What is toxoplasmosis? And why cats are not always to blame

In most people, toxoplasmosis doesn’t cause any symptoms. But for some, an infection can be serious. Find out if you’re at risk, and how to protect yourself.

Research suggests 125,000 people get toxoplasmosis in Australia each year, yet many of them never know they have it.

An infection that’s caused by a parasite called toxoplasma gondii, toxoplasmosis is closely associated with cats – cats pick it up by eating infected rodents or birds, and can then pass it on to humans.

But, while handling cat faeces is one way of contracting the parasite, another common route of infection in adults is by eating raw or undercooked meat that’s infected with toxoplasma.

Research published in 2019 highlighted a high prevalence of toxoplasma in certain types of meat sold in Australian supermarkets.

So, how dangerous is toxoplasmosis?

In 80 per cent of cases, toxoplasmosis doesn’t cause any symptoms.

Still, not only is there no cure, the parasite can cause dormant infections that persist for life and can reactivate at some stage.

For other people it can feel like the flu, causing symptoms including headache, muscle aches, a fever, and swollen lymph nodes.

In immunocompromised people, for example those undergoing treatment for cancer, toxoplasmosis can be more serious – it can cause severe brain or lung disease.

It can also cause ocular toxoplasmosis, which is an inflammation of the retina – even in people with healthy immune systems.

“Inflammation in the retina continues to be the most common disease caused by an infection with toxoplasma,” ophthalmologist and vision scientist Professor Justine Smith says.

A new Flinders University study shows women are more likely than men to experience recurrent toxoplasmosis, which can progressively damage the retina and lead to vision loss.

“For the first time, we’re showing that symptoms of toxoplasmosis vary not just depending on the age and health of the infected individual but also on their gender,” Prof Smith, who is the senior author of the study, says.

Toxoplasmosis and changes in behaviour

The toxoplasma parasite can spread to other parts of the body aside from the retina, including the brain.

“Toxoplasmosis is a weird disease, in that it can change behaviour,” Swinburne University of Technology Professor of Microbiology Enzo Palombo says.

“For example, research has shown that when mice get it, they seem to lose their fear of cats and other predators, making them more likely to engage in activities and behaviours that increase their chances of getting caught,” Prof Palombo says.

Toxoplasmosis can increase risk-taking behaviour in humans too, with some findings suggesting a link between toxoplasma infection and a greater risk of car accidents and drug abuse .

Toxoplasmosis during pregnancy

If you get toxoplasmosis for the first time when you’re pregnant, you can pass on the infection to your unborn baby.

During the early stages of pregnancy, toxoplasmosis can cause brain damage and liver, eye and spleen disorders in your baby; if you’re further along, it can cause ongoing infection in your baby’s eyes.

Can toxoplasmosis be prevented?

Immunisation against toxoplasmosis isn’t available so, as well as practising safe food preparation, you can take the following precautions to help prevent infection:

• Cook meat thoroughly and avoid eating rare or medium-rare meat dishes.
• Wash all vegetables well, to remove all traces of soil.
• Always wear gloves while gardening.
• If you have a cat, make sure litter trays are cleaned daily, wear gloves for the task and wash your hands thoroughly once you’re finished.

Read more on health conditions and diseases:

• How to know if a barking cough is croup (and what to do)
• Is Buruli ulcer the reason your skin won’t heal?
• 5 surprising causes of UTIs and how to reduce your risk
• Why you need to take a look at your eye health

Written by Karen Fittall.