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Toxoplasmosis

Background

Toxoplasmosis is an infection that is caused by the parasite Toxoplasma gondii, which affects all warm blooded animals including humans. Infection is caught by eating anything infected or contaminated with the parasite, such as undercooked or raw meat (including raw cured meat) and unpasteurised goats' milk or by contact with infected cat faeces or cat litter/soil contaminated with infected cat faeces.

Credits

Medical text written May 1996 by Contact a Family. Approved May 1996 by Dr T Brand, Toxoplasmosis Trust, London UK. Last updated August 2011 by Dr D O Ho-Yen, Director, Scottish Toxoplasma Reference Laboratory, Raigmore Hospital, Inverness, UK.

What are the symptoms?

In healthy adults and children, infection may be without symptoms. In some cases, infection may present as a mild flu-like illness. The infection can cause serious health problems for anyone with suppressed or damaged immunity, for example people on immune suppressing drugs or people with AIDS (see entry HIV infection and AIDS).

Toxoplasmosis is one of a small group of infections that can transmit to the fetus (unborn baby) if caught for the first time during pregnancy. The risk of transmission and the degree of damage done depend on when in pregnancy the woman catches the infection. In the first trimester, the damage may be very severe, however it is less likely that infection is transmitted at this stage of pregnancy. Later on in pregnancy, the damage is less severe, but the infection is more likely to transmit and cause congenital infection (infection at birth).

Severe damage includes excess fluid on the brain (see entry Hydrocephalus), calcifications of the brain tissue that can lead to developmental delay (see entry Global Developmental Delay) and epilepsy, and damage to the retina (a light-sensitive film at the back of the eye) of one or both eyes known as retinochoroiditis. More severe damage to the brain is rare.

Damage in a severely affected infant will be apparent soon after birth. However, the vast majority of babies with congenital infection will appear normal at birth. Unless these babies are treated, problems especially with the eyes, will develop in childhood, the teens or even later.

How is it diagnosed?

If a woman feels she has been at risk through something she ate, or if she has symptoms that could indicate toxoplasma infection, she can request a blood test. All positive tests should be sent to the toxoplasma reference laboratory for confirmation and an estimate of infection onset.

How is it treated?

Where an infection is diagnosed during pregnancy, specific antibiotic treatment can help limit the risk of the infection crossing to the fetus. If the fetus is found to be infected, stronger anti-parasitic drugs may be given to help limit the damage, and this treatment would also be given to all infants born with congenital infection. Treatment for congenital infection may be given for up to up to one year.

Inheritance patterns and prenatal diagnosis

Inheritance patterns
Not applicable.

Prenatal diagnosis
This requires a specific blood test on the pregnant woman. This is not done routinely in the UK. If a woman is confirmed as having toxoplasmosis infection during pregnancy and the onset of infection is considered to be recent, the fetus can be tested using amniocentesis. Ultrasound scans can show up severe damage as a result of toxoplasmosis infection, but not the minor forms. If a scan raises suspicion about damage to the unborn baby, only a blood test could confirm toxoplasmosis as the cause.

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