Musculoskeletal Disease in Small Mammals and Exotic Species Flashcards
What underlying husbandry causes can cause muskulotskeletal disease in small mammals, reptiles and birds?
Small mammals
- Inside or outside?
* Any recent changes?
* Trauma?
* Diet?
* Flooring?
* Space?
Reptiles
* Vivarium, draw or table?
* Temperatures?
* Diet and supplements?
* Any recent changes?
* Trauma?
* Bathing?
* Substrate?
Birds
* Where is the cage?
* Diet?
* UV?
* Recent changes?
* Trauma?
* Space/flying?
* Flooring?
What clinical signs are associated to musculoskeletal disease in small mammals, reptiles and birds?
Small mammals
* Anorexia, lethargy, hiding
* Wounds +/- fly strike
* Gut stasis (hind gut fermenter)
* Not eating caecotrophs/cleaning rear end
* Hunched stance
* Urine staining
* Bruxism/teeth grinding
* Aggression or being bullied
* Weakness or limping on one or more legs
Reptiles
* Can be very subtle even with severe fractures.
* Abnormal stance and gait.
* Often may just seem more lethargic.
* Deformity of spine and limbs +/- generalised limb swelling
* Wounds
* Swollen joints
* Weakness or limping on one or more legs
Birds
* Clinical signs can be very subtle, even severe fractures.
* Abnormal or wide stance +/- reduced grip.
* May use beak or ipsilateral wing for support.
* Affected leg may feel warmer.
* Bumblefoot on contralateral limb.
* Weakness or limping on one or more legs
What are disease categories for musculoskeletal disease in exotics?
Musculoskeletal diseases:
Similar to other species e.g. degenerative joint disease, infection and neoplasia.
Metabolic and nutritional causes of disease:
More common compared to dogs and cats
Trauma:
From cage mates, other pets and owners.
What should be your diagnostic plan when investigating musculoskeletal disease in exotics?
Imaging
First line: radiographs, ultrasound
Referral: arthroscopy, CT and MRI
Blood work
Biochemistry for underlying causes (include ionised calcium!)
Haematology to look for dehydration, infection or blood loss.
Joint fluid analysis
Infection or gout etc
Cytology
Joint aspirates, mass FNAs
Culture and sensitivity
Joint infections, wounds.
Biopsy histopathology
Bone or soft tissue
What are the common primary and secondary MSK problems in rabbits?
Primary
* Pododermatitis/bumblefoot
* Degenerative joint disease e.g. stifles and spine.
* Spinal deformities and injuries.
* Fractures e.g. spine, limbs.
* Osteomyelitis
* Luxation e.g. hip, elbow and tarsus
* Primary neoplasia e.g. osteosarcoma.
* Splay leg e.g. genetic or trauma
Secondary
* Abscesses: bite wounds -> systemic spread to joints (septic arthritis)
* Metastatic neoplasia e.g. uterine adenocarcinoma.
* Nutritional Secondary Hyperparathyroidism (NSHP): Muesli mix, lack of UV-B.
* Renal failure -> hypercalcaemia -> soft-tissue calcification and bone hypercalcification.
* Encephalitozoon cuniculi (parasitic) -> hind limbs paresis.
What are the most common causes for fractures in rabbits?
Fractures often occur when rabbit is dropped or jumps from height.
* Rabbits tend to make sudden, surprise escape attempts.
* Jaw fractures commonly occur but are easily over looked.
Fractures secondary to disease
- osteosarcoma
- metastasis of uterine adenocarcinomas
Why do spinal deformities occur in rabbits? What are the consequences?
Spondylosis, kyphosis, lordosis and scoliosis all occur quite commonly.
Why?
Small cages and lack of exercise are risk factors
Consequences
* May interfere with locomotion, caecotrophy, urination and grooming; often incidental finding.
* May result in faecal soiling, urine scald, unkempt coat, Cheyletiella, facial dermatitis and gut stasis due to pain.
What are common MSK problems in rodents?
- Pododermatitis is common in guinea pigs, chinchillas and rats.
- Overgrown claws and keratin horns in guinea pigs -> lameness.
- Metastatic calcification -> degenerative joint disease in guinea pigs.
- Fractures are relatively common in chinchillas and hamsters e.g. dropped or entrapped in cage bars or exercise wheel.
What are common MSK problems in ferrets?
- Hindlimb paresis is a common but often due to non-musculoskeletal diseases e.g. hypoglycaemia or cardiomyopathy.
- Trauma e.g. long bone fractures
- Luxation e.g. elbow
- Abscessation of the spine
Note: walking with arched spine is normal for a ferret
What are common primary and secondary MSK problems in birds?
Primary
* Trauma e.g. long bone fractures (often compound/open). Coracoid fractures and spinal injury (head on collision). Tethers that are too long on falconry birds will cause fractures to the tibiotarsus when they take off.
* Pododermatitis/bumblefoot
* Nutritional secondary hyperparathyroidism (NSHP).
* Osteomyelitis & septic arthritis
* Osteoarthritis, often in older birds +/- injury.
* Tenosynovitis & tendon injury e.g. infection, bites, equipment rubbing.
* Growth deformities e.g. osteodystrophy, luxated gastrocnemius tendon
* equipment injuries - need general anaesthesia when removing leg rings to avoif iatrogenic fractures
Secondary
- Kidney disease and gout
- Viral (marek’s disease in chickens)
- Egg binding
- Lead poisoning
Why does pododermatitis occur in birds and small mammals? How is it investigated?
- Pressure-sore on the plantar surface of foot often due to poor blood circulation.
- Allows entry of infection which may progress to osteomyelitis.
