I once bought some juvenile sals which appeared perfectly healthy, until next day one was seen gaping, and coughed blood on to the paper substrate. I quarantined all six in separate containers, in a makeshift room, but within the week they had all died. I also lost animals that were housed in adjacent boxes to them within the first 24 hours of acquiring them. I now quarantine all animals, for 6 weeks in a separate room.
Another good argument for strict hygiene between handling animals is cited in Amphibian Medicine and Captive Husbandry. K.M.Wright & B.R.Whitacker,2001.
"It is important not only for hygienic reasons, but to avoid the unintentional transfer of any noxious secretions or pheromone-containing substances from one animal to another. The skin and glandular secretions of one species may be deleterious to another. Amphibians have a well developed olfactory sense, and pheromones are an important mode of communication in many species. Territorial salamanders for example, communicate their dominance partly via chemical cues. It is possible to transfer these pheromones from one individual to another during handling, thus spreading stressful pheromonal cues among the animals."