Rabbits

Consultation and handling

Rabbits are prey animals and, therefore, may exhibit extreme antipredator behavior, such as jumping from the examination table.

Always weigh the rabbit at every consultation; weight loss may be the first occult sign of chronic disease such as dental disease. Most rabbits can be examined on a table with minimal restraint. If lifted, one hand is placed beneath the chest while the other supports the back end and legs. Many rabbits can have their perineum and ventral surface examined by gently turning them on their backs, such that the rabbit is held and supported upside-down between the examiner's chest and arm. The oral cavity can be examined with the use of an auroscope, although in the conscious rabbit this can never be regarded as a full oral examination.

Use of glucose and sodium as prognostic indicators in the rabbit

Stressed and ill rabbits commonly show hyperglycemia with a compensatory hyponatremia. However, the hyponatremia may be either a true sodium deficiency or an apparent, but not actual, pseudohyponatremia. Pseudohyponatremia (which can occur with congestive heart failure, severe liver disease, and hyperlipidemia) does not require treatment, whereas true hyponatremia does. These are distinguished by comparing the sodium levels with the calcu­lated tonicity. Calculated osmolarity has less diagnostic significance.

Calculated tonicity:

Ton (mOsm/L) = 2 ? (mEq/L) + Glucose (mg∕dL)∕18

Calculated osmolarity:

P_osm (mOs^L) = 2?Na (mEq/L) + Glucose (mg∕dL)∕18 + BUN (mg∕dL)∕2.8

Nursing care

Thermoregulation

This is one of the most crucial homeostatic mechanisms for rabbits (and other small mammals).

Management of hyperthermia

See Systemic Disorders.

Management of hypothermia

1. Assess the rectal temperature of the rabbit. If in doubt, assume that the animal is hypothermic and that this should be corrected as soon as possible.

2. Applying insulation such as bubble wrap is often insufficient—collapsed or otherwise inactive rabbits are not generating heat, and this may insulate it from a higher ambient temperature.

3. Place these animals onto a heat mat, onto which is placed an absorptive towel or other material to reduce the risk of localized burns.

4. Alternatives include heated operating tables, commercial warm air generators, or incubators; “hot hands” (gloves filled with warm water) carry too high a risk of burns and cool too quickly.

5. Place insulative material over the animal and heat source.

6. Areas of the body where there is a high risk of radiative heat loss such as the pinnae or feet can be covered with aluminum foil to further conserve heat.

Fig 2-1. Correct placement of a catheter into the marginal auricular vein.

7. By either quickly raising the body temperature or allowing the rabbit to maintain its core temperature with ease, we remove the need for costly hyperthermic physiologic processes, such as shivering.

8. Treat high risk of enterotoxemia following die-off of gut bacteria according to general principles outlined in Management in Gastrointestinal Tract Disorders.

Fluids

In small mammals the choice of fluid used is as indicated with other mammals. Venous access in the rabbit is via the cephalic, lateral saphenous, and marginal ear veins (Fig. 2-1). Jugular cutdown can be undertaken under general anesthesia (GA) but may result in respiratory embarrassment. Fluids can be given IV either by bolus or by infusion.

In hypovolemic patients, vascular access may be impossible and it may be better to consider either IP or IO administration. For IO it is relatively simple under GA to insert either an intraosseous catheter or a hypodermic needle into the marrow of either the femur (via the greater trochanter) or tibia (through the tibial crest). Fluids, colloids, and even blood can be given IO if necessary.

Fluid administration

• All fluids should be warmed to 38° C.

• Daily fluid maintenance requirement for a rabbit is 100 mL/kg per day.

• Fluid replacement calculations are as for other species. Recommendations for rabbits are:

• Crystalloids: For rabbits the maintenance fluid rate is 75 to 100 mL/kg per 24 hours. Shock rate is up to 100 mL/kg over 1 hour.

• Colloids: A bolus of 10 to 15 mL/kg over 30 minutes can be given up to four times daily.

• Whole blood: Transfusions from other rabbits can be done, usually over a period of 20 to 30 minutes. Transfusion reactions are rare, but a major and minor cross-match are recommended.

Nutritional support

Many rabbits are presented as emergencies after a prolonged period of ill health that will have affected their food intake (e.g., suffering from undiagnosed chronic dental disease). These animals are often hypoglycemic, so testing beforehand (a commercial glucometer is suitable) is beneficial, followed by IV or IP glucose to those cases identified.

Longer-term support can be given by syringe feeding commercially available food supple­ments, e.g., Oxbow Critical Care and Science Recovery Diet.

• Use a relatively wide-bore syringe, as blockage at the correct concentration is common.

Feeding a dilute mixture may be counterproductive.

• Nasogastric tubes can be fitted, but these are prone to blockage.

• If the rabbit is very debilitated, then choking/failure to swallow may occur; in these cases concentrate on parenteral fluids, dextrose, and vitamin B therapy.

Analgesia

Anesthesia

There are many safe anesthetic techniques described for rabbits despite the persistent myth that rabbits do not survive anesthesia. The author finds the following protocols of use:

Preanesthetic protocol

1. Rabbits rarely vomit, so starving is not only unnecessary but should be avoided due to their high metabolic rate.

2. Administering metoclopramide (0.5 mg/kg SC or PO every 6 to 8 hours) postoperatively will help to prevent a postsurgical ileus, especially following painful or abdominal surgery.

3. Monitor feeding and fecal output for 24 hours following surgery.

Anesthesia of high-risk cases

Typically these are rabbits that have chronic dental disease, have not been able to eat normally for some time, and have marked weight loss. Clinical assessment is vital and if necessary correction of fluid deficit and stabilization should be attempted prior to anesthesia. Such rabbits should ideally have a rapid induction and a rapid recovery from anesthesia to regain temperature homeostasis and imitate feeding. Masking with volatile anesthetics alone can achieve the latter although induction can be prolonged. Alternatively the author has found induction with IV propofol to be generally safe.

The advantage of gaseous anesthetic induction is rapid recovery without the need to metabolize large amounts of drug. Isoflurane appears to be less stressful for induction than halothane, based on lower corticosterone levels (Gonzalez-Gil et al 2006).

Gaseous anesthetic induction protocol

1. Preoxygenate rabbits before induction.

2. When masking down rabbits, breath holding is very common. This can lead to hypoxia, hypercapnia, and bradycardia.

3. Monitor breathing closely and only increase anesthetic concentration when rabbit is seen breathing.

4. If the concentration is increased rapidly, there is increased risk of inhalation of high concentrations of anesthetic gas quickly and increased risk of cardiovascular consequences once rabbit starts to breathe.

5. Once sufficiently anesthetized, intubate—use an uncuffed endotracheal tube. Rabbits can exhibit laryngeal spasm, so beware excessive trauma. Use local anesthetic spray.

Propofol induction

• Following the application of local anesthetic cream a catheter is placed into the marginal auricular vein (see Fig. 2-1).

• Propofol is administered at 10 mg/kg IV.

• Intubate (see below) and maintain on gaseous anesthetics.

• Anesthesia can be maintained for very short periods by repeated boluses of propofol, but the cardiac and respiratory depressant effects mean that it should not be used for longer procedures.

Blind intubation of rabbits

1. Spray glottis with local anesthetic spray.

2. Place rabbit in sternal recumbency.

3. Run endotracheal (usually 2.0, 2.5, or 3.0 mm uncuffed) tube along midline of palate to back of pharynx.

4. Look for gagging reflex.

5. Listen for breaths.

6. Feel for exhalations.

7. Feel for sensation of tube passing over tracheal rings.

8. Or use laryngoscope with long blade.

9. Having an assistant hold the mouth open with pieces of bandage gauze behind the upper and lower incisors may be of some use.

Pre-medication protocol

1. Alternatively sedate with diazepam (0.2 mg/kg IM or IV) or midazolam (2.0 mg/kg IM or IP) or a combination of butorphanol (1.5 mg/kg) and medetomidine (0.1 mg/kg) IV. These may still not prevent breath-holding.

2. Once sleepy, mask with isoflurane.

3.

