientists to develop vaccines for animals and people by using weakened germs.
An anthrax vaccine was one of the first to be developed. Louis Pasteur (1822-1895) weakened anthrax bacteria by heating so that it no longer caused disease and vaccinated a group of sheep with the weakened bacteria, causing the sheep's immune systems to produce antibodies. Pasteur later infected this vaccinated group and another non-vaccinated group with live anthrax. The vaccinated group survived whereas the non-vaccinated group died. The anthrax vaccine has saved countless farm animals and people.
Smallpox, polio, diphtheria, tetanus, whooping cough, measles, and mumps deformed and killed thousands of children a year prior to the 20th century. But, with the development of vaccines, natural smallpox has been eradicated from the world, polio has been eradicated in the western hemisphere, and whooping cough, tetanus and mumps are much more rarely seen in developed countries.
Many life-saving surgical procedures, including organ transplantation, heart-valve replacement, coronary artery bypass and open-heart surgery, have been developed using animal models first. Animal studies have also led to the development of drugs to treat epilepsy and certain forms of cancer. Animals are also considered essential for testing the safety of food additives, drugs, workplace chemicals and vaccines.
Nevertheless, there is a natural reluctance on the part of most people to inflict discomfort on animals and there is a drive to produce alternatives to animal experimentation. Use of animals in research has been significantly reduced in recent decades. Much testing and research can be done by computer modelling or using cells grown in tissue culture. However, some questions can be answered only by experimenting on animals.
Take safety testing a new drug, for example. Cell cultures and computer models can be used to screen and test the toxic potential of a new substance in the early stages of investigation, thereby sparing animals. The final test, however, must be done in a whole living system. Even the most sophisticated alternative methods cannot mimic the complicated interactions that occur between cells, tissues and organs in humans and animals. Also, our best hopes for developing treatments and cures for diseases such as Alzheimer's, Aids and cancer involve animal research.
The use of animals in biomedical research is a privilege that must be used sparingly and humanely, while at the same time developing alternative methods that might eventually make animal experiments unnecessary.
• William Reville is associate professor of Biochemistry and public awareness of science officer at UCC - http://understandingscience.ucc.ie