What have guinea pigs
ever done for us?
Millions of lives have been saved by animal experiments, say scientists. Vivienne Parry examines the key research
If you read some of the anti-vivisection websites, you could easily believe that there had been no benefits from animal research. Even the discovery of penicillin, tested on mice, which has indisputably saved millions of lives, is dismissed. Why? Because, it is claimed, penicillin is toxic to guinea pigs and rabbits and it was luck that made Oxford chemists Chain and Florey pick mice for their experiments. Should it negate the fact that without mice, a drug of enormous benefit to both humans and animals might never have been developed? Absolutely not. Nevertheless it remains controversial - last week a guinea pig farm was forced to close by animal rights protesters.
Millions of animals were used in early medical research. Some experiments make shocking reading now and did involve pain and distress of a sort that would be unacceptable and illegal now. Some of the research might not have been translatable, some indeed was misinterpreted or ignored, but there were a great many animal experiments that led to extraordinary breakthroughs in treatments, such as vaccines, transfusion, insulin, anti-retrovirals and asthma medications. There were also great leaps in surgical techniques, which have benefited both people and animals.
We and our families have already benefited from these advances, so to dismiss these experiments as being flawed and without value flies in the face of reason. Today, even though medical research has expanded enormously, the number of animals used in experiments has fallen by half in the last 30 years, reflecting not just alternative research methods, such as computer simulation and cell cultures, but a properly questioning use of animals in which the minimum possible specimens are used. So what has animal research done for humans?
1. Penicillin
In 1928, Alexander Fleming noticed that staphylococcus bacilli would not grow on a culture medium accidentally contaminated with a mould, Pencillim notatum. But test tube experiments failed to show the antibiotic properties he expected. Ten years later, Oxford chemists Ernest Chain and Howard Florey were working on antibacterial substances. Penicillin wasn’t a top priority. But when Chain injected two mice with it, they remained healthy. Delighted by this apparent lack of toxicity, Florey then decided to give his full attention to penicillin.
The animal experiment
Only by 1940 was enough penicillin available for testing. Eight mice were infected with a deadly dose of 110 million streptococci bacteria. One hour later, four of them were injected with penicillin. These survived but the untreated ones died. Florey said, ‘It looks like a miracle’.
Why animals?
The amount of penicillin needed to treat a human is 3,000 times greater than for a mouse. Without these early whole animal proofs on toxicity and effectiveness, penicillin would not have been developed further.
What’s it done for humans?
It revolutionised the ability to treat bacterial infections, which were a major cause of death. This simple animal test led directly to the saving of literally millions of lives, both human and animal.
2. Blood transfusion
The first successful blood transfusion was performed on a dog by Richard Lower in 1666 and perfected in dogs by 1907. Clotting was prevented by the addition of sodium citrate and citrated blood was shown to be safe for transfusion to dogs in 1914.
The animal experiment
In 1915, two doctors, Rous and Turner at the Rockefeller Institute, New York, demonstrated the optimum concentrations of citrate and sugars for preservation of red blood cells, in dogs and rabbits and showed that the preserved blood could be stored for as long as three weeks in rabbits and safely transfused back into the animals. Later work established longer storage times for human blood.
Why animals?
Much blood transfusion research is done in test tubes, but animals were used to establish the safety of citrated blood.
What it’s done for humans?
Blood transfusion is used after injury and surgery and to treat cancers and anaemia. Open heart surgery would not be possible without it.
3. Tuberculosis
A century ago, TB was a common cause of death. In 1907, there were 117,000 cases in Britain. It was also endemic among farm animals. Robert Koch isolated and identified the bacteria responsible, showing that it reproduced the disease when introduced into experimental animals.
The animal experiment
In 1943, Waksman and Schatz, soil microbiologists working at Rutgers University, New Jersey, injected streptomycin, the product of a soil bacteria isolated in a sick chicken, into guinea pigs infected with TB. It completely suppressed the TB without harming the guinea pigs.
Why animals?
Antibiotics need to be trialled in living organisms as there is no way of knowing whether they will penetrate tissue at the site of an infection. TB is unusual in having multiple infection sites.
