What is toxoplasmosis?
Toxoplasmosis is an infection caused by the parasite Toxoplasma gondii. In non-pregnant women it doesn’t have many symptoms. In fact, many people will never know they have had it. Some people may have mild flu-like symptoms. A few may experience a more long-term illness similar to glandular fever and swollen lymph nodes.
Although toxoplasmosis normally causes a mild illness in people with healthy immune systems, it's risky during pregnancy because it may harm your baby.
The parasite can be found in meat, cat faeces, the soil where cats defecate and unpasteurised goats’ milk. The toxoplasma parasite can infect most birds and warm-blooded animals, including humans. Cats are the only animals that can have infected faeces. After it catches the infection through eating birds, mice or other raw meat, a cat can shed infectious faeces for about 14 days.
Toxoplasmosis cannot be caught by stroking a cat or having a cat as a pet. The infection comes from coming into contact with the infected faeces of a cat.
How common is toxoplasmosis?
It is estimated that between a third and half of the UK population will have the infection at some point in their lives. Once you have had the infection, you are then immune for life – you cannot catch it again.
The chances of getting toxoplasmosis for the first time during pregnancy are thought to be very small. Even if you do become infected, this doesn't mean your baby will definitely get it. In many cases the infection doesn't spread to the baby. It's estimated that only 1 in 10,000 babies is born with toxoplasmosis in the UK.
Most pregnant women may never know they have been infected unless they experience problems during their pregnancy that mean they have tests. However the infection often has no symptoms at all.
The effects of toxoplasmosis in pregnancy
Toxoplasmosis does not usually cause any symptoms and in most cases a person does not realise they have caught the infection. It can cause symptoms similar to flu or glandular fever, sometimes including swollen lymph nodes. Once a person has had the disease they are generally thought to be protected for life, unless they suffer an impairment of their immune system.
Risks of toxoplasmosis
Toxoplasmosis is only a risk to an unborn baby if caught for the first time during pregnancy or within a few weeks before you get pregnant.
If an unborn baby catches the disease they are said to have ‘congenital toxoplasmosis’. The damage the infection may cause will depend on when in pregnancy you got the infection.
If you catch toxoplasmosis for the first time during pregnancy, it does not mean that your baby will be infected.
On average, only 4 in 10 of such infections will pass to the baby. Caught during pregnancy, toxoplasmosis can cause miscarriage, stillbirth or damage to the baby’s brain and other organs, particularly the eyes.
However, most babies born with toxoplasmosis have no obvious damage at birth but develop symptoms, usually eye damage, during childhood or even adulthood. A few will have more serious symptoms such as blindness or brain damage.
How is toxoplasmosis caught?
Toxoplasmosis is caught by swallowing anything infected with, or contaminated by, the parasite.
This could be:
- raw or undercooked meat (meat showing any traces of pink or blood), and raw cured meat such as Parma ham or salami
- unwashed vegetables and fruit
- cat faeces or soil contaminated with cat faeces
- unpasteurised goats’ milk and dairy products made from it.
The infection can also be passed:
- through the placenta if the mother becomes infected infection (mother to unborn baby).
- through infected matter entering human body fluids; if, for example, during the process of lambing, material splashes into eyes or open cuts.
- through transplanted organs or blood products from other humans that are infected toxoplasmosis
- through inhaling the parasite eggs (possible but very unusual).
Person-to-person infection is not possible, except from mother to unborn child.
Who is at risk of toxoplasmosis?
Anyone who eats anything infected with the parasite. Pregnant women who work on the land, in catering or farming may be at higher risk as they may be more likely to come into contact with the parasite. Lambing is a particular risk for pregnant women.
Tips to avoid toxoplasmosis during pregnancy
Only eat meat that has been thoroughly cooked (ie, with no trace of blood or pinkness).
- Avoid raw meat and cured meat, such as Parma ham.
- Wash hands, chopping boards and utensils thoroughly after preparing raw meat.
- Wash all fruit and vegetables thoroughly before cooking/eating to remove all traces of soil.
