A follow-up study of Toxoplasma gondii infection in southern Brazil

The role of MHC haplotypes H2d/H2b in mouse resistance/susceptibility to cyst formation is influenced by the lineage of infective Toxoplasma gondii strain

“…The highly virulent strains were more closely related to Type I genotype (Ferreira Ade et al 2006). These findings contrast with those from North America and Europe, where most isolates associated to human infections are avirulent Type II Boothroyd 1992, Howe andSibley 1995 et , Holland 1999, Silveira et al 2001, Portela et al 2004. Although speculative, we suggest that these occurrences could be attributed in part to the dominance of Type I/III virulent strains in our territory (Glasner et al 1992, Silveira et al 2001, Portela et al 2004).…”

“…These findings contrast with those from North America and Europe, where most isolates associated to human infections are avirulent Type II Boothroyd 1992, Howe andSibley 1995 et , Holland 1999, Silveira et al 2001, Portela et al 2004. Although speculative, we suggest that these occurrences could be attributed in part to the dominance of Type I/III virulent strains in our territory (Glasner et al 1992, Silveira et al 2001, Portela et al 2004). In addition to intrinsic parasite virulence factors, susceptibility to Toxoplasma is determined by host genetic characteristics and environmental factors, such as co-infections, including HIV, that affect the immunological status of the host.…”

Immunological and Immunogenetic Parameters on the Diversity of Ocular Toxoplasmosis: Evidence to Support Morphological Criteria to Classify Retinal/Retinochoroidal Scar Lesions in Epidemiologic Surveys

“…Some of those patients had "atypical" scar lesions that evolved to "typical" toxoplasmic retinal lesions in the time frame of 7 years. The description of the hyperpigmented "atypical" lesions from patients of Erechim fulfills all but one of the criteria we have used to classify type B toxoplasmic scar lesions in Campos [13]. The difference between Silveira's description and our description is that we do not consider size to define the type of scar in any of our classification criteria.…”

“…As a consequence, identifying the actual prevalence of ocular toxoplasmosis in areas highly endemic for T. gondii in Brazil constitutes a challenge in practice and may be underestimated. In fact, the existence of retinal/retinochoroidal scars most likely healed from non-typical toxoplasmic retinal/retinochoroidal lesions have been reported in endemic areas [4,7,[9][10][11]13] as discussed later in this section.…”

“…In the context of the diversity of retinal/retinochoroidal scar lesions found in epidemiologic surveys in Brazil, another important report from the Erechim area was conducted by Silveira and associates in 1999 [13], seven years after the study conducted by Glasner and associates in 1992 [4]. A group of patients that were previously examined in 1992 presented a type of hyperpigmented scar lesion presumably caused by T. gondii infection and termed as "atypical" in comparison with those were termed as "typical" lesions.…”