What it’s done for humans?
This was the first effective treatment for TB, both human and animal. It saved millions of lives.
4. Macular degeneration
Macular degeneration is the commonest cause of blindess in adults in the developed world. It is caused by the abnormal growth of blood vessels behind the macular, the part of the retina responsible for detailed vision.
The animal experiment
In 1998, a team in Liverpool announced a new surgical treatment for this condition. It involves opening the eye, detaching the retina and moving it to a new position, where it is held in place with a tuck. Called macular relocation, this technique was perfected in the eyes of monkeys, cats and rabbits starting in the 1960s.
Why animals?
Although vision surgery can be practised on the eyes of human cadavers, there is no way of knowing whether vision has been restored successfully.
What’s it done for humans?
Macular relocation is one of a large number of sight-saving surgical procedures, many now performed routinely, which are based on techniques perfected in animals.
5. Asthma
Asthma is the result of an allergic reaction of the airways. It is a chronic illness affecting 3 million people in Britain, including one in eight children. It kills around 2,000 people every year in the UK.
The animal experiments
Not one, but many animal experiments made bronchodilators, which relax smooth muscle in the airways, possible. First the frog work of Dale and Loewi in the 1920s, which established the chemical nature of neurotransmitters, such as noradrenaline, which act on receptors in the lungs. Then, further extensive animal work in the late 60s, particularly on guinea pigs, made safe long-lasting bronchodilators available.
Why animals?
There are no tissue cultures that mimic any of the symptoms of asthma, although its cellular mechanisms are studied in vitro.
What’s it done for humans?
Salbutamol and terbutraline, the most widely used bronchodilators, have prevented many thousands of deaths and enabled those with asthma to live more active lives.
6. Meningitis
Meningitis is a feared disease, especially in children. It is caused by a variety of bacteria and viruses, but until recently, the most common in childhood was Hib (Haemophilus influenzae).
The animal experiments
The Hib vaccine was technically very difficult to develop because of a shortlived antibody response, especially in children, to the main Hib antigen, a sugar. Coupling it with a protein, a technique previously shown to protect mice against pneumonia, was shown to produce a more powerful response in mice and rabbits.
Why animals?
Vaccines cannot be developed by tissue culture alone because they are used to control infections that spread through the entire body. Animals are pivotal to vaccine research.
What’s it done for humans?
When the UK vaccination programme began in 1992, there were approximately 1,500 cases of Hib meningitis, mostly in babies, with 65 deaths and 150 children surviving with major handicap. Introduction of the vaccine has reduced the number of cases by 90%.
7. Kidney transplants
Of the 5,000 people who develop kidney failure each year in the UK, one in three would die without regular dialysis or a transplant.
The animal experiments
Surgical techniques for transplantation were perfected in dogs and pigs in the 1950s and became routine in humans. However, rejection remained a problem. Cyclosporine, which is extracted from a species of fungus, was discovered in 1972 and found to be a potent immune suppressor in mice. Tests in humans found that it prolonged the survival of grafted kidneys. Research on transplants in dogs showed that combining cyclosporine with steroid produces a three-fold increase in survival time.
Why animals?
It would be impossible to perfect surgical techniques for transplant in tissue culture as an intact circulatory system is required.
What’s it done for humans?
About 2,000 kidney patients each year benefit from kidney transplants and more would do so if more organs were available.
8. Breast cancer
Breast cancer will affect one in 11 women during their lifetime and affects around 40,000 women each year in the UK.
The animal experiments
Animal studies in the 1950s showed that hormone changes can induce breast tumours in rats. This led to the development of tamoxifen which blocks the growth of hormone dependent breast cancers. Further research with mice showed its possible preventive role.
Why animals?
The initial use of animals here has now meant an alternative to animals for breast cancer research. Tamoxifen work showed that lab grown cultures of human tumour cells will respond to drugs that are effective in patients.
What’s it done for humans?
