Conditions Toxoplasmosis

Toxoplasmosis is caused by the parasite Toxoplasma gondii. This infectious disease is common worldwide and is transmitted to humans by animals (in other words, it is a zoonotic disease).

Most toxoplasmosis infections are harmless and cause no symptoms. On the other hand, they can be life-threatening for people with immune deficiency (i.e. a weakened/compromised immune system).

If women become infected with the parasite for the first time while pregnant, it can cause serious defects in their unborn babies. 

Toxoplasmosis test during pregnancy

A test to determine whether a person has already had a toxoplasmosis infection and is therefore immune can be conducted before or, at latest, at the start of a pregnancy. If there is no reason to suspect toxoplasmosis, individuals must pay for this test themselves as an individual health service (IGeL) in Germany.

Healthy individuals with an immune system that is functioning as normal usually have no symptoms when they become infected with toxoplasmosis.
 
Some may experience flu-like symptoms, such as:

• fever
• headaches
• muscle aches
• swollen lymph nodes in the head and neck area

These symptoms usually resolve by themselves. Afterwards, the pathogen remains in the body for life, generally causing no further symptoms in people with a healthy immune system. 

In rare cases, an inflammation of the retina and the choroid (underlying vascular layer) of the eye or encephalitis (inflammation of the brain) can occur in individuals with a normally functioning immune system.

Toxoplasmosis is caused by an infection with the Toxoplasma gondii parasite. 

Most infections are caused by:

• consumption of raw or undercooked meat and meat products (especially pork and poultry) containing parasitic cysts
• contact with cat feces, for example, when cleaning cat litter trays or gardening (smear infection)
• consumption of fruit and vegetables contaminated with infectious parasites

An infection can also be transmitted:

• from a pregnant mother to her unborn baby
• from the donor to the recipient of an organ transplant

The parasitic stages can enter the gastrointestinal tract of humans, for example, via contaminated fruit, vegetables or meat or through contact with contaminated soil or cat feces. They can multiply in the intestines and pass into other tissues. The parasites form permanent stages in the brain, in the retina of the eye and in the skeletal and heart muscles in particular. These are known as cysts. Cysts remain in a person's tissue for life.

In people with immune deficiency, an infection with toxoplasmosis can be life-threatening. This applies, for example, to:

• Patients with AIDS or cancer
• Recipients of stem cell or organ transplants. In these individuals, the parasite can cause inflammation of the brain (encephalitis) or other organs.

In addition to contracting a first-time infection, people with immune deficiency may also experience the recurrence of a previous infection. This occurs because the parasite remains in their tissue for life in the form of cysts.

What happens if toxoplasmosis is contracted during pregnancy?

If a woman contracts toxoplasmosis for the first time when pregnant, it can cause serious birth defects as well as damage to the brain and eyes of her unborn baby. It can also cause a miscarriage. This is particularly likely to occur if the woman is infected during an early stage of her pregnancy. 

If a woman has previously had a toxoplasmosis infection before a pregnancy, it can generally be assumed that she is immune and that there are no risks to the unborn child.

In Germany, approximately half of the population are carriers of toxoplasmosis.

Younger people are less frequently infected than older people. The risk of infection with toxoplasmosis rises steadily with age among the general population. Almost 80 percent of people aged over 70 are infected with Toxoplasma gondii. 

In Germany, between 5 and 23 cases of toxoplasmosis are reported in newborn babies every year. However, many cases do not become apparent until months or years after birth, which means that most cases are not reported. For this reason, it is assumed that the actual number of cases among newborns is significantly higher. 

People with immune system deficiency and pregnant women should protect themselves against infection with toxoplasmosis if they have never been infected with the parasite previously.

The following measures prevent infection with toxoplasmosis:

• Avoid eating meat, especially pork, that is raw or not fully cooked
• Wash fruit and vegetables thoroughly
• Wash hands regularly, in particular before eating, after contact with raw meat, after gardening, after outdoor or excavation work and after playground visits.
• If pregnant women keep a cat in the home, they should only give them canned or dry food.
• Cat litter boxes should be cleaned daily with hot water by people who are not pregnant or immunocompromised.
• Petting of free-roaming cats should be avoided.

If toxoplasmosis is suspected, doctors normally take a sample of blood for laboratory testing. In some cases, samples of other body fluids that may contain the parasites are also sent for testing. 

Laboratory tests

Laboratory tests show whether the immune system has already come into contact with the pathogen or whether this is a new infection. The blood is tested for the presence of antibodies against toxoplasmosis. A PCR test can also detect the genetic material of the parasite in a sample.

Brain imaging techniques

If a person is showing symptoms of brain inflammation, doctors may use imaging techniques to examine the brain.

Eye examination

If the eye is affected, specialists examine the back of the eye with special devices. The back of the eye is where typical inflammatory changes and scarring can be detected.

Uncomplicated toxoplasmosis acquired after birth is usually only monitored. Treatment is not normally required.

When is treatment required?

Treatment is necessary if:

• people with a weakened immune system are infected
• the eyes are affected
• pregnant women and unborn babies are infected

Which medications are used?

A range of medicines can be used disrupt the metabolism of the Toxoplasma gondii parasite. Some antibiotics are also effective against the parasite. The following active ingredients are normally used: spiramycin, pyrimethamine, sulfadiazine, clindamycin, co-trimoxazole and atovaquone. 

Pregnant women and unborn babies are also given folinic acid.