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

Abstract

Objective—To determine clinical signs, diagnostic findings, tissue tremetone concentrations, and clinical outcome or postmortem findings in horses evaluated for acute severe nonexertional rhabdomyolysis initially attributed to white snakeroot toxicosis.

Design—Retrospective case series.

Animals—14 horses.

Procedures—Records of the University of Minnesota Veterinary Medical Center or Diagnostic Laboratory were searched from 1998 to 2005. Inclusion criteria included serum creatine kinase (CK) activity > 45,000 U/L, severe nonexertional myonecrosis of proximal postural muscles at necropsy, or signs of weakness without palpably firm muscles on physical examination. Vitamin E and selenium concentrations were measured in 6 horses; tremetone concentration was measured in 7.

Results—Clinical signs occurred during unfavorable weather conditions. Clinical signs of generalized weakness (n = 11 horses), muscle fasciculations (10), lethargy (6), and prolonged recumbency (4) were common. Serum CK activity ranged from 46,487 to 959,499 U/L (reference range, 82 to 449 U/L), and aspartate transaminase activity was > 1,500 U/L (reference range, 162 to 316 U/L). Two horses survived with aggressive antioxidant and fluid treatment. Postmortem examination revealed acute severe myonecrosis with lipid accumulation primarily in neck, proximal forelimb and hind limb, intercostal, and diaphragm muscles. Histopathologic signs of myocardial necrosis were detected in 7 horses. Vitamin E and selenium concentrations were within reference limits. Tremetone was not detected in liver or urine samples.

Conclusions and Clinical Relevance—Cases of rhabdomyolysis have been attributed to white snakeroot toxicosis; however, tremetone was not detected in any horses. Similarities exist between cases of seasonal pasture myopathy and cases of atypical myopathy in Europe.

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

Abstract

Objective—To determine prevalence of Dirofilaria immitis infection among shelter cats.

Design—Cross-sectional study.

Animals—239 cats euthanatized at an animal shelter in southeastern Michigan.

Procedure—A gross necropsy focusing on the thoracic cavity, heart, lungs, and pulmonary vessels was performed within 5 hours after cats were euthanatized. Blood was collected directly from the heart of cats found to be infected and tested, using a filter test for microfilariae. Serum was tested for D immitis antigens by use of 2 antigen detection kits and for D immitis-specific antibodies by use of 2 antibody detection kits.

Results—Cats ranged from approximately 4 months to 15 years old. Adult D immitis were found in 6 (2.5%) cats. Blood could not be recovered from 1 of the cats with heartworm infection. For the 5 other cats, results of the filter test were negative, and results of both antigen and both antibody tests were positive.

Conclusions and Clinical Relevance—Results suggest that cats living in an urban area in the northern part of the United States have a low prevalence of adult D immitis infection. However, this is likely to be an underestimate of the true prevalence of infection, because no attempts were made to identify cats infected with larval or juvenile stages of D immitis. (J Am Vet Med Assoc 2000;217:211–212)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the effect of oral administration of dantrolene sodium on serum creatine kinase (CK) activity after exercise in horses with recurrent exertional rhabdomyolysis (RER).

Animals—2 healthy horses and 5 Thoroughbreds with RER.

Procedure—3 horses received 2 doses of dantrolene (4, 6, or 8 mg/kg, PO, with and without withdrawal of food) 2 days apart; 90 minutes after dosing, plasma dantrolene concentration was measured spectrofluorometrically. On the basis of these results, 5 Thoroughbreds with RER from which food was withheld received dantrolene (4 mg/kg) or an inert treatment (water [20 mL]) orally 90 minutes before treadmill exercise (30 minutes, 5 d/wk) during two 3-week periods. Serum CK activity was determined 4 hours after exercise. Plasma dantrolene concentration was measured before and 90 minutes after dosing on the first and last days of dantrolene treatment and before dosing on the first day of the inert treatment period.

Results—90 minutes after dosing, mean ± SEM plasma dantrolene concentration was 0.62 ± 0.13 and 0 µg/mL in the dantrolene and inert treatment groups, respectively. Serum CK activity was lower in dantrolene- treated horses (264 ± 13 U/L), compared with activity in water-treated horses (1,088 ± 264 U/L). Two horses displayed marked muscle stiffness on the inert treatment.

Conclusions and Clinical Relevance—In 5 horses with RER from which food had been withheld, 4 mg of dantrolene/kg administered orally provided measurable, though variable, plasma concentrations and significantly decreased serum CK activity after exercise in 4 of those horses. ( Am J Vet Res 2004; 65:74–79)

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in American Journal of Veterinary Research

Abstract

Objective—To determine the effects of dexamethasone on development of IgG subclass responses following vaccination of healthy horses.

Animals—11 mature Thoroughbreds.

Procedure—Horses received 2 IM injections at 2- week intervals of a vaccine containing inactivated infectious bovine rhinotracheitis, bovine viral diarrhea, and parainfluenza-3 viral antigens and were then randomly assigned to 2 groups. Six horses received dexamethasone (0.2 mg/kg of body weight, IM) twice weekly for 8 weeks starting the day of the first vaccination. Five control horses received an equivalent volume of saline (0.9% NaCl) solution. Antigen-specific serum IgG subclass titers were determined weekly after vaccination by use of an ELISA.

Results—Vaccination resulted in similar antigen-specific serum IgG(T) titers in dexamethasone-treated and control horses. In contrast, although control horses developed IgGa and IgGb responses after vaccination, corticosteroid administration completely inhibited these responses in treated horses.

Conclusions and Clinical Relevance—Cortico steroids can have profound effects on primary immune responses in horses and can significantly affect IgG responses to inactivated vaccines. Corticosteroid treatment regimens commonly used to treat diseases in horses may result induction of a nonprotective IgG subclass response, leaving treated horses susceptible to disease. Additionally, mechanisms regulating IgGa and IgGb responses appear to differ from those regulating IgG(T) responses. Further defining these mechanisms is a critical step in designing effective vaccines, and corticosteroid-induced immunomodulation may be a valuable tool for studying immune responses in horses. (Am J Vet Res 2000;61:1530–1533)

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in American Journal of Veterinary Research