4. Intubate once able to and maintain with isoflurane.

• Oxygen can also be delivered via the nasal cavities—a small-diameter catheter or tube is inserted into the ventral nasal meatus. Even moderate flow rates risk an explosive exit of such a tube! If necessary, a tracheotomy may need to be performed.

• Premedication with doxapram at 10 mg/kg IP, IV, or sublingually (SL) 5 to 10 minutes beforehand is occasionally recommended, but this will increase oxygen demand and the author finds it usually unnecessary.

Parenteral anesthesia

• Ketamine/medetomidine/butorphanol given IM simultaneously:

• Ketamine at 10 mg/kg

• Medetomidine at 0.1 mg/kg

• Butorphanol at 1.5 mg/kg

• At end of procedure reverse medetomidine with atipamezole at 0.75 mg/kg IM.

Cardiopulmonary resuscitation

Respiratory arrest

1. Administer 100% oxygen.

2. Assist ventilation—compress thorax at around 60x/minute.

3. Doxapram SL or at 10 mg/kg IV or IP. Note: This will increase the animal's oxygen demand.

4. If appropriate, give atipamezole.

Cardiac arrest

As for respiratory arrest but also:

1. Compress thorax at around 90x/minute.

2. If asystole—give epinephrine at 0.1 mg/kg of 1 : 10,000 IV.

3. If ventricular fibrillation—lidocaine (lignocaine) at 1 to 2 mg/kg IV.

Skin disorders

Normally rabbits have a soft, short undercoat covered with larger guard hairs. Rex breeds have short guard hairs that do not exceed the undercoat, while Angoran breeds have very long guard and undercoat hairs. Lionhead rabbits retain the long hair around the head, neck, and rump area. Satin breeds have altered hair fiber structure.

Findings on clinical examination

Signs of skin disease:

• Pruritus

• Typically hairs will be damaged. There may be areas of reddened and inflamed skin.

• Edema may accompany a cellulitis.

• Ectoparasites, especially Cheyletiella, Leporacarus, and Psoroptes. Occasionally fleas (rabbit flea—Spilopsyllus cuniculi [Pinter 1999], cat and dog fleas—Ctenocephalides spp.), lice, sarcoptic and Demodex mites, and blowfly maggots. Cheyletiella may act as a vector for myxomatosis.

• Ear mites (Psoroptes cuniculi): inflammation and pruritus of the pinnae (Fig. 2-2). Can spread onto surrounding face and neck.

• Bacterial disease, typically Staphylococcus and Pasteurella species (Fig. 2-3). Pseudomonas is typically linked to moist dermatitis under the chin (blue fur disease).

• Occasionally due to Trichophyton

Fig 2-2. Ear mite (Psoroptes cuniculi) infestation.

Fig 2-3. Severe bacterial dermatitis in a rabbit.

• Alopecia

• Self-mutilation secondary to pruritus

• Sebaceous adenitis (Whitbread et al 2002)

• Lack of dietary fiber can lead to "barbering" if two or more rabbits present

• Endocrinologic

• Cystic ovaries and other ovarian diseases

• Suckling does will remove hair from around teats

• Atypical myxomatosis

• Scaling and crusting

• Ectoparasitic infestations, especially Cheyletiella

• Thickened crustlike material on pinnae and in ear canal strongly suggestive of Psoroptes cuniculi

• Sebaceous adenitis

• Trichophyton mentagrophytes, Scopulariopsis brevicaulis (Vangeel et al 2000), and rarely Microsporum

• Myxomatosis lesions

Fig 2-4. Skin lacerations and subsequent dermal necrosis from fighting.

• Rabbit syphilis Treponema cuniculi, especially at mucocutaneous junctions. Vesicles may be present.

• Atypical myxomatosis

• Erosions and ulceration

• Bacterial disease, especially Staphylococcus and Pseudomonas

• Myiasis

• Cutaneous lymphosarcoma

• Bites and lacerations (Fig. 2-4)

• Pododermatitis

• Atypical myxomatosis

• Rabbit syphilis

• Vaccine reactions; can happen with oil adjuvant vaccines or if part of vaccine given intradermally (as manufacturer may recommend)

• Nodules, swellings, and nonhealing wounds

• Abscess. If these are around the mouth, strongly suspect underlying dental disease.

• Salivary mucocele (soft fluctuant swelling on jaw—see Gastrointestinal Disorders)

• Herpesvirus (circular, reddened skin lesions)

• Poxvirus—initial nasal discharge and fever, followed by generalized formation of papules and nodules; edema of the face and perineum

• Cuterebra larvae

• Mycobacteriosis

• Myxomatosis (may see concurrent palpebral edema, swollen pinnae, swelling of external genitalia and perineum)

• Shope papilloma virus (papovavirus)

• Shope fibroma virus (poxvirus)

• Acrochordon

• Lymphoma/lymphosarcoma

• Other neoplastic diseases

- Fibrosarcoma

- Squamous cell carcinoma

- Trichoepithelioma

- Basal cell tumor

- Lipoma

- Apocrine adenocarcinoma (Miwa et al 2006)

• Excessively pronounced dewlap

- Some breeds selected for this

- More prominent in females

- May be site of recurrent moist dermatitis, especially Pseudomonas, where the dewlap is consistently moist, as from water bowls

Investigations

1. Microscopy: examine fur pluck, acetate strips, or skin scrapes to affected area and examine for ectoparasite.

2. Examine material from ear canals for Psoroptes cuniculi.

3. Examine teeth. Rabbits with dental disease may have difficulty grooming normally.

4. Bacteriology and mycology: hair pluck or swab lesions for routine culture and sensitivity.

5. Fine-needle aspirate followed by staining with rapid Romanowsky stains

6. Biopsy obvious lesions.

7. Ultraviolet (Wood's) lamp—positive for Microsporium canis only (not all strains fluoresce)

8. Routine hematology and biochemistry

9. Serology for Treponema cuniculi titer

10. Endocrine analysis (see Endocrine Disorders)

11. Normal plasma thyroid level: 22 nM/L (Hulbert 2000)

12. If barbering suspected, examine hair under microscope to see if chewed; separate from other rabbit; supply extra hay.

Management

1. Rabbits with dental disease or those that have had incisor extractions are unable to groom and will require regular grooming by their owner.

2. Routine and regular examination of the perineum of pet rabbits is essential. The presence of caecotrophs adhered to the perineum will encourage myiasis (see Failure to Caecotroph).

TreatmentZspecific therapy

• Treat for any ectoparasites.

• Ivermectin at 200 μg∕kg SC, topically or as topical application (Beaphar Anti-Parasite Spot-On for Small Animals, USA, Genitrix Xeno 450, UK) works well for mites such as Cheyletiella, although treatment should be continued for longer than 6 weeks (life cycle = 5 weeks). Also for myiasis.

• Imidacloprid (Advantage, Bayer) applied as a 40-mg spot-on. Can be applied weekly for lice and myiasis

• Permethrin applied as either a dusting powder or shampoo

• Ear mites (Psoroptes cuniculi)

• Ivermectin at 200 μg∕kg SC, topically or as topical application (Beaphar Anti-Parasite Spot-On for Small Animals, USA, Genitrix Xeno 450, UK)

• Topical selamectin at 6 to 18 mg/kg (Hack et al 2002)

• Topical 10% imidacloprid/1.0% moxidectin (Advocate (UK), Advantage Multi, Bayer (USA)) at 10 mg/kg (imidacloprid) and 1 mg/kg (moxidectin) every 4 weeks for 3 treatments (Beck 2007)

• Soften material in ear canal using either acaricidal eardrops or nonacaricidal products.

• After 5 to 7 days the crusty exudate should have softened sufficiently to allow atraumatic removal.

• Myiasis

• Initial treatment involves clipping of the fur and cleaning the affected area, with manual removal of maggots plus flushing with a dilute chlorhexidine or povidone-iodine cleanser. Supportive treatment should be aggressive with therapy for toxic shock plus ivermectin or imidacloprid to kill any maggots or emergent larvae that cannot be removed.

• The underlying cause of the caecotroph accumulation must be addressed (see Failure to Caecotroph) and regular perineal inspection and cleaning, plus protection from exposure to flies, is crucial in preventing the condition.

