Consider monensin in feral cat food. Caution: Monensin is fearsomely powerful, a small amount will kill humans and horses so be scientific about it, run tests, handle with care. Do we even know how it behaves in cats? If you don't know what monensin is, before discarding this or flipping out, consider gathering information first, you might be able to contribute. Does it penetrate the oocyst walls? Cross the blood-brain barrier? What about when combined with papain and/or with a phenyl group added? In the β-position? Is that relevant/possible?
One of these days we're gonna hit on the right trick and knock out Toxoplasma world-wide in a week and it's going to be the dawn of a new era.