ABSTRACT: Rabbits are popular as pets, with current estimates suggesting that 0.7 million households in the UK own about 756,000 pet rabbits in total.1 In line with this growing interest in keeping rabbits, there have been significant advances in our understanding of rabbit diseases and their management.

Much of preventive medicine relates to good husbandry practice, and the avoiding of predisposing factors to disease includes the following (based on Harkness 1977).

Environmental factors

Exposure to climate changes and weather extremes should be avoided. Rabbits should be kept in housing (buildings, hutches) that protect them from extreme low and high temperatures, and from direct exposure to draughts and winds, as well as high or low humidity. All of these factors can increase the risk of disease.

•   For rabbits kept indoors, the ideal average environmental temperature range is 16-21°C, and for humidity it is 40-60 percent.

•   Poor ventilation can predispose rabbits to developing respiratory infections.

•   High ammonia concentration – resulting from an accumulation of urine in the environment – is not conducive to good hygiene and health, as it damages the mucosal lining of the respiratory tract, which predisposes to infection.

•   Poor bedding may inhibit normal behaviour patterns and can predispose to respiratory disease or conjunctivitis if it is dusty or contaminated. Bedding should be changed one to three times per week.

•   Poor lighting – as well as excessively bright light or flickering lights – may affect normal behaviour, including exercise patterns and feeding. In the wild, rabbits are particularly active at dusk, dawn and at night. For normal behaviour, lighting for rabbits kept indoors should mimic the diurnal pattern of daylight and night. Inadequate light can cause sexual depression.

•   Waste accumulation in the environment attracts rodents, flies and other insects, which can be vectors for disease. Flies increase the risk of fly strike.

•   Exposure to disease vectors should be avoided – for example, exposure to rabbit fleas or biting flies, which can transmit the myxomatosis virus – so routine management of the environment to reduce these numbers is helpful, as well as regular preventive measures for the rabbit.

•   New admissions to a rabbit household should be bought from reputable breeders and should be kept in quarantine for two to three weeks to ensure that they are not harbouring any infectious disease, before they are allowed into contact with other rabbits.

Nutritional factors

•   Insufficient water availability or contaminated water that is unacceptable to the rabbit can lead to dehydration, especially if environmental factors or diseases are causing increased water losses.

•   Poor quality water supplies should be avoided, and a supply of fresh clean water should be available at all times.

•   Insufficient food intake may result if the owner is not diligent about daily feeding. Remember that rabbits kept in hutches cannot seek out food for themselves, and it is not uncommon for them to be neglected, especially if the family expects children to look after them and their enthusiasm dwindles with time.

•   Poor quality food

•   incorrectly formulated foods should be avoided. These days there are good prepared foods which can be fed to complement good quality grass or hay. Formulated pellets 

Rabbit owners and breeders should practise good biosecurity. Direct contact between pet rabbits and wild rabbits should be avoided and breeders should close their premises and not introduce other rabbits, or allow potential carriers – including people carrying the virus on their clothing or shoes – to come into contact with their rabbits  can be useful in preventing rabbits from feeding selectively as may be the case with diets that are fed in a ‘mixture’ formulation;

•   incorrect species formulas are often selected by owners – for example, guinea pig rations may be given to rabbits by mistake;

•   storage deterioration can result in unpalatable foods, or even contamination with bacteria or moulds;

•   contamination of food with rodent urine or faeces, or inclusion of potentially toxic ingredients such as aflatoxin-contaminated grains, can occur and present a risk to rabbits. So sourcing good quality foods is important;

•   altered gut microflora, resulting from dietary change or antibiotic use, can result in diarrhoea which may lead to serious fluid and electrolyte losses;

•   good quality grass or hay containing fibre, and something in the environment to gnaw on, is necessary to maintain normal dental growth and tooth alignment, and to avoid hairball production. The teeth continue to grow throughout life (the incisors may grow 10-12cm per year and wear down at the rate of about 3mm per week) and malocclusion, overgrowth and other dental problems are increasingly seen by veterinary practices;

•   wood used in the construction of hutches or runs, or provided for gnawing should not be treated or painted with potentially toxic chemicals, such as bitumen or lead- containing substances, or be derived from potentially toxic plants, for example, laburnum; and 

•   regular weighing is helpful and should be encouraged to identify trends towards weight gain and the risk of obesity, which may arise where the ad lib feeding of commercial foods occurs; as well as weight loss which can indicate inadequate nutritional intake or the presence of disease.

Husbandry

•   All hutches, runs and pens should be constructed to protect against adverse weather conditions and predators, such as foxes; with no sharp or rough surfaces on which the enclosed rabbits could injure themselves. It is important that all surfaces can be easily cleaned and disinfected.

•   Dry, clean, good quality grass, hay and food pellets specially formulated to meet the nutritional requirements of rabbits should be available continuously, as rabbits like to graze.

•   Regular grooming is important to prevent matting and to remove contamination from the coat, which if left may cause trauma and skin damage or predispose to fly strike, especially if there is faecal or urinary contamination around the cloacal region, under the tail.

•   Nails should be kept trimmed to avoid catching in the environment and potential toe injuries. Teeth should also be kept trimmed if they tend to overgrow as the result of malocclusion.

•   Rabbits have powerful back legs and, if unsupported when being
lifted, a kick can damage and even fracture their spines, so the hind legs should always be supported when lifting them up.

Preventive medicine sometimes involves the prophylactic administration of medicines to prevent/treat disease and regular check-ups to screen for the presence of disease. This is important because early detection results in early intervention and better clinical management.