• Topical cyromazine (Rearguard (UK) Larvadex (US), Novartis) applied as a 6% solution topically every 6 to 10 weeks as a preventative for myiasis

• Cuterebra larvae: Either remove via the breathing hole, surgically, or by using ivermectin at 200 pg/kg SC, topical or as topical application (Beaphar Anti-Parasite Spot-On for Small Animals, USA, Genitrix Xeno 450, UK).

• Pododermatitis

• Risk factors (in part from Mancinelli et al 2014)

- Large breeds

- Older rabbits

- Females > Males

- Neutered > entire (of abscesses. Draining and flushing of rabbit abscesses rarely work.

• Bites and lacerations

• Clean and debride well. These are prone to infection, so it may be better to surgically excise the lesion and heal by first intention.

• Covering broad-spectrum antibiosis

• Poxvirus, Shope fibroma virus

• Supportive treatment only; usually spontaneously regress

• Shope papilloma virus

• Can trigger warts, especially on eyelids and ears

• Consider surgical resection as may eventually become carcinomas

• Spread by insect vector so antiectoparasiticidal treatment important adjunct

• Myxomatosis

• Supportive therapy is required. Fluids, assisted feeding, and covering antibiosis are essential if the rabbit is to stand any chance of survival.

• Spread by insect vectors so antiectoparasiticidal treatment important adjunct

• Atypical myxomatosis. Three atypical forms have been described:

- Partially immune (vaccinated) rabbits may develop a papillomatous form that progresses to crusting lesions, especially on the eyelids and other mucocutaneous junctions. These usually resolve with appropriate care.

- Papules and plaques appear in recently depilated areas. These progress to hemorrhagic and necrotic lesions. Recovery is spontaneous.

- Respiratory form

• Vaccines are available.

• Dermatophytosis

• Griseofulvin at 25 mg/kg PO once daily for 4 weeks

• Miconazole/chlorhexidine (Malaseb, Leo) shampoo—bathe once daily

• Itraconazole at 5.0 mg/kg PO s.i.d. for 30 days

• Treponema (rabbit syphilis)

• Responds well to penicillin at 50,000 IU∕kg SC given once weekly for 3 weeks. In view of slight risk of inducing an enterotoxemia, where possible always have serologic test done first.

• Tetracyclines and chloramphenicol can also be effective.

• Lymphoma/lymphosarcoma

• See Systemic Disorders.

• Neoplasia

• Surgical debulking, resection, or euthanasia

• Accessible cutaneous tumors can be treated by injecting cisplatin directly into the tissue mass on a weekly basis as a debulking exercise.

• Dewlap dermatitis

• Clean with chlorhexidine solution.

• Antibiosis

• Dewlap resection

Respiratory tract disorders

Rabbits are obligate nasal breathers. The back of the pharynx is comparatively small and is occupied by the main body of the tongue, preventing easy visualization of the caudal pharynx.

Disorders of the upper respiratory tract

• Dental disease

• Pasteurellosis (includes atrophic rhinitis-like condition)

• Other bacterial infections

• Poxvirus

• Treponema cuniculi

• Toxoplasmosis (see Neuromuscular Disorders)

• Allergy

Findings on clinical examination

• Nasal discharge

• Conjunctivitis (see Ophthalmic Disorders)

• Dacryocystitis (see Ophthalmic Disorders)

• Vesicles, erosions, and crusty lesions (Treponema cuniculi)

• Fever (>40° C), oculonasal discharge, increased respiratory rate, CNS signs

(toxoplasmosis)

Investigations and management

• See Differential Diagnoses for Respiratory Disorders.

Treatment

• Poxvirus—initial nasal discharge and fever; followed by generalized formation of papules and nodules; edema of the face and perineum; self-limiting

• See also Differential Diagnoses for Respiratory Disorders.

Differential diagnoses for respiratory disorders

Viral

• Myxomatosis (see Skin Disorders)

• Viral hemorrhagic disease (VHD) (calicivirus)

• Herpesvirus

• Paramyxovirus (Sendai virus)

Bacterial

• Pasteurellosis (including P. multocida)

• Bordetella bronchiseptica

• Staphylococcus aureus

• Streptococci

• Moraxella spp.

• Pseudomonas aeruginosa

• Mycobacteriosis

• Cilia-associated respiratory bacillus

• Mycoplasma pulmonis

• Chlamydophila

Protozoal

• Toxoplasmosis (see Neuromuscular Disorders)

Neoplasia

• Lung metastases from uterine adenocarcinoma

• Thymomas

Other noninfectious problems

• Allergic

• Congestive heart failure

• Traumatic tracheitis (secondary to endotracheal intubation)

• Heatstroke

Findings on clinical examination

• Rhinitis

• Sinusitis

• Conjunctivitis

• Dacryocystitis (see Ophthalmic Disorders)

• Otitis

• Abscessation (can involve skin and variety of organs or joints due to bacteremic spread)

• Increased respiratory noise

• Dyspnea/tachypnea

• Fever

• Bilateral exophthalmia (thymomas)

• Anorexia and weight loss

• Loss of exercise tolerance

• Associated cardiovascular disease (e.g., pericarditis with Pasteurella bacteremia—see

Cardiovascular Disorders)

Investigations

1. Auscultation

a. Rales and rattles: Differentiate between upper respiratory tract disease and lower respiratory tract disease (pneumonia).

b. Areas of consolidation may be silent.

2. Radiography

a. Skull (dental disease, bulla abscessation, turbinate atrophy)

b. Contrast studies on nasolacrimal ducts

c. Spine (discospondylitis)

d. Thorax (lung metastases, cardiac disease, consolidated lung tissue, effusion lines)

3. Routine hematology and biochemistry

a. Look for alterations in heterophil/lymphocyte ratios.

4. Serology for Pasteurella, Mycoplasma pulmonis, Chlamydophila, myxomatosis

5. Culture and sensitivity (including from tracheal wash)

a. Always have anaerobic culture performed as well as aerobic.

6. Chlamydophila polymerase chain reaction (PCR)

7. Cytology from tracheal wash

8. Pleural tap and cytology

9. Endoscopy

10. Ultrasonography

a. Thymoma

11. Biopsy

Management

1. Give supportive treatment (e.g., covering antibiosis).

2. Reduce stress levels. Hospitalize away from dogs and noisy cats; keep in darkened position.

3. Supply oxygen, preferably via an “oxygen tent.”

4. Mucolytics may be useful (e.g., bromhexine, N-acetylcysteine).

TreatmentZspecific therapy

• VHD

• No treatment; supportive treatment only

• Pasteurellosis and other bacterial infections: broad-spectrum antibiotics plus anaerobic cover (e.g., metronidazole at 20 mg/kg PO b.i.d.)

• Surgical removal or debridement of abscesses often necessary

• If surgery is not practical, then some abscesses may be allowed to heal by second intention. Daily topical applications of IntraSite Gel (Smith and Nephew Health) are helpful. Topical Manuka honey is also said to be useful.

• Heatstroke (see Systemic Diseases)

• Thymoma

• Radiation therapy; 24 Gy given in 3 fractions of 8 Gy on days 0, 7, and 21 (Sanchez-Migallon et al 2006)

Dental disorders

• The permanent dental formula of the rabbit (Fig. 2-5) is:

Permanent dental formula of the rabbit

Protozoal

• E. cuniculi (meningitis may produce abnormal chewing muscle movements; partial paralysis of tongue secondary to hypoglossal nerve damage)

Nutritional

• Lack of long fiber (e.g., hay) in diet

• Inappropriate nutrition

Fig 2-5. A diagram of a rabbit skull showing position of teeth and track of nasolacrimal duct.

Fig 2-6. Overgrown maxillary and mandibular incisors, with hair matted around the lower teeth.

Neoplasia

• Osteosarcoma of the mandible

Other noninfectious problems

• Congenital incisor malocclusion (esp. brachycephalic breeds such as Netherland Dwarf, Lionhead, and Mini-Lops)

Findings on clinical examination

• Incisor malocclusion (Fig. 2-6)

• Mandibular swelling (unilateral or bilateral) due to bone remodeling to accommodate tooth root overgrowth

• Gross swelling, typically in the mandibular area (Fig. 2-7), but can be at maxilla, secondary to tooth root abscess

• Excessive salivation/moist fur on chin and ventral neck

• Weight loss

• Anorexia (may be intermittent)

• Perineal accumulations of caecotrophs

• Ectoparasitic disease

• Dacryocystitis

Fig 2-7. Mandibular tooth root abscess.

