3.1.1. Handrearing recommendations

3.1.1.2. Wild rabbits

Raising/feeding wild cottontail rabbits is very different from domestic rabbits.

• These rabbits develop faster and wean much younger than domestics. They begin to sample solid foods shortly after their eyes open. They wean at 3-4 weeks and can be released once weaned.
• Their nutrient requirements are different and thus the handfeeding recommendations are different from the above recommendations for domestic bunnies.
• Some rehabilitators use a mixture of Esbilac and whipping cream, or various other combinations of commercially available products (multi-milk, etc.).
• Handrearing is very difficult and requires much experience to be successful. It is not recommended for the novice and never should be encouraged in the general public.

4.1.1. The hutch bunny

The hutch bunny is often a child's pet, school or 4-H project, with little to no involvement of the parent. The rabbit may be housed with others or alone in a pen raised up off the ground and enclosed with wire. The exercise area of the hutch should be large enough for the rabbit to complete 2 hops (6 ft. for NZW) and to stand up fully extended. Many hutch bunnies live all year round in this type of setup. They should have an area in the cage that provides shelter (wooden house) and an area that allows them to get off the wire floor of the cage (wooden platform). The cage should be placed in a protected part of the yard, free from direct sunlight and cold winds. The cage must be predator proof! The sides and top of the cage should be screened to protect from flies.

Problems with this type of husbandry may include:

• Heat stroke (rabbits are very sensitive to heat)
• Cold stress with inadequate bedding or shelter
• Fly strike (Myiasis)
• Sore hock (Pododermititis)
• Predator attacks
• Neglect due to remote location and loss of child's interest

4.1.2. The house rabbit

The house rabbit on the other hand is often a family pet or even an adult pet, usually involving a much stronger rabbit-owner bond than the hutch bunny. These individuals are often loose in the house for part or all of the day, are litter trained, get along with other pets (dogs and cats) and are very well observed.

The most common problems with house rabbits may include:

• Obesity and hepatic lipidosis
• Sore hock (hardwood floors)
• Chronic soft stools
• Foreign body ingestion (carpeting, plastic)
• Electric cord chewing
• Conflicts with other animals

5.1.1. WBC and differential

Rabbits differ from most of our familiar domestic small animals in that a leukocytosis with a heterophilia is rarely observed with bacterial infections. Most often there is only a mild absolute increase in the number of white blood cells, but instead a shift in the distribution of white blood cells is seen. The normal rabbit will usually have more lymphocytes (60%) than neutrophils with a total number of cells around 8-10,000 cells/μl. When challenged with a bacterial infection they will display a shift in the white cells to a neutrophilia and a lymphopenia, often without an overall increase in leukocytes. Stress can also produce a lymphopenia.

5.1.2. Serum chemistry

Total serum calcium levels in rabbits often appear high, compared to what is seen with dogs and cats. Levels of up to 14 mg/dl are often seen and are considered normal. However, diseases related to excessive calcium are seen in the rabbit and will be discussed below.

Fat rabbits will often demonstrate elevated triglyceride levels as with other animals with hepatic lipidosis. This is a serious consideration in a rabbit with anorexia caused by conditions such as a hairball, malocclusion, or snuffles.

Normal mean values for New Zealand White Rabbits adapted from Manning, PJ. The Biology of the Laboratory Rabbit, 2nd ed., c1994

5.3.1. Rabbit castration

Rabbit castration is commonly performed for the purposes of contraception and for reducing aggressive or territorial behaviors. It can be performed in a variety of ways as long as care is taken to close the inguinal ring. Rabbits have a very prominent open inguinal ring and are capable of prolapsing into this space following an incorrectly performed castration. The "preferred" technique for rabbit castration is described well, and involves a prescrotal approach as in a dog (Duncan, 1993).

5.3.2. Ovariohysterectomy

Female rabbits are neutered for the same reasons as the male and to prevent the future development of uterine adenocarcinoma. This is very common in the unspayed female domestic rabbit over the age of 4 years (some reports state >90%). It can be seen as early as 2 years. Ovariohysterectomy is therefore recommended before 2 years of age. This procedure is performed as for a cat with one exception. The rabbit has a bicornuate uterus and a double cervix. Separate ligation of each cervix is recommended (Sedgwick, 1982). Obesity complicates the surgery and owners are often asked to get their overweight rabbits to lose weight before the procedure is performed.

