In about 80% of cases, toxoplasmosis does not cause any symptoms and a person who is infected will not be aware that they are infected.
The immune system of healthy adults and children is usually strong enough to prevent the parasite that causes toxoplasmosis (Toxoplasma gondii or T. gondii) from causing serious illness. Once you have had the infection you become immune to it and T. gondii will live harmlessly in your body for life.
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 lead to symptoms that are similar to the flu, such as:
- aching muscles
- fever of 38°C (100.4°F) or over
- tiredness
- feeling sick
- sore throat
It is very rare for otherwise healthy people to experience any serious symptoms of toxoplasmosis.
Pregnant women
If you develop a toxoplasmosis infection either while you are pregnant or shortly before you conceive there is a chance that you could pass the infection on to your unborn baby. This is known as congenital toxoplasmosis.
You will probably not experience any symptoms of the infection yourself, but an infection that develops during the early stages of pregnancy increases the risk of:
- miscarriage - the loss of a pregnancy during the first 23 weeks
- stillbirth - where a 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 1% of cases.
About 30-40% of pregnant women who acquire toxoplasmosis infection during their pregnancy will pass the infection on to their unborn baby, leading to congenital toxoplasmosis.
Congenital toxoplasmosis
The symptoms of congenital toxoplasmosis vary depending on when the mother becomes infected. Symptoms will usually be more severe if the mother is infected around the time she becomes pregnant or during the first or second trimester (up to week 27 of the pregnancy).
Symptoms of congenital toxoplasmosis can include:
- hydrocephalus - water on the brain
- brain damage
- epilepsy - a condition that affects the brain and causes repeated seizures (fits)
- jaundice - yellowing of the skin and whites of the eyes
- deafness
- eye infections and blindness
- an enlarged liver or spleen (an organ that filters impurities from your blood)
- growth problems
- cerebral palsy - a condition of the brain and nervous system that affects a child’s movement and co-ordination
If the mother becomes infected during the third trimester of pregnancy (from week 27 to the birth), and the infection passes on to the baby, he or she may not have any symptoms at birth. However, complications may develop later in life.
For example, months or years later a child born with congenital toxoplasmosis may develop eye infections, hearing loss or learning difficulties.
Read more about the complications of congenital toxoplasmosis.
People with immune deficiencies
For someone with a weakened immune system, toxoplasmosis can be fatal. This is because their body may not be able to fight off the infection. Your immune system can be weakened if you:
- have an illness that affects your immune system, such as HIV and AIDS or cancer
- are receiving certain types of medication, such as chemotherapy (powerful cancer-killing medication)
- are taking immunosuppressant medication, for example after having had an organ transplant
There is also a risk of permanent eye or brain damage when toxoplasmosis infects someone with a weakened immune system.
If toxoplasmosis begins to affect the brain, it can cause encephalitis. This is sometimes called toxoplasmosis encephalitis (TE) and it is one of the most frequent causes of death in people with AIDS.
Symptoms of TE include:
- headaches
- confusion
- poor co-ordination
- seizures (fits)
- chest pains
- coughing up blood
- difficulty breathing
- a high temperature (fever) of 38°C (100.4°F) or over
- vision problems, such as blurred vision and floaters (small pieces of debris that can cloud your vision)
- multiple lesions (wounds) in the brain