• Conjunctivitis

• Exophthalmos (secondary to retrobulbar abscess) (see Ophthalmic Disorders)

Investigations

1. Otoscopic examination

a. Spurs on cheek teeth (tend to be lingual on the mandibular cheek teeth and buccal on the maxillary)

b. Lingual tilting of mandibular cheek teeth and buccal tilting of maxillary cheek teeth (Fig. 2-8)

c. Ulceration of tongue and cheeks

d. Purulent material in mouth

e. Otoscopic examination does not constitute a complete examination of the oral cavity as structures at the back of the pharynx can be difficult to see due to its depth and the large size of the tongue.

2. Radiography

a. Lateral, dorsoventral (DV) views of skull. Note: Skulls often appear osteoporotic, probably due to an atrophy of disuse but has been linked to hypocalcemia.

b. Left and right lateral oblique views of skull allow assessment of individual tooth roots. Any divergence of maxillary or mandibular tooth roots away from each other suggests abnormal root elongation (Figs. 2-9, 2-10).

c. Contrast study on nasolacrimal ducts

Fig 2-8. Buccal tilting and overgrowth of the upper first premolar.

Fig 2-9. Right lateral oblique view of skull showing osteolysis around the root of the left first mandibular premolar associated with a tooth root abscess; there is also overgrowth of the second premolar, first molar, and incisor roots.

3. Check patency of nasolacrimal ducts (Fig. 2-11).

4. Routine hematology and biochemistry

a. Concerns that rabbits with dental disease are hypocalcemic are ill-founded. Calcium levels are readily responsive to dietary levels, and calcium status is monitored with ionized calcium (total calcium 3.0 to 4.0 mmol/L; ionized 1.57 to 1.83 mmol/L).

5. Culture and sensitivity

a. Aerobic and anaerobic culture of abscesses

6. Endoscopy

Fig 2-10. Explanatory diagram of Fig. 2-9.

Fig 2-11. Fluorescein can be used to check nasolacrimal duct patency.

7. Examination of oral cavity under GA

8. Biopsy (osteosarcoma)

Management

1. Chronic cases often cachexic—may need parenteral fluid support. Check blood glucose levels (normal range 4.2 to 8.2 mmol/L).

2. Syringe feeding with commercial feed suspensions (e.g., Oxbow Critical Care or Science Recovery Diet); may require nasogastric tube

3. Flushing of nasolacrimal ducts and antibiosis.

TreatmentZspecific therapy

• Regular coronal reduction

• Always burr overgrown incisors in preference to clipping due to risk of fracture, pulpal hemorrhage, and infection.

• For cheek teeth, this will likely necessitate heavy sedation or GA. “Conscious” dental work on the cheek teeth is stressful to the rabbit and risks serious traumatic back injuries, including fracture of lumbar vertebrae (see Neuromuscular Disorders).

• Often coronal reduction alone is insufficient; often by the time of presentation, dental disease has progressed to a quite advanced stage.

• Use of a dental drill or equivalent is essential; dental spurs can be clipped, but the teeth must be burred down and clipping is likely to fracture the tooth.

• Incisor extraction

• Cheek teeth extraction

• Surgical debridement of tooth root abscesses, including removal of infected bone and affected tooth roots, followed by:

• Packing with antibiotic-impregnated methyl-methacrylate (bone cement or similar) and/or

• Marsupialization, leaving ostium for recurrent povidone-iodine/antibiotic application during second intention healing

• Antibiosis

- Usually a broad-spectrum antibiotic such as enrofloxacin at 5 mg/kg PO s.i.d. or co-trimoxazole at 30 mg/kg PO b.i.d. plus

- Anaerobic antibiosis, e.g., metronidazole at 10 to 20 mg/kg PO s.i.d. or b.i.d. or procaine G benzylpenicillin at 20,000 to 60,000 lU/kg IM or SC s.i.d.

• Drilling out of tooth root apices to initiate tooth root death where extraction is not viable

• Analgesia (e.g., meloxicam at 0.3 mg/kg PO s.i.d.) can be given for many weeks.

• Where possible, wean rabbit onto a diet high in long fiber (i.e., grass and hay), as this encourages normal chewing and dental wear on the back teeth.

• Osteosarcoma: Treatment is difficult even with surgical debridement and chemotherapy—consider euthanasia.

Gastrointestinal tract disorders

Viral

• Rotavirus

• Papillomatosis

• VHD

Bacterial

• The normal gut flora of the rabbit is predominantly gram-positive. Typical inhabitants include Bacteroides spp., Propionibacterium spp., and Butyrivibrio spp. plus gram-negative oval and fusiform rods. Also present are large ciliated protozoa (Isotricha) and yeasts (Cyniclomyces guttulatus). Coliforms are not present in healthy animals.

• Escherichia coli

• Staphylococcus (enteritis in newborn/suckling rabbits)

• Clostridium spiroforme

• Clostridium piliforme (Tyzzer disease)

• Salmonellosis

• Klebsiella pneumoniae (Coletti et al 2001)

• Pseudomonas

• Mycobacterium avium paratuberculosis (Greig et al 1997)

Protozoal

• Intestinal coccidiosis (especially Eimeria perforans, E. magna, E. media, and E. irresidua)

• Hepatic coccidiosis (Eimeria stiedae)

• Cryptosporidium (young rabbits)

• Giardia duodenalis (nonpathogenic)

• Monocercomonas cuniculi (nonpathogenic)

• Retortamonas cuniculi (nonpathogenic)

• Entamoeba cuniculi (nonpathogenic)

• The commensal yeast (Cyniclomyces guttulatus) should not be mistaken for Eimeria oocysts.

Parasitic

• Nematodes

• Pinworms (Passalurus ambiguus)

• Trichostrongylus

• Obeliscoides cuniculi

• Cestodes

• Cittotaenia variablis

• Mosgovoyia pectinata americana, M. perplexa

• Monoecocestus americana

• Ctenotaenia ctenoids

• Trematodes

• Hasstilesia tricolor

• Fasciola hepatica

• Cysticercosis (see Liver Disease)

Nutritional

• Insufficient fiber in diet, especially long fiber (grass and hay)

• Excessive carbohydrate intake (predisposes to Clostridium overgrowth)

• Selective feeding out of mixed pellet and grain diets is an unsubstantiated but possible problem.

Neoplasia

• Adenocarcinomas

• Leiomyomas

• Leiomyosarcoma

• Metastases from uterine adenocarcinoma

• Rectal papillomas

• Inflammatory fibroid polyps

Other noninfectious problems

• Salivary mucocele

• Gastric trichobezoars (usually secondary to gut motility problems, lack of dietary fiber, or dehydration)

• Caecoliths

• Mucoid enteropathy

• Dysautonomia

• Dental disease (see Dental Disease)

• Iatrogenic enterotoxemia secondary to antibiotic use. Problem antibiotics include clindamycin, erythromycin, lincomycin, ampicillin, and amoxicillin. Less likely, but capable of causing problems, is the cephalosporin family of antibiotics. Antibiotics that rarely if ever cause problems include the fluoroquinolones such as enrofloxacin and marbofloxacin, the potentiated sulfonamide drugs, and the aminoglycosides.

