This chapter identifies animal diseases that are host specific and reviews the effects of various human diseases on animals. It also identifies history, etiologic, human Infection, diagnosis, public health aspects and therapeutic aspects of each disease important to epidemiology and prevention. Systemic mycoses are generally pulmonary in origin but can involve any or all of the internal body organs, including bones. Blastomycosis in humans can be divided into two forms: systemic and cutaneous. Candidiasis in humans may appear as an acute or chronic disease which could involve mucous membranes, skin, nails, and internal organs. Candida albicans and other Candida spp. are common inhabitants of the mucous membranes and gastrointestinal tract of humans and lower animals. Humans and a large variety of wild and captive animals as well as such domesticated animals as cats, cattle, dogs, horses, sheep, and swine are infected by C. immitis.