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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

Objective—

To determine whether prevalence of naturally developing chronic infection with Trypanosoma cruzi in dogs in Texas changed between 1987 and 1996 and to characterize clinical aspects of the disease.

Design—

Retrospective study.

Animals—

11 dogs with chronic infection with T cruzi.

Procedure—

Number of positive serologic test results for T cruzi obtained between 1987 and 1996 were compared with the number of tests for T cruzi performed during the same period. Survival time, signalment, and clinical signs of dogs and results of thoracic radiography, electrocardiography, and echocardiography were evaluated. The Mann-Whitney test was used to assess the association between age at time of initial examination and survival time.

Results—

The proportion of positive test results increased, compared with the number of tests submitted, during the 9-year period. Clinical signs in affected dogs were consistent with right-sided cardiac disease. Results of thoracic radiography were nonspecific. Conduction disturbances and supraventricular and ventricular arrhythmias were evident. Echocardiographic abnormalities, including chamber enlargement and functional impairment, were detected. Dogs were characterized on the basis of survival time; group-1 dogs (n = 6) survived 0 to 5 months, and group-2 dogs (5) survived 31 to 60 months. Age at time of initial examination was associated with survival time.

Clinical Implications—

Clinical course of disease varied. Electrocardiographic and echocardiographic changes may be detected. Clinicians should be aware of the potential for T cruzi infection in dogs with clinical signs of right-sided cardiac dysfunction and unexplained conduction disturbances and arrhythmias. Prevalence of this disease may be increasing in some regions of Texas. (J Am Vet Med Assoc 1998;213:497-500)

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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
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the threshold for acute toxicosis of parenterally administered zinc phthalocyanine tetrasulfonate (ZnPcS4), a candidate second-generation photosensitizer, in mice and evaluate the compound's safety in a phase I clinical trial of ZnPcS4-based photodynamic therapy (PDT) in pet dogs with naturally occurring tumors.

Animals—Male Swiss-Webster mice and client-owned dogs with naturally occurring neoplasms.

Procedures—For the study of acute toxicosis, mice were given graded doses of ZnPcS4. To determine safety, a rapid-titration phase I clinical trial of ZnPcS4-based PDT in tumor-bearing dogs was conducted.

Results—In mice, administration of ≥ 100 mg of ZnPcS4/kg resulted in renal tubular necrosis 24 hours after IP injection. In tumor-bearing dogs, ZnPcS4 doses ≤ 4 mg/kg induced no signs of toxicosis and resulted in partial to complete tumor responses in 10 of 12 dogs 4 weeks after PDT. Tumor remission was observed with ZnPcS4 doses as low as 0.25 mg/kg.

Conclusions and Clinical Relevance—A conservative starting dose of ZnPcS4 was arrived at on the basis of mouse toxicosis findings. Zinc phthalocyanine tetrasulfonate–based PDT was tolerated well by all dogs and warrants further study. The identification of the maximum tolerated dose through traditional phase I clinical trials may be unnecessary for evaluating novel PDT protocols.

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