Download Risks associated with toxoplasmosis during pregnancy

CONSULTATION DRAFT
7.6 Toxoplasmosis
There is limited evidence to support screening 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.
7.6.1
Background
Toxoplasmosis, which is caused by the parasite Toxoplasma gondii, is usually asymptomatic and selflimiting. 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 (Di Mario et al 2009). The
likelihood of a woman acquiring a primary infection during pregnancy varies, depending on local
prevalence (Pappas et al 2009):
•
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; and
•
high prevalence: primary infection during pregnancy is unlikely due to previous exposure.
Toxoplasmosis infection can be acquired by (Di Mario et al 2009):
•
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.
Prevalence and incidence
In Australia, primary infection with toxoplasmosis during pregnancy is rare (Gilbert 2002) although it is
estimated that between 60% and 80% of Australians are non-immune (Pappas et al 2009).
•
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 (Pappas
et al 2009).
•
Congenital toxoplasmosis: The incidence of congenital toxoplasmosis has been reported to range
from 0.03/1,000 live births in England and Wales (Gilbert et al 2006) to 0.3/1,000 live births in southeastern Brazil (Carvalheiro et al 2005).
Risks associated with toxoplasmosis during pregnancy
•
Mother-to-child transmission rates have been reported to range from 11.3% (Ricci et al 2003) to 18.5%
(Varella et al 2009). The risk of transmission increases with gestational age (from 5% at 12 weeks to
80% just before birth) (Dunn et al 1999). However, babies infected early in pregnancy have a greater
risk of congenital abnormalities (Di Mario et al 2009).
•
Congenital toxoplasmosis has been associated with stillbirth, intracranial abnormalities and/or
developmental delay, ocular inflammation (Gilbert et al 2006) and impaired hearing (Andrade et al
2008; Brown et al 2009). 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 (Freeman et al 2005).
CONSULTATION DRAFT
7.6.2
Screening for toxoplasmosis
Summary of the evidence
The evidence on the benefits to women and babies of screening for toxoplasmosis is limited and
inconclusive. Routine screening for toxoplasmosis during pregnancy is not recommended in the United
Kingdom (NICE 2008).
Diagnostic accuracy of tests
Screening 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 (Petersen et al 2005; Thalib et
al 2005; Flori et al 2008; Bobic et al 2009; Kasper et al 2009; Lachaud et al 2009; Elyasi et al 2010; Wallon et al 2010;
Jost et al 2011; Lesle et al 2011; Robert-Gangneux et al 2011; Yamada et al 2011). 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 screening are limited and inconclusive (Gilbert & Gras 2003).
No evidence on the cost-effectiveness of screening for toxoplasmosis was identified.
Harms and benefits of screening
No high-level evidence on the harms and benefits of screening for toxoplasmosis was identified. A
narrative review found that psychological consequences of screening included parental anxiety due
to false positive results and uncertainties related to prognosis of children with an antenatal diagnosis of
congenital toxoplasmosis (Khoshnood et al 2007).
Recommendation 18
Grade C
Do not routinely offer screening for toxoplasmosis to pregnant women.
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 (Peyron et al 2010).
A systematic review (Thiébaut et al 2007) found weak evidence for an association between early
maternal treatment and reduced risk of congenital toxoplasmosis. A subsequent review (Peyron et al
2010) 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 (Berrebi et al 2007; 2010; Cortina-Borja et al 2010), current research is inadequate to assess
whether the possible benefits outweigh the potential harm to the baby from treatment (Peyron et al
2010).
7.6.3
Discussing toxoplasmosis
There is suggestive evidence that women may have low levels of knowledge about the risks associated
with T. gondii (Ferguson et al 2011) and that health education approaches may help reduce risk of
congenital toxoplasmosis (Gollub et al 2008).
Recommendation 19
Grade C
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; and
•
avoiding cat faeces in cat litter or in soil.
CONSULTATION DRAFT
7.6.4
Practice summary: toxoplasmosis
When: Early in pregnancy.
Who: Midwife; GP; obstetrician; 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.
7.6.5
Resources
SA Perinatal Practice Guidelines Workgroup (2004; reviewed 2010) Chapter 53 Toxoplasmosis in pregnancy. In: South
Australian Perinatal Practice Guidelines. Adelaide: SA Health.
http://www.health.sa.gov.au/ppg/Default.aspx?PageContentID=742&tabid=35
7.6.6
References
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CONSULTATION DRAFT
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