Since the GP won't let me be tested for toxoplasmosis immunity on the basis that they would need clinical evidence of likely toxoplasmosis infection (which, as I pointed out, is a circular argument since it's an asymptomatic infection) I have been assuaging my salami-based paranoia by nerding out on the Internet. I now know more about Toxoplasma Gondii infection than is possibly normal, and thought I would share my findings with the only community of people likely to take a similarly close interest.
I shall try to summarise my findings, though of course I am no expert and also I have heard that some things on the Internet are Not True. So due caution and scepticism are called for.
Essentially, the TG parasite completes it's lifecycle via cats, and meat animals catch it by eating stuff contaminated by cat poo or eating infected rodents. Humans also catch it by eating stuff contaminated by cat poo or eating infected meat animals. As we all know, if you catch it for the first time in pregnancy this is a Bad Thing and causes all manner of baby destruction and deformity. The parasite in meat is killed by temperatures of over about 70C, so the advice is therefore to avoid all undercooked or uncooked/cured meat.
So far so lovely in a perfect world. But what if you are a Bad Person and forget this sterling advice, and allow some Parma ham or a juicy steak to pass your lips while up the duff? Are you doomed to despair, or are there some mitigating factors that might nuance the message of 'you have harmed your unborn child, but we won't test you so go and stew for 5 months'?
Here is some stuff I have found out:
1. The parasite is killed by freezing. Being in a domestic freezer for 24 hours should do it. So if your meat has been frozen, you can probably have it as rare as you like (it might still give you food poisoning, but that's a different story)
2. The thing about steak being OK if it's seared on the outside applies to food poisoning, where the bacteria grow on the surface of the meat, but not to toxoplasmosis, where the infective cysts from an infected animal are throughout the meat tissue. But see freezing, above.
3. Toxoplasmosis is pretty rare in beef cattle. Some studies go so far as to state it isn't found, though this may be country-specific. So the risk with even non-frozen steak should be very low.
4. Toxoplasmosis is more common in sheep, deer and pigs. Pork isn't normally served rare, so it looks as though if meat hasn't been frozen, pink lamb, rare venison steaks or undercooked sausages would be the main things to watch out for.
5. The exception to the 'pork is well cooked' rule is of course cured meats, where the preservation doesn't involve heating or freezing. But from what I can gather, the curing process does kill a lot of parasites (just not necessarily all of them) so even cured meat from an infected pig will in all likelihood not contain parasites.
6. Also, the incidence of toxoplasmosis in 'modern' i.e. Industrial pig farming is allegedly practically negligible. (Industrially farmed pigs don't get to hang round with other pigs, let alone cats). One study in the Netherlands cited 0% infection in standard pig farms and up to 3% infection in organic ones. So if your salami/Parma ham probably came from an industrial farm rather than a nice organic one, the chances of infection are very low indeed. (That's the bit that makes me feel better - the cured ham I ate was a cheap pack from Tesco and almost certainly from poor sad industrial pigs. Not good for the pigs, but reassuring for me!)
So that's that. Obviously the advice to avoid all undercooked and cured meat is very sound and sensible, but if you've ever dared to fall short of the standards of perfection required of you as a pregnant lady, maybe some of the above might help you work out what risk you're actually at, and sleep a bit better at night.
Bemused parent to the Bear (2009) and Smudge (2011).