TOXOPLASMOSIS
It is a protozoan infestation caused by Toxoplasma gondii, derived from cats (definitive host). Humans and other animals (cattle, sheep and pigs) are intermediate hosts. The disease primarily affects central nervous system (brain and retina). Systemic toxoplasmosis occurs in humans in two forms: congenital and acquired.
Congenital toxoplasmosis. It is much more common than the acquired form, and the infestation is acquired by the foetus through transplacental route from the mother contracting acute infestation during pregnancy. When pregnant females catch disease, about 49 percent infants are born with the disease which may be active or inactive at birth. The characteristic triad of congenital toxoplasmosis includes: convulsions, chorio-retinitis and intracranial calcification. In active stage the typical lesion is necrotic granulomatous retinochoroiditis involving the macular region. Most of the infants are born with inactive disease, characterised by bilateral healed punched out heavily pigmented chorioretinal scars in the macular area which is usually discovered when the child is brought for defective vision or squint check up.
Acquired toxoplasmosis. It is very rare (of doubtful existence). The infestation is acquired by eating the under-cooked meat of intermediate host containing cyst form of the parasite. Most of the patients are subclinical (asymptomatic); and the typical chorioretinal lesion similar to congenital toxoplasmosis is discovered by chance.