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in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association


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



To determine whether oral administration of erythromycin alters the inflammatory response to bronchoalveolar lavage (BAL) in young horses.


12 healthy, unweaned, mixed-breed foals of either sex, between 2 and 4 months old.


BAL was performed; 250 ml of phosphate-buffered saline solution (300 mOsm, pH 7.4) was administered in 50-ml aliquots. Foals were carefully monitored for 4 days, then erythromycin base (25 mg/kg of body weight, PO, q 12 h) was given to foals of the treated group. After 4 days, foals were re-anesthetized, and the same lung was relavaged. Cytologic examination was performed on BAL fluid (BALF) samples from both groups of foals. At 12 hours after administration of the final dose, erythromycin A and anhydroerythromycin A concentrations were determined in plasma of treated foals.


In the second BALF sample from the same lung of control foals, percentage of neutrophils was significantly increased (3 ± 38.0%), compared with that from erythromycin-treated foals (4.88 ± 3.66%, P < 0.05), and was associated with apparent decrease in the ability of BALF cells from erythromycin-treated foals to migrate toward a chemoattractant source. Significantly fewer BALF cells adhered to a cell culture substratum after erythromycin treatment of foals. Erythromycin A was not detected in plasma of any treated foal at the time of the second BAL; anhydroerythromycin A, a degradation product of erythromycin, was detected in plasma of 5 of 6 foals (mean concentration, 0.2 ± 0.06 µg/ml).

Conclusion and Clinical Relevance

BAL induces neutrophilic inflammation, which persists for at least 4 days in the lungs of young horses. Erythromycni (25 mg/kg, PO, q 12 h) diminishes this inflammatory response through a mechanism that may involve alteration of BALF cell function. Degradation of erythromycin to biologically active products or presence of parent drug in pulmonary secretions may be responsible for alterations in pulmonary lavage cell Chemotaxis and adherence. Erythromycin administered orally to foals at clinically relevant doses appears to have nonantimicrobial effects that may interfere with host cell metabolism and decrease inflammatory reponses in airways. (Am J Vet Res 1997;58:56–61)

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in American Journal of Veterinary Research


Objective—To establish the route of infusion (IV or intraosseous) that results in the highest concentration of amikacin in the synovial fluid of the tibiotarsal joint and determine the duration of peak concentrations.

Animals—21 horses.

Procedure—Regional perfusion of a limb on 15 horses was performed. Amikacin sulfate was infused into the saphenous vein or via intraosseous infusion into the distal portion of the tibia (1 g in 56 ml of lactated Ringer's solution) or proximal portion of the metatarsus (1 g of amikacin in 26 ml of lactated Ringer's solution). Amikacin concentrations were measured in sequential samples from tibiotarsal joint synovial fluid and serum. Samples were obtained immediately prior to release of the tourniquet and 0.5, 1, 4, 8, 12, and 24 hours after the tourniquet was released. Radiographic contrast material was infused into the same locations as the antibiotic perfusate to evaluate distribution in 6 other horses.

Results—Infusion into the saphenous vein produced the highest concentration of amikacin in the tibiotarsal joint, compared with the distal portion of the tibia (mean ± SE, 701.8 ± 366.8 vs 203.8 ± 64.5 µg/ml, respectively). Use of a lower volume of diluent in the proximal portion of the metatarsus produced a peak value of 72.2 ± 23.4 µg/ml.

Conclusions and Clinical Relevance—For regional perfusion of the tarsus, IV infusion is preferred to intraosseous infusion, because higher concentrations are achieved in the synovial fluid, and the procedure is easier to perform. (Am J Vet Res 2002;63:374–380).

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in American Journal of Veterinary Research


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
in Journal of the American Veterinary Medical Association