If mites are not present in your cat and it is still subject to repeated ear problems, it should be tested for feline immunodeficiency virus and feline leukemia. (2ndchance.info)
For example, a cat with feline immunodeficiency virus (FIV) might be overcome by an infection that a healthy cat would easily fight off. (cat-lovers-only.com)
Other Foundation - funded research has improved our understanding of canine distemper outbreaks in African lions and Siberian tigers, and has helped to gauge the prevalence and health effects of feline immunodeficiency virus in African lions, mountain lions and bobcats. (morrisanimalfoundation.org)