- Avoid unpasteurised goats’ milk and dairy products made from it.
- Wear gloves when gardening and wash hands and gloves afterwards – if you eat while gardening wash your hands first, and try to avoid gardening in areas that may have been soiled with cat faeces.
- Cover children’s sandpits to prevent cats using them as litter boxes.
- Remove faeces from cat litter tray every day wearing rubber gloves (or ask someone else do this), scald trays regularly with boiling water.
- If you are handling litter trays, wash gloves and hands thoroughly afterwards.
- Do not handle lambing ewes and do not bring lambs into the house.
Can I change the cat litter tray while pregnant?
Cats are the only animals that can shed this parasite in their faeces. Provided precautions are taken, cats are not a particular risk to a pregnant woman. If you are handling litter trays, wash gloves and hands thoroughly afterwards.
What should I do if I think I may have toxoplasmosis?
Toxoplasmosis is not routinely tested for during pregnancy in the UK. You may however request a blood test from your GP if you feel you may have put yourself at risk, you are concerned about symptoms.
The blood test looks for antibodies – the body’s natural defences – to the infection. It may take three weeks for these antibodies to be present following an infection, so the blood test will only pick up an infection that you’ve had for at least three weeks. Depending on the type of antibodies found and whether levels are stable, rising or falling, it’s possible to determine when the infection took place.
The results may come back in a week, or longer if they have been passed on to a Toxoplasma Reference Laboratory .
Tests for toxoplasmosis in pregnancy
Blood tests for toxoplasmosis can be done at any stage before or during pregnancy. The blood test can usually only show possible infection two to three weeks after any risk incident, as it can take this long for antibodies to be detectable.
The blood test involves taking a small amount of blood from the mother. There is no risk to the unborn baby. The blood test aims to show whether certain antibodies indicating toxoplasmosis are present or not, and, if they are present, to find out when the infection happened.
If the tests show that there is a recent or current infection, there is a risk that the baby will be infected. The obstetrician or GP will make a recommendation about any further action that might be required. It may take several weeks for the infection to pass from you to your baby. The degree of risk and severity of damage depends on when you were infected.
A positive result due to a current/recent infection
If the test shows a current or recent infection the blood must be sent on from the local laboratory to the Toxoplasma Reference Laboratory, for confirmation and further testing.
A small percentage of tests will appear positive when in reality a woman has never had the disease.
If further tests show that you have a current or recent infection, it means you are suffering from an acute toxoplasma infection. Further action needs to be taken to assess the risk of passing the infection on to your baby.
If you were infected shortly before conception
Infection caught shortly before conception (within a few weeks before) carries a one percent risk or below of transmission to the baby, but there is a risk of miscarriage if the baby does become infected.
If you were infected in the first trimester (week one to 12)
Infection caught at this stage of pregnancy carries about 10-15% risk of transmission to the baby. A baby infected at this stage has a risk of being miscarried or born with severe symptoms such as hydrocephalus (water on the brain), calcifications of the brain, or retinochoroiditis (inflammation of the retina).
If you were infected in the second trimester (week 13 to 28)
Infection caught at this stage of pregnancy brings about 25% risk of transmission. A baby infected at this stage is less likely to be miscarried, but is still at risk of developing severe symptoms as above.
If you were infected in the third trimester (week 29 to 40)
Infection caught later in pregnancy is more likely to spread to your baby, the risk of transmission may be as high as 70–80%, but if problems develop, they are less likely to be as serious. Most babies infected will be apparently healthy at birth, but a large proportion will develop symptoms later in life, usually eye damage.
Finding out if the baby has been infected
Further tests can be carried out to find out whether or not the baby is infected, although the tests will not show how severe the damage is. An obstetrician or GP can explain the risks and benefits of conducting these tests.
Amniocentesis is a technique where amniotic fluid is removed by a fine needle from the amniotic sac – the fluid-filled sac around the baby.
Cordocentesis is a technique where a sample of the baby’s blood is removed from the umbilical cord.
