Toxoplasmosis

Toxoplasmosis.

Toxoplasmosis is a common condition that occurs worldwide in most birds and warm-blooded mammals, including humans.

In most cases, toxoplasmosis does not have any symptoms. This is because a healthy immune system is usually able to defend the body from the parasite and prevent it from causing illness.

What causes toxoplasmosis?

Toxoplasmosis is caused by infection with Toxoplasma gondii (T. gondii), which is one of the world's most common parasites. T. gondii can be found in:

  • undercooked or raw meat,
  • raw cured meat, such as parma ham or salami,
  • unpasteurised goat's milk,
  • cat faeces, and
  • soil or cat litter that is contaminated with infected cat faeces.

Toxoplasmosis cannot be passed on through person-to-person contact, but it can be passed from a pregnant woman to her unborn baby. This is only possible if a women catches the infection either:

  • during pregnancy, or
  • up to three months before she conceives.

If a baby is born with the infection, it is known as congenital toxoplasmosis.

How common is toxoplasmosis?

Up to half of the population will have a toxoplasmosis infection at some point in their lives. Once infected, a person is then immune from further infection for life.

In Europe, it is estimated that between 0.2-1.6 per cent of pregnant women become infected with the T. gondii parasite.

Outlook

Toxoplasmosis can cause mild flu-like symptoms, such as a high temperature and muscle aches, but these will usually pass without treatment after a few weeks.

Congenital toxoplasmosis can cause serious health problems in babies and can sometimes be fatal. It can cause:

  • jaundice (yellowing of the skin),
  • eye infections, or
  • seizures.

Toxoplasmosis is also dangerous for people with immune deficiencies (weakened immune systems) - for example, those with HIV and AIDS, or cancer. In these cases, the infection can cause serious complications, including vision problems and brain damage.

Disease

A disease is an illness or condition that interferes with normal body functions.

Faeces

Stool (also known as faeces) is the solid waste matter that is passed from the body as a bowel movement.

Immune system

The immune system is the body's defence system, which helps protect it from disease, bacteria and viruses.

High temperature

A fever is when you have a high body temperature (over 38C or 100.4F).

Aches

An ache is a constant dull pain in a part of the body.


Illness

A disease is an illness or condition that interferes with normal body functions.

Jaundice

Jaundice is a condition that causes yellowing of the skin and the whites of the eyes, brought on by liver problems.

Brain

The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.

 

In about 80 per cent of cases, toxoplasmosis causes no symptoms and you are not even aware that you are infected. In healthy adults and children, the immune system is usually strong enough to prevent the T. gondii parasite (which causes toxoplasmosis) from causing any illness. You become immune to it and it will live harmlessly in your body for life.

However, in some cases, toxoplasmosis can cause the lymph nodes (glands that form part of your immune system) to swell, particularly in the throat or armpits. This can cause symptoms that are similar to the flu including:

  • body, or muscle, aches,
  • a high temperature (fever) of 38C (100.4F) or over,
  • tiredness,
  • feeling sick, and
  • a sore throat.

It is very rare for otherwise healthy people to experience any serious symptoms of toxoplasmosis.

Pregnant women

If you become infected with toxoplasmosis, either while you are pregnant, or during the 2-3 months before you conceive, there is a chance that you could pass the infection onto your unborn baby (congenital toxoplasmosis).

While you will probably not experience any symptoms of the infection yourself, if this happens in the early stages of pregnancy, there is a risk of:

  • miscarriage (the loss of a pregnancy during the first 23 weeks), or
  • stillbirth (when the baby is born after 24 weeks of pregnancy without any signs of life).

One large study found that toxoplasmosis caused stillbirth in pregnant women in just less than one per cent of cases.

Around 30-40 per cent of pregnant women who become infected with toxoplasmosis will pass the infection onto their unborn baby, leading to congenital toxoplasmosis.

