GUNNER
Gunner is a 2-year-old Golden Retriever mix who lives on a 5-acre property in a semi-rural subdivision in Montgomery County. He's an "only pet," whose owners have an Invisible Fence, which Gunner treats with 
deep respect, never venturing off his home turf. He is brought into the clinic because for the past month he's been scratching constantly, and nibbling at his flanks, and in the past two weeks the hair on his rump and flanks has fallen out and he's developed crusty, oozing patches in several places. His owners are worried he's got "mange" and will have to be put down.
A thorough examination of Gunner's remaining fur and the use of a fine comb reveal that he has fleas. A fecal floatation test also establishes that he has tapeworms. The diagnosis of this condition is simple: flea bite dermatitis, the most common veterinary dermatologic condition in the world.
He's given steroids and an anti-flea bath, and sent home, with instructions to the owners on how to deal with the situation in the future.
Points to ponder:
1. What's the mechanism that caused the hair loss and the inflamed regions of his skin? What cells are affected, and how do the skin's architecture and physiology play a role in the processes of injury and healing?
2. Why does he have tapeworms? How is this related to his flea issues?
3. What's the key to preventing this from recurring? What advice were the owners given?
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