Produção Nacional
Revisado por pares
Genetic Divergence of Toxoplasma gondii Strains Associated with Ocular Toxoplasmosis, Brazil
2006; Centers for Disease Control and Prevention; Volume: 12; Issue: 6 Linguagem: Inglês
10.3201/eid1206.060025
ISSN1080-6059
AutoresAsis Khan, Catherine Jordan, Cristina Muccioli, Adriana Lima Vallochi, Luiz Vicente Rizzo, Rubens Belfort, Ricardo Wagner Almeida Vítor, Cláudio Silveira, L.David Sibley,
Tópico(s)Rabies epidemiology and control
ResumoPrevious studies have shown a high prevalence of toxoplasmosis and the frequent occurrence of ocular disease in Brazil.To identify the genotypes of parasite strains associated with ocular disease, we compared 25 clinical and animal isolates of Toxoplasma gondii from Brazil to previously characterized clonal lineages from North America and Europe.Multilocus nested polymerase chain reaction analysis was combined with direct sequencing of a polymorphic intron to classify strains by phylogenetic methods.The genotypes of T. gondii strains isolated from Brazil were highly divergent when compared to the previously described clonal lineages.Several new predominant genotypes were identified from different regions of Brazil, including 2 small outbreaks attributable to foodborne or waterborne infection.These findings show that the genetic makeup of T. gondii is more complex than previously recognized and suggest that unique or divergent genotypes may contribute to different clinical outcomes of toxoplasmosis in different localities.T oxoplasma gondii is an obligate intracellular parasite that infects a wide range of warm-blooded vertebrates and causes disease in agricultural animals and humans (1).T. gondii has a complex life cycle that includes an asexual cycle and sexual cycle; the asexual cycle occurs in a wide range of intermediate hosts, and the sexual cycle occurs exclusively in feline hosts, which shed infectious oocysts in their feces (1).T. gondii is mainly transmitted by ingesting cysts contained within tissues of a chronically infected host or by ingesting sporulated oocysts from fecally contaminated food or water (2).T. gondii is an influential foodborne pathogen in the United States (3) and a frequent cause of waterborne infection in parts of Brazil (4,5).Despite having a sexual phase in its life cycle, the population structure of T. gondii is markedly clonal (6).Most strains analyzed from North America and Europe belong to 1 of 3 clonal lineages known as types I, II, and III (7-9).A small number (<5%) of isolates contain different combinations of the same alleles seen in the clonal types, which indicates that recombination occurs infrequently in the wild (7).Additionally, strains with more divergent genotypes have been isolated from locations such as French Guiana (10).The serologic prevalence of T. gondii infection in Brazil includes 50%-80% of the adult population, with the highest values found in northern and southern states (5).Waterborne transmission has been implicated in high rates of T. gondii seropositivity in northern Rio de Janeiro State (5) and in a toxoplasmosis outbreak in Santa Isabel do Ivai in southern Paraná (4).High levels of ocular disease are associated with toxoplasmosis in Brazil (11).In the southern city of Erechim, Brazil, 184 (17.7%) of 1,042 adults were found to have retinal scars, thought to be caused by toxoplasmosis (12).Epidemiologic data indicate that many cases of ocular disease are acquired after birth rather than congenitally (13-15).Whether the increased prevalence and severity of ocular toxoplasmosis in Brazil are attributable to host or parasite genetic factors or differences in exposure rate is uncertain.Polymerase chain reaction (PCR)-based typing at the SAG2 locus has been used previously to suggest that type I strains predominate in Brazilian patients with ocular toxoplasmosis (16).While the SAG2 marker provides accurate genotyping for most strains within the clonal lineages, Genetic Divergence of Toxoplasma gondii Strains Associated with Ocular Toxoplasmosis, Brazil
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