Brain parasites: how to protect yourself from toxoplasmosis

There are a number of inconvenient things about being pregnant. One of those inconveniences, the Toxoplasma gondii parasite, however, offered me a silver lining during my own pregnancy: for a whole nine months, I didn’t have to clean out our cat’s litter tray. Allow me to explain why.

Toxoplasma gondii, a single-celled organism found all over the world, causes a zoonosis (a disease transmitted from animals to humans) known as toxoplasmosis. It’s a parasite with the ability to embed itself into our cells – the cells in our muscles and brain, to be precise. As spine-chilling as that sounds, most people who become infected at some point in their lives don’t suffer any consequences. Many of them don’t even realise that they’ve caught it. The pathogen can, however, be dangerous to people with compromised immune systems. Unborn children can also be at risk if their mother becomes infected with toxoplasmosis during pregnancy.

How do these infections happen?

In Switzerland, the number of people with Toxoplasma gondii antibodies has been steadily decreasing since the 1980s, from over 50 per cent of the population at that time, to less than 30 per cent today. The figures in Germany are significantly higher, with an average of 50 per cent for adults. In the USA, however, only one in ten people on average have been infected with the pathogen in the past.

There are two main ways that a toxoplasmosis infection can occur:

1. Because the pathogens are commonly found in slaughtered animals such as pigs, sheep, and poultry, you can become infected by eating raw or inadequately treated meat or meat products if they contain live T. gondii cells. However, freezing (-21°C) or heating to at least 50°C for 20 minutes will kill the pathogen.
2. The parasite is also found outdoors, so you can catch the infection when doing activities like gardening too. This is down to the fact that the pathogen’s cells are excreted in animal faeces. Once they’re in the ground, they can survive for up to five years. If you have a cat, you can also get infected while cleaning out their litter box. It’s why I was able to leave the cat poo clean-up to somebody else for the duration of my pregnancy without a smidge of guilt.

In some cases, unborn babies become infected in the womb if their mother comes into contact with toxoplasmosis during pregnancy. However, if the mother is infected before falling pregnant, the embryo is protected by the mother’s antibodies.

The parasites can enter the brain without you noticing

Eighty to 90 per cent of all toxoplasmosis infections are symptom-free. However, even when symptoms do appear, their resemblance to flu means people infected with toxoplasmosis are often unaware of it.
Prenatal Toxoplasma infections, on the other hand, (that is, when a woman becomes infected during pregnancy and transmits the pathogens to her unborn child), can have more serious consequences. If the infection occurs during the first trimester of pregnancy, it can severely damage the embryo or cause miscarriage. If the infection occurs later in pregnancy, the effects are varied, ranging from retinitis, to calcification of the brain’s vascular structures, to other changes in the brain.
A T. gondii infection isn’t just dangerous to unborn children. People with compromised immune systems are also at risk of severe consequences, including encephalitis (inflammation of the brain).

How to protect yourself from infection

The Robert Koch Institute has issued some advice to help prevent infection with the parasite:

• Don’t eat raw meat or meat products that haven’t been heated up or frozen properly (e.g. minced or mildly cured sausages).
• Wash raw vegetables and fruits thoroughly before eating.
• Wash your hands before eating.
• Wash your hands after preparing raw meat, doing gardening, fieldwork or other forms of work involving soil, and after visiting play areas with sandboxes.
• If you’re pregnant and have a cat at home, feed your cat pet canned and/or dry food. Litter boxes, especially those of outdoor cats, should be cleaned daily with hot water – but not by the pregnant person.

If you want to find out more, you’ll find more information (in German) on the Swiss Federal Office of Public Health or Robert Koch Institute websites.