I. Epidemiology and transmission
- Caused by Toxoplasma gondii, a protozoan; definitive host is cats. Most exposure actually occurs with ingestion of undercooked meat; also can be acquired by inhaling dust from feces of infected cats (most likely if cat hunts rodents)
- Disease in humans occurs mostly with immunocompromised people & pregnant women.
- 30-60% of women of childbearing women are seropositive.
- Acute toxoplasmosis occurs in 0.1-0.5% of pregnancies in U.S.
- Infection in pregnancy is symptomatic in 60-90% with fever, chills, headache, malaise, myalgias, & lymphadenopathy; self-limited.
II. Congenital infection
- Rates of evident infection of fetus with maternal acute infection during various trimesters of pregnancy:
- 9% 1st trimester
- 29% 2nd trimester
- 59% 3rd trimester
- Treating mother with acute toxoplasmosis reduces risk of perinatal transmission and/or serious sequelae
- 75% of infected neonates are asymptomatic at birth, but most will eventually develop some sequela of infection.
- Sequelae tend to be less severe with late than with early infection: IUGR, Chorioretinitis, hydrocephalus, intracranial calcifications, and microcephaly can occur.
- In a retrospective study of 131 infants with confirmed congenital toxoplasmosis, only 48% of the mothers recalled having any signs, symptoms, or known risk factors (Am. J. Obs. Gyn. 192:564, 2005--JW)
- Don't change litterbox & keep away from litterbox area when pregnant; also, someone should change litterbox frequently, since aerosolized oocysts can remain infective for a while.
- Routine serologic screening not recommended
- Do check serology with suspicious neonatal illness of abnormality; some labs don't do it well.
- Can diagnose prenatally with culture/serology on amniotic fluid, serial u/s on fetal brain.
- CAN BE TREATED during pregnancy, with reduction in damage to fetus, with spiramycin, the sooner the better (not FDA approved in U.S., can be obtained on case-by-case basis from Rhone-Poulenc-Rorer), or with pyrimethamine or sulfonamides