Symptoms of congenital toxoplasmosis

The symptoms of congenital toxoplasmosis vary depending on when the mother became infected. Symptoms are usually more severe if the mother was infected either just before becoming pregnant, or in the first and second trimesters (up to week 27 of the pregnancy).

Symptoms can include:

  • hydrocephalus (water on the brain),
  • brain damage,
  • epilepsy (seizures),
  • jaundice (yellowing of the skin and whites of the eyes),
  • deafness,
  • eye infections and blindness,
  • an enlarged liver, or spleen (an organ that helps filter impurities from your blood),
  • growth problems, or
  • cerebral palsy (a condition of the brain and nervous system that affects a child's movement and coordination).

If the mother becomes infected during the third trimester (from week 27 to the birth of the baby) there may not be any symptoms at birth. However, complications may develop later in life. For example, months, or even years, later a child born with congenital toxoplasmosis may develop:

  • eye infections,
  • hearing loss, or
  • learning difficulties.

See the complications section for more information.

People with immune deficiencies

If you have a weakened immune system, toxoplasmosis can be fatal. This is because your 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 cancer,
  • you are having chemotherapy treatment, or
  • you are taking immunosuppressant medication - for example, after having an organ transplant.

There is also a risk of developing permanent eye or brain damage. If toxoplasmosis begins to affect your brain, it can cause encephalitis (brain inflammation). This is sometimes called toxoplasmosis encephalitis (TE) and is one of the most frequent causes of death in people with HIV and AIDS.

Symptoms of TE include:

  • headaches,
  • confusion,
  • poor coordination,
  • seizures,
  • chest pains,
  • coughing up blood,
  • difficulty breathing,
  • a high temperature (fever) of 38C (100.4F) or over,
  • problems with your vision, such as blurred vision and floaters (small pieces of debris that can cloud your vision),and
  • multiple lesions (wounds) in the brain.

Lymph nodes
Lymph nodes are small oval glands that remove unwanted bacteria and particles from the body.

Immune system
The immune system is the body's defence system, which helps protect it from disease, bacteria and viruses.

High temperature
A fever is when you have a high body temperature (over 38C or 100.4F).

Aches
An ache is a constant dull pain in a part of the body.

Jaundice
Jaundice is a condition that causes yellowing of the skin and the whites of the eyes, brought on by liver problems.

Liver
The liver is the largest organ in the body. Its main jobs are to secrete bile (to help digestion), detoxify the blood and change food into energy.

Brain
The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.

The toxoplasmosis infection is caused by the T. gondii parasite. Some of the ways that you may come into contact with this parasite are outlined below.

  • Contact with cat faeces, either in a litter tray, or in soil. The parasite breeds in the bowels of cats, and is released in their faeces. Cat faeces can also contaminate (infect) soil, fruit and vegetables, water, and other animals.
  • Undercooked or raw infected meat - either by eating it, or touching your mouth after handling it. Grazing animals can become infected after eating contaminated grass and animal feed. Venison, lamb, and pork are more likely to be infected.
  • Contaminated knives, cutting boards, and other utensils that have been in contact with contaminated undercooked or raw meat.
  • Eating or drinking infected unpasteurised goat's milk, or products that are made from it, such as cheese.

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

It may also be possible to get the infection from sheep during the lambing season. This is because the T. gondii parasite can be found in the afterbirth and on newborn lambs after an infected sheep has given birth. Coming into contact with an infected sheep or lamb, or contaminated afterbirth, may lead to you also becoming infected. 

Toxoplasmosis cannot be caught from another person. This means that:

  • you cannot catch toxoplasmosis from contact with someone who is infected,
  • you cannot pass toxoplasmosis on to your children if you have had the infection before, and
  • it is not possible to pass the infection on through breastfeeding.

Congenital toxoplasmosis

Congenital toxoplasmosis is when a baby is born with toxoplasmosis. The mother passes on the infection 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 became infected for the first time either:

  • during pregnancy, or
  • during the 2-3 months before she conceived.

