I forgot to mention how Parker is feeling. The antibiotics (only one of which had to be re-inserted in his food after he spat it out) seem to have done their job. Of course, on the way to visit his friends Sam and Hershey last night, he got to eat his dinner a second time. (Yeah, ew.)
Here's the problem: there is no effective way to keep him from eating rabbit poop. He will get another crypto infection; and he'll have to be on heartworm pills year-round to prevent hookworm. He's not likely to grow out of it, either. But at least now that it looks almost certainly like parasitic infections and not something with his own plumbing, I can start re-introducing him to non-prescription dog food next week, and I don't need to worry as much about him eating sticks.
Finally, I promise, really I do, to post about other topics over the weekend.