Chapter 12
Carnivores
The overwhelming majority of animals used in research are rodents or fish. However, some studies require the use of higher species, including carnivores. In 2010, 5319 carnivores were used in research in the UK, mainly for applied studies such as safety testing of human drugs and development of veterinary medicines. This represents less than 0.15% of the total number of animals used in research1. Approximately 3727 of these animals were dogs, with cats and ferrets accounting for much of the remainder (152 and 727 respectively). Since the use of cats is negligible this species will not be considered further in this book. Further information can be found in The UFAW Handbook on the Care and Management of Laboratory and Other Research Animals, 8th edn (edited by R Hubrecht and J Kirkwood, Wiley-Blackwell, 2010).
Dogs and cats are familiar as companion animals, and are afforded particular protection under the Animals (Scientific Procedures) Act 1986. The most appropriate animal for the studies to be undertaken will be selected according to criteria including species most likely to produce accurate and relevant results, biological and behavioural characteristics, least number of animals required and practical and economic considerations2. If companion animals are selected for use, particular and additional scientific justification will be required before their use will be authorised. In general, they may only be obtained from licensed breeding establishments, although in particular circumstances animals from the general population may be used. For example, clinical cases may be used with the permission of the owners for research into the efficacy of treatments or control of pain after surgery.
Dog
The domestic dog, Canis familiaris, has been domesticated for thousands of years. Other members of the genus include jackals and wolves, and dogs are thought to have descended from a Eurasian subspecies of the grey wolf3. Dogs have been used in research for many centuries; for example, in the 1600s, William Harvey used them in his studies of the circulation4. They have been popular for research in the past as they are cooperative, they are a suitable size for testing of paediatric devices and protocols for anaesthesia and surgery are well established. However, their use has declined due to ethical considerations and increasing costs, and as research interest has moved towards genetics. Dogs are still used for some types of research, mainly in pharmacology and toxicology3, but also for studies in dentistry, surgery and radiation oncology. In addition, some breeds of dog develop spontaneous conditions which are useful models for human diseases, such as muscular dystrophy and cardiovascular diseases. Dogs are particularly suited to studies requiring close monitoring and frequent sampling. Over 400 breeds of dog are recognised, and purpose-bred laboratory dogs are usually beagles, which are of medium size and generally have a good temperament. Dogs for use in the laboratory in the UK must usually be sourced from a licensed breeder, and permanently marked for identification purposes; for example, with a tattoo in the ear flap, or with a microchip implanted between the shoulders.
Behaviour
Dog behaviour is increasingly understood, and is very complex. In the natural situation, dogs are thought to live like wolves in packs, tightly knit groups consisting of a breeding pair and offspring, in which the animals demonstrate a complex range of social behaviour. In this situation, dominance and aggression are rare: the breeding animals are dominant, and offspring disperse as they approach puberty. Leadership behaviour in younger pack members tends to be followed by dispersal5. Members of a pack cooperate in activities such as hunting. Dogs are crepuscular, being most active at dawn and dusk6. Therefore they may rest for much of the day and night.
In captivity, dogs can learn to exist in groups of unrelated animals without aggression. Properly socialised dogs can interact harmoniously with both unfamiliar dogs and humans. It is believed that dogs learn how to relate to other dogs and avoid conflict through play with their littermates at a young age. Dogs need to be socialised, to humans and other dogs, when they are young, and it is recommended that they be socialised and familiarised with conditions to be encountered during procedures between 4 and 20 weeks of age7. This social contact is vital for normal social development. Puppies must therefore be allowed to mix and play together from a young age, so they learn how to take part in complex social behaviour. It is believed that dogs cooperate with humans because they can integrate into a human ‘pack’; again, early socialisation is essential if this is to occur. Well-socialised dogs trained using positive reinforcement training techniques will easy to handle and make good experimental subjects, as they will be only minimally stressed by handling and procedures. Purpose-bred laboratory dogs will usually have been raised in a pack environment with the opportunity to experience natural social behaviour, thus producing dogs that are likely to be temperamentally suited to the laboratory.
