Toxoplasmosis in pregnancy: Difference between revisions

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== Clinical Manifestations ==
 +
==Clinical Manifestations==
   
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* Often no history of illness during pregnancy
 +
*Often no history of illness during pregnancy
−
* Symptoms, if present, tend to be mild with low-grade fever, malaise, and lymphadenopathy
 +
*Symptoms, if present, tend to be mild with low-grade fever, malaise, and lymphadenopathy
  +
*Only half of women can identify a significant risk factor[[CiteRef::boyer2011un]]
  +
*Risk of transmission to fetus is with parasitemia associated with primary infection, so women who are seropositive are ''not'' at risk of having a child with congenital infection
   
−
== Diagnosis ==
 +
==Diagnosis==
   
 
*Molecular
  
*Molecular
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**Can also be done on fetal blood
  
**Can also be done on fetal blood
 
*Serology
  
*Serology
−
**Can check maternal IgM and IgG
 +
**Can check maternal IgM and IgG, both of which appear within the first week after infection
 
**IgM is not specific to recent infection, however, as it can be present for more than a year
  
**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
  
**IgG avidity testing is used to determine recency of infection
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***Low avidity is unhelpful, as avidity can remain low for more than a year
  
***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
  
***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
 +
**Therefore, if infection is suspected in the first 16 weeks of gestation, high avidity effectively rules out infection acquired during pregnancy
 
*Needs serial head ultrasound to monitor for hydrocephalus and intraparenchymal brain calcifications
  
*Needs serial head ultrasound to monitor for hydrocephalus and intraparenchymal brain calcifications
 
**May also see hepatic calcifications, splenomegaly, and ascites
  
**May also see hepatic calcifications, splenomegaly, and ascites
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==Management==
  
==Management==
 
{| class="wikitable"
  
{| class="wikitable"
⚫
!IgG
  
 
!IgM
  
!IgM
  ⚫
!IgG
 
!Interpretation
  
!Interpretation
 
!Management
  
!Management
 
|-
  
|-
  ⚫
| +
 
|–
  
|–
⚫
|–
  
−
|no prior infection; at risk
  
⚫
|counsel on prevention of primary infection
  
⚫
|-
  
−
|–
  
⚫
| +
  
 
|acute primary infection or false positive
  
|acute primary infection or false positive
 
|repeat serology in 2 to 3 weeks; if unchanged, then was false positive
  
|repeat serology in 2 to 3 weeks; if unchanged, then was false positive
 
|-
  
|-
  +
| rowspan="2" | +
  +
| rowspan="2" | +
  +
| rowspan="2" |recent or prior infection
  ⚫
|high IgG avidity: infection was >4 months ago so unlikely to be acute
  ⚫
|-
  +
|low IgG avidity: cannot determine when infection occurred
  +
|-
  ⚫
|–
 
| +
  
| +
  ⚫
|remote infection
−
|–
  
⚫
|prior infection
  
 
|no risk of transmission except rare cases of immunocompromise
  
|no risk of transmission except rare cases of immunocompromise
 
|-
  
|-
−
| +
 +
|–
−
| +
 +
|–
−
|recent or prior infection
 +
|no prior infection; at risk
  ⚫
|counsel on prevention of primary infection
⚫
|do avidity testing: if high avidity, infection was >4 months ago so unlikely to be acute; if low avidity, uncertain
  
 
|}
  
|}
   
  +
*In general, for highly suspected or confirmed infection, it is reasonable to start [[Is treated by::spiramycin]] while confirming the infection
−
===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 amniocentesis after week 18
−  
⚫
*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, [[Is treated by::spiramycin]] 3 g/day until delivery
  
*If infected < 14 weeks gestation, [[Is treated by::spiramycin]] 3 g/day until delivery
 
**However, it doesn't cross the placenta and it's unclear whether it affects outcomes in the baby
  
**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
  
**Likely most effective if given within 8 weeks of maternal infection
  +
**[[Pyramethamine]] is contraindicated in pregnancy before 14 weeks gestation
 
**Second-line would be monotherapy with [[Is treated by::sulfadiazine]] or [[Is treated by::clindamycin]]
  
**Second-line would be monotherapy with [[Is treated by::sulfadiazine]] or [[Is treated by::clindamycin]]
 
*If age ≥ 14 weeks gestation and documented fetal infection by amniocentesis, or if suspected infection was ≥14 weeks gestation, use standard therapy
  
*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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**Therefore, if initially started on [[spiramycin]], then switch to standard therapy if amniotic fluid PCR is positive or ultrasound is abnormal
  
**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
  
**However, it is teratogenic until 14 weeks gestation so [[spiramycin]] is used until then
  +
*If age ≥33 weeks gestation, then continue [[spiramycin]] and await a postnatal diagnosis
   
−
=== Prevention ===
 +
==Prevention==
   
−
* Prevention mostly focusses on counselling around risk reduction:
 +
*Prevention mostly focusses on counselling around risk reduction:
−
** Wash hands after changing cat litter
 +
**Wash hands after changing cat litter
  +
**Wear gloves in the garden and when changing cat litter
−
** Cook meat thoroughly
 +
**Cook meat thoroughly
−
** Avoid raw eggs and unpasteurized dairy
 +
**Avoid raw eggs and unpasteurized dairy
  +
**Wash fruits and vegetables
  +
**Do not obtain a new cat while pregnant
   
−
[[Category:Infectious diseases]]
  
−
[[Category:Obstetrical medicine]]
  
 
[[Category:Obstetrical infections]]
  
[[Category:Obstetrical infections]]

Latest revision as of 12:24, 20 September 2020

Clinical Manifestations

  • Often no history of illness during pregnancy
  • Symptoms, if present, tend to be mild with low-grade fever, malaise, and lymphadenopathy
  • Only half of women can identify a significant risk factor1
  • Risk of transmission to fetus is with parasitemia associated with primary infection, so women who are seropositive are not at risk of having a child with congenital infection

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
  • Serology
    • Can check maternal IgM and IgG, both of which appear within the first week after infection
    • 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, high avidity effectively rules out infection acquired during pregnancy
  • Needs serial head ultrasound to monitor for hydrocephalus and intraparenchymal brain calcifications
    • May also see hepatic calcifications, splenomegaly, and ascites

Management

IgM IgG Interpretation Management
+ – acute primary infection or false positive repeat serology in 2 to 3 weeks; if unchanged, then was false positive
+ + recent or prior infection high IgG avidity: infection was >4 months ago so unlikely to be acute
low IgG avidity: cannot determine when infection occurred
– + remote infection no risk of transmission except rare cases of immunocompromise
– – no prior infection; at risk counsel on prevention of primary infection
  • In general, for highly suspected or confirmed infection, it is reasonable to start spiramycin while confirming the 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 amniocentesis 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
    • Pyramethamine is contraindicated in pregnancy before 14 weeks gestation
    • 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
  • If age ≥33 weeks gestation, then continue spiramycin and await a postnatal diagnosis

Prevention

  • Prevention mostly focusses on counselling around risk reduction:
    • Wash hands after changing cat litter
    • Wear gloves in the garden and when changing cat litter
    • Cook meat thoroughly
    • Avoid raw eggs and unpasteurized dairy
    • Wash fruits and vegetables
    • Do not obtain a new cat while pregnant

References

  1. ^  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.

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