Selected parasite
Toxoplasma
Toxoplasmosis is an infection caused by the intracellular parasite Toxoplasma gondii. The infection is acquired by ingestion of toxoplasma tissue cysts (sporocysts).
This may be secondary to eating inadequately washed vegetables or salads contaminated with cat litter, or from inadequate hand washing following gardening, or consumption of undercooked or cured meats containing viable parasitic tissue cysts.Epidemiology
In developed countries, improvements in hygiene have led to a fall in the incidence of toxoplasma infection. In the United Kingdom, 90% of women of childbearing age are susceptible to toxoplasma infection and the incidence of maternal infection is approximately 2 per 1000 pregnancies (141). Reproductive-age women are at risk of acquiring an infection if they live in a high prevalence area, eat undercooked/raw meat, have contact with contaminated soil, drink contaminated water, and/or own a cat. Fetal transmission risk increases with gestational age at seroconversion (from 1% before 4 weeks, between 4-15% at 13 weeks, to 60% at 36 weeks) (142-145). The risk of congenital abnormality is greatest when infection occurs during the first trimester.
Clinical diagnosis
Primary infection is often asymptomatic (60-70%) but some women suffer from fever, fatigue, and lymphadenopathy. Toxoplasmosis mainly affects the central nervous system and eyes and can cause microcephaly, ventriculomegaly, hydrocephalus, and chorioretinitis. The affected child may experience learning difficulties, convulsions, spasticity, chorioretinitis, and blindness. Other consequences of congenital toxoplasmosis include hepatosplenomegaly, anaemia, rash, pneumonitis, and jaundice.
Diagnosis is mainly serological and based on testing for Toxoplasma-specific IgG and IgM antibodies. Diagnosis should be confirmed in relation to maternal history and with a specialist virologist’s opinion. An acute infection in pregnancy is most accurately diagnosed when at least two blood samples drawn at least 2 weeks apart show seroconversion from negative to positive.
Cases of confirmed primary maternal infection should be referred to a fetal medicine unit. Fetal diagnosis is based on the detection of T gondii DNA in amniotic fluid. Amniocentesis should be considered from 16 weeks of gestation, as a positive result would lead to a change from treatment with spiramycin to a pyrimethamine/sulfadiazine regimen (125).Treatment
When primary maternal infection is confirmed before 16 weeks of gestation, it is advisable to treat with spiramycin empirically rather than delay starting until after amniocentesis (125). Spiramycin administered to the mother reduces the risk of fetal infection by 60-70% (146, 147). In cases where amniocentesis is not possible, spiramycin should be started and continued throughout pregnancy with the aim of reducing transmission to the fetus. In cases where the amniotic fluid is positive for Toxoplasma DNA, transmission to the fetus is assumed. In proven fetal infection with ultrasound abnormalities, the outcome can be poor including fetal demise, neonatal death, neurological impairment (intellectual disability, seizures, need for ventricular shunt placement), and/or chorioretinitis. In cases of confirmed fetal infection, the treatment options include termination of pregnancy or maternal drug therapy with a pyrimethamine/sulfa- diazine regimen throughout pregnancy along with ultrasound surveillance for assessment of fetal damage. Prevention of infection is the best strategy. This involves thorough cooking of meats and thorough washing of fruits, vegetables, cutting boards, dishes, utensils, and hands. Pregnant women should wear gloves when gardening and should avoid changing a cat litter box.