There is limited evidence to support testing for toxoplasmosis during pregnancy. As infection may be transmitted to the baby during pregnancy, the focus is on providing women with advice about how to avoid sources of toxoplasmosis.
Toxoplasmosis, which is caused by the parasite Toxoplasma gondii, is usually asymptomatic and self-limiting. Symptoms when they occur include swollen lymph nodes, muscle aches and pains and fever.
When women who have not previously been exposed to the parasite (eg are non-immune) become infected during pregnancy, the infection can be transmitted to the baby. The likelihood of a woman acquiring a primary infection during pregnancy varies, depending on local prevalence :
- low prevalence: the potential for a woman to become infected is low but if she is infected during pregnancy it will most likely be a primary infection
- high prevalence: primary infection during pregnancy is unlikely due to previous exposure.
Toxoplasmosis infection can be acquired by:
- eating raw or insufficiently cooked meat
- not washing hands thoroughly after handling raw meat or gardening
- contact with cat faeces (directly or indirectly through the soil or cat litter); or
- contact with contaminated raw vegetables or fruits.
43.1.1 Prevalence and incidence
In Australia, primary infection with toxoplasmosis during pregnancy is rarealthough it is estimated that between 60% and 80% of Australians are non-immune .
- Country of origin: The prevalence of immunity to toxoplasmosis is high in Latin America, parts of Eastern/ Central Europe, the Middle East, parts of South-East Asia and Africa. There is a trend towards lower prevalence of immunity in many European countries and the United States .
- Congenital toxoplasmosis: The incidence of congenital toxoplasmosis has been reported to range from 0.03/1,000 live births in England and Wales to 0.3/1,000 live births in south-eastern Brazil .
43.1.2 Risks associated with toxoplasmosis during pregnancy
Mother-to-child transmission rates have been reported to range from 11.3%to 18.5% . The risk of transmission increases with gestational age (from 5% at 12 weeks to 80% just before birth) . However, babies infected early in pregnancy have a greater risk of congenital anomalies .
Congenital toxoplasmosis has been associated with stillbirth, intracranial anomalies and/or developmental delay, ocular inflammationand impaired hearing . In a prospective cohort study (n=620), babies with congenital toxoplasmosis had lower gestational age but there was no significant association with low birth weight or small for gestational age .
43.2 Testing for toxoplasmosis
The evidence on the benefits to women and babies of testing for toxoplasmosis is limited and inconclusive. Routine testing for toxoplasmosis during pregnancy is not recommended in the United Kingdom.
43.2.1 Diagnostic accuracy of tests
Tests for toxoplasmosis aim to identify whether maternal infection is acute or chronic. Studies have compared a range of tests for IgG and IgM antibodies and IgG avidity. There is great heterogeneity between the studies, making it difficult to comment on the predictive and diagnostic accuracy of one test over another. Studies into the timing of testing are limited and inconclusive .
No evidence on the cost-effectiveness of testing for toxoplasmosis was identified.
43.2.2 Harms and benefits of testing
No high-level evidence on the harms and benefits of testing for toxoplasmosis was identified. A narrative review found that psychological consequences of testing included parental anxiety due to false positive results and uncertainties related to prognosis of children with a diagnosis of congenital toxoplasmosis.
Do not routinely offer testing for toxoplasmosis to pregnant women.
Approved by NHMRC in June 2014; expires June 2019
43.2.3 Availability of safe and effective treatments
Spiramycin and sulphonamide medications have been used to treat toxoplasmosis with the aim of reducing mother-to-child transmission and the severity of fetal infection.
A systematic reviewfound weak evidence for an association between early maternal treatment and reduced risk of congenital toxoplasmosis. A subsequent review concluded that despite the large number of studies performed, it is still not known whether treatment of pregnant women with presumed toxoplasmosis reduces the transmission of T. gondii.
While some studies have reported a lack of symptoms among babies whose mothers were treated during pregnancy, current research is inadequate to assess whether the possible benefits outweigh the potential harm to the baby from treatment .
43.3 Discussing toxoplasmosis
There is suggestive evidence that women may have low levels of knowledge about the risks associated with T. gondiiand that health education approaches may help reduce risk of congenital toxoplasmosis .
Advise pregnant women about measures to avoid toxoplasmosis infection such as:
- washing hands before handling food
- thoroughly washing all fruit and vegetables, including ready-prepared salads, before eating
- thoroughly cooking raw meat and ready-prepared chilled meals
- wearing gloves and thoroughly washing hands after handling soil and gardening
- avoiding cat faeces in cat litter or in soil.
Approved by NHMRC in June 2014; expires June 2019
43.4 Practice summary: toxoplasmosis
Early in pregnancy.
- Aboriginal and Torres Strait Islander Health Practitioner
- Aboriginal and Torres Strait Islander Health Worker
- multicultural health worker.
- Discuss sources of toxoplasmosis
Explain that becoming infected with toxoplasmosis during pregnancy can lead to the infection being transmitted to the baby so it is important to take measures to avoid infection.
- Take a holistic approach
Women who are originally from an area of low prevalence are at risk of primary infection if they travel to countries where toxoplasmosis is highly prevalent.
- Document and follow-up
If a woman is tested for toxoplasmosis, tell her the results and note them in her antenatal record. Have a system in place so that women who become infected with toxoplasmosis during pregnancy are given ongoing follow-up and information.
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