Toxoplasma gondii infects over a third of the world's humanity and toxoplasmosis constitutes a life-long threat since humans remain infected throughout life. This PhD dissertation aimed to enrich the knowledge on toxoplasmosis in Portugal and to implement updated approaches regarding T. gondii propagation in the reference laboratory.
We started by evaluating the seroprevalence in Portugal by comparing three cross-sectional studies spanning three decades (1979/80, 2001-2002, 2013), with focus on childbearing women. Seroprevalence showed a decreasing trend over time (from 47 % in 1979/80 to 22 % in 2013) and increased with age. The scenario observed for childbearing women indicates that more than 80 % of these are susceptible to primary infection and thus to congenital toxoplasmosis.
We also focused on the parasite and genetically characterized 48 strains isolated from biological samples from patients attending to the NIH, for which a retrospective evaluation estimated 1.6 % of new cases of congenital toxoplasmosis in the last 10 years. This study revealed genetic variations in T. gondii and more specifically the existence of a considerable proportion (21 %) of recombinant strains, which are believed to be associated with specific phenotypes.
Finally, we evaluated laboratory approaches towards the reduction of sacrificed mice in toxoplasmosis reference laboratories. We observed that the alternate passaging of the parasite in a cell line and in mice constitutes a promising laboratory procedure as, besides the reduction of sacrificed mice in more than 80 %, it enabled T. gondii to retain the virulence potential while keeping a putative stable genome.
Globally, this PhD dissertation not only increased the knowledge on toxoplasmosis in Portugal by elucidating the chronological trend of the immune status of the population and the general genetic profile of the T. gondii strains causing human infection, but it also modified the modus operandi of the reference laboratory towards the significant reduction of scarified mice