- Poor perching surfaces (birds) or substrates/flooring (small mammals) +/- trauma, poor hygiene, obesity, hypovit A
- Important to examine and radiograph both limbs
- until grade 3 - medical management is enough
- above grade 3 - surgical debridement is needed and prognosis is poorer
What are common primary and secondary MSK problems in reptiles?
Primary
* Luxation
* Tendon/ligament injury or infection
* Spinal injury e.g. trauma, NSHP, burns
* Septic arthritis/osteomyelitis (remember they have solid pus!
Secondary
* Fractures: Commonly due to NSHP/RSHP (MBD)
* Gout
Space occupying
* Pre- and post-ovulatory oostasis
* Urolithiasis (if they have bladders e.g. tortoises)
How can you treat simple fractures in reptiles?
simple fractures can be treated by splinting the affected limb against the body, tail or within the shell
What causes gout in birds and reptiles? What are the 2 types of gout?
- Birds excrete nitrogenous wastes as urates.
- Renal dysfunction decreases the clearance of uric acid from the blood -> hyperuricemia
- Hyperuricemia -> precipitation of insoluble products within the body (urate deposition or urolithiasis).
- Urate deposits are white and semisolid.
Two types of gout:
* Visceral urate deposition -> urate deposits in soft tissues.
* Articular urate deposition -> urate deposits on synovial membranes -> chronic granulomatous reaction -> Lameness
How would you treat metabolic bone disease (NSHP or RSHP)?
- Heavy external coaptation and/or surgical fixation are contraindicated with NSHP.
- Cage rest, analgesia, supplement calcium and vitamin D, provide UV-B and start to correct the diet.
- Diet changes slow and graduate in birds.
What are the general principles of treating MSK disease in small mammals and exotics?
- Most treatments are the same as cats and dogs.
- Treatment for secondary causes are covered in other year 4 lectures.
- Clean, dry, comfortable bedding e.g. cover perches in vet wrap.
- Clean wounds and in rabbits clean perineum (fly strike risk).
- Surgical fixation of fractures is often preferred but not if MBD!
- Osteomyelitis is a significant risk with exotics and small mammals with open wounds or with poor surgical technique.
- Antibiotics may be needed e.g. open wounds, joint infections.
What are the different methods of fracture repair in small mammals and exotics? What are considerations you need to take into account?
- Cage rest only (pelvis or clavicle).
- External stabilisation (if a bone is too small for internal stabilisation).
- Internal fixation (IM pins work well in avian bones).
- “Hybrid” fixation (IM pins with external skeletal fixators).
General considerations small mammals
* Casts and splints are generally contraindicated.
* External fixation is useful for most fractures.
* Rabbit bone has thin cortices -> shatters easily!
* Fractures heal quickly with appropriate fixation (6-8 weeks)
* Casts and splints are generally contraindicated.
* External fixation is useful for most fractures.
* Rabbit bone has thin cortices -> shatters easily!
* Fractures heal quickly with appropriate fixation (6-8 weeks)
General considerations birds
* Bird’s lifestyle should be considered when assess prognosis and treatment (cage bird vs. wildlife). The main aim is to restore limb function as soon as possible.
* Hybrid fixator is able to oppose axial, shear, bending, torsional and compressive forces acting on fractured. In the case of falconry birds or bird of prey wildlife casualties this is necessary.
* Higher bone mineral content, so high risk of open, comminuted fractures.
* Vertebral, pelvic, sternal and costal bones are contain the diverticula of the air sac system.
* Avian bones heal very fast (3-4 weeks).
* Surgical repair only once the patient is stabilised.
- Immobilisation of joints for more than 3-5 days may lead to permanent disability so casts and splints are generally contraindicated.
- Exceptions are distal tarsometatarsal fractures and tibiotarsal fractures in very small birds.
- Supportive body sling if trouble standing.
- External skeletal fixator + IM pin most useful
When should you consider euthanasia in birds with fractures?
- Fractures which are compound and/or close to joints carry a poor prognosis for return to normal function/release.
- Ocular damage occurs in 80% of impact injuries.
- If in doubt, stabilise, give analgesia and send radiographs to a specialist for guidance/to refer for surgery.
How would you treat grade 1-3 and grade 4-5 pododermatitis in birds and small mammals?
Grade 1-3
* Non-surgical
* Husbandry changes.
* Topical or systemic antibiotics if needed.
* Pain relief, such as an NSAID.
Grade 4-5
* Surgery needed to debride, remove the core and flush.
* Radiographs to assess bone involvement.
* Send swab/material away for culture and sensitivity.
* Dressings in birds (ball bandage/shoe bandage)
* Cannot use collars in hind gut fermenters.
* Pain relief, such as a opioids.
How is husbandry related to pododermatitis, trauma and metabolic bone disease?
Pododermatitis
* Incorrect flooring/hard perches of the same thickness
* Obesity
* Lack of exercise
* Poor Hygiene
* Nutritional deficiencies
Trauma
* Incorrect or dangerous environment e.g. wire cage.
* Incorrect or dangerous handling e.g. rabbits.
* Tethering and using equipment incorrectly.
* Poor protection from other animals e.g. wildlife or other pets.
* Unbalanced flight e.g. one sided wing clipping.
* Escaping an enclosure e.g. falling out of viv or flying out of cage.
Metabolic bone disease
* Incorrect diet +/- supplements.
* Low environmental temperatures.
* Lack of UV-B light.
What are potential limitations with MSK diseases in reptiles, birds and small mammals?
- Tendency to hide disease well.
- Normal gait varies across species.
- Patient size and demeanour can make a full clinical examination difficult or impossible.
- Sedation or general anaesthesia often required.
- Subtle lesions and even some fractures can be difficult to diagnose, especially in smaller patients.
- Equipment hard to find due to sizes and requirements.
