Backyard Mystery - Any Ideas?

VetMed forum member COODOVE asks: Early this morning we let out our 8 month old Chihuahua mix puppy out to go potty. A few minutes later, he was found almost comatose in the back yard, which is fenced. We have 2 other dogs that went out also. They were fine.

I brought him back into the house to check for snake bite or any marks. There were none. He seemed to be almost paralyzed. His mouth was shut tight and his normally red gums were white! His pupils were dilated and glazed looking. It took about 20 minutes until he finally could lift his head... and another hour later was back to normal!

My husband went out when it was daylight to see if anyone had thrown something over the fence - but there were no tracks anywhere. There is nothing growing that is poisonous. It was like he had been shot with a tranquilizer gun - but again no marks or swelling. We cannot figure out what happened. Any suggestions to this mystery?

As always, it is good to check in with a vet after an event like this, even if the pet appears normal. At least to get a baseline physical and document any clinical findings and history. Forum Host KAHLUADANES has some good input, and you are invited to add your thoughts to the discussion too.

_{Photo credit: Belle © DMBFreakNo41 on Flickr.}