Anyone who knows anything about the captive care of reptiles and amphibians will tell you those books are absolutely worthless. Those books have no credibility with me. I absolutely believe that if you were to follow the instructions in those books exactly as they say, in a lot of cases it would directly result in the death of the animal. How do they get away with publishing those books? They simply are not peer-reviewed books like other scientific literature.
I would have to say that with the presence of other perfectly handleable animals, there is no reason to put any undue stress on an animal such as an amphibian.
At the very minimum, you should wash your hands directly before touching the amphibian. The hands should also be wet, like dripping wet. Ideally, you would use disposable latex gloves that our rinsed free of any powder and allowed to be wet. Even the ridges and whirls of your fingerprints are enough to damage the epidermis of amphibians. The Amphibian Medicine and Captive Husbandry book (a $140 scientific book for professionals, not the pet store books!) goes one step further and recommends using water conditioner such as Novaqua to lubricate the gloves. This particular water conditioner is rather viscous and is intended to provide a slime coat to fishes. I have used the water conditioner when I have had to restrain a larval tiger salamander for medical procedures.
Using latex gloves has become a professional standard in the zoo and research field. I can assure you I have done more than adequate research on the subject. I've spoken to over 1 dozen zoos and aquariums across the country, and had personal interviews with many top-notch professionals in the amphibian field. Where I work every single amphibian is touched only with a gloves, and we have only on rare occasions had any problems with epidermal abrasions, and no skin diseases of any type.
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*Humans aren't the only species on earth... we just act like it.
".the oldest task in human history: to live on a piece of land without
spoiling it."
Aldo Leopold (1938)