The cottontail rabbit papillomavirus (CRPV) was the first animal model of cancer caused by a mammalian virus. It played a critical part of the development of vaccines against cervical cancer because the Human papilloma virus - cervical cancer causing virus - could not be replicated in cell culture, nor could it be transmitted to animals. Using CRPV, canine papillomavirus and the bovine version of the virus, researchers found that, whichever the animal, it was possible to protect against infection by papillomaviruses. Thus they could stop the development of papillomas or cancer through various modes of immunisation.
Richard Shope of the University of Rochester actually discovered CRPV in 1933. Alerted by a friend to cotton tail rabbits with ‘horns’ which were actually large warts; Shope ground up the horns, filtered them and injected the filtrate into other rabbits – and in turn these rabbits grew horns.
Moreover, in 1911, the chicken provided to one of the earliest models of cancer growth and spread, which lead to the discovery of the Rous sarcoma virus by Peyton Rous. The identification of the Rous sarcoma virus led to studies of how viruses cause tumours and subsequent use of hormone treatments to limit growth of tumours in rabbits among others.
One of the most common uses of rabbits in the laboratory is for the production of antibodies, used to detect the presence or absence of disease and for research into infectious diseases and immunology. Antibodies are a key component for the adaptive immune system – the part of the immune system that recognises a foreign agent. They are complex molecules that can only be produced by the immune system of a living animal.
To produce antibodies the rabbit is injected with a protein sequence taken from the disease-causing organism to be studied. New Zealand white rabbits are generally used, as their large size ensures that plenty of antiserum is produced. Antibody is produced by the rabbit’s immune system, and the progress of antibody production is monitored by taking small samples of blood at regular intervals. Once a sufficient level of antibody has been produced, blood is then taken from the rabbit under anaesthetic. The antiserum from a single rabbit keeps for a long time, and produces a large amount of antibody, which is often used for several years. There are currently no alternatives to using animals for antibody production, but there is ongoing research into developing a suitable method.
The general physiology of rabbits is similar to that of humans, and like mice and rats, rabbits suffer from many diseases with human equivalents. Young rabbits often die from a disease called mucoid enteritis, which resembles cystic fibrosis and cholera. Rabbits are therefore used as models which can contribute to our understanding of these illnesses.
Pasteur is particularly renowned for his work on the vaccine for rabies, a highly contagious infection which attacks the central nervous system. It enters the body through the bite of an infected animal or through infected saliva entering an existing wound. After experimenting with the saliva of animals suffering from the disease, Pasteur concluded that the disease rests in the central nervous system of the body. When an extract from the spinal column of a rabid dog was injected into healthy animals, symptoms of rabies appeared. By studying the tissues of infected rabbits, Pasteur was able to produce an attenuated form of the virus, which he later used to develop a vaccine against the disease.
Studies in rabbits are key to many aspects of medical research, including cancer, glaucoma, ear infections, eye infections, skin conditions, diabetes and emphysema.
The rabbit has provided an excellent model system to simulate the response of human tissue to the radiation produced by surgical lasers. Examples of laser advancements made possible by research on rabbits include eye surgery and the dissolving of plaque build-up on the walls of arteries.
The Watanabe rabbit suffers from fatally high blood-cholesterol levels due to a genetic defect, which mirrors the fatal human condition and they suffer heart attacks by the age of two. These rabbits are used as a model to provide better treatments for children with this disease, and for general research into high cholesterol. Research using these rabbits has included the development of an artificial liver to remove excess cholesterol from the blood of children suffering from hypercholesterolemia.
Rabbits love liquorice … but it is very bad for them because they cannot digest sugars
10. Rabbits use a litter and purr like cats
Rabbits can easily be trained to use a litter tray, sometimes better than the average cat. The natural instinct of a wild rabbit to use one area as its latrine is still apparent in its domestic counterparts.
Rabbits can make a purring noise by grinding their teeth. A quiet tooth purr means the rabbit is happy, whereas a louder, crunchy type of teeth grinding can indicate that your rabbit is in pain.