• Failure to caecotroph

• Gastric stasis and bloat

• Foreign body

• Ingestion of toxin

• Intussusception (can be secondary to severe coccidiosis, cecal polyp)

• Liver lobe torsion (see Hepatic Disorders)

Findings on clinical examination

• Diarrhea (may be hemorrhagic, e.g., due to coccidiosis or Klebsiella, or green, e.g., due to rotavirus)

• Abnormal feces (jelly-like mucus with mucoid enteropathy, dysautonomia)

• Lack of feces (gut stasis, occasionally mucoid enteropathy, dysautonomia)

• Depression

• Dehydration

• Perineal accumulations of caecotrophs (see Failure to Caecotroph)

• Anorexia, weight loss

• Abdominal distension (gastric bloat, ileus, gut stasis)

• Collapse, hypothermia

• Hepatomegaly, ascites, jaundice (E. stiedae, liver neoplasia, cysticercosis)

• Fever, diarrhea, abortions, sudden death (salmonellosis)

• Small white growths on ventral tongue (papillomatosis)

• Gut stasis, raised liver enzymes, abdominal pain (liver lobe torsion—see Hepatic Disorders)

• Soft fluctuant mass on jaw (salivary mucocele)

Investigations

1. Radiography

a. Lateral and DV. Normal rabbit abdomen very variable in appearance

b. Contrast studies. Can be complicated by reingestion of caecotrophs

2. Microscopy

3. Parasitology

4. Gram stain

5. Staining/cytology

6. Routine hematology and biochemistry

a. Slightly raised liver enzymes (cysticercosis)

7. Serologil test for rotavirus, VHD, Clostridium piliforme

8. Culture and sensitivity

9. Endoscopy

a. Gastroscopy

10. Laparoscopy

11. Ultrasonography

12. Exploratory laparotomy and biopsy

13. Postmortem

Management

1. Fluid therapy (see Nursing Care)

2. High-fiber diet

3. May need to syringe feed

4. Probiotics

a. May be of benefit—the natural low pH of the rabbit stomach may reduce the amount of probiotics gaining access to the large intestine/cecum.

b. Transfaunation, using caecotrophs from a healthy rabbit, may help natural gut flora to reestablish.

5. Only use antibiotics if indicated. Many cases do not require their use, which can be counterproductive.

6. Gut motility modifiers

a. Metoclopramide at 0.5 mg/kg SC or PO every 6 to 8 hours

b. Cisapride 0.5 mg/kg PO s.i.d. or b.i.d.

7. Analgesics can be necessary but avoid those likely to exacerbate gastrointestinal tract ulceration (e.g., flunixin).

TreatmentZspecific therapy

1. Salivary mucocele

a. Drain aseptically as required.

b. Should heal spontaneously

c. Likely to be due to trauma, but radiograph skull to assess for underlying pathologies such as dental disease.

2. Rotavirus

a. Usually just in young rabbits

b. Supportive treatment

3. Papillomatosis

a. Covering antibiotics and analgesia if required. Usually self-limiting (Supplement with long fiber (grass and hay)

• Copper deficiency

• Anemia in weanlings, decreased growth, hair loss, dry scaly skin, and graying of black hairs

• Recommended daily intake is 2.7 mg, and foods should have an absolute minimum of around 8 mg copper/kg

• Excess calcium intake

• Calcium levels are readily responsive to dietary levels, and there is a theoretical risk of hypercalcemia. This has been linked to urolithiasis and arteriosclerosis.

• Total calcium 3.0 to 4.0 mmol/L; ionized 1.57 to 1.83 mmol/L

Hepatic disorders

Viral

• VHD (calicivirus—see Systemic Disorders)

Bacterial

• Bacterial hepatitis

Protozoal

• Eimeria stiedae

Parasitic

• Cysticercosis

Nutritional

Hepatic lipidosis

Aflatoxicosis

Neoplasia

• Bile duct adenoma

• Bile duct adenocarcinoma

• Metastatic spread of uterine adenocarcinoma

Other noninfectious problems

• Heart disease (see Cardiovascular Disorders)

• Liver lobe torsion

Findings on clinical examination

• Reduced or loss of appetite

• Vague signs of ill health

• Abnormal feces

• Hepatomegaly

• Jaundice

• Ascites

Investigations

1. Radiography

a. Hepatomegaly

b. Ascitic fluid

2. Routine hematology and biochemistry

a. Raised liver enzymes

b. Raised alkaline phosphatase, aspartate transaminase, and alanine transaminase associated with painful anterior abdomen, and occasional borborygmi (liver lobe torsion); pallor of mucous membranes

3. Culture and sensitivity

4. Cytology

5. Peritoneal tap

6. Endoscopy

7. Laparoscopy

8. Ultrasonography

9. Biopsy

10. Postmortem

a. Demonstration of E. stiedae oocysts from characteristic yellow-colored liver lesions or distended bile ducts

11. Feed analysis—food concentrations of aflatoxin B₁ >100 ppm are toxic.

Management

1. Fluid therapy (see Nursing Care)

2. Lactulose at 0.5 mL/kg PO b.i.d.

3. Milk thistle (Silybum marianum) is a hepatoprotectant. Dose at 4 to 15 mg/kg PO b.i.d. or t.i.d.

TreatmentZspecific therapy

• Bacterial hepatitis

• Appropriate antibiosis

• E. stiedae

• Usually seen in rabbits younger than age 12 to 14 weeks

• Toltrazuril at 7.0 mg/kg PO daily for 2 days. Repeat after 12 days.

• Co-trimoxazole at 30 mg/kg PO b.i.d.

• Often have concurrent gastric bloat and gut stasis, so treat as in Gastrointestinal Tract Disorders.

• Improve hygiene to prevent ingestion of contaminated feces.

• Cysticercosis

• Praziquantel at 5 mg/kg SC or PO one off treatment

• Regular worming of in-contact dogs and cats

• Neoplasia

• No treatment

• Liver lobe torsion

• Stabilization and lobectomy

Pancreatic disorders

Noninfectious problems

• Diabetes mellitus (see Endocrine Disorders)

Cardiovascular disorders

Viral

• Coronavirus (pleural effusion/dilated cardiomyopathy [DCM])

Bacterial

• Pericarditis and endocarditis (especially Pasteurella, Staphylococcus spp., Salmonella spp., and Streptococcus viridans)

Protozoal

• Encephalitozoon cuniculi (myocarditis)

• Trypanosoma cruzi (ventricular hypertrophy and dilatation)

Nutritional

• Hypovitaminosis E (myocardial muscular dystrophy)

Neoplasia

• Thymomas (exophthalmos)

Other noninfectious problems

• Congenital

• Ventricular septal defects

• Atrial septal defects

• Valvular cysts

• Hypertrophic cardiomyopathy

• DCM

• Bicuspid valve insufficiency

• Mitral valve insufficiency

• Coronary atherosclerosis

• Doxorubicin administration (DCM)

• Alpha agonist drugs (myocardial fibrosis)

• Catecholamines (coronary vasoconstriction with resultant myocardial fibrosis)

• Arteriosclerosis (possibly linked to hypercalcemia)

• Atherosclerosis (possibly linked to hyperlipidemia)

Findings on clinical examination

• Cyanosis or pallor of the mucous membranes

• Slow capillary refill time

• Exophthalmos (venous congestion of retrobulbar venous plexus)

• Dyspnea (normal respiratory rate = 30 to 60/min)

• Precordial thrill

• Arrhythmia (normal rate = 180 to 250 beats/min; excited healthy rabbits increase to

330 beats/min)

• Lack of thoracic percussion with auscultation

• Abnormal lung sounds

• Abnormal heart sounds

• Exercise intolerance

• Ascites

• Weight loss

Investigations

1. Routine hematology and biochemistry

a. Renal and hepatic parameters may be raised due to congestion and/or poor perfusion.

b. Raised cholesterol (0.1 to 2.0 mmol/L) and triglycerides (2.67 to 4.29 mmol/L)

2. E. cuniculi serology

3. Blood plasma K-tocopherol (vitamin E). Should be >0.5 pg/mL

4. Blood calcium (total calcium 3.0 to 4.0 mmol/L; ionized 1.57 to 1.83 mmol/L)

5. Serology for coronavirus

6. Pleural tap

a. Cytology of effusions

7. ECG

a. P waves are positive in standard limb leads

b. Normal ECG values (from Reusch and Boswood 2003, see Table 2-6)

8. Radiography

a. Lateral and DV views

b. Note that thymus is persistent into adulthood

c. Lateral view: normal heart around two rib spaces; 2.5 to 3 rib spaces suggests cardiomegaly (Fig. 2-12)

9. Echocardiography

a. Normal values for echocardiographic parameters in rabbits (from Marini et al 1999, see Table 2-7)

Fig 2-12. Cardiomegaly.

