Toxoplasmosis, which is caused by Toxoplasma gondii, an obligate intracellular protozoan, is worldwide, albeit a rare infection. The definitive host in its life cycle is the cat (or pig or sheep) and the human is an intermediate host. However, clinical toxoplasmosis is very uncommon. Infection in humans usually occurs through eating foodstuffs contaminated by infected cat faeces. Its main clinical importance is an opportunistic infection. The five major clinical forms of toxoplasmosis are: 6
1. asymptomatic lymphadenopathy (the commonest)
2. lymphadenopathy with a febrile illness, similar to EB mononucleosis
3. acute primary infection: a febrile illness similar to acute leukaemia or EB mononucleosis; a rash, myocarditis, pneumonitis, chorioretinitis and hepatosplenomegaly can occur
5. congenital toxoplasmosis: this is a rare problem but if it occurs it typically causes CNS involvement and has a poor prognosis
In the immunocompromised, clinical forms 3 and 4 are typical features with meningoencephalitis being a serious development.
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