This study was done by using 10 clinically healthy adult dogs divided to two groups of five each. In the first group candida albicans and in the second group, Aspergillus niger were inoclded in their right ear
canals respectively. Clinical signs in both groups included pain of affected ear during palpation, head shaking, lowering the affected ear, turning head toward the affected ear, rubbing and scratching the affected area. But overall outlook were satisfactory and they had good appetite too. Otoscopic examination of the external canal showed sticky black and dark brown secretions (Tar), inflammation and reddness of ear canal wall. Neither otoscopic examination nor clinical signs could differentiate the changes occurred by these two organisms but the biopsy which was taken from one cases of each group showed only candida’s invasion to external canal wall and formation of pseudomycellium, whereas in aspergillus group the fungus has remained and localized in canal itself. The smears prepared from each group showed the presence of actived alive fungus too. Immunosuppression was accomplished by using cyclophosphamide and dexamethasone in 3 dogs of each group. The animal’s blood cell count comparison confirmed immunosuppression by significant decrease of leukocyte and neutrophil cells. Depression, decreasing physical activity, lack of appetite and increasing in temperature were noted in candida affected dogs but comparatively all the dogs of aspergillus affected one were in a good condition. One week after immunosuppression all dogs were euthanized for macroscopic studies and sample collection for fungal and histopathological examinations. The macroscopic examination confirmed the changes observed by otoscope in all dogs ear and changes resulting by injection of cyclophosphamide such as cystitis and atrophy of external and internal lymph nodes in immunosuppressed animals. The results obtained from fungal culture showed that the candida albicans invaded to other organs in all the three dogs that were inocluded by this organisms. In these animals kidney and lung had the highest contamination rate respectively. Smears obtained from serial tissue samples taken from kidney of these animals which were stained with G.M.S. method showed the changes of budding yeast with hyphae without septal wall in this tissue.
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