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Read about toxoplasmosis, a parasitic infection that can be dangerous for pregnant women and people with weak immune systems.

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

The infection is common worldwide, including in the UK, but it's rarely reported because there are often no symptoms.

Around 350 cases are reported in England and Wales each year, but it's thought the actual number of infections could be as high as 350,000.

Estimates suggest up to a third of people in the UK will be infected by toxoplasmosis at some point in their life, but most people won't notice it.

Is toxoplasmosis serious?

Toxoplasmosis is usually nothing to worry about because the immune system is normally strong enough to fight the infection and stop it from causing serious illness. After getting the infection, most people are immune to it for the rest of their life.

However, it can lead to serious problems in:

  • women who become infected while they're pregnant –toxoplasmosis could cause a miscarriage or stillbirth, or the infection could spread to the baby and cause serious complications (congenital toxoplasmosis)
  • people with weak immune systems, such as those who've had an organ transplant, those with HIV, and those having chemotherapy – this could mean the infection is able to spread to the eyes, heart, lungs or brain

Congenital toxoplasmosis is rare in the UK, with estimates suggesting only around 1 in every 10,000 to 30,000 babies are born with the condition.

Read more about the symptoms of toxoplasmosis and complications of toxoplasmosis.

How do you get toxoplasmosis?

The parasite that causes toxoplasmosis is found in the poo (faeces) of infected cats and in infected meat.

You can become infected if the parasites get into your mouth – for example, by:

  • handling or eating raw, cured or undercooked infected meat – particularly lamb or pork
  • eating food (such as unwashed fruit and vegetables) or drinking water contaminated with infected cat's poo
  • accidentally getting contaminated soil or cat litter in your mouth

Toxoplasmosis can't be passed from person to person, other than in rare cases, such as receiving an infected organ 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.

Testing for toxoplasmosis

blood test can be carried out to see if you have been infected with the T. gondii parasite.

Testing may be carried out if there's a chance you have the infection and you have symptoms or you're at risk of serious problems. For example, it may be recommended if you're diagnosed with HIV.

In the UK, testing for toxoplasmosis isn't routinely carried out during pregnancy. If you're concerned you might have been infected while you're pregnant, talk to your midwife, GP or obstetrician about the possibility of getting tested.

Read more about how toxoplasmosis is diagnosed.

Treating toxoplasmosis

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

Medication to treat the infection is usually only used to treat severe cases or prevent complications in people at risk, such as those with a weak immune system. Pyrimethamine plus sulfadiazine or azithromycin alone are the main medications used.

Pregnant women infected with toxoplasmosis for the first time may be given medication to reduce the risk of the unborn baby also becoming infected or damaged, although it's not clear exactly how effective this is.

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
  • washing your hands before handling food
  • not eating raw or undercooked meat
  • washing utensils and other kitchenware thoroughly after preparing raw meat
  • washing fruit and vegetables thoroughly before eating them
  • emptying cat litter trays every day
  • avoiding direct contact with cat poo in cat litter or soil

It's particularly important to take these precautions if you're pregnant or have a weakened immune system.

Read more about preventing toxoplasmosis.

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Read about the main symptoms of toxoplasmosis, including what problems the infection can cause during pregnancy and in people with weak immune systems.

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

This is because the immune system is normally strong enough to fight the infection and stop it causing serious illness.

However, some people will develop flu-like symptoms. There's also a risk of more serious problems if a woman becomes infected while she's pregnant, or if someone with a weak immune system becomes infected.

Flu-like symptoms

About 10-20% of people infected with toxoplasmosis will develop symptoms similar to flu or glandular fever, such as:

These symptoms are usually mild and will normally pass within a few weeks.

Problems in pregnancy

Toxoplasmosis can be serious if a woman becomes infected while she's pregnant or a few weeks before conceiving. This is because there's a chance the infection could be passed to her baby.

However, the risk of getting toxoplasmosis during pregnancy is very low. In the UK, it's estimated that less than 5 in every 1,000 pregnant women will become infected for the first time.

A woman won't usually have any symptoms if she becomes infected during pregnancy, but if the infection spreads to her baby, it can cause:

  • miscarriage
  • stillbirth
  • congenital toxoplasmosis – where the baby develops toxoplasmosis while they're developing in the womb

Congenital toxoplasmosis can cause serious problems that are either noticeable from birth or develop several months or years later, such as brain damage, hearing loss and vision problems.

