Congenital toxoplasmosis: continued parasite proliferation in the fetal brain despite maternal immunological control in other tissues.
BACKGROUND
Congenital toxoplasmosis is a serious condition but little is known of the natural history of parasite development and associated fetal tissue destruction.


METHODS
Two cases identified by ultrasound underwent induced abortion at 21 and 30 weeks' gestation. At autopsy, the placenta and fetal organs were examined by histology and immunocytochemistry employing anti-Toxoplasma stage-specific antibodies to confirm diagnosis and also provide information on the stage of parasite development.


RESULTS
In both cases, maternal serology prior to termination showed both specific immunoglobulin M (IgM) and immunoglobulin G (IgG), whereas retrospective analysis of an earlier sample (12-14 weeks' gestation) showed only IgM reactivity consistent with infection occurring in the first trimester. The finding of a number of tissue cysts but few or no tachyzoites within the placenta and fetal adrenal and heart is characteristic of a chronic infection. However, in contrast, there were still areas of the fetal brain with large numbers of actively dividing, tissue-destructive tachyzoites.


CONCLUSIONS
These observations show that continued parasite proliferation and tissue destruction can occur within the fetal brain even when there is a marked maternal immune response including maternal IgG. This finding strongly suggests that there may be benefits from treating cases of recently acquired congenital infection to destroy any remaining proliferating parasites located in immunologically protected sites such as the fetal brain.
Nuffield Department of Clinical Laboratory Science, Oxford University Hospital, UK. david.ferguson@ndcls.ox.ac.uk
David J P
DJ
Ferguson
Colene
C
Bowker
Katie J M
KJ
Jeffery
Paul
P
Chamberlain
Waney
W
Squier
D000328:Adult; D000913:Antibodies, Protozoan / Q000276:immunology; D001706:Biopsy; D001921:Brain / Q000196:embryology / Q000469:parasitology* / Q000473:pathology; D005260:Female; D005315:Fetal Diseases / Q000175:diagnosis / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology; D010920:Placenta / Q000469:parasitology / Q000473:pathology; D011247:Pregnancy; D011296:Prenatal Diagnosis; D014122:Toxoplasma / Q000254:growth & development / Q000276:immunology; D014125:Toxoplasmosis, Congenital / Q000175:diagnosis / Q000276:immunology / Q000469:parasitology*
D000913:Antibodies, Protozoan; D007074:Immunoglobulin G; D007075:Immunoglobulin M