These procedures carry a .5-1% percent risk of causing miscarriage. They are normally carried out after 15 weeks of pregnancy. The amniotic fluid or blood from the umbilical cord is then tested at the Toxoplasma Reference Laboratory using a range of specialised tests.
If this is positive, the baby will be considered to be infected. Results typically take two to five days. A detailed ultrasound scan will show if there is major damage, such as hydrocephalus (water on the brain), but a scan that shows no damage, while reassuring, does not rule out the possibility that the baby is both infected and affected.
Treatment of toxoplasmosis in pregnancy
If you have a positive blood test result, you may be prescribed an antibiotic called spiramycin, which reduces the risk of the infection being passed from you to the baby. Spiramycin only reduces the risk of transmission from mother to baby and is not active against the parasite. It therefore cannot limit any damage if a baby has already become infected.
If the baby is found to be infected, a combination of pyrimethamine and sulphadiazine can be taken. These are both stronger antibiotics and help limit any damage to the baby, although again, they cannot undo any damage.
At 20 weeks an ultrasound scan may also highlight any obvious physical problems in the baby. Termination of pregnancy is also an option for some women, when an infected baby with severe developmental problems has been confirmed.
All babies born to women with confirmed toxoplasmosis in pregnancy will be monitored closely by paediatricians and receive blood tests during their first year.
Side effects of treatments
Spiramycin is used routinely in France for treatment of toxoplasmosis in pregnancy, with little evidence of adverse effects. Experts consider that it is safe to use in pregnancy when a baby is at risk. Women taking spiramycin sometimes experience side effects such as nausea or rashes. Pyrimethamine and sulphadiazine can have side effects for both the mother and baby related to red-blood cell production. Although not normally prescribed in pregnancy, they can be used in extreme circumstances. They are taken with folinic acid, which helps to reduce the worst side effects.
All babies born to women who have had a recent or current infection in pregnancy should be given a thorough physical examination after birth, followed by blood tests during the first year of the baby’s life.
Treatment after the baby is born
A blood sample should be taken from at-risk babies shortly after birth. A blood sample should also then be taken from you to compare the levels of specific antibodies between you and your baby.
Tests will be carried out to look for different types of antibodies to toxoplasmosis in the baby’s blood. Your baby carries some of your antibodies, so a positive result is expected and not necessarily alarming. If additional antibodies are present, this may indicate that your baby is infected.
Babies who are known to be at risk of having congenital toxoplasmosis should be checked for signs of neurological damage. The eyes will be examined for signs of any problem, preferably by an ophthalmologist (eye specialist). Long-term follow-up by an ophthalmologist might be necessary if eye damage is confirmed.
Your baby’s general health will also be checked. If there is any possibility that the baby has brain damage, special head X-rays might be carried out to check for calcifications, enlarged ventricles or any other abnormalities.
Treatment for babies who have been infected with toxoplasmosis
If blood tests showed that your baby has been infected, antibiotics might be prescribed, even if your baby shows no symptoms. Treatment can sometimes be continued for as long as one year, to help prevent or limit the eye damage that can possibly occur later.
A blood sample taken every few months, up to the age of one year, can show whether your baby’s antibody level is falling. By that age, the level should be completely negative. This means that your baby will have lost the antibodies acquired from you and is not infected. When your baby’s blood sample is completely antibody-negative, it means they are definitely not congenitally infected. A falling antibody level is a good sign, but is not conclusive and tests should continue until the antibody level is completely negative.
Breastfeeding is safe if you have toxoplasmosis, the disease cannot be transmitted this way. You are also passing on extra antibodies to your baby, making their immune system stronger. Breastfeeding is therefore recommended, unless you are being treated with pyrimethamine. This medication should be changed before breastfeeding.
UK government policy on toxoplasmosis screening
The UK National Screening Committee recently reported that screening for toxoplasmosis in pregnancy should not be offered routinely as there is not enough evidence that it would help .
The Committee suggests that getting pregnant women to avoid undercooked or cured meat and communicating the best ways of avoiding infection is a better way of controlling toxoplasmosis than antenatal screening.