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In most cases, toxoplasmosis doesn't cause any symptoms and a person isn't aware that they're infected.

In most cases, toxoplasmosis doesn't cause any symptoms and a person is not aware they are infected.

In healthy children and adults, the immune system is usually strong enough to prevent the Toxoplasma gondii (T. gondii) parasite causing serious illness.

After a toxoplasmosis infection, most people are immune to further infection for the rest of their life. This means that if a woman who has previously been infected becomes pregnant, there will be no risk to her baby.

However, a blood test would be needed to check for immunity. You should also still take precautions if you're pregnant, such as wearing gloves while gardening or cleaning out your cat's litter tray.

Flu-like symptoms

In some cases, toxoplasmosis can cause the lymph nodes (glands that are part of your immune system) to swell, particularly in the throat or armpits. This can lead to flu-like symptoms, such as: 

  • a high temperature (fever) of 38°C (100.4°F) or over
  • aching muscles
  • tiredness
  • feeling sick
  • sore throat

People who are otherwise healthy rarely experience any serious symptoms of toxoplasmosis.


The risk of getting toxoplasmosis when you're pregnant is low. For example, a 2008 study showed that in non-immune women (those who haven't had the infection before), about 5 in 1,000 may get a toxoplasmosis infection.

However, if you develop toxoplasmosis when you're pregnant or shortly before conceiving, there's a risk that you'll pass it on to your baby. If a baby gets toxoplasmosis from their mother, it's known as congenital toxoplasmosis.

Although you probably won't experience any symptoms of the infection yourself, an infection that develops during the early stages of pregnancy also increases the risk of:

  • miscarriage – the loss of a pregnancy during the first 23 weeks
  • stillbirth – where a baby is born after 24 weeks of pregnancy without any signs of life

Congenital toxoplasmosis

The symptoms of congenital toxoplasmosis vary depending on when the mother becomes infected. The baby's symptoms will usually be more severe if the mother is infected around the time she became pregnant or during the first or second trimester (up to week 27 of the pregnancy).

Symptoms of toxoplasmosis in babies can include:

  • hydrocephalus – water on the brain
  • brain damage
  • epilepsy – a condition that affects the brain and causes repeated seizures (fits)
  • jaundice – yellowing of the skin and the whites of the eyes
  • deafness
  • eye infections and reduced vision
  • an enlarged liver or spleen (the organ that filters impurities from your blood)
  • growth problems
  • cerebral palsy – a brain and nervous system condition that affects a child's movement and co-ordination

If a mother becomes infected during the third trimester of pregnancy (from week 27 to birth) and the infection is passed on to her baby, the baby may not have any symptoms at birth.

However, complications may develop later in life. For example, months or years later a child born with congenital toxoplasmosis may develop reduced vision, hearing loss or learning difficulties.

Read more about the complications of congenital toxoplasmosis.

People with immune deficiencies

Toxoplasmosis can be fatal for someone with a weakened immune system. This is because their body may not be able to fight off the infection.

Your immune system can be weakened if you:

  • have an illness that affects your immune system, such as HIV and AIDS or cancer
  • are receiving certain types of medication, such as chemotherapy (powerful cancer-killing medication)
  • are taking immunosuppressant medication – for example, after having an organ transplant

There's also a risk of permanent eye or brain damage when toxoplasmosis infects someone with a weakened immune system.

If toxoplasmosis begins to affect the brain, it can cause encephalitis. This is sometimes called toxoplasmosis encephalitis (TE) and it can be fatal in people with AIDS.

Signs and symptoms of TE and toxoplasmosis in people with immune deficiency include:

  • headaches 
  • confusion
  • poor co-ordination
  • seizures (fits)
  • chest pains
  • coughing up blood
  • difficulty breathing
  • a high temperature (fever) of 38°C (100.4°F) or over
  • vision problems, such as blurred vision and floaters (small pieces of debris that can cloud your vision)
  • multiple lesions (wounds) in the brain
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The toxoplasmosis infection is caused by the Toxoplasma gondii (T. gondii) parasite.

The toxoplasmosis infection is caused by the Toxoplasma gondii (T. gondii) parasite.

