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- Author or Editor: Elizabeth M. Santschi x
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Abstract
Objective—To determine incidence of the Ile118Lys endothelin receptor B (EDNRB) mutation responsible for overo lethal white syndrome (OLWS) and its association with specific types of white patterning.
Animals—945 horses of white-patterned bloodlines and 55 solid-colored horses of other breeds.
Procedure—Horses were genotyped by use of allelespecific polymerase chain reaction to determine incidence of the Ile118Lys EDNRB mutation.
Results—Genotypes detected were homozygous Ile118, homozygous Lys118, and heterozygous. All foals with OLWS were homozygous for the Ile118Lys EDNRB mutation, and adults that were homozygous were not found. White patterning was strongly associated with EDNRB genotype. Color patterns with highest incidence (> 94%) of heterozygotes were frame overo, highly white calico overo, and frame blend overo. White-patterned bloodlines with lowest incidence of heterozygotes (< 21%) were tobiano, sabino, minimally white calico overo, splashed white overo, nonframe blend overo, and breeding-stock solid. The mutation was not detected in solid-colored horses from breeds without white patterning.
Conclusions and Clinical Relevance—In homozygotes, the Ile118Lys EDNRB mutation causes OLWS. In heterozygotes, the mutation is usually responsible for a frame overo phenotype. The frame pattern can be combined with other white patterns, making accurate estimation of EDNRB genotype by visual inspection difficult. Wide range of incidence of heterozygotes in various subtypes of white-patterned horses indicates different genetic control of these color patterns. Determination of EDNRB genotype by use of a DNA-based test is the only way to determine with certainty whether white-patterned horses can produce a foal affected with OLWS. ( Am J Vet Res 2001;62:97–103)
Abstract
CASE DESCRIPTION 4 horses were examined because of signs of chronic hind limb lameness.
CLINICAL FINDINGS 3 horses had a history of lameness for > 6 months; specific duration was unknown for 1 horse. On initial evaluation, grade 3 to 4 (on a scale from 1 to 5) hind limb lameness was present in all 4 horses. Radiography of the stifle joint of the affected limb revealed medial femoral condyle subchondral lucencies or subchondral cystic lesions (SCLs) in all 4 horses, medial femorotibial osteoarthritis in 3 horses, and medial tibial condyle SCLs in 3 horses.
TREATMENT AND OUTCOME 2 horses were treated medically (stall rest and oral NSAID administration), and 2 horses were treated surgically by means of medial femoral transcondylar lag screw placement through the medial femoral condyle SCLs. The 2 horses treated medically did not improve and were euthanized. Necropsy confirmed the presence of medial femoral condyle and medial tibial condyle SCLs. Surgical treatment did not resolve the lameness in 1 horse with SCLs in the medial tibial condyle and medial femoral condyle, and euthanasia was performed 150 days after surgery. In the second horse, a medial tibial condyle SCL was evident on radiographs obtained 3 months after surgery; however, this was not addressed surgically, and signs of lameness resolved 11 months after surgery.
CLINICAL RELEVANCE Results of this small case series suggested that SCLs in the medial tibial condyle can occur in association with SCLs of the medial femoral condyle, with a poor prognosis for return to athletic function in affected horses. Further investigation is indicated.
Abstract
Objective—To determine the effects of exercise on the distribution and pharmacokinetics of technetium Tc 99m medronate (99mTc-MDP) following intra-articular (IA) injection in horses.
Animals—5 horses.
Procedures—1 antebrachiocarpal joint (ACJ)/horse was assigned to the exercised group (n = 5), and the contralateral ACJ was evaluated in the nonexercised group (5) after a minimum washout period of 7 days. Following IA injection of 99mTc-MDP (148 MBq), blood and scintigraphic images of the carpus were obtained at 5, 10, 15, 20, 25, 30, 45, 60, 90, 120, 240, 360, 480, 600, 720, and 1,440 minutes. Plasma and scintigraphic radioactivity were determined over time, and pharmacokinetic parameters were generated via noncompartmental and compartmental analyses. Each horse was monitored via physical and lameness examination and ACJ synovial fluid analysis before injection and at days 1, 2, 3, and 7
Results—Lameness was not observed. Mean ± SD synovial fluid WBC count increased at day 1 (exercised, 721 ± 234 cells/μL; nonexercised, 948 ± 223 cells/μL), but returned to baseline at days 3 and 7 Mean time to maximum plasma radioactivity was earlier in the exercised group (16.00 ± 2.35 minutes) than the nonexercised group (43.75 ± 3.64 minutes). Linear regression of the scintigraphic radioactivity-time curves revealed a greater negative slope in the exercised group within the first 25 minutes. There was no difference in absorption or elimination rate constants in a 2-compartment model.
Conclusions and Clinical Relevance—IA injection of 99mTc-MDP was safe and effective for evaluating synovial solute distribution. Exercise significantly increased early transfer of 99mTc-MDP from the ACJ into plasma, although absorption and elimination rate constants were not affected. Exercise may affect synovial clearance and withdrawal times of medications administered IA.
Abstract
Objective—To determine clinical features of horses with a slab fracture of the central or third tarsal bone and to report outcome of horses in which treatment did not include surgery.
Design—Retrospective study.
Animals—25 horses (14 Standardbreds, 6 Thoroughbreds, 5 Quarter Horses).
