Toxoplasma gondii – or toxoplasmosis – you may have heard of this parasite or infection if you have ever been pregnant and owned a cat. But what is it and what are the actual risks?

*Disclaimer: This blog is intended for informational purposes only. The information on this blog should not be used as a substitute to medical advice or medical treatment. As always, your Primary Care Provider, a doctor, or another health professional is your best resource for specific questions and medical advice. If you believe you or a loved one are experiencing a medical emergency, please contact 911.*

What is toxoplasma gondii?

It is a parasite – well actually to be more specific, it is protozoan parasite. This means that it is a tiny single-celled organism – which is what a protozoa is – but it has adapted to invade the cells of another living organism (like a parasite).

These organisms produce cysts (also known as oocysts). This is probably exactly what you’re picturing – a difficult to penetrate wall around a protozoan parasite (it’s a bit more complicated than that, but I’m trying to keep it simple here). This helps it survive in rougher environments. Some types of protozoan parasites can also be found in our food, water, or the earth.

Toxoplasma gondii specifically likes to infect cats as its “other living organism”. They usually get the infection from eating something that has tissue cysts from the protozoan parasite (for example by eating a mouse or rat outdoors – this is just one example), or from directly eating the cysts. They then release more cysts in their own feces – either outdoors (if they go outside) or in their litter box.

How do humans get this infection?

There are several ways in which humans can acquire toxoplasmosis. You’re probably most familiar with the “cat litter method” – this could occur if your cat was infected and you changed their litter and didn’t perform the sanitary measures after to safeguard yourself against it. It can also be via anything that has been contaminated by said infected-cats-feces (such as soil outdoors where an outdoor cat has gone to the washroom, fruit/vegetables from a garden in a similar situation, or even from countertops where an infected cat has walked – that’s why proper food preparation and hygiene is really important always).

Other pathways to infection include consuming meat that is undercooked (and where the animal was infected and therefore had cysts in their tissue); through organ transplant or blood transfusion from someone who is/was infected; or via the placenta – from a mother who was infected to the fetus (or fetuses) they are carrying.

What are symptoms of this infection?

It can very often be asymptomatic or mild in an otherwise healthy person.

Some people may develop a “flu-like” illness with swelling of the glands, body aches, fever, and fatigue.

Why is this infection a particular concern for pregnant women?

The risk in pregnancy is transmission to the fetus – unfortunately it can pass through the placental barrier (unfortunately, and you’ll know this if you’re pregnant – things like some medications and some other infections, can too). Infection with toxoplasmosis and passage to the fetus can cause many issues (sometimes not till some time after birth) such as brain damage, vision loss, and disability.

If you are pregnant and were infected within 3 months of conception, there are still risks for the above complications. Infection around the time of conception or in early pregnancy appears to be the most hazardous if fetal transmission occurs. Third trimester appears to be when risk for transmission to the fetus from the mother is the highest.

Treatment can be provided – an antibiotic if only mom is infected, or a combination of antibiotic and another medication(s) if fetal infection is suspected. With fetal infection, even after treatment there would likely be continued monitoring for several years following and often ongoing antibiotic therapy. Treatment can be helpful in reducing the complications (making them less severe).

Any infection prior to 3 months before conception has been shown to have little to no risk for the fetus.

Infection can also be related to an increased risk for preterm labor, miscarriage, or stillbirth.

How will I know if I have it or have previously been infected?

Blood work can be done in pregnancy (and is done in some places in the world as part of regular prenatal bloodwork) – in Canada, it’s not routine because there are a couple issues with it such as high cost of the test, high false-positive rates, and the fact that the infection is not that common here (or the US).

I personally had this test done because I reported a past history of 1) regularly changing the litter, but also 2) working in a veterinary office for 2 years. I was negative for any previous or current infection.

Ultrasound and amniocentesis can also be used to diagnose – however depending where you are there is specific criteria for the use of amniocentesis in this situation.

I have cats or work with them; I have a garden where I’ve seen outdoor cats; my cats walk on the countertops, ETC. Do I need to live in fear of this infection now?!

The “good” news about this infection is that:

1. If you’re in Canada, the US, or the UK – this infection is relatively uncommon.
2. If you have pet cats – they’re less likely to be carriers of this infection since they are most likely eating cat food. The risk is even less is they stay indoors – since they’d have less risk of eating anything outside or being exposed to any cysts in the environment.

The best first defense is often prevention – even though it’s lower risk here, it’s wise and advised to take precautions anyways. That means making sure you are practicing proper food handling and hand hygiene; having someone else take over litter duty (if that’s not possible, be protected – wear gloves) and make sure the litter is being changed regularly; and avoiding direct skin contact with soil or sand (wear gloves). There may be further guidance for those who work in high risk areas – like a veterinary office, or based on whatever your unique situation might be.

There are also a few more suggestions for prevention here and here.

I’m breastfeeding – if I get infected, can I pass it on to my baby via breast milk?

There is currently no evidence that this parasite is passed via breast milk.

The CDC says there may be a possibility of passing it via bleeding nipples (due to cracks and damage) but it is unlikely. As always – I advise discussing any particulars with your healthcare provider.

It should also be noted that toxoplasmosis is not passed by person-to-person contact – so if your partner, husband, friend, or loved one has the infection, there is no evidence that they will pass it on to you or your baby.

Someone told me to avoid being around sheep during the season they have babies… is this because of the same infection?

I heard/read this when I was travelling to Ireland during early pregnancy – luckily, lambing season was over and I actually just (still – because safety) avoided the scenario all together (there are a lot of places with sheep in Ireland though, if you didn’t know).

But yes – one of the infections you can get from female sheep at that time of the year (January to April in the UK – however it may vary in different places) is toxoplasmosis (among others). However, similar to transmission from cats – it is generally rare. Preventative measures are still advised though – they can be found here if you need to refer to them for any reason.

You say it’s uncommon but I’ve seen sources say that a lot of people have been exposed to it or test positive for past infection. How common is it actually?

This is complicated and I am not an epidemiologist or an infectious disease expert so I am not the right person to ask this question to. I cede to my expert friends on Twitter, and those I don’t know who have so much more knowledge than me on the subject – another good resource is of course – your healthcare provider.

What I can tell you is that the rate (of the entire population 6 or older) of past infection in the US is ~11%. Infection is tied to location as places with higher humidity or hotter climates tend to have increased rates (the cysts are more easily able to survive in these climates vs cold ones).

The parasite itself is common, however human infection in the US and Canada is generally low and in most people – low risk or mild.

If you are taking the proper precautions when you’re pregnant, the rate of transmission to pregnant women is also low in these countries. How? Well, you may already be immune due to previous infection. If you get sick, you may not transmit it to your baby (but this is one of the many reasons it’s important to KEEP and ATTEND prenatal appointments, and also to discuss any concerns you may have with your HCP).

Finally, if you’ve never been exposed the chance of your first exposure occurring during pregnancy is just, not super likely (still possible but not likely – especially if you are following the precautions as advised by your care provider).

So – there is a bit more information on this infection. I know I personally spent a strange amount of time worrying about this because I’m a cat owner – however my cats are both indoors and eat dry food (not raw meat – is that really a thing?!). I also volunteered my husband as tribute to clean the litter boxes while I was pregnant to reduce risks just in case, and followed the other recommendations for food handling and avoidance. If you’re concerned – talk to your provider about your risk factors and ask them any questions you may have. They are there to help, guide, and support you.

As always, friends of higher knowledge, let me know if anything needs correction or updating!