Congenital toxoplasmosis is more likely to occur if you become infected later in your pregnancy.

For example, if you become infected with toxoplasmosis 2-3 months before you conceive, there is a one per cent chance that your baby will also develop the infection.

However, if you become infected in the third trimester of your pregnancy (from week 27 to the birth) there is about a 65 per cent chance that 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 the baby increased by 12 per cent.

Faeces

Stool (also known as faeces) is the solid waste matter that is passed from the body as a bowel movement.

Placenta

The placenta is the organ that links the mother's blood supply to her unborn baby's. Oxygen and nutrients are passed through the placenta to the baby, and waste porducts from the baby pass back through the placenta to the mother.

If you are infected with the T. gondii parasite, your immune system will start to produce special antibodies to fight it. Antibodies are proteins that are produced by the body to neutralise, or destroy, disease-carrying organisms and toxins.

If toxoplasmosis is suspected, you will need to have a blood test to check for the antibodies.

A negative result

Occasionally, early testing can produce a negative result even if you are infected (a false negative). This is because your body has not had a chance to start producing antibodies to the parasite, which usually takes up to 23 days. Therefore, your GP may want to retest your blood 2-3 weeks later. If the result is still negative, it is unlikely that you have the infection.

A positive result

A positive result does not necessarily mean that you are actively infected with the T. gondii parasite. When you have had toxoplasmosis, the antibodies remain in your blood for life, protecting you from further illness. A positive result will only show that you have been infected at some point.

To find out if this is a new infection, you will need to have further blood tests, which may need to be sent to a laboratory to be analysed.

Checking the levels of antibodies in your blood a second time can determine when the infection occurred. For example, if the levels of antibodies are:

  • rising - this suggests a new, active infection (perhaps a few weeks old),
  • still the same - this suggests an old infection and that you are now  immune, or
  • falling - this suggests a recent, but no longer active, infection (perhaps a few months old).

Further testing is important if you are pregnant or you have an immune deficiency.

Pregnant women

If you are pregnant and tests have confirmed that you have a new toxoplasmosis infection, you will need a further test to determine if your unborn baby has the infection as well.

The most effective and common test performed is amniocentesis. This can be done after around 15 weeks of pregnancy. A fine needle is inserted through the mother's abdomen to collect a sample of amniotic fluid (the fluid that surrounds the foetus in the womb). The sample is then tested for evidence of toxoplasmosis.

The procedure usually takes between 10 minutes and half an hour, and can be slightly uncomfortable for the mother. Having amniocentesis does carry about a one per cent risk of causing a miscarriage.

Congenital toxoplasmosis

Amniocentesis can confirm whether your baby has been passed the infection and has congenital toxoplasmosis. However, it is not possible to determine whether the infection has caused any damage to your unborn baby, or how much.

If your baby does have congenital toxoplasmosis, treatment will be started with medications. Once your baby is born, they will be examined for any damage from the infection and treatment may continue.

If necessary, your baby will continue to have blood tests for up to a year, or longer, until the blood tests are negative for the toxoplasmosis antibodies. Once there are no antibodies, your baby no longer has congenital toxoplasmosis.  

People with immune deficiencies

If you have a weak immune system - for example, due to an illness such as cancer, routine blood tests for antibodies can produce a false negative. This is because it is very likely that your immune system will not produce antibodies to fight off the infection.

Your doctor may want to perform the following tests to create images of your brain and check for evidence of toxoplasmosis.

  • computerised tomography (CT or CAT) scan takes a series of X-rays of your body at slightly different angles to produce a clear image of the inside of your body.
  • magnetic resonance imaging (MRI) scan uses a strong magnetic field and radio waves to produce detailed images of the inside of your body. 

Both of these procedures are non-invasive (performed outside of the body) and will not put any further risk on your health. These tests will reveal if you have any lesions (wounds) in your brain, which are typical of toxoplasmosis in about 90 per cent of cases.

