Toxoplasmosis in pregnancy: Difference between revisions
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== Clinical Manifestations == |
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* Often no history of illness during pregnancy |
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* Symptoms, if present, tend to be mild with low-grade fever, malaise, and lymphadenopathy |
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== Diagnosis == |
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*Molecular |
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**Definitive diagnosis is based on PCR of amniotic fluid around 18 months, usually done after maternal serology to confirm intrauterine infection |
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***Sensitivity is 64 to 92% and specificity 100% (NPR around 88 to 98%) |
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***Earlier than 18 weeks has unknown sensitivity and specificity, and has a higher risk of spontaneous abortion |
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**Can also be done on fetal blood |
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*Serology |
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**Can check maternal IgM and IgG |
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**IgM is not specific to recent infection, however, as it can be present for more than a year |
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**IgG avidity testing is used to determine recency of infection |
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***Low avidity is 35-50% and high is >60% |
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***Low avidity is unhelpful, as avidity can remain low for more than a year |
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***High avidity, on the other hand, suggests infected at least 3-4 months prior |
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**Therefore, if infection is suspected in the first 16 weeks of gestation, avidity testing may be able to rule out infection during pregnancy |
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*Needs serial head ultrasound to monitor for hydrocephalus and intraparenchymal brain calcifications |
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**May also see hepatic calcifications, splenomegaly, and ascites |
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==Management== |
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=== |
===Acute Infection=== |
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*If infected < 14 weeks gestation, [[Is treated by::spiramycin]] 3 g/day until delivery |
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**However, it doesn't cross the placenta and it's unclear whether it affects outcomes in the baby |
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**Likely most effective if given within 8 weeks of maternal infection |
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**Second-line would be monotherapy with [[Is treated by::sulfadiazine]] or [[Is treated by::clindamycin]] |
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*If age ≥ 14 weeks gestation and documented fetal infection by amniocentesis, or if suspected infection was ≥14 weeks gestation, use standard therapy |
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**Standard therapy is: [[Is treated by::pyrimethamine]] 50 mg q12h for 2 days followed by 50 mg daily (plus [[folinic acid]] 10-20 mg daily until 1 week after stopping pyrimethamine), and [[Is treated by::sulfadiazine]] 75 mg/kg load followed by 50 mg/kg q12h (maximum 4 g/day) |
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**This treatment crosses the placenta, which is why it is used in cases of documented or suspected fetal infection, as well as in later-term infections when the risk of fetal infection is higher |
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**Therefore, if initially started on [[spiramycin]], then switch to standard therapy if amniotic fluid PCR is positive or ultrasound is abnormal |
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| ⚫ | |||
=== Prevention === |
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* Prevention mostly focusses on counselling around risk reduction: |
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** |
** Wash hands after changing cat litter |
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** Cook meat thoroughly |
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*** If PCR positive, treat with [[pyrimethamine]] and [[sulfadiazine]] plus [[folinic acid]], until delivery |
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** Avoid raw eggs and unpasteurized dairy |
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*** If PCR negative, continue prophylaxis with [[spiramycin]] 1 g po TID |
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* Choice of antiparasitic |
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** [[Spiramycin]] does not cross the placenta, while [[pyrimethamine]] and [[sulfadiazine]] do |
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[[Category:Infectious diseases]] |
[[Category:Infectious diseases]] |
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Revision as of 17:13, 30 July 2020
Clinical Manifestations
- Often no history of illness during pregnancy
- Symptoms, if present, tend to be mild with low-grade fever, malaise, and lymphadenopathy
Diagnosis
- Molecular
- Definitive diagnosis is based on PCR of amniotic fluid around 18 months, usually done after maternal serology to confirm intrauterine infection
- Sensitivity is 64 to 92% and specificity 100% (NPR around 88 to 98%)
- Earlier than 18 weeks has unknown sensitivity and specificity, and has a higher risk of spontaneous abortion
- Can also be done on fetal blood
- Definitive diagnosis is based on PCR of amniotic fluid around 18 months, usually done after maternal serology to confirm intrauterine infection
- Serology
- Can check maternal IgM and IgG
- IgM is not specific to recent infection, however, as it can be present for more than a year
- IgG avidity testing is used to determine recency of infection
- Low avidity is 35-50% and high is >60%
- Low avidity is unhelpful, as avidity can remain low for more than a year
- High avidity, on the other hand, suggests infected at least 3-4 months prior
- Therefore, if infection is suspected in the first 16 weeks of gestation, avidity testing may be able to rule out infection during pregnancy
- Needs serial head ultrasound to monitor for hydrocephalus and intraparenchymal brain calcifications
- May also see hepatic calcifications, splenomegaly, and ascites
Management
| IgG | IgM | Interpretation | Management |
|---|---|---|---|
| – | – | no prior infection; at risk | counsel on prevention of primary infection |
| – | + | acute primary infection or false positive | repeat serology in 2 to 3 weeks; if unchanged, then was false positive |
| + | – | prior infection | no risk of transmission except rare cases of immunocompromise |
| + | + | recent or prior infection | do avidity testing: if high avidity, infection was >4 months ago so unlikely to be acute; if low avidity, uncertain |
Acute Infection
- If acute infection, such as IgM + / IgG – that converts to IgG +, or IgM + / low IgG avidity with compatible clinical picture, then rule out fetal infection with an mmniocentesis after week 18
- If infected < 14 weeks gestation, spiramycin 3 g/day until delivery
- However, it doesn't cross the placenta and it's unclear whether it affects outcomes in the baby
- Likely most effective if given within 8 weeks of maternal infection
- Second-line would be monotherapy with sulfadiazine or clindamycin
- If age ≥ 14 weeks gestation and documented fetal infection by amniocentesis, or if suspected infection was ≥14 weeks gestation, use standard therapy
- Standard therapy is: pyrimethamine 50 mg q12h for 2 days followed by 50 mg daily (plus folinic acid 10-20 mg daily until 1 week after stopping pyrimethamine), and sulfadiazine 75 mg/kg load followed by 50 mg/kg q12h (maximum 4 g/day)
- This treatment crosses the placenta, which is why it is used in cases of documented or suspected fetal infection, as well as in later-term infections when the risk of fetal infection is higher
- Therefore, if initially started on spiramycin, then switch to standard therapy if amniotic fluid PCR is positive or ultrasound is abnormal
- However, it is teratogenic until 14 weeks gestation so spiramycin is used until then
Prevention
- Prevention mostly focusses on counselling around risk reduction:
- Wash hands after changing cat litter
- Cook meat thoroughly
- Avoid raw eggs and unpasteurized dairy
References
- ^ K. Boyer, D. Hill, E. Mui, K. Wroblewski, T. Karrison, J. P. Dubey, M. Sautter, A. G. Noble, S. Withers, C. Swisher, P. Heydemann, T. Hosten, J. Babiarz, D. Lee, P. Meier, R. McLeod. Unrecognized Ingestion of Toxoplasma gondii Oocysts Leads to Congenital Toxoplasmosis and Causes Epidemics in North America. Clinical Infectious Diseases. 2011;53(11):1081-1089. doi:10.1093/cid/cir667.