Five personality traits have been identified in dogs: playfulness, curiosity/ fearlessness, chase-proneness, sociability and aggressiveness8. The first four of these seem to be related, and describe a broad factor similar to the shyness–boldness axis seen in humans. This can be used to identify the social status of the animal at any time, and aid the selection of suitable dogs for particular studies or breeding. Social status affects behaviour and biochemical parameters such as cortisol levels, although it is not fixed and the social status of an individual animal will vary depending on the situation. Dogs show ‘dominant’ and ‘subordinate’ behaviour towards each other. However, many ‘submissive’ signals are essentially appeasement signals, and are designed to avoid aggression, but not necessarily in the context of a hierarchy9. Dogs with more confident/curious personalities may perform so-called dominant behaviours more often than other dogs5. Such behaviours include begging for food, standing over another dog, territory marking, holding the tail and ears erect, circling and sniffing and looking directly at other dogs, and growling. Behaviours shown by ‘shy’ or ‘subordinate’ dogs include adopting postures that are physically lower than other dogs, rolling over, lowering the tail, flattening the ears, dribbling urine, and freezing or fleeing from other dogs.
Dogs use many methods of communication, including behaviour, vocalisation and olfactory signals, and this should be considered when designing dog housing. People can learn the signals associated with greeting, nervousness, submission and aggression, making interaction with the animals easier10.
Housing
Dogs are active animals, which need a lot of exercise and a complex environment. They can be kept in indoor pens, ideally with removable partitions, to allow linking of adjacent pens so the dogs can interact as a group, or be separated for procedures if required. Pens need to provide stimulation for the dogs, and may include platforms to allow the dogs to look out of the pens, secluded areas for privacy and toys such as chew sticks or balls11. There must be facilities for adequate exercise, either in the individual runs or in a communal exercise yard where dogs can go in pairs or groups and interact with each other and with the handler. Cages are unsuitable for dogs in the long term as there is little room for exercise or human contact. Environments that are inadequate lead to stereotypic behaviour and poor welfare.
The floors and walls of the accommodation area need to be of smooth, impervious material, which can withstand frequent cleaning. Partitions should be paw- and nose-proof to prevent aggressive encounters between neighbouring dogs and to reduce disease transmission, and flooring should be non-slip to prevent injuries to the dogs or handlers. Noise can be a significant problem in dog accommodation, and thought should be given to minimising this during construction. There must be a warm dry area for the dog to sleep in, containing a suitable bed and comfortable bedding material.
If the runs are large enough there will be no soiling of the bedding area, but faecal material should be removed from all areas daily. Puppies are not as clean as adults, and pens for nursing bitches may need to be cleaned two to three times daily. Scattering bedding material such as sawdust on the floors can help absorb waste and keep the pen and the dogs clean.
It is important that dogs in kennels have clear lines of sight to each other – this can reduce barking12. Males mark territory by cocking their legs, and frequent cleaning of the pen often results in frequent urination to re-mark the territory. Dogs can be encouraged to urinate in particular places by the selective use of odour eliminators. These will inhibit territory marking if used in areas which are required to be clean, such as the bed area and feeding area.
Dogs should be group or pair housed. They can become distressed if they are separated from their pack, although this can be overcome or decreased to an extent with training: young puppies can be habituated to periods alone from an early age. Therefore, single housing should be avoided unless it is essential for the study. Justification is required if dogs are to be singly housed for more than 4 h7, and dogs to be single-housed should first have been acclimatised to isolation. Singly housed animals should still be able to see and hear other dogs and should be handled at intervals throughout the day to reduce the development of stereotypic behaviour12.
For more information about appropriate housing for dogs see references 13 and 14.
