Authors

Discussion

Toxoplasma gondii is a common intracellular parasite that has the ability to infect any warm-blooded animal or bird, including people..  Human infection is widely distributed throughout the world with prevalence rates of between 10 – 90% reported from different countries. Infection by T. gondii is usually benign and self-limiting, but severe and possibly life threatening disease does occur in immune-compromised patients or if acquired during pregnancy.  Studies focussed on strain type relative to disease outcome in humans have  identified some strain-type specific disease associations;  the most striking of these is the association of atypical strains on severe ocular disease outcomes in South America.  In order to investigate human toxoplasmosis and strain diversity in Australia we examined clinical material from Toxoplasma infected  patients from various locations to determine both Toxoplasma prevalence and the infective strain-type. Whilst overall prevalence appears to be dropping in comparison to historical reports, our longitudinal analysis over a 40 year time span suggests a shift of age where peak prevalence plateaus from 30 -40 years olds through to those who are older than 70 years of age, indicative of a birth cohort effect.  Furthermore, examination of sera by serotyping indicates an abundance of Type II strains are infecting the human population.  Investigation by High Resolution Multi Locus Sequence Typing (MLST) PCR shows that many of these Type II infections in humans contain drifted alleles that are unique to the Australian continent.