Breast cancer is now the second most survivable female cancer, with a 77% five-year survival rate. Following tamoxifen’s introduction in the 90s, there was a 30% fall in death rates. It has now been proved that tamoxifen can also prevent breast cancer in high-risk women.
The Guardian
The most endangered cat
A heavy fog enveloped the vast horizon of Doñana and seemed to lord over its inhabitants. Slowly, true to the old Spanish proverb ‘misty morning, afternoon out walking’, the sun began to bring the park to life. Cat specialist, Peter Jackson, and Miguel Delibes, the world expert on the Iberian lynx, watched and waited. The previous day, Peter had shocked Spanish scientists by referring to the Iberian lynx as a small cat. The scientists, including Miguel, maintained that the lynx; though smaller than lions, tigers and jaguars, was a big cat.
Looking for lynx
Peter was hoping for a glimpse of one of the last remaining wild Iberian lynxes, while Miguel was keen to show him that these creatures were far from small. Soon, they were both to achieve their goal.
Quietly scanning through binoculars, Miguel suddenly shouted: ‘Over there.’ It looked like a male, with extremely long whiskers and hairs on the tips of its ears. Its head was raised proud, and one huge front paw rested on the motionless torso of a deer. ‘Big cat or small cat?’ said Miguel. Peter smiled, then admitted: ‘the way it’s lying, it looks like a tiger.’
Classified as a medium-sized cat by the IUCN, the Iberian lynx measures between 85cm and 100cm from nose to tail and weighs 8-15kg (females are smaller than males). Its dark, flecked, tawny coat provides perfect camouflage and, usually, it is detected only from footprints, scratches on trees, faeces and ‘lynx stones,’ which are formed from concentrated urine, which solidifies into stone-like fragments.
Catwalk
Following individual cats has provided valuable information on the problems affecting the lynx. One Sunday, an exotic birdcage containing a starving lynx appeared at the gates of Doñana National Park. Domingo, as he came to be known, was nursed back to health, fitted with a radiocollar and set free in Hornachuelos Natural Park in the Sierra Morena. With researchers tracking him closely, he crossed local roads, large cultivated areas and several motorways. He went through the provinces of Córdoba and Seville and had reached as far as Cádiz when the radiocollar failed and the team lost him.
Lynx numbers
Of the 16 lynxes born in Doñana between 1993 and 1994, only two are known to survive. Five were shot, three were hit by vehicles and the remaining six haven’t been located for some time. Recent censuses indicate a maximum of about 500 lynxes in Spain, while isolated populations exist in Portugal. It’s the most endangered cat species in the world.
The struggle continues to avert a huge embarrassment for Europe - the first well-documented extinction of a wild cat species for at least 2,000 years. Whether big or small, this cat is very special, and we can’t afford to lose it for good.
Cat’s life
The Iberian lynx Lynx pardinus is the most threatened cat species in the world. The total population is thought to number 500 individuals at most, which inhabit Mediterranean scrubland in isolated pockets of the South-east Iberian Peninsula.
Rabbits make up at least 75 per cent (sometimes more than 90 per cent) of the Iberian lynx’s diet. It also eats birds such as magpies and pigeons, rodents, wild boar and young deer.
The Iberian lynx is thought to have experienced an 80 per cent loss in range between 1960 and 1990. The lack of rabbits is one of the main threats to its survival. Overhunting, habitat changes, myxomatosis and rabbit haemorrhagic disease (RHD) have together reduced rabbit levels to just 5 per cent of what they were in the 1950s.
Other key threats to the lynx are changing habitat, unselective trapping methods (many lynxes are killed by snares), road accidents and hunting (including deliberate and accidental shooting). Because remaining populations are tiny and fragmented, inbreeding is also a problem - more than 60 per cent of lynx sperm shows abnormalities.
WWF-Spain is working with organisations such as the Biodiversity Foundation and the Spanish Ministry for the Environment, to address these problems, for example, by establishing links between isolated lynx populations, raising awareness among hunters and farmers and researching a vaccination against myxomatosis and RHD (with the Spanish Hunting Federation).
BBC
MAIN PAGE | TOP
|
|
|
