✍️Toxoplasma gondii is an obligate intracellular parasite
✍️infect almost up to 50% of the world’s population.
✍️lifetime risk of ocular toxoplasmosis is around 18/100,000 in the UK, but up to 20 times this level in West Africa.
✍️Prevalence and incidence of ocular symptoms after infection depend on socio-economic factors and the circulating parasite genotypes.
✍️ocular toxoplasmosis is more common in South America, Central America, and the Caribbean and parts of tropical Africa, as compared to europe and Northern America, and is quite rare in China.
✍️ocular disease in South America is more severe than in other continents due to the presence of extremely virulent genotypes of the parasite.
✍️drinking untreated water is considered the major source of Toxoplasma infection in developing countries vs eating raw or undercooked meat products in more developed countries.
✍️Acquired infection is now a more important source of ocular toxoplasmosis than congenital infection, and so prevention should be directed toward the whole population.
✍️the definitive host is the cat
✍️livestock and humans are only intermediate hosts.
✍️oocysts are excreted in cat faeces which are ingested by humans or livestock in which they may become encysted (bradyzoite) or actively pro- liferate (tachyzoite).
✍️Human infection arises from
☝️contact with cat faeces or contaminated soil
☝️ingestion of undercooked meat (bradyzoites)
☝️drinking contaminated water
☝️transplacentally(Vertical transmission ) increases from 15% in the first trimester to 60% in the third trimester but the severity is, however, much greater if acquired in early pregnancy.
✅ ToxoplasmosisClinical features
☝️Affects both eyes in 40%, sequentially
☝️if simultaneously active, suspect immunocompromise
☝️may be Asymptomatic
☝️floaters, dropped VA.
☝️Vitritis (may have ‘vitreous precipitates’ akin to KPs on posterior surface of PVD)
• white, fluffy area when active ( headlights in fog )
• circumscribed and pigmented as it heals
• atrophic scar with pigmented border when inactive
• satellite lesions adjacent to old scars commonly seen
• retinal vasculitis (periphlebitis)
• may have punctate outer retinitis (with quiet vitreous) large lesions (especially in the elderly) endophthalmitis-like
• serous retinal detachments
• pigmentary retinopathy.
☝️may have an anterior uveitis often with high IOP
☝️retinochoroiditis (more commonly bilateral and affecting the macula).
• usually asymptomatic
• may have fever and lymphadenopathy
• usually HIV-positive patients with life threatening infections
• intracerebral cysts
✅ Toxoplasmosis Investigation
✍️essentially a clinical diagnosis.
✍️Interpret positive serological tests with caution.
✍️Many of the adult population are positive for anti-Toxoplasma IgG
✍️IgM antibodies do suggest acquired infection, and negative serology in undiluted serum makes the diagnosis unlikely.
✍️PCR of intraocular samples may also be used.
✅ Toxoplasmosis Treatment
✍️indications for treatment
☝️lesions involving disc, macula, or papillomacular bundle.
☝️lesions threatening a major vessel.
☝️Any lesion in an immunocompromised patient.
☝️≥4wk of prednisolone with
• clindamycin/ sulfadiazine
• pyrimethamine/sulfadiazine/folinic acid (weekly
☝️Steroids must not be used without effective ective umbrella of anti-toxoplasmosis therapy and should not be given if immunosuppressed.
☝️For maternal infection acquired during pregnancy, use spiramycin (named-patient basis) to reduce transplacental spread.
☝️Atovaquone may theoretically reduce recurrences, as it is active against bradyzoites as well as tachyzoites.
☝️Azithromycin is used in some centres.
☝️In immunocompetent patients , the disease is self-limiting and hence does not require treatment unless sight-threatening.
☝️Recurrence is common and average number of recurrences is two, but a wide range is seen.
✅ Toxoplasmosisand pregnancy
✍️Advice Wash all fruit and vegetables
✍️Avoid unpasteurized goat’s milk
✍️Cook all meat thoroughly
✍️Avoid handling cat litter (or use rubber gloves)
✍️Risk of transmission 15–60% risk if acquired during pregnancy
✍️No risk otherwise (even if recurrence of active disease during pregnancy).