toxo Flashcards
toxo overview
-opportunistic
-causes toxoplasmosis
-final host is felines
-intermediate host is mammals
-transmitted fecal-oral
3 forms of toxo
-tachyzoites
-tissue cysts (bradyzoit)
-oocysts
tachyzoite stage
-rapidly growing stage in early infection
-acute phase lives in body fluids
-crescent-shaped (pear)
-asexual form
-multiples by endodyogeny
-can infect phagocytic & non-phagocytic cells
-anti-toxo Abs in serum bind to Ag on live trachyozoites
-killed by complement mediate lysis
bradyzoites
-slow growing inside tissue cysts
-mark the chronic phase of infection
-resistant to low pH & digestive enzymes
-protective cyst wall dissolves & infects tissues
-released in intestine & highly infectious if consumed
oocysts
-in cat feces
-gametocyte develop in the small intestine
-sexual cycle produces oocysts which is excreted in feces
-appear in cat poop 3-5 days after ingestion
-require oxygen
-sporulate in 1-5 days
-sporulated oocysts are infectious
pathogenesis
-systemic disease (extra-interstitial phase)
-explosive replication of tachyzoites: massive direct destruction of cells & acute immune response
-affects brain, liver, lungs & striated muscles
-tissue cysts cause physical call damage & are source for latent disease
toxo vaccine?
no
detection of toxo (serology)
-antigen by ELISA
-antibody by: sabin dye test
-IgM ELISA
-IgG ELISA
-IgG avidity test
-ToRCH in newborns
diagnosis of congenital toxo
-Ag in amniotic fluid
-PCR (research only)
-IgM Abs in fetal blood by ELISA
-fetal ultrasound around 20-24 weeks
sabin dye test
-gold standard
-only in reference labs
-complement mediated neutralization test requiring live tachyzoites
-incubated with complement & serum
-alkaline methylene blue is added & reincubated
diagnosis of toxo
-direct microscopy
-detection of tachyzoites in blood & tissue cyst in tissue biopsy
-staining methods: geimsa, PAS, silver stains, immunoperoxidase stain
neural effects
in CT & MRIs congenitally infected children show periacqueductal inflammation & necrosis
-microcephaly: zika
hydrocephaly: toxo
babies with congenital toxo manifest with:
-brain damage
-enlarged spleen & liver
-eye damage
-jaundice
-poor motor coordination
-unusually small head
-rash
neonatal toxo infection can lead to:
-still birth
-chorioretinitis
-intracelluar calcification
-psychomotor disturbances
-hydrocephaly
-microcephaly
-blindness
toxo implications on human health
-congenital toxoplasmosis
-post natal toxoplasmosis
CMV IgM serology
-if (+) in cord/infant’s blood in 1st 3 weeks of life
-if (-), congenital infection not ruled out
-insensitive compared with urine culture for diagnosis of CMV
rubella serology
-specific IgM remains detectable for 6-12 months
-persistence of IgG Abs in the infant’s serum beyond 3-6 months
toxo serology
-specific IgG Abs detectable indefinitely 1-2 months post infection
-specific IgM testing often yields false pos or false neg
-IgM can persist for 6-24 months
-sendout confirmation testing
syphilis serology
-quantitative non-treponemal serologic (RPR) titer > fourfold the mother’s titer
rubella culture
virus isolation from nasal secretion
CMV urine culture +/-
-shell vial assay or early antigen determination (EAD)
-inoculated culture cells in small vials are stained with fluorescein-conjugated monoclonal Ab to CMV Ag at 24-48 hours
HSV viral culture
from vesicular swab, CSF, whole blood
PCR CMV-DNA assay
-rapidly replacing viral culture- more sensitive & efficient for CMV detection (urine, saliva, serum, liver tissue)
-saliva PCR method of choice
HSV viral PCR
DNA & rapid immunofluorescence assay (IFA)
