We ran in and called my nephew and his wife (who have had many more years than us at raising pigs). Worms, poisoning, a snake-bite possibly . . . these were all suggestions. I quickly searched the internet for "poisoning in a pig". I found some great info right away. It is amazing how useful the internet can be.
This is what I found - Algae poisoning. I found this very informative site www.thepigsite.com . Well, the day this happened, we changed our morning routine a little bit and the pigs ended up out in the pasture by the algae filled pond for 4 hours longer than normal. She was fine at noon but by 2pm or so, she was circling. We gave her a gallon of raw cow milk and then more with charcoal in it. Being a pig, she willingly slurped it down, even in her miserable condition! Within an hour (or less) she was not so wobbly. Soon, she was back to her herself, rooting around and being a bother! Here is the link to info about algae poisoing - http://www.thepigsite.com/pighealth/article/634/algae