Ask Elizabeth: 01/09

Q:Dear Elizabeth: Help! I am pregnant and really need some answers about Toxoplasmosis. I know (from reading CatWatch!) that people can be infected by eggs in a cats feces. I also understand that Toxoplasmosis is really dangerous during pregnancy, so I had my cat tested last week.

When my veterinarian called with Twitchys negative result, I breathed a sigh of relief …. but then she went on to recommend that I consult with my doctor and have myself tested! Whats that about? Why should I be tested if Twitchy is negative?

A:Toxoplasmosis is one of my favorite topics so Ill be happy to help you! You may recall that one of my previous lives was spent as an outdoor, homeless cat. During that time, I often dined on small critters that I caught, so although I havent been tested, it is likely that I am among the 30 percent of American cats who have been infected with Toxoplasmosis.

When first infected, cats go through a one- or two-week period of oocyst (egg) shedding. During that early phase, millions of oocysts are passed in the stool. After that initial phase, oocyst shedding stops and rarely happens again. Some cats get sick with Toxoplasmosis after the early oocyst-shedding phase and

Bev Caldwell


others do not; regardless, infected cats all continue to harbor Toxoplasmosis organisms (encysted in their muscle) for life.

So, what about me? If my people decided to have me tested, it is likely that I would have a positive antibody titer (IgG) indicating that I was infected at some time in my checkered past. We know that oocyst shedding occurs in the first two weeks of infection, and we know that cats take several weeks to produce IgG antibody. Putting these two facts together means that an IgG positive cat is unlikely to be shedding oocysts.

Now, what about you and Twitchy? Since she is negative, it is unlikely that Twitchy is currently shedding oocysts – so your sigh of relief was absolutely warranted! However, IF she becomes infected for the first time while you are pregnant, she will pass oocysts, and those oocysts represent a risk to your fetus.

The last piece of the Toxoplasmosis puzzle is you. Like cats, many people in the U.S. have been infected with Toxoplasmosis – most often without even being aware of the infection. Studies have shown that between 25 to 50 percent of people tested in the U.S. are positive on antibody testing.

When a pregnant woman is infected (via oocysts in a cats stool or by eating undercooked meat) for the first time, there is real risk of the organism passing through the placenta to infect the fetus. Prenatal infection can be devastating to the developing baby, especially if it occurs during the first three or four months of pregnancy.

This explains your veterinarians recommendation to have yourself tested. If you have an IgG antibody titer (indicating previous infection), your developing baby has much less risk of transplacental infection, even if you are exposed again during pregnancy.

To summarize the situation that you, your baby and Twitchy are potentially faced with:

(1) People can be infected with Toxoplasmosis organisms by eating undercooked meat, or by accidental ingestion of oocysts from a recently infected cats stool. (Ingestion of oocysts in stool seems like a long shot, doesnt it? Oral infection happens most often when garden vegetables are contaminated by outdoor cats feces and then eaten without adequate washing.)(2) Your developing baby is at risk of transplacental infection if you are infected for the first time during pregnancy.

(3) Since she is negative for antibodies, it is unlikely that Twitchy is shedding Toxoplasmosis oocysts at this time. Our goal is to keep her free of infection during the sensitive time of your pregnancy; therefore she should be fed cat food only (no critters!) and kept indoors to prevent hunting.

(4) For extra information wed like to know your status: If you are IgG negative, you should be extra cautious about avoiding infection during your pregnancy. If you are IgG positive already, your developing baby is at much less risk of transplacental infection – even if you are re-exposed during pregnancy.

I hope this is helpful! Congratulations on your new family member, and regards to Twitchy. Love, Elizabeth .

Editor’s Note: Guess how the majority of Toxoplasmosis-positive Americans are infected? Dont blame it on cats! Studies have estimated that the majority of human cases of Toxoplasmosis in the U.S. are due to eating undercooked meat.