Ethics of Research involving animals
Sources of harm for laboratory animals - continuation II
Identification
4.48 Scientists often need to mark experimental animals permanently so that they can be identified throughout the duration of a project. This can sometimes be achieved using noninvasive techniques such as noting coat patterns or applying non-toxic stains. Other methods include inserting microchips under the skin, which can cause momentary pain, or moreinvasive techniques which include marking the ears using tags, notches or tattoos. Primates may be tattooed on the chest or fitted with collars. Methods used for amphibians include tattooing on the abdomen, sewing coloured plastic beads onto the muscle mass of the leg or back, attaching tags to the webs of the feet and freeze-branding (see paragraph 5.4). In field studies, toes may be removed from mice and frogs as a means of identification. This is usually a painful procedure which also affects normal behaviour and in some cases the animals’ survival chances.41
Procedures and their effects
4.49 The technical procedures to which animals are subjected can cause a range of negative states such as discomfort, pain, distress, fear and anxiety, either during or as a result of procedures. Some examples of common types of procedure are given below. More specific information on the effects of various types of experiment or animal model is provided in the relevant sections of Chapters 5–9. Refinements, which can and should be put in place to lessen the effect of any procedure, are described in Chapter 12.
Administration of substances
4.50 Many experiments begin with the act of administering a substance to an animal, the effects of which may not be limited merely to a pinprick or a change in diet. We describe below a range of generic effects that may arise for rats used for the purpose of safety assessments of a candidate pharmaceutical.
4.51 The administration process can be stressful and possibly painful unless the substance is being administered within a treat. The route chosen should be the most appropriate to produce the best-quality experimental results, and similarly, the most appropriate site needs to be used. This will most commonly be under the skin in the scruff of the neck, or intravenously. Occasionally substances may be injected into the joints, brain, muscle, skin, peritoneum, footpads, veins or arteries of an animal. Substances may also be introduced into the lung or nasal cavity (often under whole-body restraint), rectum or vagina. If very accurate oral dosing is required, the substance is placed directly into the stomach using a tube that is passed down the oesophagus or nose rather than being administered with a treat or food.
4.52 Once test sub stances have been administered, the animal is likely to experience some form of effect which depends on the nature of the substance administered and the end points of the procedure. For example, if the animal is a disease model and the compound is an effective therapeutic intervention, the animal will experience an improvement of the disease-specific symptoms. However, some compounds, and very occasionally the solutions that they are dissolved in, may also be irritants; for example substances that are highly acidic or alkaline. Other compounds may cause disease or may be given at toxic doses, in which case they could cause nausea, pain or seizures. The latter phenomena can result in significant suffering, even with the implementation of humane endpoints.42
Removal of blood
4.53 Much research involves the sampling of blood. Under ideal circumstances, this procedure only has relatively minor welfare implications for the animals, although it may sometimes cause discomfort, pain and distress, as is the case for human patients. Restraint is usually necessary, which can be stressful. In some cases animals such as primates are trained to cooperate in the process, for example by presenting a limb for sampling. This approach, which constitutes best practice, requires staff to be adequately skilled in the technique, as required by the provisions of the A(SP)A (see paragraphs 13.12–13.13).
4.54 Independent of the handling-related aspects of taking blood, further possible adverse effects can in some cases result from soreness, persistent bleeding (which may lead to the loss of a significant proportion of circulating blood volume in small animals) and the formation of blood clots. In very small animals, it can be difficult to access veins that are large enough for blood removal. Techniques such as refined capillary tube sampling have been developed to address this problem.43 Sometimes more invasive and potentially painful techniques such as tail-tip amputation, or occasionally retro-orbital bleeding (taking blood from behind the eye) are used. The latter method is usually carried out under general anaesthetic, but if complications such as blood clots occur, the animal is likely to be in pain once it has regained consciousness.
Surgery
4.55 Animals used in research and testing may undergo surgery for a variety of reasons: to implant osmotic minipumps for delivery of substances or telemetry devices (see paragraph 4.56), to ligate nerves or blood vessels for ‘models’ of pain or stroke and to test medical devices such as pumps to assist the heart or to open the skull in order to form lesions of the brain for neurological studies. Surgery is carried out using appropriate anaesthesia and pain relieving medicines are also widely used. Although such provisions greatly reduce the impact of the actual intervention, animals may experience varying levels of discomfort or pain following surgery. They must therefore be monitored closely in the recovery period in order to minimise any negative effects.
