Case Report

By Stephanie Silberstang                      

Cornell University

Signalment: Adult Short-eared owl, undetermined sex

            Case # 702287

Common reasons for presentation of Short-eared Owls include collisions with vehicles or flying into windows. SEO opportunistically inhabit areas with small mammals, they are ground nesting birds and are also vulnerable to attacks by predators. SEO have an endangered status by the Department of Environmental Conservation.

History and clinical presentation:

The owl presented to the Wildlife Health Center on 11/21/10 after it was found on the side of the road on 11/20/10. Physical examination revealed dehydration, a thin body condition (3/9), and an open fracture of the right humerus. A contaminated wound was also present. No other abnormalities were revealed.

Presenting problems:

Open transverse fracture of the right humerus

Dehydration

Thin body condition score (3/9)

Differential diagnoses for the thin body condition included inappetence due to a metabolic disturbance, inability to apprehend food, neoplasia in the gastrointestinal tract, pain, sepsis, weakness, parasites of the gastrointestinal tract, or an inability to find food due to adverse environmental conditions.

Triage plan

Subcutaneous fluids were administered to combat dehydration and promote cardiovascular stabiliy.

Enrofloxacin was administered to treat infections of gram positive and negative organisms. This antibiotic is concentration-dependent and does not treat for anaerobic organisms.

Clindamycin is a broad spectrum antibiotic administered to treat many anaerobes, gram positive aerobic cocci, Toxoplasma and other organisms.

Butorphanol is a partial opiate agonist/antagonist used as an analgesic in birds. The action of butorphanol is thought to occur primarily at kappa and sigma receptors, which is effective for birds because they have a majority of kappa receptors. This analgesic is more effective in birds than morphine which target mu receptors.

Meloxicam is a non-steroidal anti-inflammatory drug (NSAID) administered to reduce inflammation and pain through its inhibition of cyclooxygenase, phospholipase A2, and inhibition of prostaglandin synthesis. Meloxicam is considered COX-2 preferential and should be used with care in a dehydrated animal due to the possibility of increased renal toxicity.

Diagnostic plan:

Complete blood count (CBC) and chemistry panel to determine overall health by observation of red and white blood cell morphology and relative counts, and the extent of inflammation.

Radiographs to determine the extent of the fracture and to reveal any other internal injuries the owl may have acquired.

Fecal evaluation to determine if certain internal parasites are present in the gastrointestinal tract.

The results of these tests provide initial evaluation of the owl’s status. In addition, they provide a data point for monitoring the animal over time. Blood work should be rechecked after treatment has had time to take effect to monitor for improvement or if no apparent improvement is observed. Radiographs should be repeated to check for bony callus formation that indicates proper healing of the fracture site. In birds, callus formation is expected after about 5 weeks, but a prolonged healing time is expected in open and contaminated fractures.

Results of the CBC showed a packed cell volume of 39% and a white blood cell count of 17,100/uL with 13,900/uL heterophils and no band heterophils. No toxic changes were observed. Results of the chemistry panel revealed an elevated uric acid of 16.1 mg/dL.

Results of the radiographs confirmed a mid-diaphyseal fracture of the right humerus.  

Isospora and Capillaria revealed on routine fecal examination

These results revealed a parasitic infection that was likely the primary cause of the Short-eared Owl’s thin body condition. Open mid-diaphyseal transverse fracture of the right humerus was confirmed.

Iatrogenic/Nosocomial problems:

Increased body condition score (~100 grams over average weight for female SEO)

Early signs of bumblefoot

Surgery:

This mid-diaphyseal humeral fracture was surgically repaired in an attempt to restore the owl’s ability to fly. An alternative way to manage this case would have been partial amputation of the right wing distal to the shoulder joint. This would have avoided the risks encountered in placing an IM pin including spreading infection throughout the medullary cavity and having open wounds that communicated with the medullary cavity where the ESF pins were placed. Disadvantages of this procedure would be that the owl would no longer be able to fly, although this may also be true with a repaired fracture. Prognoses for fracture repair can range from poor to excellent based on many factors. Factors such as open, comminuted, infected and fractures involving a joint decrease the prognosis. Factors such as closed, simple, aseptic fractures and fractures not involving the joint increase the prognosis. Humeral fractures in birds have a lower prognosis than in mammals because the humerus in birds is pneumatic and is in direct contact with the air sacs. If a fracture becomes infected which is common in open fractures the infection can spread into the air sacs causing air sacculitis, significantly decreasing the life expectancy of the bird. This airsacculitis can appear as a diffuse whitening of the coelomic cavity in the regions of the air sacs

Monitoring:

This owl was monitored by checking the bandage for discharge and inspecting the incision and fractures sites for any signs of infection or deterioration as should be performed with all surgical incisions . Because the humerus was repaired with an external skeletal fixation device and an intramedullary pin, inspection of the device for bending, breaking or displacement of the pins was done during routine bandage changes. The skin around the wound healed after about two weeks as was expected. This owl had an intramedullary pin that needed to be cut and removed which was performed about three weeks post-op. Radiographs are used to monitor bone healing. A bony callus is expected to be seen approximately three weeks post-op, however, this owl took longer to have a callus observed on radiographs. In addition, the radiographs also revealed poor coelomic detail with air sacculitis being the main concern. Antibiotics can be discontinued after the wound appears to be closed and healing well with no signs of infection.

References:

Plumb, Donald C. Plumb’s Veterinary Drug Handbook, 6^th Edition.  PharmaVet Inc. Stockholm, Wisconsin. 2008.

Cascades Raptor Center. “Resident Raptor- Short-eared Owl.” http://www.eraptors.org/rr_shortEaredOwl.htm. Eugene, Orgeon. 2011.

New York State Department of Environmental Conservation. http://www.dec.ny.gov/animals/7080.html.