Hi RichardD,
I work in a malaria biochemistry lab, so I was curious to dig into your question a bit (malaria is similar to toxoplasma). The short answer is that AquaMira almost certainly does not work against toxo.
The tricky thing with toxoplasma gondii (the parasite that causes toxoplasmosis) is that, like giardia and cryptosporidium, it is not bacteria. Like humans, it must undergo sexual reproduction and also like humans, it produces single-cell eggs. These eggs can infect mammals and are much harder to kill than the hatched adults. In water, the adults are probably killed by most purification techniques, but the eggs are much more resilient. This site
http://www.waterbornepathogens.org/i...d=65&Itemid=73 suggests that chemicals are not effective at killing toxoplasma eggs. It doesn't specifically address AquaMira, which is chlorine dioxide, but I am fairly certain that it would not work if bleach doesn't work. Bleach is sodium hypochlorite and like chlorine dioxide, it works by releasing chlorite ions into water solutions, which is what kills stuff. The site suggests that UV irradiation might be somewhat effective, so a SteriPen might work. If the SteriPen is strong enough to kill cryptosporidium, it should also kill toxo eggs, but the problem is that the dose needed to become infected is very low (one egg can be enough), so even if you kill most of them, it might not matter. Filters with very small pores might be the best. Boiling kills everything if you do it for long enough (5+ minutes, protazoan eggs are tougher than bacteria).
I guess you have to decide whether you should bother with the filter. Sounds like the stream you drank from wasn't downstream of a farm. Could it have been a burger or steak that was less than very well done?