Ocular Toxoplasmosis

Most cases are presumed reactivation of congenital infection
2 to 6/1000 women acquire infection while pregnant, 40% risk of transmission to fetus.
Of infected infants: 70% chorioretinal scars, 5% will die or severe disability, 1-2% severe visual impairment
Northern Brazil has high rate of acquired disease

Keratic Precipitates, anterior chamber cell and flare, posterior synechia, cataract
Retinochoroiditis
Vitritis- concentrated over lesion, scaffolding of vitreous strands
Macular edema
Retinal vasculitis
VF defect in area of scar
FFA of active lesion- early blockage and subsequent leakage

In early infection: gray-white fine punctate lesions in deep retina and RPE, progress to more classic lesions
Papillitis, vitreal inflammation, nerve fiber bundle defects
Bullous like inflammatory lesions in mid-periphery
Wide ring-like lesion near extreme periphery resembling pars planitis
Scleritis

Typical lesions
Toxoplasmosis titers are supportive
- IgM titers- can be missed
- IgG titers- high rate of false positives
Immunoflourescence, ELISA
Western blot for Toxo antigens
PCR and Southern Blot for Toxo DNA
Angiography: flourescein tagged Ab (successful in rabbit studies)

Sulfadiazine 1g PO QID
Pyrimethamine 75-100mg load and 25-50mg PO BID (bone marrow suppression, nausea)
- Use concurrently: Folinic Acid 3-5mg PO 3 times/week (Baseline CBC, follow q week)
Clindamycin 150-300mg PO TID-QID (?reduces recurrence, risk of pseudomembranous colitis)
Trimethoprim-sulfamethoxazole (DS) I PO BID
Atovaquone (Mepron) 750mg PO BID (kills cysts in vitro)
Tetracycline 2g load and 250mg PO QID (to replace clindamycin)
Prednisone 20-60 mg/day not used alone

Recurrence rates not statistically significant
Size of retinal lesion correlated with duration of inflammation
All side-effects were reversible
Delay in starting medication (even up to 1 week) did not alter duration of inflammation
Sub-tenon's steroid- risk of increasing activity of organism
Vitrectomy- for vitreal haze reducing vision, perioperative antibiotics advocated
Cryotherapy and Laser photocoagulation generally not successful