5.3.3. Fracture repair

Fracture repair options in the rabbit differ somewhat from the traditional considerations for dogs and cats. External fixation with casts or bandages are usually acceptable if the rabbit will leave the bandage alone. They are prone to chewing at the bandage or self-mutilation of any toes or distal parts of an exposed limb. Internal fixation of difficult fractures of the humerus or femur must be considered, but are not without problems. Rabbits bones are very fragile, brittle and lightweight. The rabbit's skeleton constitutes only 7-8% of their body weight, compared to a cat skeleton which represents 12-13% bodyweight. Long bone fractures will split longitudinally very easily with little manipulation. Great care must be taken by the surgeon to handle the bones gently and to use the minimal implant devices required to repair the fracture. Once stabilized, rabbit fractures heal very quickly.

Amputation is sometimes considered for fractures that are too fragmented, or where the internal fixation attempt results in a shattered bone. Amputation of a forelimb is not a problem. However, amputation of a hindlimb will usually result in severe arthritis/ skeletal deviation in the front quarters of the animal within a year following surgery. This problem must be considered and discussed with the owner before proceeding with a rear limb amputation.

5.3.4. Management of broken back

The rabbit is constructed to be able to deliver a very powerful kick. This is most often used for power and speed in fleeing from a predator. It can also be used to kick a restrainer or to "thump" in the cage as an expression of anger. Under the right conditions a rabbit can kick so strongly that it will result in moderate to severe back injury, from a sprain to an actual displacement or fracture.

An animal presenting with signs of a back injury (hind limb paresis), may not have an associated event or known trauma. Diagnosis should proceed as for a dog or cat, including radiographs and neurologic assessment. Rule-outs should include other causes of neurologic impairment including a spinal cord abscess (often Pasteurella multocida, E.cuniculi).

Treatment may also follow traditional recommendations, however a myelogram and surgical stabilization is rarely considered by the owner. Prognosis for severe injury is grave and euthanasia is often elected. Some cases involving moderate injury (+deep pain) do respond to steroid administration and cage rest.

6.2.1. Viral Hemorrhagic Disease (calicivirus)

Over the last 10 years there has been an increased incidence of a severe hemorrhagic enteric disease in domestic rabbits. This is caused by the rabbit calicivirus also called Rabbit hemorrhagic disease virus (RHDV). In 2000 an outbreak in the US occurred for the first time and was successfully contained. The source of the infection was not determined. Another outbreak was reported again in August 2001 without finding the source of infection (see references).

Historical perspectives and characteristics of the virus

The disease was first recognized in China (1984), but it appears to have originated in Europe (serologic evidence from 1978). It is now endemic in Asia, most parts of Europe, including Britain, and also occurs in Mexico and North Africa. The disease was seen initially in domestic (including commercial) rabbits and also wild rabbits, all Oryctolagus cuniculus. There is an overall high morbidity and mortality with possible devastating effects: in one year in Italy (1989), 64 million rabbits died of this disease. It has been suggested that the disease has been spread around the world through frozen rabbit meat from China.

The disease is caused by a calicivirus. It is antigenically similar to the calicivirus causing European brown hare syndrome (reported 1st in Sweden in the early 80's). In most locations, European brown hare syndrome appeared in hares several years before the emergence of viral hemorrhagic disease in rabbits. Most studies show that these two viruses do not cross infect hares and rabbits.