Telemetry
4.56 Telemetry is a technique that is being increasingly used and one that is often introduced as a refinement (because it enables large quantities of data to be obtained without restraining animals), or as a means of reduction (because more information can be obtained from one animal). Nevertheless, there are three possible sources of harm associated with telemetry that need to be considered in order to minimise implications for welfare. First, surgery is required to implant transmitters or loggers in most cases; secondly, devices have a physical impact on animals that can be significant, especially in rodents (they can weigh up to ten percent of the body mass44); and thirdly, most commercially available devices at present transmit at the same frequency, a problem that is frequently addressed by housing animals individually.
GM animals
4.57 As we have said, there are concerns about the unpredictable consequences that the deletion or addition of one or a combination of genes may have on animals that have been modified (see paragraphs 3.41–3.43). It has frequently been pointed out that many modified animals are phenotypically ‘normal’ in appearance and that they do not experience compromised well-being. One report suggested that no more than ten percent will experience harmful consequences. Another analysis, based on reports on GM mice made to the Danish Animal Experiments Inspectorate, found that 21 percent of strains were reported as experiencing minor discomfort, 15 percent experienced severe discomfort and 30 percent suffered increases in mortality and susceptibility to disease.45 Since possible harms can only be assessed on a case by case basis, we consider specific examples in Chapters 5 and 7.
4.58 There are a range of implications for welfare which may arise during the creation and use of GM animals. For example:
- In small species such as rodents, surgical procedures are required for the transfer of embryos into recipient females. These procedures can be painful, and pain relief may also be required following surgery.
- All animals that are used in GM procedures must be tissue-typed to ascertain whether or not they actually have the desired modification. There are four main techniques for tissue-typing mice: saliva sampling, removing tissue from the ear, removing the tail tip or removing blood from the tail. A commonly used protocol is tail-tipping, which is painful for even very young pups. It involves cutting through nerves and bone and can lead to the formation of neuromas, which may give rise to ‘phantom limb’ type pain. A less invasive but still painful alternative is ear notching, which does not require cutting through bone and can be combined with identification.
- Recipient female mice are mated with sterile or vasectomised male mice so that the transferred embryos have an increased chance of implantation and development. While it is desirable to use small and passive males, large, aggressive animals might also be used to mate small, immature females, which can cause stress and even injury.
- The different methods of producing GM animals vary in their efficiency. Some often entail increased fetal mortality (see Box 5.6).
Euthanasia
4.59 Euthanasia literally means a ‘good death’, and should not, if it is carried out properly, cause animals any pain, suffering or distress. Whether it is wrong to prematurely end an animal’s life is a subject of debate (see paragraphs 3.47–3.49). Apart from the question of whether an animal is harmed by being killed, in the case of sociable animals such as dogs or primates, the implications for other members of the group of losing a group member also need careful consideration.
Footnotes42 Ways of implementing Refinement and Reduction are discussed in Chapter 12. We note that in practice, if the effects of the
compounds on the animals are unknown, pilot studies using a small number of animals are usually carried out to ascertain the
optimum dose, so that any adverse effects can be kept to a minimum.
43 Hem A, Smith AJ and Solberg P (1998) Saphenous vein puncture for blood sampling of the mouse, rat, hamster, gerbil,
guineapig, ferret and mink Lab Anim 32: 364–8.
44 Morton DB, Hawkins P, Bevan R et al. (2003) Seventh report of the BVAAWF/FRAME/RSPCA/UFAW Joint Working Group on
Refinement: Refinements in telemetry procedures Lab Anim 37: 261–99.
45 Reported in BVAAWF/FRAME/RSPCA/UFAW Joint Working Group on Refinement (2003) Sixth Report: Refinement and reduction
in production of genetically modified mice Lab Anim 37: 3, Supplement S1–49, available at:
http://www.ingentaconnect.com/content/rsm/lab. Accessed on: 21 Apr 2005; Thon R, Lassen J, Kornerup Hansen A, Jegstrup IM,
Ritskes-Hoitinga M (2002) Welfare evaluation of genetically modified mice – An inventory study of reports to the Danish
Animal Experiments Inspectorate Scand J Lab Anim Sci 29.