The T. gondii parasite can be found in the faeces of infected cats and the meat of infected animals.

T. gondii can reproduce inside a cat's bowel. An infected cat can pass the parasite in its faeces for the following few weeks. The cat won't usually have any symptoms, so you may not know it's infected.

Infection via the food chain and environment

There are four ways the T. gondii parasite can enter the food chain and cause a toxoplasmosis infection. You can become infected by: 

  • ingesting food, such as fruit and vegetables, water or soil contaminated with infected cat's faeces
  • eating or handling raw or undercooked infected meat, usually pork, lamb or venison (grazing animals can become infected after eating contaminated grass or animal feed)
  • using knives, cutting boards and other utensils that have been in contact with contaminated, undercooked or raw meat
  • eating or drinking infected unpasteurised goats' milk or products made from it, such as cheese

There's also a small risk of the toxoplasmosis infection being passed from sheep during the lambing season. This is because the T. gondii parasite is sometimes found in the afterbirth and on newborn lambs after an infected sheep has given birth.

Toxoplasmosis can't be passed on through person-to-person contact. This means that:

  • you can't catch toxoplasmosis from coming into contact with an infected person
  • you can't pass toxoplasmosis on to your children if you have previously had the infection
  • it's not possible to pass the infection on through breastfeeding

However, in rare cases, people have developed toxoplasmosis from an infected organ transplant or blood transfusion.

Congenital toxoplasmosis

Congenital toxoplasmosis is where a baby is born with toxoplasmosis. The mother passes the infection to her baby through the placenta (the organ that links the mother's blood supply to her unborn baby's).

However, congenital toxoplasmosis can only occur if the mother becomes infected for the first time, either while she's pregnant or shortly before conceiving.

Congenital toxoplasmosis is more likely to occur if a woman becomes infected later in her pregnancy. For example, if you become infected around the time of conception, there's a less than 5% chance that your baby will also develop the infection.

However, if you become infected during the third trimester of your pregnancy (from week 27 until the birth), there's about a 65% chance your baby will also be infected.

One study calculated that for every week further along the pregnancy that the mother was infected, the likelihood of the toxoplasmosis infection being passed on to her baby increased by 12%.

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If you're infected with the Toxoplasma gondii (T. gondii) parasite, your immune system will start producing antibodies to fight it.

If you're infected with the Toxoplasma gondii (T. gondii) parasite, your immune system will start producing antibodies to fight it.

Antibodies are proteins that neutralise or destroy invaders such as bacteria or parasites. If toxoplasmosis is suspected, you'll have a blood test to check for these antibodies.

Negative result

Early testing can sometimes produce a negative result when a person is actually infected. Known as a false-negative, it occurs when the body hasn't had time to start producing antibodies to the parasite, which usually takes up to 23 days after the initial infection. However, a person who has developed symptoms of toxoplasmosis will nearly always have a positive blood test.

If you're symptom-free but concerned, your GP may recommend another blood test two to three weeks later. If the result is still negative, it's unlikely you have the toxoplasmosis infection.

Positive result

A positive result doesn't necessarily mean you have an active toxoplasmosis infection. After having toxoplasmosis, the antibodies will remain in your blood for the rest of your life, protecting you from being infected again by the parasite. A positive result usually indicates you've been infected at some point in the past.

You will need more blood tests to find out whether you have a new infection. Checking the levels of antibodies in your blood a second time can help determine when the infection occurred. For example, if the levels of antibodies are:

  • increasing – suggests a new active infection (perhaps a few weeks old)
  • still the same – suggests an old infection and that you are now immune
  • decreasing – suggests a recent infection that is no longer active (perhaps a few months old)

Specialised testing is important if you're pregnant or have a weakened immune system.

Pregnant women

If you are pregnant and tests confirm you have a recent toxoplasmosis infection, you'll need a further test to determine whether your unborn baby is also infected.

Amniocentesis is the most effective and commonly used test and can be carried out any time from 15 weeks of pregnancy onwards. It involves inserting a fine needle through the mother's abdomen to collect a sample of amniotic fluid (the fluid surrounding the foetus in the womb). The sample will be tested for toxoplasmosis.