New research is also looking into other ways to diagnose 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 is hoped that this may offer a faster and/or more reliable form of diagnosis by being able to confirm that the damage to the brain is caused by toxoplasmosis, and not by another disease. 

Immune system
The immune system is the body's defence system, which helps protect it from disease, bacteria and viruses.

Antibodies
Antibodies are proteins that are produced by the body to neutralise, or destroy, disease-carrying organisms and toxins.

Amniocentesis
Amniocentesis is a medical test that is carried out during pregnancy in order to assess whether the unborn baby (foetus) could develop or has developed an abnormality or serious condition.

Amniotic fluid
The fluid that surrounds the foetus in the womb. The fluid contains cells that have been shed by the foetus.

DNA
Deoxyribonucleic acid (DNA) contains molecules that store genetic information. Genes consist of coiled strands of DNA, with each cell containing the same genetic material.

 

In most cases, healthy people do not require treatment for toxoplasmosis. Either no symptoms develop, or a full recovery is made without complications.

If you experience more severe symptoms of the infection (particularly if you have any immune deficiencies), you will usually be prescribed pyrimethamine and sulfadiazine. You may also be prescribed folinic acid.

This treatment is usually given for between 3-6 weeks. If further courses of treatment are required, there will be a rest period of two weeks in between.

The most appropriate treatment plan for you will be decided with your GP. It will depend on your health, what symptoms you have, and their severity. People living with HIV or AIDS may need to take these medications for life to keep the parasite at bay.

Pregnant women

If you are pregnant when you become infected with toxoplasmosis for the first time, you may be treated with antibiotics. These could be:

  • spiramycin, or
  • pyrimethamine and sulfadiazine.  

These medications are widely used across Europe for two reasons:

  • to reduce the risk of the unborn baby becoming infected, and
  • to limit the severity of congenital toxoplasmosis if the baby is, or becomes, infected. 

There is some evidence to suggest that the earlier the treatment starts, the lower the risk of congenital toxoplasmosis although, in most cases, whether or not your baby becomes infected will depend on when you were infected. Overall, about a third of mothers who are infected with toxoplasmosis give birth to a baby with congenital toxoplasmosis.

These treatments are less effective at preventing the damage that is caused by congenital toxoplasmosis in the unborn baby. One research review that evaluated a number of different studies found that treatment with these antibiotics did not decrease the risk of either intracranial lesions (wounds in the brain) or ocular lesions (wounds in the eye) in the baby when it is born.

However, until more research has been carried out, these antibiotics remain the most effective form of treatment.

Treating congenital toxoplasmosis

If your baby is born with congenital toxoplasmosis, they will be examined to see whether the infection has caused any damage.

  • Blood will be taken from either a vein in your baby's arm, or by pricking the skin of their heel, and tested for the toxoplasmosis antibodies.
  • An ophthalmologist (a doctor who specialises in diagnosing and treating eye conditions) will examine your baby's eyes to check for any ocular lesions.
  • A scan or an X-ray of your baby's head may be taken to check for any brain damage.

In most cases, even if your baby does not have any symptoms, they will be given antibiotics to treat the congenital toxoplasmosis. These will probably be either pyrimethamine or sulfadiazine.

These have been found to be effective even for moderate or severely affected babies. One study found that 72% of babies with moderate or severe congenital toxoplasmosis had normal intelligence and motor function by their early teenage years.

Treatment with these medications may continue for up to a year, or longer, along with regular blood tests. Once your baby's blood tests negative for toxoplasmosis antibodies, they no longer have congenital toxoplasmosis and the antibiotics can be stopped.  

Unfortunately, some babies do develop lasting disabilities because these antibiotics cannot undo any damage that has already been done. It is also possible that eye infections can reoccur later on during childhood. See the complications section for more information about this.

Immune system
The immune system is the body's defence system, which helps protect it from disease, bacteria and viruses.

Antibiotics
Antibiotics are medicines used to treat infections caused by bacteria.