10. Table 2-8 (Fontes-Sousa et al 2006) gives these values for 2-dimensional, M-mode, and Doppler echocardiographic variables in male New Zealand white rabbits anesthetized with a combination of ketamine and medetomidine.

11. Blood pressure (cited in Reusch 2005, Table 2-9)

Management

1. Reduce stress (e.g., keep in a cool, shaded or darkened area away from dogs, cats, ferrets, and other “predators”).

2. Monitor closely—diuretics can produce dehydration, which in rabbits can present as a gastric or cecal impaction.

3. Supply oxygen.

TreatmentZspecific therapy

• Cardiomyopathy

• Taurine at 100 mg/kg s.i.d. PO for 8 weeks

• Arrhythmias

• Digoxin at 0.003 to 0.03 mg/kg PO every 12 to 48 hours

• Lidocaine 1 to 2 mg/kg IV or 2 to 4 mg/kg IT

• Congestive heart failure

• Furosemide 0.3 to 4 mg/kg PO, SC, IM, or IV s.i.d. or b.i.d.

• Enalapril 0.1 to 0.5 mg/kg PO every 24 to 48 hours. Beware hypotensive side effects.

• Nitroglycerin ointment (2%) at 3 mm applied topically to the inner pinna every 6 to 12 hours

• Other medications

• Atenolol 0.5 to 2 mg/kg PO s.i.d.

• Verapamil 0.2 mg/kg PO, SC, or IV t.i.d.

• Diltiazem 0.5 to 1 mg/kg PO b.i.d. or s.i.d.

• Atropine 0.05 to 0.5 mg/kg SC or IM. Note that rabbits have high tissue and serum atropinase levels.

• Glycopyrronium (glycopyrrolate) 0.01 to 0.1 mg/kg SC, IM, or IV

• Pimobendan at 0.2 mg/kg PO s.i.d.

• Benazepril at 0.1 to 0.5 mg/kg PO s.i.d. Note that rabbits appear very susceptible to the hypotensive side effects of benazepril.

• Enalapril 0.25 to 0.5 mg/kg PO every 24 to 48 hours

Systemic disorders

Viral

• VHD, calicivirus.

Bacterial

• Salmonellosis

Neoplasia

• Lymphosarcoma/lymphoma (Gomez et al 2002)

Other noninfectious problems

• Hypoglycemia (especially with chronic dental disease)

• Heatstroke

• Pregnancy toxemia/ketosis

• Severe cardiovascular disease

Findings on clinical examination

• Anorexia: A recent history of anorexia (e.g., with dental disease or other ill health) suggests hypoglycemia or ketosis.

• Weight loss/poor physical condition

• Marked dental disease

• Lethargy

• Ataxia, convulsions (ketosis)

• Collapse

• Pale mucous membranes (lymphosarcoma)

• Hyperthermia (>40.5° C) (heatstroke)

• Lymphadenopathy (lymphosarcoma)

• Tachypnea/dyspnea (heatstroke, lymphosarcoma)

• Obesity (ketosis)

• Late pregnancy (pregnancy toxemia)

• Acute onset epistaxis and/or respiratory signs and/or diarrhea (VHD)

• High mortalities (VHD)

• Fever, diarrhea, abortion, sudden death (salmonellosis, VHD)

• Dyspnea

Investigations

1. Radiography

2. Routine hematology and biochemistry

a. WBC count and differential

b. Blood glucose levels (normal glucose 4.2 to 8.2 mmol/L)

c. Ketosis

3. Serology for VHD

4. Urinalysis

a. Ketonuria (ketosis/pregnancy toxemia)

b. Aciduria (pH 5 to 6—ketosis)

5. Culture and sensitivity

6. Cytology

7. Bone marrow aspirate/biopsy

8. Laparoscopic endoscopy

9. Ultrasonography

10. Biopsy

a. Multiorgan biopsies for lymphosarcoma

11. Necropsy

a. Hepatic necrosis, hemorrhagic viscera (VHD)

b. Hepatomegaly, splenomegaly, mesenteric lymphadenopathy (lymphosarcoma)

Management

1. Supportive therapy—parenteral fluids, assisted feeding

2. May require additional heat if recumbent

TreatmentZspecific therapy

• Lymphosarcoma

• The author has found that a chemotherapy regimen, modified from that used for ferrets (Brown 1997), can be beneficial (Table 2-10).

• Hypoglycemia

• IV glucose by bolus and infusion

• Assisted feeding

• Hepatic lipidosis/ketosis/pregnancy toxemia

• Aggressive fluid therapy

• Parenteral nutrition with glucose and vitamins

• Assisted feeding either by syringe or nasogastric tube. Calcium gluconate PO or propylene glycol PO may be of use.

• Dexamethasone at 0.2 mg/kg IV, SC, or PO once only. Repeat doses may immune compromise.

• Heatstroke

• Monitor core body temperature.

• Cool (not cold) body (e.g., damp towels, water bath)

• Dexamethasone at 2 to 4 mg/kg IV once only

• Supportive treatment such as cool IV fluids; heatstroke may have unforeseen sequelae (e.g., gut stasis).

• VHD: Supportive treatment only

• Environmental cleaning with 0.5% sodium hypochlorite will inactivate virus.

• Virus can survive for some time in the environment and can be carried on fomites.

• Vaccine available; recommended annual vaccination. Vaccinated rabbits can develop a subclinical infection.

Neuromuscular disorders

Viral

• Herpes simplex

• Rabies

Bacterial

• Pasteurellosis (otitis media/interna, encephalitis)

• Other bacteria frequently isolated from otitis media are Staphylococcus aureus and Bordetella bronchiseptica.

• Discospondylitis

• Osteomyelitis

• Listeria monocytogenes

Protozoal

• E. cuniculi

• Toxoplasma gondii

• Sarcocystis (myositis)

Parasitic

• Baylisascaris procyonis

• Other aberrant migrant parasites (e.g., Ascaris spp.)

• Psoroptes cuniculi (predisposes to otitis media)

Nutritional

• Hypovitaminosis A (hydrocephalus and other CNS defects)

• Hypovitaminosis E (muscular dystrophy)

Neoplasia

• Osteosarcomas

• Osteochondromas

• CNS metastases

Other noninfectious problems

• Trauma

• Vertebral fracture—typically L6 or L7

• Other fractures

• Electrocution (lumbar or pelvic fractures following spasm of lumbar musculature)

• Intervertebral disc disease

• Metastatic calcification of cerebral vasculature/arteriosclerosis

• Atherosclerosis

• Splay leg—autosomal recessive defect (unable to adduct one or more limbs, accompanies distortion of joints and long bones)

• Idiopathic epilepsy

• Intoxication

• Heavy metals

• Fertilizers, herbicides, insecticides

• Fipronil application

Findings on clinical examination

• Otitis media/externa (see also “Ear Mites” in Skin Disorders)

• Mild head tilt or torticollis

• Nystagmus (only in acute disease)

• Extreme twisting of the body along the longitudinal axis.

• Hind-limb paresis or paralysis

• Paresis or paralysis of one or more legs

• Seizures

• Anorexia

• Fever (>40° C), oculonasal discharge, increased respiratory rate (toxoplasmosis)

• Ophthalmic disease (see Ophthalmic Disorders)

Investigations

1. Neurologic examination

2. Radiography

a. Skull—check tympanic bullae

b. Lateral and DV spinal radiographs

c. Myelography

d. Ingested metal in gut

3. Routine hematology and biochemistry

a. Triglycerides and cholesterol for atherosclerosis

b. Blood lead levels; basophilic stippling of RBCs

4. Serology for E. cuniculi, T. gondii, Pasteurella, Sarcocystis, and rabies

5. Culture and sensitivity

a. Swab if perform bulla osteotomy

6. Cytology from CSF tap (Table 2-11)

Collection of CSF

• Collect as from the cat.

• Undertake ventral flexion of neck.

• Collect from the atlantooccipital joint, using a 22G needle, and direct toward nose.

7. Toxicology

8. Endoscopy of ear canal

9. Ultrasonography

10. Exploratory laparotomy

11. Biopsy

Management

1. May require food and fluid support if unable to feed. Consider fluid therapy, syringe feeding, or nasogastric tube.

2. Supportive harnesses may be useful where there is hind-limb paresis/paralysis.

3. Nursing care to prevent pressure sores, urine scalding, and perineal caecotroph accumulation

TreatmentZspecific therapy

• Otitis media: Treat with appropriate antibiotics, both topical and systemic. Ensure eardrum is intact before treatment.