Amniocentesis carries around a 1% risk of causing a miscarriage. The procedure usually takes 10 to 30 minutes, and you may find it slightly uncomfortable.

Congenital toxoplasmosis

Amniocentesis can confirm whether your baby has congenital toxoplasmosis. However, it can't determine whether the infection has caused any damage to your unborn baby or, if it has, how much.

If your unborn baby has congenital toxoplasmosis, treatment with medication will be started as soon as possible. After your baby is born, he or she will be examined for any signs of damage from the infection and treatment may continue.

If necessary, your baby will continue to have blood tests for up to a year, or possibly longer, until the test results for toxoplasmosis antibodies are negative. When results indicate there are no antibodies, your baby has been shown to be infection free.

Immune deficiencies

If you have a weakened immune system (because of chemotherapy, for example), routine blood tests for antibodies can produce a false-negative result. This is because it's possible your immune system won't produce antibodies to fight the infection.

Your doctor may request the following tests:

  • computerised tomography (CT) scan – where several X-rays are taken at slightly different angles and assembled by a computer to produce a clear, three-dimensional image of the inside of your brain
  • magnetic resonance imaging (MRI) scan – where a strong magnetic field and radio waves are used to produce detailed images of the inside of your brain

The test results will reveal if you have any lesions (wounds) in your brain, which occur in some cases of toxoplasmosis.

New research

New research is looking at other ways of diagnosing toxoplasmosis – for example, by identifying the DNA of the T. gondii parasite in samples of cerebrospinal fluid (the fluid that surrounds your brain and spinal cord).

It's hoped that this may be a quicker and more reliable method of diagnosis, and will help confirm whether the damage to the brain has been caused by toxoplasmosis rather than by another condition.

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A toxoplasmosis infection can sometimes spread to the eyes (ocular toxoplasmosis).

A toxoplasmosis infection can sometimes spread to the eyes (ocular toxoplasmosis).

Ocular toxoplasmosis

The Toxoplasma gondii (T. gondii) parasite, which causes toxoplasmosis, can lie dormant (inactive) in the retina for many years. But if the parasite becomes active again, it can start a new infection.

Ocular toxoplasmosis causes ocular lesions, which are wounds in the eyes caused by inflammation and scarring. These can appear in the:

  • retina – the light-sensitive layer of tissue at the back of the eye
  • choroid – the layer behind the retina that contains major blood vessels

This damage to the eyes is called retinochoroiditis and can cause eye problems, such as:

  • a partial loss of eyesight in one eye
  • squint – where one eye looks in a slightly different direction to the other one
  • clouding of the eye's lens (cataracts)
  • eye shrinking (microphthalmia)
  • loss of cells and tissue from the optic nerve, which connects the eye to the brain, resulting in poor vision (optic atrophy)

Antibiotics and steroids are often used to treat the lesions. The scarring caused by toxoplasmosis will not clear up, but treatment may prevent it from getting worse.

If the infection keeps returning, antibiotics may be prescribed on a long-term basis. While this may help prevent the infection recurring, the long-term side effects of these medications are not yet known.

Congenital toxoplasmosis

In most cases, babies born with congenital toxoplasmosis develop normally after treatment with antibiotics.

However, in up to 4% of cases, serious complications can develop within the first years of life. These include:

  • permanent visual impairment (partial or, very rarely, complete sight loss)
  • permanent brain damage

Retinochoroiditis is a common complication of congenital toxoplasmosis.

One study found that 18% of children with congenital toxoplasmosis had at least one ocular lesion as a result of retinochoroiditis. Of these, 42% developed a second ocular lesion later in life.

Cases of ocular toxoplasmosis can also occur years after infection. One study found the average age at which it appeared was nine years old.

It's also possible for someone to develop complications in their 20s or 30s. These may include:

Further research is needed to follow-up cases of congenital toxoplasmosis. Regular eye tests may help detect any abnormalities as they develop, and treatment with antibiotics can limit damage toxoplasmosis causes. However, at present it's not possible to reverse damage already done.

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