Objective—To determine whether the reported drug-drug interaction between the flea medication spinosad and ivermectin is attributable to inhibition of P-glycoprotein by spinosad.
Animals—6 healthy adult dogs with the ABCB1 wildtype genotype.
Procedures—The study was conducted as a prospective, masked, randomized crossover design. Six dogs were allocated to 2 groups; each dog served as its own control animal. Dogs in one of the groups received spinosad at the manufacturer's recommended dose; the other group received no treatment. Forty-eight hours later, scintigraphic imaging of the head and abdomen were performed with the radiolabeled P-glycoprotein substrate methoxy-isobutyl-isonitrile (sestamibi) in both groups of dogs. After a washout period of 60 days, the dogs in each group received the alternate treatment, and scintigraphic imaging again was performed 48 hours later. Gallbladder-to-liver and brain-to-neck musculature ratios of technetium Tc 99m sestamibi were calculated for each dog and compared between treatments.
Results—No significant differences in gallbladder-to-liver or brain-to-neck musculature ratios were found between treatments.
Conclusions and Clinical Relevance—Results provided evidence that spinosad did not inhibit P-glycoprotein function 48 hours after spinosad was administered at the manufacturer's recommended dose. Further investigations will be necessary to elucidate the mechanism of the reported toxic interaction between spinosad and ivermectin.
Case Description—A 5-year-old Appaloosa mare was examined for severe left forelimb lameness of 4 months' duration.
Clinical Findings—Lameness was evident at the walk and trot and was exacerbated when the horse circled to the left. Signs of pain were elicited in response to hoof testers placed over the frog of the left front hoof, and a palmar digital nerve block eliminated the lameness. Radiographs revealed no abnormalities, but magnetic resonance imaging (MRI) revealed increased bone density in the medullary cavity of the distal sesamoid (navicular) bone in the proton density and T2-weighted images and a defect in the fibrocartilage and subchondral bone of the flexor cortex.
Treatment and Outcome—Because of the absence of improvement after 4 months and the poor prognosis for return to soundness, the mare was euthanatized. An adhesion between the deep digital flexor tendon and the flexor cortex defect on the navicular bone was grossly evident, and histologic evaluation revealed diffuse replacement of marrow trabecular bone with compact lamellar bone. Changes were consistent with blunt traumatic injury to the navicular bone that resulted in bone proliferation in the medullary cavity.
Clinical Relevance—Use of MRI enabled detection of changes that were not radiographically evident and enabled accurate diagnosis of the cause of lameness. Navicular bone injury may occur without fracture and should be considered as a differential diagnosis in horses with an acute onset of severe unilateral forelimb lameness originating from the heel portion of the foot.
OBJECTIVE To assess the effect of low-level laser therapy (LLLT) on markers of synovial inflammation and signs of pain, function, bone healing, and osteoarthritis following tibial plateau leveling osteotomy (TPLO) in dogs with spontaneous cranial cruciate ligament rupture (CCLR).
ANIMALS 12 client-owned dogs with unilateral CCLR.
PROCEDURES All dogs were instrumented with an accelerometer for 2 weeks before and 8 weeks after TPLO. Dogs were randomly assigned to receive LLLT (radiant exposure, 1.5 to 2.25 J/cm2; n = 6) or a control (red light; 6) treatment immediately before and at predetermined times for 8 weeks after TPLO. Owners completed a Canine Brief Pain Inventory weekly for 8 weeks after surgery. Each dog underwent a recheck appointment, which included physical and orthopedic examinations, force plate analysis, radiography and synoviocentesis of the affected joint, and evaluation of lameness and signs of pain, at 2, 4, and 8 weeks after surgery. Select markers of inflammation were quantified in synovial fluid samples. Variables were compared between the 2 groups.
RESULTS For the control group, mean ground reaction forces were greater at 2 and 4 weeks after TPLO and owner-assigned pain scores were lower during weeks 1 through 5 after TPLO, compared with corresponding values for the LLLT group.
CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that the LLLT protocol used had no beneficial effects on signs of pain or pelvic limb function following TPLO. Further research is necessary to evaluate the effects of LLLT and to determine the optimum LLLT protocol for dogs with CCLR.
Objective—To describe the signalment, clinical features, and most common MRI characteristics in dogs with diskospondylitis and investigate whether a correlation exists between the degree of spinal cord compression and neurologic status of the patient.
Design—Retrospective case series.
Procedures—The medical records and imaging database of the Veterinary Teaching Hospital at Washington State University were retrospectively cross-referenced for cases of diskospondylitis in dogs from 1997 through 2010. Signalment, clinical signs, MRI characteristics, and results of bacteriologic cultures of urine, blood, CSF, or intervertebral disk material were reviewed.