Feeding
Dogs are carnivores, although they can eat a variety of foodstuffs including vegetable matter15. Dogs have few specific dietary needs, although they do require a dietary source of polyunsaturated fatty acids, deficiency of which can lead to skin problems3. Many commercial tinned and dry diets are available. Complete dry or semi-moist diets are often used and just need to be fed with water. These can be fed ad libitum, so the dog adopts a little-and-often pattern of feeding. Feeding infrequent, large meals of dry food predisposes to acute gastric dilatation and should be avoided. Sudden changes in diet may lead to digestive disturbances. To avoid competition for food in group-housed animals, several food stations should be available. It may also be beneficial to utilise toys into which food can be inserted, to provide stimulation and reduce boredom.
Dogs are very adaptable and deficiencies are rare. Diets usually contain over 50% carbohydrate, 19–22% protein and 5–10% fat, although dogs can survive on much lower protein levels. Feeding excess protein can lead to renal damage, but protein deficiency leads to reduced feed intake3. A 13 kg beagle needs 0.8 kg of canned food or 0.25 kg of dry food daily for maintenance, depending on the energy density of the diet. The ration should be increased by 30% for the last 3 weeks of gestation, and raised to three or four times the maintenance amount during lactation. For peak lactation, a high-energy food with a high calcium level should be fed, to prevent metabolic problems such as hypocalcaemia.
In addition to their maintenance diet it may be necessary to feed dogs additional materials aimed at reducing dental and periodontal disease. Chews and biscuits designed for this purpose are available.
Water
Water should be provided ad libitum. The average water requirement is 70–80 ml/kg/day, and active dogs will require more than this. An adult beagle therefore needs approximately 1 L daily, which will be provided by food and water. Dogs fed on dry diets will need more water than those on moist diets.
Environment
Dogs are very adaptable. They can cope with temperatures between 15 and 24°C, and lower temperatures are tolerated if there are no draughts and the dogs are in groups. Indoor pens are usually kept between 15 and 21°C. Extremes should be avoided. Neonatal dogs require higher temperatures (30–32°C) for the first 10 days: some of this is provided by the bitch but the air should be at least 26–28°C. By 4 weeks 24°C is adequate. Natural daylight is preferred, but if this is not possible a 12 h/12 h light/dark cycle is acceptable. A gradual increase or decrease in light intensity simulating dawn and dusk may be beneficial and avoid startling the dogs.
Breeding
Puberty is reached at 5–12 months of age. Bitches are monoestrous, and typically come into season twice yearly. Each season is followed by a period of anoestrus lasting 4–14 months. The season starts with pro-oestrus, characterised by a high oestrogen levels and a sanguinous vaginal discharge, which reduces as the bitch enters oestrus, after 6–10 days. The bitch is then receptive for 6–12 days, then she enters dioestrus, which is characterised by high progesterone levels and lasts about 60 days3. The bitch only permits mounting during oestrus, and the male and female ‘tie’ for 20–30 min during copulation, in which the male dismounts and turns to be rear to rear with the female. Ovulation is spontaneous and pseudopregnancy is common. Oestrus can occur at any time of the year, but is most common in the spring. Gestation lasts 59–67 days. Parturition (whelping) typically takes 3–6 h once the cervix is open. An average of six puppies is born, at intervals of up to 1 h. The bitch needs bedding material to provide comfort and aid thermoregulation in the pups.
To breed dogs in packs, one male is put with up to 12 bitches, and bitches are removed from the pack for whelping. Alternatively, bitches can be kept in pairs and moved in with the male 10 days after the onset of pro-oestrus for 5 days.
Growth
Pups are born blind and deaf and unable to stand. They will normally stand at about 10 days, and can walk by day 21.The eyes open at about 12 days, and ears open from 12–20 days. Puppies begin feeding immediately after birth. Puppies must get colostrum during the first 24 h, and are fed initially every 2–4 h. The bitch licks the puppies to stimulate respiration at first, then regularly licks the perineal area of each puppy to stimulate urination and defaecation for the first 3 weeks.
Puppies can start to eat solids from about 3 weeks, and may be weaned at 6 weeks. Growing puppies need to eat twice the maintenance level of an adult of similar size. Puppies should multiply their birth weight by a factor of 40 or 50 in their first year, and adult weight is reached at 9 months.
