Introduction 

Toxoplasmosis is an infection caused by a common parasite called Toxoplasma gondii (T. gondii).

Most warm-blooded animals, including sheep, cattle, dogs and humans, can be infected with this tiny single-celled parasite.

However, the parasite can only be passed on if it enters the environment or food chain, or if it passes from an infected mother to her unborn baby (known as congenital toxoplasmosis). Rarely, the parasite can also be passed from human to human through organ transplantation.

Although toxoplasmosis is common worldwide, it's not reported that often in the UK. This may be because the symptoms of toxoplasmosis tend to be mild and general in otherwise healthy people, which may lead to a large proportion of cases going unnoticed.

Most people who get toxoplasmosis don't have symptoms. Around 10-15% of people develop symptoms similar to mild flu or glandular fever, such as a temperature, sore throat and muscle aches.

Severe toxoplasmosis

Toxoplasmosis is more serious in people with weakened immune systems, such as those who have had an organ transplant, those with HIV and AIDS, and those receiving certain types of chemotherapy treatment.

Ocular toxoplasmosis is a possible and serious complication of toxoplasmosis. The infection spreads to the eye, where ocular lesions (wounds) develop, which can lead to a partial or complete loss of vision in the affected eye.

Read more about the complications of toxoplasmosis.

Congenital toxoplasmosis is also serious. It occurs when a woman becomes infected during pregnancy and passes the infection on to her unborn baby. This can result in the baby developing serious health problems, such as brain damage and partial blindness.

Read more about toxoplasmosis during pregnancy.

How is toxoplasmosis spread?

The T. gondii parasite that causes toxoplasmosis is often found in the faeces of infected cats. Cats don't usually show any symptoms of toxoplasmosis, so you may not know whether your cat is infected. 

Infected cats usually only excrete the parasite for a short period of time, usually two to three weeks after they're first infected.

If the T. gondii parasite gets into the environment or food chain, it can be ingested by humans. Infection can occur by:

  • consuming food, water or soil that's contaminated with infected cat's faeces
  • eating or handling raw, undercooked infected meat, such as pork, lamb or venison, or infected cured meat, such as salami 
  • using knives and other utensils that have been in contact with undercooked or raw infected meat
  • drinking unpasteurised goats' milk or eating products made from it, such as cheese

Toxoplasmosis can't be passed from person to person, other than in rare cases, such as receiving an infected organ or blood products during an organ transplant, or if a newly infected mother passes the infection on to her unborn baby.

Read more about the causes of toxoplasmosis.

Diagnosing toxoplasmosis

If you're infected with the T. gondii parasite, your immune system will start to produce antibodies (infection-fighting proteins). If toxoplasmosis is suspected, you'll have a blood test to check for antibodies.

If you're pregnant and tests confirm that you've had a recent toxoplasmosis infection, you'll need a further test to determine whether your unborn baby is also infected. Amniocentesis is the test most commonly used.

Read more about how toxoplasmosis is diagnosed.

Treating toxoplasmosis

In otherwise healthy people, toxoplasmosis doesn't usually require treatment.

Medication is usually only prescribed to treat severe or prolonged cases of toxoplasmosis, particularly in people with a weakened immune system. Pyrimethamine plus sulfadiazine or azithromycin are the medications often prescribed.

Pregnant women infected with toxoplasmosis for the first time may be prescribed antibiotics. This aims to reduce the risk of the unborn baby becoming infected, and limit the severity of congenital toxoplasmosis if the baby does become infected.

Read more about treating toxoplasmosis.

Preventing toxoplasmosis

There are a number of measures you can take to reduce your risk of developing toxoplasmosis, including:

  • wearing gloves while gardening, particularly when handling soil
  • not eating raw or undercooked meat
  • washing utensils and other kitchenware thoroughly after preparing raw meat
  • washing fruit and vegetables thoroughly before cooking and eating them

Read more about preventing toxoplasmosis.

Coloured transmission electron micrograph (TEM) of Toxoplasma gondii parasites inside a human cell  

Who is affected by toxoplasmosis?

Estimates suggest that up to a third of the UK population will acquire a toxoplasmosis infection at some point in their life. However, most people won't notice any symptoms.

Severe congenital toxoplasmosis – where a mother passes the infection on to her unborn baby, who then goes on to develop significant complications – is rare, with about 3 in every 100,000 babies born with the condition in the UK.

How to prepare and cook food safely

How to prepare and cook food correctly to reduce the risk of food poisoning, including E. coli

Page last reviewed: 09/09/2013

Next review due: 09/09/2015