Disease in rabbits

• The virus affects rabbits over 8 weeks of age, most often adults. Young animals appear resistant (reason unclear).
• Incubation period is 1-3 days.
• The disease is spread through direct contact (fecal-oral) or through contaminated feed or water, contaminated equipment, clothing, vehicles, etc. The virus is quite stable in the environment.
• Symptoms include: depression, anorexia, respiratory signs, ataxia. Up to 100% of affected animals develop internal bleeding and die within in 1-2 days. Many animals are found dead without observing any clinical signs (peracute).
• Peracute, acute, subacute and chronic forms of the disease exist.
• Post-mortem findings include: hepatic necrosis, pulmonary hemorrhage, tracheal hemorrhage, petechiation on the surface of the kidneys, epicardium and endocardium (hemorrhage mostly due to DIC). More recently, cases without hemorrhage have been noted. Spenomegaly may also be seen. Virus is found in highest concentrations in the liver.
• Diagnosis can be made at post mortem and through serology utilizing hemagglutination inhibition assays, IFA or ELISA tests.
• Vaccination is available and effective for control of this disease in domestic rabbits. Killed vaccine is used and is protective from 5 - 15 months. It is felt that vaccinated animals may shed virus if exposed to natural infection, although they do not become ill. Vaccine is currently not available in the US.

Implications for pets, laboratory animals and wildlife

This disease is REPORTABLE to the USDA-APHIS as a foreign animal disease. To decrease potential risks for pets and lab animals in the US, discourage or ban importation of live rabbits or rabbit parts from endemic areas, possibly including frozen meat products. Recommend quarantine of any "new" rabbits to a facility for at least 1 week. Wild rabbits in the US (sylvilagus) should not be susceptible (mutation possibilities?).

Currently both New Zealand and Australia are using this virus as a form of biological control for feral oryctolagus rabbits which are classified as introduced pests in their countries. Lost agricultural production and damage to the environment is significant including destruction of flora and habitat which support important native species (wombat, bilby endangered due to the rabbit). Use of biocontrols in this manner are very controversial. For more information see Supplemental Readings.

6.3.1. Pasteurella associated diseases

Pasteurella multocida is a ubiquitous organism so commonplace in domestic rabbits that it may be considered normal nasopharyngeal flora. Animals are exposed to the organism from birth onwards and will demonstrate a wide variety of diseases involving the organism at any stage of its life. Many animals of course, harbor the bacteria, but never develop disease. There are no effective vaccines for pasteurellosis in rabbits.

Diagnosis is made based on clinical signs, culture (if possible), and response to treatment. Rule-outs should include other bacteria, especially Staphylococcus aureus. Antibiotic treatment should ideally be designed based on culture and sensitivity. Specific considerations must be given to the rabbits unique response to infection and the accessibility of any antibiotics. Surgical debridement is often indicated in addition to antibiotic therapy. Prognosis for a well established infection is often poor.

Syndromes associated with Pasteurella in the domestic rabbit:

• Septicemia
• Snuffles - rhinitis, conjuncitivitis
• Abscesses - Dermal, Mandibular, Maxillary, Vertebral
• Vestibular disease
• Pneumonia
• Urogenital disease
• Meningitis

By far the most common form is "snuffles" which refers to an upper respiratory infection. Snuffles may begin as a conjunctivitis or a rhinitis or both. Chronic cases can lead to blocked nasolacrimal duct and eventually osteomyleitis or maxillary abscesses. A simple case of conjunctivitis or even very mild rhinitis may respond well to topical ophthalmic treatments. The nasolacrimal duct may need to be cannulated and flushed.

Rabbit with conjunctivitis

Conjunctivitis leading to facial abscess in a rabbit

6.6.1. Dental malocclusion

As stated above dental malocclusion, particularly of the incisor teeth is a common problem in rabbits. Malocclusion of the incisors is largely thought to be genetic, although trauma to the teeth (teeth trimming, chewing on cage wire, etc.) can also result in malocclusion.

• Usually incisors (genetic)
• Definitive treatment through removal of all incisors (4 upper and 2 lower), otherwise periodic trimming may be performed
• Molars less common
• Special dental instrument pack very useful (see end of chapter)

6.6.2. Chronic soft stools

This condition is extremely common in pet rabbits, especially house rabbits. It should be distinguished from true diarrhea which is life threatening in the rabbit. Chronic soft stools is usually related to high carbohydrate, lower fiber diet, obesity, lack of exercise, stress, or a sudden change in diet. This induces a change in gut flora resulting in the abnormal stool consistency - sticky, smallish pellets, often pasted to the perineal area. Most indoor rabbit owners notice right away since little presents are left on furniture, etc. and the odor of feces is unpleasant. If left unattended, the perineal soiling can develop into serious dermatitis, attract flies, etc. and lead to greater problems. Rabbits generally feel fine and show no signs of illness.