Antibodies
An antibody is a protein that is produced by the body to neutralise or destroy disease-carrying organisms and toxins.

Ocular toxoplasmosis

The toxoplasmosis infection can sometimes spread to the eyes. This is called ocular toxoplasmosis and is possible even after the initial infection. The T. gondii parasite, which causes toxoplasmosis, can lie dormant (asleep) in the retina for many years. It can wake up at any time and start a new infection.

Retinochoriditis

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

  • the retina (the nerve tissue that lines the back of the eye), and
  • the choroid (the layer behind the retina that contains major blood vessels).

The damage to the eyes is sometimes called retinochoroiditis and can cause eye problems including:

  • loss of eyesight,
  • squint (when one eye looks in a slightly different direction to the other one),
  • clouding of the eye lens (cataract),
  • eye shrinking (microphthalmia), and
  • 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 actual scarring that is caused by toxoplasmosis will not clear up, but treatment will prevent it from getting worse. If the infection keeps returning, long-term antibiotics can be prescribed. While this may help to prevent the infection from reoccurring, the long-term side effects of these medications are not yet known. 

Complications of congenital toxoplasmosis

In most cases, babies born with congenital toxoplasmosis develop normally after treatment with antibiotics. However, in up to four per cent of cases, serious complications can develop within the first years of life. These include:

  • death,
  • permanent brain damage, or
  • permanent visual impairment (partial or complete loss of sight) in both eyes.

A common complication of congenital toxoplasmosis is retinochoroiditis. The risk of this occurring is around 10 per cent in infants born with congenital toxoplasmosis. One study found that the 18 per cent of children with congenital toxoplasmosis had at least one ocular lesion as a result of retinochoroiditis. Of these children, 42 per cent developed a second ocular lesion.

Cases of ocular toxoplasmosis can also occur years later. For example, one study of cases of congenital ocular toxoplasmosis found that the average age at which it appeared was nine years old.

It is also possible for someone to develop complications when they are in their twenties or thirties. These may include:

  • learning disabilities,
  • hearing loss, or
  • ocular toxoplasmosis.

More research is still needed in following up cases of congenital toxoplasmosis. Regular eye tests may help detect any abnormalities as they develop and treatment with antibiotics can limit the damage toxoplasmosis causes. However, at present, it is not possible to reverse any damage already done. 

Antibiotics
Antibiotics are medicines used to treat infections caused by bacteria.

Steroids
Steroids are a type of hormone. Hormones are groups of powerful chemicals that have a wide range of effects on the body.

The following advice may help you to reduce your risk of becoming infected with toxoplasmosis. Pregnant women and those with immune deficiencies should take extra precautions to try to avoid becoming infected.

  • Wear gloves when gardening, particularly when handling soil. Also, be sure to wash your hands thoroughly afterwards with soap and hot water.
  • Do not eat raw, or undercooked, meat, particularly lamb, pork, and venison, including any ready-prepared chilled meals. Cook all red meat until no trace of pinkness remains and the juices run clear, and do not taste meat before it is fully cooked. Wash your hands thoroughly after handling raw meat.
  • Avoid sheep and their newborns during the lambing season if you are at extra risk. Although unlikely, an infected sheep or its newborn lamb could pass the infection to you at this time.
  • Wash all kitchenware thoroughly after preparing raw meat.
  • Wash all fruits and vegetables before cooking and eating, including ready-prepared salads.
  • Avoid un-pasteurised goat's milk or products that are made from it.
  • Do not handle or adopt stray cats.
  • Avoid cat faeces in cat litter or soil. Wear gloves if you are changing a cat litter tray, and if you are pregnant, or immune deficient, ask someone else to do this for you. Wash your hands thoroughly afterwards.
  • Feed your cat dried, or canned, cat food, rather than raw meat.
Faeces
Stool (also known as faeces) is the solid waste matter that is passed from the body as a bowel movement.

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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