r/Opossums

We live out in the woods. we've got a few hills, a bunch of trees, a shed in the back. We have one or two opossums that live around the area, and one who has made a burrow underneath our shed along with a groundhog, although I have not seen the groundhog for a few days. The groundhog was always very shy and ran away at the sight of us, but the opossum was relaxed. He would come at night to get some of the sunflower seeds that were around our bird feeder.

Earlier today, we found this opossum out of the shed, in daylight. It was afternoon, and we saw him in front of the shed doors. He was writhing around in pain, breathing very heavily, and eventually started passing vivid green diarrhea. He crawled halfway back under the shed, cried out a few times and then died. As he died, it looked like blood came out from his anus. This all happened within about a half hour of us finding him. I also noticed he had a pattern of red circles down the underside of his tail, but perhaps this is a part of how their tails look and I never noticed?

My stepmother is concerned that he was poisoned, but I find that unlikely as we live relatively alone in the woods and there's no reason for the opossum to walk all the way to another house, and there's no reason for a neighbor to make the hiking trip up to our shed. But is it possible that it ate a poisonous plant, or perhaps it was bitten by something venomous? He was a well-sized adult, fully grown, but did not look old. I could not see any obvious injuries or bloody spots on him.

Any ideas what could have happened? I especially am concerned about our cats or the various other animals who might be affected if there is something dangerous around our area.

So my sister and I found a small baby opossum in our backyard a few hours ago on a high surface that he was about to slip off of in the cold rain. We felt so bad and after trying and failing to reach him we heard the Momma gave up and seems to have just left. My sister quickly put on 2 sets of winter gloves and a cardigan so she could hold him. He was a little bit startled and shaking at first. We had him inside for about 2 hours before we put him back out in a box with some water and banana mush (not sure if he’ll eat it). Now we’re thinking, why would we do something so crazy? Can we contract anything from him, like rabies or ticks/fleas? We had him on our beds, how do we know if we do have something and what do we do from there? Honestly we’re just panicking and would appreciate some answers.