Problems in people with weak immune systems

Toxoplasmosis can cause serious problems and be life-threatening for someone with a weakened immune system as their body may not be able to fight off the infection.

Your immune system may be weakened if you:

  • have an illness that affects your immune system, such as HIV and AIDS or some types of cancer
  • are having chemotherapy
  • are taking immunosuppressant medication – for example, after having an organ transplant

If your immune system is weak, the infection could spread to organs such as the eyes, heart, lungs and brain. This can cause problems such as headaches, confusion, poor co-ordination, seizures (fits), difficulty breathing and vision problems.

Read about the complications of toxoplasmosis for more information.

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Read about how you can get toxoplasmosis and whether the infection can be spread between people.

Toxoplasmosis is caused by the Toxoplasma gondii (T. gondii) parasite. This is found in the poo (faeces) of infected cats and the meat of infected animals.

T. gondii can reproduce inside a cat's bowel and is passed out in its poo for a few weeks after it became infected. The cat won't usually have any symptoms, so you may not know it's infected. The parasites can survive outside in soil or water for many months.

The parasites can get into animal meat if an animal eats soil, grass, animal feed or another animal that has been contaminated by an infected cat's poo.

How you can get toxoplasmosis

You can get toxoplasmosis if the T. gondii parasites get into your mouth.

This can happen by: 

  • eating food (such as unwashed fruit and vegetables) or drinking water that's contaminated with infected cat's poo
  • getting your hands contaminated by touching soil or cat litter, and then putting them in or near your mouth
  • eating raw, cured or undercooked infected meat – particularly lamb and pork
  • accidentally getting the parasite in your mouth after handling contaminated meat, or handling knives, cutting boards and other utensils that have been in contact with contaminated meat
  • eating or drinking infected unpasteurised goats' milk or products made from it, such as cheese

There's also a small risk of the 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.

Can toxoplasmosis spread between people?

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 
  • 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.

There's also a chance the infection could be passed to an unborn baby if the mother becomes infected while pregnant.

Can I be infected more than once?

After being infected, most people are immune to toxoplasmosis for the rest of their life. However, the parasites that cause the infection can remain inactive in the body for many years, and potentially for life.

These inactive parasites won't usually cause any problems, including for pregnant women who were infected before becoming pregnant, although there's a chance they could become active again if your immune system weakens. For example, the infection may start to cause problems if you get HIV or have chemotherapy.

Toxoplasmosis in pregnancy

If a pregnant woman becomes infected with toxoplasmosis, there's a risk the infection could spread to her baby through the placenta (the organ that links the mother's blood supply to her unborn baby's).

However, this can only occur if the mother becomes infected for the first time while she's pregnant or shortly before conceiving. This is thought to happen very rarely in the UK.

Even if you do become infected while pregnant, it doesn't necessarily mean the infection will spread to your baby. The chances of your child becoming infected are higher the later you become infected.

For example, the risk of passing the infection on is only around 10-15% if you become infected in the first 12-13 weeks of pregnancy, but can be as high as 70% if you become infected from weeks 26-28 onwards.

If your baby does become infected, it can cause a serious condition known as congenital toxoplasmosis. Read about the complications of toxoplasmosis for more information about this.

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Read about the tests used to diagnose toxoplasmosis, including about testing in pregnancy.

A blood test can be carried out to see if you have been infected with the Toxoplasma gondii (T. gondii) parasite.

This blood test looks for specific antibodies produced by your immune system to fight the infection.

When might a blood test be recommended?

The blood test for toxoplasmosis may be carried out if there's a chance you have the condition and you have symptoms of the infection, or you're at risk of serious complications of toxoplasmosis. For example, the test may be recommended if you're diagnosed with HIV or are scheduled to have an organ transplant.

In the UK, testing for toxoplasmosis isn't routinely carried out during pregnancy because the risk of picking up the infection while you're pregnant is very small and there are some concerns about the reliability of the test in pregnant women. It's also not clear exactly how effective treatment during pregnancy is in stopping the infection spreading to the baby.

You may be tested during pregnancy if you develop symptoms of the infection, problems with your baby are picked up during a routine ultrasound scan, or you have a weak immune system. Discuss the possibility of having a blood test with your midwife, GP or obstetrician if you're concerned.

