Toxoplasmosis is an infection which 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 raw or under cooked meat, food contaminated with infected cat faeces or the soil where cats mess, and unpasteurised goat's milk. In healthy adults and children infection may be without symptoms, a mild flu-like illness and occasionally symptoms similar to glandular fever. 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.

Toxoplasmosis is one of a small group of infections which can transmit to the fetus 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 as the fetus is so vulnerable, 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.

Severe damage includes hydrocephalus (excess fluid on the brain), calcifications of the brain tissue that can lead to developmental delay and epilepsy, and damage to the retina of one or both eyes called retinochoroiditis. The majority of people with congenital toxoplasmosis have impaired sight in one or both eyes. The more severe damage to the brain is rare.

Damage in a severely affected infant will be apparent soon after birth, but in most cases the congenital infection will only show in childhood, the teens or even later, and this will be as retinochoroiditis.

In most cases congenital infection will only be detected after birth when there are eye problems and the patient presents with retinochoroiditis. These patients need to be carefully investigated by Reference Laboratories, and treatment for congenital infection may be up to one year.

Inheritance patterns
Not applicable

Prenatal diagnosis
This requires a specific blood test on the pregnant woman. This is not done routinely in the UK, although in other European countries there are national screening programmes. If a woman feels she has been at risk through something she ate, or if she has symptoms which could indicate toxoplasma infection, she can request a blood test. All positive tests should be sent to the Toxoplasma Reference Laboratory for confirmation and in the case of current infection, for tests which estimate the onset of infection. If the onset of infection is considered to be recent, the fetus can be tested, using amniocentesis or cordocentesis: but as these tests carry a risk of miscarriage, they are only offered where the risk of infection to the fetus is high and must be performed by a specialist in this field. Ultrasound scans can show up severe damage, but not the minor forms and only a blood test could confirm toxoplasmosis as the cause. Specific antibiotic treatment can help limit the risk of the infection crossing to the fetus where an infection is diagnosed during pregnancy. If the fetus is found to be infected, stronger antiparasitic drugs may be given to help limit the damage, and this treatment would also be given to all infants born with congenital infection.

Medical text written May 1996 by Contact a Family. Approved May 1996 by Dr T Brand, Toxoplasmosis Trust, London UK. Last updated February 2004 by Dr D Ho-Yen, Director, Scottish Toxoplasma Reference Laboratory, Raigmore Hospital, Inverness, UK.

Further Online Resources
Medical texts in The Contact a Family Directory are designed to give a short, clear description of specific conditions and rare disorders. More extensive information on this condition can be found on a range of reliable, validated web sites and links to them are included in the CD-ROM version of this Directory. Further information on these resources can be found in our Medical Information on the Internet article.

TOMMY'S, THE BABY CHARITY

Tommy's, the baby charity
Nicholas House
3 Laurence Pountney Hill
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EC4R 0BB
Tel: 0870 777 3060 Pregnancy Information Line
Tel: 08707 70 70 70
Fax: 08707 70 70 75
e-mail: info@tommys.org
Web: http://www.tommys.org

Tommy's is a National Registered Charity No. 1060508. It funds a national programme of medical research and information. It provides information for parents, parents-to-be, health professionals and the general public, to help maximise the chance of having a healthy pregnancy, through a telephone pregnancy information line, e-mail and web access to health professionals, plus a range of free publications.