Handling
To facilitate procedures, it helps if the dog is submissive, so an understanding of dog behaviour can help establish a relationship with the dog where the handler is dominant. The dog should be approached quietly but confidently, talking to the dog to provide reassurance and avoid startling them. Lower yourself to the animal's level, which is less threatening, then offer the back of a hand for the animal to sniff. Make sure you can escape if necessary, and do not trap the dog in a corner. The lead and collar, or the scruff of the neck if there is no lead, can then be grasped in the other hand once the dog has accepted the person15.
To lift a dog, approach the dog from the left-hand side. Restrain the head with the left hand by either placing the arm under the neck and holding the dog's head against the handler's chest, or by holding its collar or scruff (gently), and lift the dog by placing the right arm over the body of the dog and taking its weight on its sternum. Alternatively, the dog may be lifted by placing one arm around the chest in front of the forelegs and the other behind the hindlegs, holding on to the outer legs. If a dog is nervous or aggressive, it may be muzzled, using a ready-made plastic or fabric muzzle, or with a tape (see Figure 12.1).
FIGURE 12.1 How to put a tape muzzle on a dog.
Pain and stress recognition
Familiarity with the individual dog's normal behaviour allows identification of any changes brought about by the presence of pain. A dog in pain or distress may show physiological or behavioural signs (see Table 12.1). They may whimper or howl, and growl without provocation. They may bite and scratch at painful areas and may become more vicious or aggressive. The animal may guard a painful area by altering its normal behaviour to avoid moving it.
Table 12.1 Signs of pain and distress in dogs15.
| Physiological signs |
| Increased or decreased respiratory rate, or panting |
| Pallor, cyanosis or jaundice |
| Poor skin and coat condition |
| Discharge from eyes, nose, urinary or genital tracts or ears |
| Increased or decreased body weight |
| Vomiting or diarrhoea |
| Increased or decreased appetite or water consumption |
| Increased or decreased urination |
| Shivering |
| Abnormal posture: hunched, tense or guarded abdomen |
| Behavioural signs |
| Dullness, depression or lethargy |
| Unresponsiveness |
| Increased aggression |
| Increased sleep time |
| Isolation from group or hiding |
| Vocalization |
| Restlessness |
Common diseases and health monitoring
The major risks for disease entry in dog colonies are personnel or new arrivals. Disease entry can be minimised by providing quarantine facilities and serological screening for new arrivals, and by personnel adhering to strict entry requirements. New arrivals should be acquired from known sources with clean health records, effectively quarantined on arrival, and given a veterinary health check as soon as possible.
There should be a regular health monitoring and preventive care programme, including regular veterinary health checks, routine screening and investigation of any unusual occurrences and illnesses. Routine laboratory screening every 3 months is recommended16. Samples of blood, skin/hair and faeces should be analysed for a range of diseases. Most of the major diseases of dogs are preventable by regular vaccination: screening for these diseases in vaccinated dogs is not necessary. Other diseases can be prevented by adhering to strict entry requirements, good hygiene and by regular preventive treatments.
Dogs can be vaccinated against canine adenovirus, canine distemper, canine parainfluenza virus, canine parvovirus, Bordetella bronchiseptica and leptospirosis. They may also develop clinical disease caused by coronavirus, rotavirus or parasite infestations. Zoonotic diseases potentially carried by dogs include leptospirosis, rabies, Salmonella, Campylobacter, Toxocara canis, Lyme disease and brucellosis. Many of these can also affect research; for example, respiratory pathogens compromise studies involving anaesthesia and Toxocara affects toxicological pathology studies.
Biological data and useful reference data
See Table 12.2.
Table 12.2 Useful data: dog (beagle).
Anaesthesia
A period of at least 12 h starvation should precede anaesthesia in the dog. It is not necessary to withold water. It is usual to induce anaesthesia by intravenous injection following suitable premedication, then to maintain anaesthesia by inhalation using isofluane and oxygen with or without nitrous oxide. Premedication is essential to alleviate any anxiety and ensure a smooth induction and recovery from anaesthesia. See Table 9.3c for doses for premedication, anaesthesia and analgesia in dogs.
