Toxoplasmosis

Toxoplasmosis belongs to the group of infectious diseases caused by the parasite Toxoplasma gondii. The infection occurs with great frequency in all age groups, whereby most toxoplasmosis infections proceed without abnormality. However, if the disease occurs for the first time during pregnancy, it can lead to complications, as the miscarriage rate increases and malformations of the unborn child can occur. A toxoplasmosis infection is also threatening if the affected person has a weakened immune system.

With increasing age, the number of people who have experienced a toxoplasmosis infection increases steadily. By the age of 40, an average of one in two people in Central Europe has been infected with Toxoplasma gondii. Once the infection has been overcome, there is a lifelong immunity against toxoplasmosis if no immune deficiency occurs later.

The vector of toxoplasmosis is the unicellular blood parasite Toxoplasma gondii. Cats and feline predators serve as the main host, humans assume the role of intermediate host. The parasite multiplies in the cat intestine where it forms oocytes, which are excreted in large quantities in the faeces. If the oocytes remain exposed to air for a few days, they become infectious within four days and retain this state for several months.

In mammals, birds and humans, toxoplasmosis oocytes are mainly ingested with food, and in particular by eating raw meat (tartar) or food that may be contaminated with cat faeces (vegetables, fruit). Smear infection also plays a role in transmission, which can also occur directly after contact with cats or their excrement (cat litter).

If pregnant women are affected by a toxoplasmosis infection, the unborn child is infected in about 50% of cases (connatal toxoplasmosis). In Germany, a toxoplasmosis examination is only carried out if an infection is suspected. However, a blood test for toxoplasmosis is usually carried out in early pregnancy.

The incubation period for toxoplasmosis is about one to four weeks. If the infected person has an intact immune system, the disease is symptom-free in nine out of ten cases. In rare cases, there is a slight fever, headache and pain in the limbs, fatigue and swelling of the lymph nodes in the neck.

However, if there is an immune deficiency (for example in AIDS patients), toxoplasmosis can affect all organs, but most frequently the brain. As a result, large foci of inflammation form, which can bring symptoms such as changes in character, signs of paralysis, seizures, fever and headaches.

In unborn children, the extent of symptoms depends on the time of infection. If the infection occurs in early pregnancy, there may be severe changes in the organs, and especially the brain. Miscarriages cannot be ruled out either. Characteristic damage to the newborn is inflammation of the brain (encephalitis), accumulation of water in the cranial cavity (hydrocephalus), and eye damage (chorioretinitis).

If infection occurs in late pregnancy, only mild changes can be expected. About 50% of children infected with toxoplasmosis who do not show signs of the disease at birth may develop late sequelae. These include mental retardation, developmental disorders, deafness and eye damage.

If toxoplasmosis is suspected, a blood sample is taken, which is then tested for the body's own antibodies against toxoplasmosis. This is mainly done if a pregnant woman has had contact with cats, and in particular with cat faeces. This examination method can determine whether the person has been infected with toxoplasmosis before and, if there is a current infection, at what stage it is. Further detection of toxoplasmosis can be done in animal tests or via the virus genome (using PCR).

If a pregnant woman is affected by toxoplasmosis, treatment must be given immediately. Amniocentesis can be used to determine whether the unborn child is already infected. In rare cases, a blood sample taken from the umbilical cord (ultrasound-guided umbilical cord puncture) can also provide information about a child's toxoplasmosis infection.

Ultrasound can be used to determine whether organ changes are already present in the child. Newborns can also be tested for toxoplasmosis using a blood sample.

If a toxoplasmosis disease is asymptomatic, the patient does not need to undergo treatment.

However, treatment is required for patients with a weak immune system (AIDS patients), for first-time infections during pregnancy or for patients who show symptoms. If newborns are affected by toxoplasmosis, antibiotic therapy must also be given. Which antibiotic is used depends on the stage of pregnancy.

Normally, the toxoplasmosis disease is quite harmless. Rarely, however, complications can occur, for example, if the affected person suffers from an immune deficiency. In this case, the disease worsens. As a result, inflammation of the brain, heart or retina can occur.

Consistent antibiotic therapy during pregnancy can prevent damage to the unborn child. Nevertheless, scars on the retina can occur in some cases. Some children may still suffer from symptoms such as attention deficit disorder years later, which is why sufficiently long medical treatment (up to one year) should be applied at an early stage.

To prevent a toxoplasmosis infection, some rules should be followed that keep the risk relatively low. This is especially true for pregnant women who have never come into contact with the toxoplasmosis pathogen.

• Hand washing with soap is a particularly high priority, especially after contact with raw meat or vegetables. Hands should also be cleaned after gardening
• Cats should never be kissed and hand washing is again especially important after contact with those same cats. During pregnancy, another family member should clean the litter box with hot water (70 degrees Celsius). This will prevent the pre-stages from reaching adolescence and becoming infectious.
• The consumption of meat or sausage products that have not been sufficiently heated should be avoided. The mere tasting of such food can lead to infection. Special care should be taken with pork, lamb and goat meat. On the other hand, complete roasting or boiling of meat products offers safety.
• Vegetables, lettuce and fruit should be washed thoroughly before consumption.
• During pregnancy, a cat does not necessarily have to be removed from the household. Nevertheless, care should be taken to feed the animal mainly on canned and/or dry food.