Parasites

Ear mites (Psoroptes cuniculi) are common causes of otitis externa, and infection may be more common in rabbits kept in poor hygienic environments because low temperatures and high humidity favour survival of mites in the environment. Prevention involves the use of anti-parasiticide strips in the environment and regular prophylactic treatment of infected animals with a licensed acaricide.

Tapeworms can infest rabbits. Measures used to prevent them involve avoiding contact with carnivores, such as dogs and cats which may transmit the parasites via faecal contamination of the environment; regular worming of in-contact cats and dogs; and avoiding contact with insect or arthropod vectors. Cestode eggs survive best in high humidity environments.

Hepatic and intestinal coccidiosis (Eimeria spp.) is best prevented by avoiding contact with carrier animals, and good hygiene. Oocysts are resistant in the environment and disposal of all bedding, cages and soil in runs may be necessary to prevent re-infection.

Ringworm (usually Trichophyton mentagrophytes, occasionally Microsporum spp.) can be prevented by good hygiene including sterilisation of equipment, temperature and humidity control and screening of individuals for dermatophytes to detect and avoid contact with carriers.

The microsporidium, Encephalitozoon cuniculi, can be transmitted to humans and thus is a zoonosis. Exposure to this is very high in domestic rabbits in which it causes neurological signs, such as head tilt and renal disease. Prevention involves only buying in rabbits that are clear of the infection; and good hygiene practice, including preventing contact with infected urine. The spores from this organism can survive four weeks in dry environments. Contact with wild rabbits or rodents should be avoided.

Regular treatment may be indicated in infected animals, as well as regular disinfection of the environment, including food and water bowls. Avoid feeding fresh greens originating from areas where it could be contaminated by wild rabbits or rodents.

Vaccinations

There are two rabbit diseases for which vaccines are available in the UK.

Myxomatosis

Myxomatosis is a debilitating, usually fatal, disease caused by a pox virus that affects the eyes and face. It is endemic in wild rabbits in the UK with sporadic cases occurring in rabbits kept as pets. There is no effective treatment, so prevention by vaccination is the best policy. The vaccine can be given to rabbits as young as six weeks of age and produces immunity 14 days after vaccination. Normally, rabbits are re-vaccinated annually but if there is a high risk of infection then revaccination every six months is advisable. Myxomatosis vaccinations should not be given within 14 days of viral hemorrhagic disease vaccinations.

Viral Haemorrhagic Disease (VHD)

VHD is caused by a calicivirus that is highly contagious. Sudden death usually occurs 12 to 36 hours after the onset of a fever. If the disease course is longer and other signs are seen, these can be distressing for owners, especially when the rabbit shows haemorrhages, fitting or has difficulty breathing (Figures 1-2).

Figure 1: VHD has spread worldwide since it first emerged in China

Figure 2: Multiple pulmonary haemorrhages seen at post-mortem

A small percentage of infected rabbits – especially those under four months of age – may show mild signs and survive, but these can become carriers of the disease and may shed virus into the environment via their urine or droppings for 30 days or longer.

The virus is very stable and resistant and can survive freezing and persist in the environment for months. This means that VHD virus can easily be carried and transmitted through contact with hair from infected rabbits, on clothing, shoes, boots, bedding, feeding or drinking bowls or other utensils.

Unfortunately, there is no specific treatment for VHD in rabbits, but the clinical signs and deaths from VHD can be prevented by vaccination with a single dose given from five to 10 weeks of age resulting in protection being active six to 21 days after vaccination. Protection lasts for 12 months, so annual boosters are necessary.

Vaccinated rabbits are fully protected against challenge with virus and the vaccine is safe to administer to pregnant rabbits, although they should be handled with care.

It is estimated that fewer than 25 per cent of rabbits visiting veterinary practices are vaccinated against VHD, so the vast majority of pet rabbits in the UK are at high risk.

Biosecurity

Rabbit owners and breeders should practise good biosecurity. Direct contact between pet rabbits and wild rabbits should be avoided and breeders should close their premises and not introduce other rabbits, or allow potential carriers – including people carrying the virus on their clothing or shoes – to come into contact with their rabbits.

Good biosecurity to prevent disease transmission involves wearing protective, disposable clothing (plastic, aprons, shoe covers) regular sterilisation of cages, runs and all utensils, and hand washing between handling individual animals.

Any rabbits showing clinical signs should be put into isolation as soon as possible and a disinfectant that is active against viruses, such as 0.5% bleach, sodium hydroxide or formalin, should be used to clean the environment and feeding utensils. Utensils should never be shared between infected and non-infected rabbits.

If new rabbits have to be introduced into a colony, they should be kept in quarantine and isolated from contact with other rabbits for at least one month.

Author

Mike Davies

BVetMed CertVR CertSAO FRCVS

Mike Davies qualified from the RVC, London, in 1976 and worked in primary and second opinion referral veterinary practices before moving to Hill's Pet Nutrition as director of scientific affairs. After this, he became director of the RVC's Beaumont Animals' Hospital, and in 2007, he joined Fort Dodge Animal Health as technical services manager. Mike is a well known speaker, holds postgraduate Certificates in Veterinary Radiology and Small Animal Orthopaedics, and in 1992 earned his Fellowship of the RCVS by examination.

References

1.   < /span>Pet Food Manufacturers Association website www.pfma.org.uk.

2.   HARKNESS, J. E. and WAGNER, J. E. (1989) The Biology and Medicine of Rabbits and Rodents 3rd Edition Published by Lea & Febiger pp 3-4.

3.   Fort Dodge Index, www.fortdodgeindex.co.uk

• VOL 25 • No4 • April 2010 • Veterinary Nursing Journal