Ferret
The ferret, Mustela putorius furo, is important as a laboratory animal because it is a carnivore that is small enough to be kept easily in the laboratory. There are two main varieties, the fitch ferret, which is buff with a black mask and points, and the albino. Both male and female ferrets show marked seasonal variations in the hair coat, and body weight fluctuates by up to 30–40%, as subcutaneous fat is laid down in the autumn and shed in the spring17. Male ferrets are called hobs, and females jills.
Domestic ferrets are believed to be a domesticated form of the wild European polecat. They appear to have been used by humans for at least 2500 years. References to ferret-like animals used for hunting have been found in ancient Greek and Roman records17,18. Ferrets have been used for hunting, and for the control of rodents and snakes. They can be trained to work on leads or lines and have been used to lay cables. They have also been bred for their fur, known as fitch. Ferrets are still used for hunting today but increasingly are kept simply as pets.
The domestic ferret belongs to the family Mustelidae which includes stoats, weasels, badgers and mink. All mustelids secrete a strong smelling musk from their anal glands, and ferrets are no exception. Their Latin name, Mustela putorius furo, translates as ‘weasel-like smelly thief’.
Mustelids typically have sleek, flexible, elongated tubular bodies, with short legs and small rounded ears. These characteristics allow them to move freely and turn round in confined spaces.
Behaviour
Ferrets are domesticated animals, and are not generally found in the wild. Studies of feral ferrets and the European polecat suggest that they are largely solitary19. However, domestic ferrets are sociable and gregarious, and seem to benefit from being kept in compatible groups.
Ferrets are highly intelligent, lively and curious. They spend up to 75% of the day asleep, but the remainder of the time will be very active. They are more active at night20. They like to sleep in dark, enclosed areas. They are agile and like to explore and burrow, and they will make good use of three-dimensional environments containing playthings and multilevel perches. They are not frightened of humans or human environments18. Their curious nature means they are prone to escape through any hole large enough to get a head through. This can have tragic consequences for both the ferret and any rodents or birds housed in adjacent areas21. Housing design should take these factors into account.
Ferrets have an ill-deserved reputation for being aggressive. Although they have retained many of their natural behaviour patterns, they are more docile than polecats. They may bite if nervous, particularly if handled roughly, and may mistake a tentatively approaching hand for food, but otherwise they are usually friendly, particularly if handled frequently from an early age. Females with litters are protective and may also bite. Young ferrets may nip when first handled, but this abates with frequent handling.
Ferrets communicate by using musk glands, which are situated lateral to the anus. The secretion may also be expressed when excited or frightened, or during the breeding season. They also vocalise and produce a number of different sounds: they may hiss and chuckle when playing, and may scream if frightened or threatened.
Housing
Ferrets will demarcate a number of different areas in their accommodation: a sleeping area, an area for food storage, several escape holes and a latrine area. They prefer to urinate and defaecate in one or two latrine areas within the enclosure, often vertical surfaces, keeping the rest of the cage clean, and ferrets can be trained to use a litter box.
Groups of jills without litters, young animals and castrated males (hobbles) can be kept together, although group housing is not advisable for adult hobs, jills with litters and females that are in oestrus or have been mated. Young ferrets will readily play together.
Housing for ferrets needs to be particularly secure. Their slender bodies and extreme flexibility allow them to exploit the smallest gaps, and they are notorious escapers. Ferrets prefer solid floors with bedding such as sawdust or shavings rather than grid floors.
Plastic tubes, boxes and paper bags will add to the richness of the environment, and the animals will readily explore and play with them. Ferrets will make good use of three dimensional space if given the opportunity (see Figure 12.2). However, ferrets are also prone to chewing and eating such objects, so they should be chosen with care to avoid intestinal foreign bodies. For breeding females, nest boxes should be provided to afford security and warmth for kits.
