Hi Lymegirl. Immuno assays for toxoplasma gondii might produce a hit, but the testing needs to be expanded.
If you have some money to invest, you could have your blood sceened for DNA that encompasses a wider variety of species.
Immuno assays can show false positives, because the parasite has numerous phases, with different antigen presentations.
I will investigate this further, and place it in detail on my blog.. Shroom