• Otitis interna

• Covering antibiotics

• May require bulla osteotomy. Swab for culture and sensitivity if so.

• E. cuniculi

• Co-trimoxazole at 30 mg/kg b.i.d. PO for at least 3 weeks

• Albendazole at 10 mg/kg PO s.i.d. for 6 weeks

• Fenbendazole at 10 to 20 mg/kg PO s.i.d. for 1 month

• Also treatment protocol for Toxoplasma effective (see “T. gondii”)

• T. gondii

• Combination therapy consisting of:

- Co-trimoxazole at 30 mg/kg PO b.i.d.

- Pyrimethamine at 0.5 mg/kg PO b.i.d.

- Folic acid at 3.0 to 5.0 mg/kg PO s.i.d.

• Rabbits with acute toxoplasmosis have congested tissues and marked splenomegaly.

• Avoid access to soil/food contaminated with Toxoplasma oocysts.

• Sarcocystis

• Treat with co-trimoxazole and pyrimethamine at Toxoplasma dose rates.

• The Virginia opossum is the primary host; cockroaches can act as paratenic hosts.

• Baylisascaris procyonis

• Adults found in raccoon (Procyon lotor)

• Attempt treatment with fenbendazole at 20 mg/kg PO daily for 5 days, plus supportive therapy. Consider euthanasia.

• Vertebral fracture usually requires euthanasia.

• Other fractures, especially long-bone fractures, usually respond well to orthopedic procedures. Because they are relatively light, external fixation techniques are especially useful providing chewing can be avoided.

• Intervertebral disc disease

• Spondylitis—antibiotics and NSAIDs (e.g., meloxicam at 0.3 mg/kg PO s.i.d.)

• Intervertebral disc prolapse—may require surgery (e.g., disc fenestration); guarded prognosis

• Metastatic calcification of cerebral vasculature/arteriosclerosis

• Guarded prognosis. Consider cerebral vasodilators such as nicergoline and propentofylline

• Atherosclerosis

• Switch to a lower fat/carbohydrate diet.

• Toxin ingestion

• Supportive therapy. Antidote if applicable (e.g., calcium EDTA for lead poisoning at 27.5 mg/kg q.i.d. IM for 5 days; repeat after week if required)

• Fipronil application

• Supportive therapy only

• Rabies: euthanasia

• Idiopathic epilepsy/control of seizures

• Phenobarbital at 1 to 4 mg/kg PO every 8-12 hours

Ophthalmic disorders

The rabbit eye differs from that of carnivores in several respects. A tapetum is absent, and there is a merangiotic retina with a horizontal band of myelinated nerve fibers and blood vessels. These provide a horizontal, photoreceptor-rich, macula-like region. It may be that, combined with lateral positioning of eyes, a band of high-resolution vision across the whole horizon is produced. There is a large ventral retrobulbar venous sinus, which can cause serious intraoperative complications during enucleation.

Differential diagnoses of ocular disorders

Viral

• Myxomatosis

Bacterial

• Retrobulbar abscess (often secondary to dental disease)

• Staphylococcus spp., Pasteurella, Haemophilus

• Treponema cuniculi

Protozoal

• E. cuniculi (uveitis)

Neoplasia

• Thymoma

Other noninfectious problems

• Glaucoma in New Zealand white rabbits (autosomal recessive disorder)

• Corneal occlusion syndrome—aberrant covering of cornea by conjunctiva

• Entropion

• Foreign bodies

• Diabetes mellitus (cataracts)

Findings on clinical examination

• Ulceration

• Severe blepharitis and whitish ocular discharge (myxomatosis). Look for other signs of myxomatosis (see Skin Disorders).

• Conjunctivitis (distinguish from dacryocystitis)

• Dacryocystitis is common in rabbits (often secondary to dental disease as the nasolacrimal duct runs close to roots of incisor teeth and premolars).

• Microabscesses in eyelid margins—often a sequel to severe or chronic periocular infection

• Nasal discharge

• Uveitis

• Corneal edema, hypopyon, and synechiae; may see large iridial abscesses; occasionally secondary cataracts

• Exophthalmos

• Third eyelid may be prolapsed and swollen

• Megaglobus/glaucoma

• Cataracts

Investigations

1. Ophthalmic examination

a. Conjunctivitis is common in rabbits, often associated with dacryocystitis. Differentiate from dacryocystitis by cannulation of nasolacrimal duct (single ventral nasolacrimal punctum at medial canthus) (Fig. 2-13).

b. Topical fluorescein to assess extent of ulceration (Fig. 2-14)

2. Schirmer tear test 2.0 to 11.0 mm/min (Biricik et al 2005)

3. Phenol red thread test 15 to 27 mm/15 seconds

4. Tonometry

a. Normal intraocular pressure is 15 to 23 mm Hg. With hereditary glaucoma in New Zealand white rabbits it is 26 to 48 mm Hg.

5. Radiography

a. Assess tooth roots for underlying dental disease.

b. Contrast studies of nasolacrimal duct to determine if occluded

6. Cannulate and flush the nasolacrimal duct to collect sterile samples for culture, sensitivity, and cytology if appropriate.

7. Ultrasonography

Fig 2-13. Proliferative lymphatic tissue response of the conjunctiva in chronic dacryocystitis.

Fig 2-14. Fluorescein-positive corneal ulcer in a rabbit with keratitis.

TreatmentZspecific therapy

• Corneal ulceration

• Topical and systemic antibiosis

• Once infection cleared, treat as for other small animals (e.g., scarification to encourage healing, conjunctival grafts). Note that third eyelid may not cover whole cornea if attempt a third eyelid flap

• Dacryocystitis

• Topical ophthalmic antibiotic preparations. Conjunctival bacterial flora can be both gram-positive and gram-negative, so select antibiotic according to sensitivity results.

• Regularly cannulate and flush the nasolacrimal ducts.

• Incisor or premolar extraction if linked to nasolacrimal disease

• Encephalitozoon cuniculi

• Can cause cataracts or even lens capsule rupture, producing a phacoclastic uveitis

• Co-trimoxazole at 30 mg/kg b.i.d. PO for at least 3 weeks

• Albendazole at 10 mg/kg PO s.i.d. for 6 weeks

• Fenbendazole 10 to 20 mg/kg PO s.i.d. for 1 month

• Combination therapy consisting of:

- Co-trimoxazole at 30 mg/kg PO b.i.d.

- Pyrimethamine at 0.5 mg/kg PO b.i.d.

- Folic acid at 3.0 to 5.0 mg/kg PO s.i.d.

• Consider lens removal, preferably by phacoemulsification

• Retrobulbar abscess

• Start on antibiotics—treat for anaerobic as well as aerobic (see under “Treatment/ specific therapy” in Dental Disorders).

• Remove affected teeth.

• May require enucleation. Hemorrhage is likely to be a significant complication due to the large retrobulbar abscess.

• Dental disease: Treat as under Dental Disorders.

• Corneal occlusion syndrome: Surgery and topical cyclosporine

• Diabetes mellitus (see Endocrine Disorders)

Endocrine disorders

• Diabetes mellitus

• Adrenal disease

• Hypertestosteronism in castrated males secondary to adrenal hyperplasia/neoplasia

Findings on clinical examination

• Sudden-onset cataracts

• Polydipsia

• Polyuria

• Weight loss despite good appetite

• Increased aggression and sexual behavior in castrated male rabbits

(hypertestosteronism)

Investigations

1. Radiography

2. Routine hematology and biochemistry

a. High blood glucose usually associated with stress (see Use of Glucose and Sodium as Prognostic Indicators in the Rabbit); for diabetes mellitus, correlate with glycosuria, polydipsia, and polyuria. Normal glucose is 4.2 to 8.2 mmol/L.

b. Normal rabbit fructosamine is 289 to 399 pmol/L.

ACTH stimulation test

• Cortisol (resting) 1.0 to 2.04 μg∕dL

• Qive ACTH at 6.0 μg∕dL IM.