What the blood test result means

Negative result

Testing soon after an infection can sometimes produce a negative result when a person is actually infected. This is known as a false negative. It occurs when the body hasn't had time to start producing antibodies to the parasite, which can take up to three weeks after the initial infection.

If you don't have any symptoms but there's a possibility you may be infected, your doctor may recommend another blood test a few weeks later. If the result is still negative, it's unlikely you've had the toxoplasmosis infection.

However, you may be at risk of becoming infected at some point, so you might be advised to take steps to prevent toxoplasmosis if you're at risk of developing complications of the infection.

Positive result

A positive result means you've been infected with toxoplasmosis at some point, but doesn't necessarily mean you have an active infection.

Normally, two different types of antibody are tested for to help decide whether or not you have an active infection – these are called IgG and IgM antibiodies.

IgG antibodies will stay in your blood for life, protecting you from being infected again. IgM antibodies appear soon after you have been infected and then disappear, usually over a period of a few months.

If you have IgG antibodies, but no IgM antibodies, this indicates you have been infected at some time in the past, but you have not had a recent infection.

If you have IgM antbodies, this indicates you have been infected relatively recently (probably within the past year), although it still doesn't determine for certain whether any symptoms you have are caused by toxoplasmosis.

You may need more blood tests to check the levels of antibodies in your blood a second time to help determine whether the infection is currently active. For example, if the levels of antibodies are:

  • increasing – suggests a new active infection
  • still the same – suggests an old infection and you're now immune
  • decreasing – suggests a recent infection that is no longer active

Diagnosis during pregnancy

If you're pregnant and blood tests confirm you have a recent toxoplasmosis infection, you may 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 tummy 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.

The procedure can confirm whether your baby has the infection, but it can't determine whether the infection has caused any serious damage.

Diagnosis after birth

After your baby is born, he or she will be examined for any signs of damage from the infection and treatment may continue. They may also have a blood test to help determine if they have the infection.

Treatment for the infection will continue for up to a year after birth, and regular blood tests may be carried out during this time.

Diagnosis in people with a weak immune system

If you have a weakened immune system, 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 also request the following tests to see if you have physical signs of the infection in your brain:

  • 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

You may also have an eye examination to check for signs of damage that could be caused by the infection.

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Read about how toxoplasmosis is treated, including how the infection is treated in pregnant women and babies.

Most cases of toxoplasmosis are mild and don't require treatment. Either no symptoms develop, or a full recovery is made without complications.

You may need treatment if you're diagnosed with toxoplasmosis and:

Babies diagnosed with toxoplasmosis before or after they're born (congenital toxoplasmosis) will also need treatment. 

Most people will be treated with a combination of medicines called pyrimethamine, sulfadiazine and folinic acid. These medications usually need to be taken for at least four to six weeks. Sometimes a medication called azithromycin is given alone instead.

Treating pregnant women

If you're pregnant and develop toxoplasmosis for the first time, you may be treated with an antibiotic called spiramycin until you give birth or tests show your baby is also infected.

It's thought spiramycin may reduce the chance of the infection spreading to your baby, although it's not clear exactly how effective it is. In some cases, the infection may spread to your baby despite treatment.

If tests show the infection has already spread to your baby, you'll normally be treated with courses of pyrimethamine plus sulfadiazine, alternating with courses of spiramycin.

Treating toxoplasmosis in babies

If your baby is born with congenital toxoplasmosis, he or she will be examined and have tests to see whether the infection has caused any damage.

Your baby will usually be treated with pyrimethamine and sulfadiazine because this may help reduce the risk of serious or long-term problems. These medications may need to be taken for up to a year.

Unfortunately, these medicines can't undo any damage that has already occurred, so some babies with congenital toxoplasmosis will develop long-term or recurrent problems despite treatment.

Read about the complications of toxoplasmosis for more information about this.

Treating people with a weak immune system

If you have a weak immune system – for example, because you have HIV or you are taking medication to weaken your immune system after an organ transplant – you may be given medications called trimethoprim and sulfamethoxazole to prevent the symptoms of toxoplasmosis developing.

This is because the toxoplasmosis parasite remains inactive in the body even if you were infected a long time ago. If your immune system weakens, the parasite can reactivate and cause serious problems.

It may be possible to stop taking these medicines if your immune system recovers.

If you have an active infection, you'll normally be given pyrimethamine and sulfadiazine treatment. These medicines may need to be taken for a few months or more.

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