Procedure—Medical records of horses with a slab fracture of the central (n = 9) or third (16) tarsal bone were reviewed. Only horses for which treatment consisted of confinement to a stall were included in this study. Clinical features and radiographic findings were recorded and summarized. Outcome was determined for racing breeds by obtaining official lifetime race results. Outcome for Quarter Horses was determined by phone survey of the owners.
Results—16 (64%) horses had a successful outcome. Ten of 14 (71%) Standardbreds and 2 of 6 Thoroughbreds returned to racing and started at least 5 races after injury. Four of 5 Quarter Horses for which follow-up information was available successfully returned to their previous activity. Sex, age, limb affected, or gait was not associated with final outcome. Percentage of racehorses with central tarsal bone fractures that had a successful outcome (2/7) was significantly less than percentage with third tarsal bone fractures that did (10/13).
Conclusions and Clinical Relevance—Results suggest that enforced rest without surgical fixation can be an effective therapeutic option for horses with a slab fracture of the central or third tarsal bone, even if athletic function is expected. (J Am Vet Med Assoc 2000;216:1949–1954)
Abstract
Objective—To evaluate long-term outcome of repair of femoral capital physeal fractures with 7.0-mm cannulated screws in juvenile bulls that weighed > 350 kg (770 lb).
Design—Retrospective study.
Animals—20 bulls.
Procedure—Medical records of affected cattle were identified and reviewed. Follow-up information was obtained by means of a written questionnaire, 1 to 15 years after discharge, from the veterinarians who supervised the postoperative care at bull stud facilities.
Results—Mean age and body weight at time of repair were 19 months (range, 11 to 27 months) and 513 kg (1,128.6 lb; range, 364 to 720 kg [800.8 to 1,584 lb]), respectively. Surgical repair was performed with 7.0- mm cannulated screws. A second surgery to replace malpositioned implants was required in 1 bull. Fourteen of the 20 bulls were considered serviceable for semen collection after surgical repair, and persistent lameness was evident in 11 of the 14. Mean duration for bulls to become serviceable was 5.5 months (range, 2 to 11 months). Age, weight, duration of injury at the time of repair, and degree of reduction did not have a significant effect on whether surgical repair was successful. Six bulls remained severely lame and were euthanatized.
Conclusions and Clinical Relevance—Results indicated that surgical repair of femoral capital physeal fractures in adolescent bulls with 7.0-mm cannulated screws placed in lag fashion has a good prognosis for long-term function in a semen collection facility. (J Am Vet Med Assoc 2005;227:964–969)
Abstract
Objective—To describe signalment; surgical findings; short-, medium-, and long-term outcome; and recurrence rate for cattle undergoing celiotomy because of jejunal hemorrhage syndrome (JHS) and to analyze risk factors associated with outcome and recurrence.
Design—Retrospective case series.
Animals—31 dairy cattle with JHS.
Procedures—Medical records were analyzed. Follow-up information was obtained from owners of cattle surviving until discharge.
Results—18 of 31 (58%) cattle undergoing celiotomy survived to initial discharge. Fifteen (48%) and 13 (42%) were alive 6 and 12 months after discharge, respectively. All 5 deaths within 12 months after discharge were attributed to JHS recurrence. Survival time was 12 to 85 months for the 13 long-term survivors. Six of 7 that died > 12 months after celiotomy did so for reasons unrelated to JHS. Recurrence rate among short-term survivors was 7 of 18; 1 of these survived long-term. A significant proportion of affected cattle were Brown Swiss, compared with proportions for other breeds. Manual massage of the bowel to break down clots was associated with a significantly higher short-term survival rate than was en-terectomy or enterotomy. Medium- and long-term survival rate was higher in cattle referred 24 to 48 hours after onset of signs. Length of obstructing blood clots was not associated with outcome. Other factors were not significantly associated with recurrence.
Conclusions and Clinical Relevance—Survival rates were higher than those in other reports. Prompt celiotomy and resolution by use of manual massage were associated with higher survival rates. In this population, JHS recurred in 7 of 18 short-term survivors.
Abstract
Objective—To determine changes in the distal ends of the third metacarpal and metatarsal bones (MCIII and MTIII) of Thoroughbred racehorses that had sustained a catastrophic condylar fracture during highspeed exercise.
Sample Population—Fractured and contralateral MCIIIs and MTIIIs from 11 Thoroughbred racehorses that sustained a displaced condylar fracture during racing, both MCIIIs from 5 Thoroughbred racehorses euthanatized because of a catastrophic injury other than a condylar fracture, and both MCIIIs from 5 horses of other breeds that had not been professionally trained or raced.
Procedure—Macroscopic observations were made of the distal ends of the bones before and after digestion of the articular cartilage with NaOH.
Results—In all 11 racehorses with a displaced condylar fracture, the fracture was associated with a branching array of cracks in the condylar groove. In this region, fracture margins were smooth, and there was loss of subchondral bone. Comminution of the dorsal cortex was also seen. Parasagittal linear wear lines in the articular cartilage, erosions in the articular cartilage of the condyles, loss of the underlying subchondral bone, and cracking of condylar grooves were all more severe in the Thoroughbred racehorses than in the horses that had not been professionally trained or raced.
Conclusions and Clinical Relevance—Results suggest that condylar fractures in horses are pathologic fatigue or stress fractures that arise from a preexisting, branching array of cracks in the condylar groove of the distal end of MCIII or MTIII. (Am J Vet Res 2003;64:1110–1116)