• Resample after 30 minutes; cortisol 12.0 to 27.8.

• Note that corticosterone is the principal adrenocortical hormone in rabbits, with an approximate ratio of 20: 1 corticosterone : cortisol.

3. Blood testosterone levels

a. Normal intact New Zealand white rabbits (reported in Lennox and Chitty 2006) = 0.51 to 9.16 ng/mL. Castrated males have significantly lower testosterone levels >0.1 ng/mL.

4. Urinalysis—should be glucose negative, but glycosuria can also occur after periods of stress and certain diseases (e.g., ketosis)

5. Cytology

6. Endoscopy

7. Ultrasonography

8. Biopsy

TreatmentZspecific therapy

• Diabetes mellitus

• Insulin is not usually required.

• Maintain on a high-fiber, low-carbohydrate diet.

• Hypertestosteronism secondary to adrenal hyperplasia/neoplasia

• Adrenalectomy

• Trilostane

• The poor result of trial treatment with leuprolide acetate described in Lennox and Chitty (2006) suggests that hormonal antagonism as a treatment is likely to be of limited value.

Urinary disorders

Bacterial

• Pyelonephritis (Staphylococcus aureus, Pasteurella multocida)

• Cystitis (S. aureus, P. multocida)

Protozoal

• E. cuniculi

Nutritional

• Urolithiasis (usually combined with a cystitis)

• Renal calcinosis (hypercalemia, hypervitaminosis D)

• Fatty degeneration

Neoplasia

• Embryonal nephroma

• Renal carcinoma

• Renal leiomyoma

Other noninfectious problems

• Congenital abnormalities

• Renal

• Inguinal hernias

• Poor mobility (e.g., discospondylitis) contributes to calciuria/urolithiasis

• Hemolytic anemias

• Nephrotoxic drugs (gentamicin, zolazepam)

Findings on clinical examination

• Polydipsia, polyuria

• Urinary tenesmus

• Apparent hematuria (uterine adenocarcinoma, endometrial venous aneurysms, porphyrinuria). Differentiate from porphyrinuria by either urinalysis dipstick test or expose to ultraviolet light: porphyrins fluoresce a purple-like color.

• Anorexia

• Depression

• Urolithiasis

• Sandlike material in the urine

• Small stones present in the urine or lodged in the penis

Investigations

1. Urinalysis (Table 2-12)

a. Culture and sensitivity

b. Sediment examination/cytology

2. Urolith analysis

3. Radiography

a. Uroliths or calciuria in the renal pelvices, ureters, bladder, or urethra

b. Radiodense lesions in the kidney (E. cuniculi)

c. Intravenous urograms

4. Routine hematology and biochemistry

a. Renal parameters may be raised (i.e., raised urea, creatinine, calcium, phosphate, and potassium)

5. Serology for E. cuniculi, Pasteurella

6. Endoscopic laparotomy

7. Ultrasonography

8. Exploratory laparotomy

9. Biopsy

Management

1. Fluid therapy if appropriate

2. Consider whether diet is too high in calcium; dietary modification alone unlikely to resolve or prevent recurrence of excess sand/urolithiasis.

TreatmentZspecific therapy

• Acute and chronic renal failure

• Fluid therapy

• Daily fluid maintenance requirement for a rabbit is 100 mL/kg per day.

• Recommended approximate volumes for fluid replacement therapy (mL) are 10 to 15 mL/kg SC in divided sites or 15 mL/kg IR Fluids can also be given IV either by bolus or by infusion.

• Pyelonephritis

• Appropriate antibiosis (avoid aminoglycosides and other known nephrotoxic drugs)

• Fluid therapy

• Calciuria

• Catheterization and flushing of the bladder under anesthetic may work.

• Cystotomy, removal of sand, and flush

• Urolithiasis

• Surgery to remove stones (White 2001)

• Antibiosis as it is often accompanied by cystitis

• E. cuniculi

• Co-trimoxazole at 30 mg/kg PO b.i.d. for at least 3 weeks

• Albendazole at 10 mg/kg PO s.i.d. for 6 weeks

• Fenbendazole at 10 to 20 mg/kg PO s.i.d. for 1 month

Reproductive disorders

Viral

• Myxomatosis (see Skin Disorders)

Bacterial

• Pasteurella

• Staphylococcus

• Streptococcus

• Mycoplasmosis (especially Mycoplasma pulmonis)

• Enteric bacteria

• Leptospira interrogans (Boucher et al 2001)

• Rabbit syphilis (Treponema cuniculi)

Nutritional

• Hypovitaminosis A (see Nutritional Disorders)

• Hypovitaminosis E (see Nutritional Disorders)

Neoplasia

• Uterine adenocarcinoma (common in entire does over age 3 to 4 years) (Fig. 2-15)

• Testicular neoplasia (Bucks age 5+ years)

• Ovarian tumors

• Mammary adenocarcinomas

• Hypertestosteronism (see Endocrine Disorders)

Other noninfectious problems

• Ovarian cysts

• Endometrial hyperplasia

Fig 2-15. Uterine adenocarcinoma.

• Uterine polyps

• Vaginal prolapse

• Uterine torsion

• Hydrometra

• Pseudopregnancy

• Dystocia

• Cystic mastitis (may progress to mammary adenocarcinomas)

Findings on clinical examination

• Septic mastitis: swollen, painful mammary glands; abnormal milk

• Cystic mastitis: glands swollen, firm, not painful; may have a clear or serosanguineous discharge

• High temperature

• Anorexia

• Vaginal discharge

• Apparent hematuria (uterine adenocarcinoma, endometrial venous aneurysms, porphyrinuria)

• Pyometra

• Enlarged palpable viscus (pyometra, uterine adenocarcinoma)

• Epididymitis

• Orchitis

• Vesicles, ulcers, and crusty lesions on the external genitalia; may also be present at the mouth and nares (T. cuniculi)

• Poor reproductive performance

• Increased aggression and sexual behavior in castrated male rabbits (hypertestosteronism)

Investigations

1. Radiography

a. Include thoracic radiographs for metastases from uterine or mammary adenocarcinomas

2. Routine hematology and biochemistry

3. Serology for T. cuniculi, Mycoplasma pulmonis

4. Culture and sensitivity

5. Cytology

6. Endoscopy

7. Laparoscopy

8. Ultrasonography

9. Exploratory laparotomy

10. Biopsy

TreatmentZspecific therapy

• Rabbit syphilis (see Skin Disorders)

• Mastitis

• Septic mastitis (typically Staphylococcus, Pasteurella, and Streptococcus spp.)

- Appropriate antibiosis

- Supportive care including parenteral fluids, analgesia, fostering or hand rearing of young

- Surgical mastectomy

• Cystic mastitis

- Ovariohysterectomy

- Surgical mastectomy as may progress to adenocarcinomas)

- Can be associated with uterine hyperplasia and adenocarcinoma

• Metritis and pyometra (typically Pasteurella, mycoplasmosis; occasionally T. cuniculi and enteric bacteria)

• Appropriate antibiosis

• Supportive care

• Ovariohysterectomy

• Endometrial venous aneurysms

• Ovariohysterectomy

• Orchitis, epididymitis

• Appropriate antibiosis

• Castration

• Uterine adenocarcinoma

• Ovariohysterectomy

• Very poor prognosis if metastatic spread

• Can be seen in neutered females if significant uterine stump remains

• Recommend routine ovariohysterectomy at 4 months of age

• Deslorelin implants may prove to be preventative.

• Ovarian tumors or cysts

• Ovariohysterectomy

• Testicular neoplasia

• Castration

• Vaginal prolapse

• Fluid therapy

• Surgical replacement or resection of prolapse

• Consider ovariohysterectomy

• Pseudopregnancy

• Will usually resolve spontaneously within 2 to 3 weeks

• Hormonal treatment (e.g., proligestone at 10 to 30 mg/kg SC once only)

• Cabergoline at 5 pg/kg PO s.i.d. for 4 to 6 days

• Dystocia

• If no obvious obstruction, oxytocin at 1 to 2 IU IM or SC

• Uterine inertia: 5 to 10 mL 10% calcium gluconate PO 30 min prior to oxytocin

• Cesarean section