The hottest viral image on Facebook right now shows a handful of ham, cheese, and nails purportedly found in a dog park in Chicago, Illinois; Tucson, Arizona; Regina, Saskatchewan; or some unspecified town in Massachusetts, depending on which version of the rumor you happen to read.
Moreover, placing this deadly concoction in dog parks is a new "trend," the rumormongers say meaning either there's an epidemic of animal cruelty sweeping North America or an epidemic of gullibility sweeping Facebook.

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Sorry I do not speak English well. I am using a translator online.
This news just happened in Spain (February 2012):
“Pin Dog Food”
http://fabulasurbanas.com/comida-para-perros-con-alfileres/