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in Journal of the American Veterinary Medical Association


Objective—To determine the incidence of complications and identify risk factors associated with development of complications following routine castration of equids.

Design—Retrospective case series.

Animals—311 horses, 10 mules, and 3 donkeys.

Procedures—Medical records of equids undergoing routine castration were reviewed. Age, breed, surgical techniques (closed vs semiclosed castration and use of ligatures), anesthesia method (general IV anesthesia vs standing sedation with local anesthesia) and repeated administration of IV anesthetic agents, administration of antimicrobials and anti-inflammatory drugs, and details regarding development, management, and outcome of complications were recorded. Odds ratios and 95% confidence intervals were determined. Associations between additional doses of anesthetic agents during surgery and development of complications were analyzed with a Jonckheere-Terpstra test.

Results—33 of 324 (10.2%) equids developed a complication after surgery; 32 recovered and 1 was euthanized because of eventration. Equids that underwent semiclosed castration had significantly higher odds of developing a complication (OR, 4.69; 95% confidence interval, 2.09 to 10.6) than did those that underwent closed castration. Equids that received additional doses of anesthetic agents to maintain adequate general anesthesia developed complications more frequently than those that did not require this treatment.

Conclusions and Clinical Relevance—Incidence of complications was low, and most evaluated variables were not significantly associated with development of complications following castration in equids. However, findings suggested that the choice of surgical technique (closed vs semiclosed) is an important factor in this regard. Future studies should investigate whether duration of surgery is associated with complications following castration in equids.

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in Journal of the American Veterinary Medical Association



To determine pharmacokinetics and pharmacodynamics after oral administration of a single dose of clopidogrel to horses.


6 healthy adult horses.


Blood samples were collected before and at various times up to 24 hours after oral administration of clopidogrel (2 mg/kg). Reactivity of platelets from each blood sample was determined by optical aggregometry and phosphorylation of vasodilator-stimulated phosphoprotein (VASP). Concentrations of clopidogrel and the clopidogrel active metabolite derivative (CAMD) were measured in each blood sample by use of liquid chromatography–tandem mass spectrometry, and pharmacokinetic parameters were determined with a noncompartmental model.


Compared with results for preadministration samples, platelet aggregation in response to 12.5μM ADP decreased significantly within 4 hours after clopidogrel administration for 5 of 6 horses. After 24 hours, platelet aggregation was identical to that measured before administration. Platelet aggregation in response to 25μM ADP was identical between samples obtained before and after administration. Phosphorylation of VASP in response to ADP (20μM) and prostaglandin E1 (3.3μM) was also unchanged by administration of clopidogrel. Time to maximum concentration of clopidogrel and CAMD was 0.54 and 0.71 hours, respectively, and calculated terminal-phase half-life of clopidogrel and CAMD was 1.81 and 0.97 hours, respectively.


Clopidogrel or CAMD caused competitive inhibition of ADP-induced platelet aggregation during the first 24 hours after clopidogrel administration. Because CAMD was rapidly eliminated from horses, clopidogrel administration may be needed more frequently than in other species in which clopidogrel causes irreversible platelet inhibition. (Am J Vet Res 2019;80:505–512)

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in American Journal of Veterinary Research


Objective—To describe clinical manifestations of cutaneous and ocular habronemiasis in horses and evaluate outcome of treatment.

Design—Retrospective study.

Animals—63 horses.

Procedure—The diagnosis was made on the basis of history, clinical signs, and identification of calcified concretions (sulfur granules) in lesions. Histologic examination of biopsy specimens was used to confirm the diagnosis. Case horses were compared with a control population of 12,720 horses examined during the same period.

Results—Arabians, gray horses, and horses with diluted coat colors were overrepresented; Thoroughbreds were underrepresented. Lesions were identified most often during the summer and early fall. The medial canthus of the eye, male genitalia, third eyelid, and distal portions of the extremities were the most commonly affected locations. Twenty-five lesions were biopsied, and results of histologic examination were consistent with a diagnosis of habronemiasis. However, nematode larvae were seen in only 11 (44%) biopsy specimens. Treatment consisted of surgical removal (7 horses) or medical treatment (56) consisting of debulking granulation tissue and topical, intralesional, or systemic treatment with corticosteroids. All horses were treated with ivermectin.

Conclusions and Clinical Relevance—Results suggest that cutaneous and ocular habronemiasis should be considered when examining a horse during the summer months with a proliferative, moist, granulomatous lesion. Treatment should be aimed at decreasing the size of the lesion, reducing inflammation, and preventing recurrence. In general, the prognosis was good, and healing occurred within a few weeks. Fly control and regular deworming with ivermectin are recommended to reduce the incidence of habronemiasis. (J Am Vet Med Assoc 2003;222: 978–982)

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in Journal of the American Veterinary Medical Association


OBJECTIVE To investigate the impact of age and inferred prior vaccination history on the persistence of vaccine-induced antibody against rabies in horses.

DESIGN Serologic response evaluation.

ANIMALS 48 horses with an undocumented vaccination history.

PROCEDURES Horses were vaccinated against rabies once. Blood samples were collected prior to vaccination, 3 to 7 weeks after vaccination, and at 6-month intervals for 2 to 3 years. Serum rabies virus–neutralizing antibody (RVNA) values were measured. An RVNA value of ≥ 0.5 U/mL was used to define a predicted protective immune response on the basis of World Health Organization recommendations for humans. Values were compared between horses < 20 and ≥ 20 years of age and between horses inferred to have been previously vaccinated and those inferred to be immunologically naïve.

RESULTS A protective RVNA value (≥ 0.5 U/mL) was maintained for 2 to 3 years in horses inferred to have been previously vaccinated on the basis of prevaccination RVNA values. No significant difference was evident in response to rabies vaccination or duration of protective RVNA values between horses < 20 and ≥ 20 years of age. Seven horses were poor responders to vaccination. Significant differences were identified between horses inferred to have been previously vaccinated and horses inferred to be naïve prior to the study.

CONCLUSIONS AND CLINICAL RELEVANCE A rabies vaccination interval > 1 year may be appropriate for previously vaccinated horses but not for horses vaccinated only once. Additional research is required to confirm this finding and characterize the optimal primary dose series for rabies vaccination.

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in Journal of the American Veterinary Medical Association