FIGURE 12.2 Ferrets will make good use of three-dimensional environments.
Feeding
Ferrets are obligate carnivores. The nutritional requirements of ferrets have not been studied extensively. They have little ability to digest fibre, and they eat to energy requirements. The gut transit time is short (3–4 h), so they need highly digestible diets. They need a diet high in protein (30–40%) and fat (18–20%), with low fibre and carbohydrate. Dry diets are often soaked for ferrets and fed as a stiff paste17,18,21.
Water
Water is given ad libitum from bottles or cups. Galvanised water and food bowls should not be used for ferrets as they are susceptible to zinc toxicity.
Environment
Ferrets can tolerate a wide range of temperatures. The temperature should be between 15 and 24°C, and the humidity 45–65%. Ferrets can tolerate low temperatures, but are susceptible to heat exhaustion above 30°C because they have poorly developed sweat glands. Unweaned young should be kept above 15°C7. Good ventilation is required. A 12 h light cycle is usual, but changes in the light cycle can be used to manipulate the breeding cycle.
Breeding
Puberty occurs at 9–12 months, in the spring following birth. Breeding is seasonal, and the breeding season is determined by photoperiod. Males come into season as the day shortens, whereas females respond to increasing day length. In the northern hemisphere males are therefore in breeding condition between December and July, and females between March and September. The males need to come into season before the females to allow for sperm maturation. Ferrets are usually mated at the start of the season, and have a litter in late spring or early summer. Lactation then prevents a return to oestrus, and once the offspring are weaned the days are getting shorter so fertility is reduced. Rarely, a second litter may be born in late summer. Year-round breeding can be achieved by manipulation of the light cycle, by having summer (e.g. 16 h light/8 h dark) and winter (8 h light/16 h dark) rooms, or ‘northern’ and ‘southern’ hemisphere rooms. Artificial lighting can induce oestrus early and prolong the season. Females are induced ovulators, with no obvious breeding cycle. The vulva of the female enlarges to signal oestrus at the beginning of the breeding season, and if not mated ovulation does not occur. In this event, persistent oestrus may develop, in which the prolonged high levels of oestrogen can lead to bone marrow depression. To prevent persistent oestrus it is advisable to spay female ferrets that are not to be bred17.
Jills should always be checked prior to mating to make sure they are in good condition. Inadequate diets may result in failure to conceive or lactation failure, particularly if the diet lacking in animal protein17. Oestrous females should be taken to the male for mating about 14 days after the onset of vulval swelling, and left for 2 days. The male will grasp the female by the scruff of the neck and drag her around the cage. Mating can take several hours and may be rough and noisy. Coitus results in ovulation after 30–35 h. If unfertilised, pseudopregnancy may develop. After mating, jills should be housed away from stud males, and moved into their littering cages about 2–3 weeks prior to parturition. Otherwise, gestation lasts around 42 days, and seven or eight kits are born. Jills often look scruffy during gestation, and may need additional nutrition.
Dystocia (difficult birth) is fairly common in ferrets, and neonatal mortality can reach 8–10%21. Weaning occurs at 6–7 weeks. If bred early in the year, a female may have two litters in a year. Breeding performance declines after approximately 3 years of age in males, or after three or four litters in females.
Pregnant females can become aggressive as gestation progresses, and are very protective of their young, so should be handled with care.
Growth
All kits have white hair regardless of their eventual coat colour. They weigh 6–12 g at birth. They have voracious appetites, attaching to the nipples immediately after birth if possible, and they develop rapidly, doubling their birth weight in 5 days. They are active from about 14–21 days, they begin eating solid food by 2–3 weeks, and can be weaned at 6–8 weeks. They are born blind and deaf: the eyes open at 28–34 days and they hear from 32 days. Adult weight is reached by 4 months of age, and males are twice the size of females.
