Agreed with above. It is toxoplasmosis. Listeria comes from deli meats, hot dogs, etc. Not that pregnant women should not have them, but caution should be given. I will be an ob/gyn by this July
As for toxoplasmosis, the majority of cases come from humans consuming contaminated meat. Half of the US is already seropositive. Cats are considered a carrier but this is how it happens: the cat consumes an infected animal such as a rodent, the toxoplasmosis is passed through the stool and into the litter box. Human cleans litter box and contaminates himself/herself via the fecal oral route. If a woman during pregnancy acquires this as a primary infection, especially in the first trimester, it is considered a threat to the fetus (she will test positive for IgM antibodies). Being positive for IgG does not confer a threat as that suggests she was already infected some time ago, it is the primary infection that is a threat.
I have seen some women go so far as even get rid of their cats during their pregnancy, as in forever. That is overkill imho. Aside from the fact that she is more likely to get it from what she eats, so long as she does not touch the litter, she should be fine.
Theoretically, if someone is really concerned, perhaps frequent handwashing will further reduce risk of a primary infection as a large proportion of infections that arise from stool are from the fecal oral route (you know, didn't wash hands, trace amount of stool on hands gets consumed during dinner, etc.....gross
---actually, studies have shown that the average person consumes a small/trace amount of stool on a daily basis...yum
). Alcohol rub should never take the place of handwashing if you can avoid it. Handwashing actually removes certain pathogens that alcohol will not.