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Toxoplasmosis

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

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.

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Toxoplasmosis

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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Toxoplasmosis

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

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

If you're diagnosed with toxoplasmosis, your GP will recommend the most appropriate treatment for you. This will depend on your health and symptoms.

If you have severe symptoms, you may be prescribed a combination of pyrimethamine and sulfadiazine, or a medication called azithromycin, which is given on its own. Folinic acid supplements may also be recommended.

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

If you have HIV or AIDS, you may need medication until anti-HIV therapy has restored your immune function.

Pregnant women

If you're pregnant and develop toxoplasmosis for the first time, you may be treated with an antibiotic called spiramycin.

Spiramycin may reduce the risk of your unborn baby becoming infected and limit the severity of congenital toxoplasmosis if your baby does become infected.

There's some evidence to suggest that the earlier treatment starts, the lower the risk of congenital toxoplasmosis. However, in most cases, whether or not your baby becomes infected will depend on when you were infected.

Overall, about 30-40% of mothers who have a toxoplasmosis infection during pregnancy give birth to a baby with congenital toxoplasmosis.

Antibiotic treatments aren't always effective at preventing the damage caused by congenital toxoplasmosis in the unborn baby. Sulfadiazine plus pyrimethamine is usually prescribed in cases where tests show the baby has become infected in the womb (congenital infection).

Other antibiotics are being investigated, but until more research has been carried out, sulfadiazine and pyrimethamine remain the most effective treatment for toxoplasmosis.

Congenital toxoplasmosis

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

  • blood test – blood will be taken either from a vein in your baby's arm or by pricking the skin of their heel, and the sample will be tested for toxoplasmosis antibodies
  • eye examination – an ophthalmologist (an eye specialist) will examine your baby's eyes to check for any lesions (wounds) at the back of the eye affecting the retina choroid
  • an X-ray or scan – may be taken of your baby's head to check for any brain damage

Congenital toxoplasmosis is usually treated with antibiotics. These will probably be a combination of pyrimethamine and sulfadiazine. These drugs have been shown to be effective for treating moderately and severely affected babies. One study found 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. Unfortunately, some babies with congenital toxoplasmosis develop long-term disabilities because it's not possible for antibiotics to undo the damage already sustained. It's also possible for eye infections to recur at a later stage of childhood.

Read more about the complications of congenital toxoplasmosis.

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Toxoplasmosis

There are a number of measures you can take to help reduce your risk of developing a toxoplasmosis infection.

There are a number of measures you can take to help reduce your risk of developing a toxoplasmosis infection.

For example, you should:

  • wear gloves when gardening, particularly when handling soil – wash your hands thoroughly afterwards with soap and hot water
  • avoid eating raw or undercooked meat, particularly lamb, pork and venison, including any ready-prepared chilled meals – read more about how to prepare and cook food safely
  • wash all kitchenware thoroughly after preparing raw meat
  • always wash fruit and vegetables before cooking and eating them, unless they are labelled as 'ready to eat'
  • avoid drinking unpasteurised goats' milk or eating products made from it
  • avoid handling or adopting stray cats
  • avoid cat faeces in cat litter or soil – wear gloves when changing a cat's litter tray and wash your hands thoroughly afterwards; if you're pregnant or immune deficient, ask someone else to change it for you
  • give your cat dried or canned cat food rather than raw meat

It's very important that pregnant women and those with a weakened immune system follow this advice to avoid becoming infected.

If you're pregnant, you should also avoid coming into contact with sheep and newborn lambs during the lambing season as there's a small risk that an infected sheep or lamb could pass the infection on at this time.

Read more about why it's important for pregnant women to avoid sheep during the lambing season.

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