Results—On T2-weighted sequences, vertebral endplates were most often of mixed signal intensity, whereas the vertebral body was hypointense. The intervertebral disk space was most often hyperintense on T2-weighted and short tau inversion recovery sequences and of mixed signal intensity on T1-weighted sequences. Paravertebral soft tissue hyperintensities were noted commonly on T2-weighted and short tau inversion recovery sequences. Heterogenous contrast enhancement of endplates and intervertebral disk spaces also occurred commonly, whereas contrast enhancement of vertebral bodies and paravertebral soft tissues was uncommon. Intramedullary spinal cord intensity was noted at 10 of 27 sites on T2-weighted sequences. Static spinal cord compression occurred in 17 of 23 dogs, and a significant direct correlation was found between the percentage of spinal cord compression and the patient neurologic score.
Conclusions and Clinical Relevance—Results suggested that diskospondylitis in dogs has a characteristic MRI appearance, and in some patients, MRI may aid in the identification of severe spinal cord compression, which could warrant surgical intervention.
Objective—To assess the use of magnetic resonance
(MR) imaging for identifying subchondral bone damage
in the distal limbs of horses.
Procedure—Medical records of horses with lameness
and subsequent evidence of subchondral bone
damage as determined by MR imaging were
reviewed. Severity and duration of lameness, results
of diagnostic local anesthesia and diagnostic testing,
surgical and necropsy findings, and treatment were
recorded. Outcome was determined by follow-up
information obtained from the owner or referring veterinarian.
Results—Lameness was localized by physical examination
and diagnostic local anesthesia. Lameness was
localized to the metacarpophalangeal or metatarsophalangeal
joint in 4 horses, distal interphalangeal joint in 5
horses, and tarsocrural joint in 2 horses. The duration of
lameness ranged from 2 weeks to 20 months. Magnetic
resonance imaging of the affected joints revealed abnormal
fluid accumulation within the subchondral bone.
None of the abnormalities observed by MR imaging
were detected by radiography. Subchondral bone damage
was diagnosed in all horses. Arthroscopy of the
affected joint was performed in 4 horses. Communication
with the articular surface of the affected bone was
suspected on the basis of results of MR imaging in 4
horses and was confirmed by arthroscopy in 1 horse and
by necropsy in 1 horse.
Conclusions and Clinical Relevance—Magnetic resonance
imaging was useful for providing a diagnosis
when other imaging techniques did not definitively
identify the cause of lameness. Subchondral bone
damage was clearly identified by MR imaging and
should be considered as a cause of lameness in horses
in which radiographic findings are unremarkable.
( J Am Vet Med Assoc 2004;224:411–418)
Objective—To determine clinical signs, diagnostic
findings, and outcome for horses with desmitis of the
straight sesamoidean ligament (SSL) near its insertion
on the middle phalanx.
Procedure—Medical records were reviewed, and
information on signalment, history, clinical signs, diagnostic
findings, and treatment was obtained. Followup
information was obtained through telephone conversations
Results—In all horses, the diagnosis was made by
use of high-resolution ultrasonography. Seven horses
had moderate lameness on initial examination; lameness
was exacerbated in 6 horses following flexion of
the distal limb joints. The cause of lameness could
not be determined on the basis of clinical signs, and
diagnostic local anesthesia was necessary to localize
the source of lameness to the distal portion of the
limb. Five horses had forelimb involvement (1 bilateral),
and 4 had hind limb involvement (1 bilateral).
Treatment consisted primarily of a 6-month rest and
rehabilitation program. Six of the 9 horses were able
to return to their intended use.
Conclusions and Clinical Relevance—Results suggest
that injury to the SSL proximal to its insertion on
the middle phalanx should be considered as a possible
cause of lameness in horses, particularly performance
horses, with lameness localized to the distal
portion of the forelimb or hind limb that do not have
any radiographic abnormalities. High-resolution ultrasonography
was necessary to make the diagnosis.
Horses with an acute injury appeared to have a reasonable
chance of responding to treatment and
returning to their intended use. (J Am Vet Med Assoc 2003;222:973–977)
Case Description—A 3-year-old Thoroughbred mare was evaluated because of abnormal upper respiratory tract sounds (that had become apparent during race training) of 3- to 4- months' duration.
Clinical Findings—On initial physical evaluation, there were no abnormal findings. During trotting, an abnormal upper airway expiratory sound was audible. Endoscopic examination revealed a small mass protruding into the right ventral nasal meatus. Radiographic images of the skull revealed no abnormal findings. Computed tomography of the head revealed an abnormal structure in the same location as the mass that was observed during endoscopy. The x-ray attenuation of the mass was identical to that of dental tissue.
Treatment and Outcome—The mass was surgically removed with endoscopic guidance. On gross examination, the excised mass appeared to be a nearly normal molariform tooth. Histologic examination revealed that it was a well-formed tooth, with no other associated cellular populations. The mass was determined to be a molariform supernumerary intranasal tooth. Six months following discharge from the hospital, the trainer reported that the abnormal respiratory tract sound was no longer audible. During a follow-up endoscopic examination performed at the training facility, no abnormalities were detected.
Clinical Relevance—In horses, an intranasal tooth should be considered as a differential diagnosis for expiratory stridor. Clear definitions of heterotopic polyodontia, dentigerous cyst, and temporal teratoma can be used to clinically diagnose these separate anomalies. In the horse of this report, computed tomographic findings contributed to determination of a diagnosis and formulation of a treatment plan.