Treatment for this problem involves dietary correction: increasing fiber and decrease carbohydrates, decreasing stress, increasing exercise, etc. Antibiotics are contraindicated and may complicate the situation. This process is very slow, and may require quite a bit of patience and frequent bathings, cleaning up around the house!

6.6.3. Diarrhea

• Mucoid enteropathy

  Mucoid enteritis or enteropathy affects young rabbits (7-14 weeks). Anorexia, depression and accompanying diarrhea with mucous may progress to cecal impaction and death. The etiology is unknown, but is likely diet based. A high fiber, low carbohydrate diet appears to be protective.

• Enterotoxemia -

  Enterotoxemia is very serious in rabbits, usually resulting in death. Lethal toxin is produced by overgrowth of Clostridia spiriforme, (difficile or perfringens). Overgrowth can occur in young rabbits, be induced by certain antibiotics, brought on by severe stress (including surgery). Acute death with or without diarrhea is very common. Watery brown or blood tinged diarrhea may develop in some cases. Animals quickly go into shock and die. Presumptive diagnosis is based on history (stress? antibiotics?) and clinical signs. Treatment with cholestyramine and metronidazole may be attempted, along with aggressive fluid therapy and treatment for shock. Prognosis is grave.

• Other bacterial causes of enteritis:
  • Tyzzer's disease - Clostridium piliformes
  • E.Coli
  • Salmonella
  • Pseudomonas

6.6.4. Hepatic lipidosis

Obese rabbits will necessarily deposit large amounts of fat in their liver. This change can present a problem, as in other animals, if the rabbit is suddenly starved for any reason (e.g. hair ball, dental disease, prolonged pre or post-operative fasting). A hepatic lipidosis crisis can develop into a critical care emergency. As mentioned above, serum elevations in triglycerides and cholesterol may indicate hepatic lipidosis.

6.6.5. Hairballs (trichobezoar), gastric stasis and gastric obstruction (carpeting)

Gastric obstruction, partial and complete, is not unusual in rabbits. Gastric stasis can be brought on by many different things, including stress. Build up of material in the stomach, often palpated or seen on radiographs is not necessarily the root of the problem, but will contribute or complicate the clinical picture. Rabbits are unable to vomit and swallowed material (such as hair and carpet can easily build up if not properly digested. If motility is disrupted, the rabbit becomes dehydrated, the material condenses, becomes mucinous, the stomach wall collapses against it, and obstruction ensues.

Clinical signs are very vague, usually consisting of decreased appetite or anorexia and decreased fecal production. Like many herbivores, rabbits motility is directly related to intake. Once intake ceases, motility also ceases. Observing fecal quantity and quality (small and dry pellets) is a good indication of motility.

Diagnosis is based on history, clinical signs, physical findings, and sometimes radiographs. Radiographic findings of material in the stomach is not abnormal and should not be overinterpreted. Radiographs are most useful for determining partial from complete obstruction, based on characteristic gas patterns. Surgery is indicated only for complete obstruction, partial obstructions are managed medically and constitute the majority of cases.

Treatment is first and foremost centered on rehydration and stimulation of motility. Use of enzymes to dissolve hairballs is controversial but appears to do no harm. Oral hydration and syringe feeding usually results in return of the rabbit's appetite in a day or two. Metoclopromide can be helpful, but is contraindicated in acute abdomen. Complete obstruction (hairball lodged in duodenum, foreign body ingestion) is a surgical emergency and carries a poor prognosis. Remember that anorexic overweight rabbits are susceptible to hepatic lipidosis and should be supported aggressively. Prevention of hairballs and gastric stasis is best achieved through proper dietary management: feeding high fiber, low carbohydrate diet, and avoiding obesity.