Handling
Although friendly, ferrets will bite if startled. They have relatively poor eyesight, and will bite a tentatively proffered finger, thinking it is a prey object. The important rules when handling ferrets are (1) be positive, calm and confident, (2) know what you are doing, (3) keep movements smooth and decisive and (4) use your voice as well as your hands22. This way, the ferret will not be startled. Well-handled ferrets may be picked up by simply slipping a hand under the animal just behind the forelegs, supporting the rump with the other hand. Alternatively, approach the ferret by distracting him with a cloth or sleeve held in one hand, then grasp him with the other hand using an over the shoulder grip, or with the thumb and forefinger encircling the neck with the other fingers under the forelimbs (see Figure 12.3). Lift the animal up and support the hind quarters with the other hand. When dealing with unknown animals gloves may be advised. Ferrets will normally wriggle when first picked up, but should soon calm down. See also Figure 7.6 for jugular venepuncture in the ferret.
FIGURE 12.3 Handling a ferret.
Pain and stress recognition
Ferrets are stoic animals and may not show clinical signs until a disease is advanced. Ferrets should be active and explore vigorously once they are awake. A sick ferret will be lethargic and disinterested in its environment. There may be reduced food intake and weight loss. If approached they may offer little resistance to handling, or may react with aggression and try to bite. The eyes may become puffy and half closed, and the coat will be ungroomed and take on a scruffy appearance.
Common diseases and health monitoring
Zoonotic diseases
Ferrets may carry a number of enteric pathogens, such as Salmonella and Campylobacter, so good hygiene is essential.
Subclinical and clinical diseases
Ferrets are prone to several viral diseases, the most significant of which are influenza, canine distemper, Aleutian disease and ferret coronavirus.
Influenza can spread from people to ferrets, and vice versa. The disease in adult ferrets is usually mild, but it can cause mortality in kits. Care should be taken to wear a mask when dealing with ferrets if you have a respiratory infection.
Canine distemper virus can cause an acute disease in ferrets with nearly 100% mortality17. There is no treatment, and affected animals should be euthanased. Animals entering the colony should be of known health status and should be tested serologically to avoid bringing the disease in, or a vaccination policy should be employed.
Aleutian disease was originally a disease of mink, but has been found in pet and working ferrets23. It can cause many clinical signs, depending on the organs affected. It can be detected by serology on a small blood sample, and positive animals should be removed from the colony. There is no treatment or vaccine available.
Ferret coronavirus occurs in two forms, an intestinal form which causes green diarrhoea, and a systemic form. The intestinal form is self-limiting but animals may take several months to recover fully.
Jills are induced ovulators, and if not bred will remain in season for a prolonged period, lading to hyperoestrogenism. High levels of oestrogen produced cause bone marrow depression. If animals remain in oestrus for more than 2 months they can develop life-threatening anaemia and haemorrhage17,20,21. Females should not remain in heat for longer than 1 month. This condition can be prevented by either spaying non-breeding females, changing the lighting to the winter cycle, hormone treatment or housing with a vasectomised male to induce ovulation.
Diseases affecting research
Many diseases can potentially affect research. Ferrets are often used in auditory research, and may suffer from ear mite (Otodectes cynotis) infestation. Aleutian disease virus can interfere with neurological research and any respiratory infection will increase the chances of anaesthetic deaths.
Ferrets may develop gastric ulcers caused by Helicobacter mustelae17. Clinical disease is rare but under stress it can lead to ulceration and death. Clinical signs include anorexia, weight loss, vomiting, ptyalism, tooth grinding and black stools.
Biological data and useful reference data
See Table 12.3.
Table 12.3 Useful data: ferret17,24.
Anaesthesia
Before inducing anaesthesia it is important to weigh the animal, since a thick coat may lead to overestimation of body weight, and the seasonal weight fluctuation may mean that the animal's weight has changed significantly between weighings. Injectable agents should be dosed by weight, but in the winter ferrets accumulate fat and may require relatively more anaesthetic. Ferrets vomit readily, and should be fasted for 3–4 h prior to induction of anaesthesia to minimise the risk of vomiting. Longer periods of fasting are not necessary, since the gut transit time is short, and may lead to hypoglycaemia.
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