Resumen

"Toxoplasma gondii is one of the most widespread obligate intracellular pathogen within the phylum Apicomplexa, affecting nearly one third of the world population (Pappas et al., 2009). This protozoan parasite can infect almost all warm-blooded animals and is the causing agent of toxoplasmosis (Boothroyd JC. & Grigg ME., 2002). Toxoplasmosis is generally clinically asymptomatic in healthy individuals but may cause severe complications in immunocompromised patients. If infection occurs during pregnancy, the parasite can cross the placental barrier and cause severe damage to the foetus (Jacobs D. et al., 1999). T. gondii has been classified into three distinct strains according to the symptoms in murine models. Type I strain causes lethal infection in all strains of mice; Type II is much less virulent while Type III strain is practically avirulent (Chunlei S. et al., 2002). There has been great interest in determining whether different strains of T. gondii are associated with different clinical outcomes of the disease or infection in specific groups of patients (Boothroyd JC. & Grigg ME., 2002; Sibley D. et al., 1995). The majority of human infections that have been studied in North America and Europe are caused by Type II strains, wich are also common in agricultural animals from these regions. Research done in Colombia has shown mainly Type I strains of T. gondii. Mice act as intermediate hosts of T. gondii and play an important role in its persistence and propagation. (Murphy RG. et al., 2008). Defining the population structure of T.gondii from new regions has important implications for transmission, immunogenicity and pathogenesis of toxoplasmosis (Sibley D. et al., 2009)..."