Toxoplasmosis and Pregnancy
Toxoplasmosis is caused by a parasite called toxoplasma gondii. This is found in different forms in raw meat, within cats who eat raw meat and their faeces. Toxoplasmosis infection is common in both men and women outside of pregnancy, however it is infection during pregnancy that is of most concern as it can lead to infection in the unborn infant: congenital toxoplasmosis.
Who is at Risk?
Once you have had toxoplasmosis, the body develops immunity and new exposure during pregnancy is not an issue. Peak incidence is between ages 25 and 30 years and in the UK by this time, about 30% of people will have had toxoplasmosis, hence will not be at risk of any problems during pregnancy. In the US, about 30-35% have antibodies and in France more than 65% of women will have already had toxoplasmosis. Because infection is more common in France, congenital toxoplasmosis occurs at over twice the rate in the UK or US.
It is not known for sure how many women catch toxoplasmosis during pregnancy, but some research suggests it is of the order 2 in every 1000, which means about 1400 each year in the UK.
What are the Symptoms of Toxoplasmosis?
It is unusual for otherwise healthy people to be ill when infection occurs. The most common symptoms are a viral, glandular fever-like illness or swollen glands in the neck.
How is it Diagnosed?
A blood test can indicate whether you are susceptible to getting an infection, hence at risk. It can also diagnose new infection in the mother. In France all women are screened at the beginning of pregnancy to see if they are susceptible to infection. In the UK this is not the case as the incidence of infection is low. In any case, risk can be avoided with simple measures, and although ascertaining your antibody status may reassure you if you are immune, it's not as though there is a vaccine to prevent infection, as is the case with Rubella, for example.
What are the Risks to the Baby?
In only about 30-40% of women who catch toxoplasmosis during pregnancy, does the infection pass to the unborn baby. The actual risk appears to be related to the gestation at which it is acquired. It is greatest in the third trimester at 70%, whereas in early pregnancy only 15% of infants will become infected.
Toxoplasmosis infection may lead to miscarriage, stillbirth, or survival with growth problems, blindness, water on the brain (hydrocephalus), brain damage, epilepsy, or deafness. This often develops after birth, so even normally born infants of women with known infection should be kept under observation for some time.
If a woman is found to have acquired toxoplasmosis during pregnancy, she will be offered an ultrasound scan to look for signs of fetal infection. After 20 weeks gestation, she may be offered a definitive test - cordocentesis. This involves a scan and blood sample being taken from the umbilical cord.
What is the Treatment?
The evidence that antibiotic treatment can help to prevent some of the sequelae of toxoplasmosis infection is unfortunately contradictory. If a scan suggests severe damage, the woman is offered the option of terminating the pregnancy.
How can I Avoid Catching Toxoplasmosis?
Although toxoplasmosis is quite serious when it occurs, as you will see from the figures above, it is relatively rare. Women with cats do not need to get rid of them when they become pregnant; it is just necessary to take a few precautions.
Be sure to only eat meat which has been cooked right through. Wash your hands, cooking utensils and food surfaces after preparing raw meat and wash all the soil from fruit and vegetables before eating. Keep raw meat and cooked foods on separate plates. If possible get someone else to clean out the dirty cat litter or use gloves and wash your hands afterwards. Always use gloves when gardening and wash your hands afterwards.
Try not to worry excessively or become paranoid about this - if you take these precautions, chance of infection is practically eliminated - you can still pet your cat, without fear!
Finally, it is important for pregnant farmers to be aware that toxoplasmosis can be caught from sheep at lambing time.
Where can I get More Information?
The Toxoplasmosis Trust has information sheets for women with current infection, for those with congenital toxoplasmosis and their families, and for sufferers of acute acquired toxoplasmosis. The address is: 61-71 Collier Street, London N1 9BE. Tel: 0171 713 0599
Thanks to Dr Roger B. Eaton, Infectious Disease Division, New England Regional Newborn Screening Program, Boston for additional information.