Penny caught the grasshopper on the deck. I've read that insects (inlcuding earthworms) can carry parasite eggs and deposit them in the soil. However, I don't believe she got infected by eating the grasshopper. She ate the thing late last week, and I believe the roundworm cycle is longer than a couple of days. I don't use pesticides or herbicides on my lawn or gardens, and neither do my neighbors. In fact, other than the immediate area around our respective homes, we allow our properties to grow wild. In doing so, we attract a large variety of wildlife; turkey, woodchuck, skunk, deer, pheasant, etc.
I don't think the third eye problem was caused by the parasite infection. Instead, it was caused by a body temp of 107.2. I'm sure I don't have to tell you this, but for the benefit of those who are new to the cat world...cats generally have a body temp of 101 to 102.5. A feline temp of 107.2 is equivalent to a human temp of 103 - 105. Temperature that high is a life-threatening situation for both man and beast!
Had I not taken Penny to the A.E.C., she most likely would have been dead by morning; and if not dead, then (neurologically) injured. It's quite possible Penny caught a mouse in the basement and was thusly infected by roundworm. Field mice, moles and voles are at a premium around here. Occasionally they make their way into the garage, and sometimes into the basement. My 16yo female catches a mouse in the basement every now and again, but she doesn't eat them. Instead, she brings them to me (usually still alive and kicking.) I don't use mouse traps or poisons in my basement, but now will find an alternative method for trapping mice inside the house.