Can a person who was infected with toxoplasmosis during his or her mother's pregnancy donate blood? Or is it unsafe and thus rejected?
People who have had toxoplasmosis are not barred from donating blood (at least in the places I checked). While toxoplasmosis during pregnancy is dangerous for the embryo/fetus, if they don't have lasting damage from it, that person is just like any other person who once had toxoplasmosis, of which there are many (in some countries up to 80 percent of people are immune because they had toxoplasmosis at one time).
People with a currently active infection would probably be sent away, but since toxoplasmosis infection usually presents like a generic mild infection (muscle ache, mild temperature) and isn't tested for, that's no different than sending away someone with a cold.
When in doubt, ask the place where you are donating.
Red Cross blood donation eligibility requirements
First, it'll be necessary to know if only the mother was infected during pregnancy, or if the parasite responsible for toxoplasmosis (Toxoplasma gondii) was really transmitted to the foetus. This was possibly done during pregnancy via amniocentesis.
If the person was infected in utero, then they are likely to carry the parasite, although they won't necessarily express symptoms. This can be verified by a specialized blood test (specific IgM and IgG antibodies will be searched).
Toxoplasmosis can be transmitted via blood donation. People who have been infected by toxoplasmosis are however eligible for blood donation, but they must give this information to the blood center as their blood will be specifically not given to people with immune deficiency (who could then be severely infected by the parasite).
These rules can vary from country to country. Be sure to check with the closest blood center.
Sources : recommendations on blood donations from the Pan American Health Organization Transmission of toxoplasmosis by blood donation described in 1970
"If the person was infected in utero, then they are likely to carry the parasite" do you have a citation for this kind of lifelong infection?– YviDeNov 27, 2015 at 15:23
@YviDe This is an example of recommendations for the follow-up of children infected in utero. There's also the case of patients presenting an immune deficiency that will make the previously asymptomatic infection by Toxoplasma gondii turn into an active infection. Source– DennNov 27, 2015 at 15:41
I'm sorry, I don't see how that first paper supports this? There's a lot in there about how to treat pregnant women who get infected and how to treat newborns who were exposed in the womb, for both the active infection (if they are still infected at birth) and the effects that infection had, but nothing about them still carrying the parasite well into adulthood when they could be donating blood– YviDeNov 29, 2015 at 14:01
Toxoplasma gondii forms cysts in tissue while in their latent phase (bradyzoites) and that creates a latent infection that's detected via IgG levels. The study I linked to kind of presuppose that and you're right, it isn't very clear. I tried to find better: this that mentions reactivation of congenital toxoplasmosis 20 years after birth in the discussion, and this, an example of a transmission from an asymptomatic woman infected and treated 20 years ago to her newborn (for the transmission aspect)– DennNov 29, 2015 at 16:31