Pneumocystis pneumonia in the dog

Pneumonia caused by Pneumocystis carinii occurred in 6 young, male, miniature dachshunds producing severe dyspnoea, although the dogs were afebrile and otherwise alert. The diffuse nature of the pulmonary disease and the resultant cardiac enlargement were visible radiographically. Diagnosis was confirmed by lung biopsy in 3 of the dogs and at post-mortem examination in the remaining 3. Specific treatment with pentamidine isethionate was attempted in one of the dogs and resulted in considerable improvement although a severe reaction was produced at the injection site. The post-mortem appearance of the lungs was characteristic as were the histological changes. Electronmicroscopic examination of portions of lung from one dog allowed detailed examination of the morphology of the organism. Examination of the 5 available pedigrees indicated that the dogs were closely related, suggesting the possible existence of an heritable immune-deficiency state which allowed the organisms to become pathogenic.