Epidemiologia molecular de isolados de toxoplasma Gondii na região metropolitana de Goiânia, Goiás, Brasil
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2018-01-12
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Universidade Federal de Goiás
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The protozoan Toxoplasma gondii is the etiological agent of toxoplasmosis and its definitive hosts are domestic cats (Felis catus) and other wild felids. Within the cities, stray cats are responsible for the dissemination of the parasite in the environment as they release oocysts which are the infective forms for humans and other animals. Backyard chickens (Gallus gallus) are in constant contact with the environment and feed directly from the soil. Therefore they are important indicators of environmental conditions. The knowledge regarding prevalence, biological and genetic characteristics of T. gondii are of utmost importance for the comprehension of the complex host-parasite relationship. Thus the aim of this study was to evaluate the concordance of laboratory techniques used to detect the parasite; to determine the prevalence, biology and molecular epidemiology of T. gondii isolated from stray cats and backyard chickens from the metropolitan region of Goiania, in order to better comprehend the infection. This is the first performed study to determine the genetic and biologic characterization of T. gondii in the state of Goias. This study used 24 stray cats captured by the Center for the Zoonosis Control in Goiania and 50 backyard chickens from the Metropolitan Region of Goiania, Goias. The serologic triage was performed by IHA and showed positivity of 87.4% (21/24) cats and 96% (48/50) backyard chickens for T. gondii. The bioassay was performed using the brain and hearts of the cats and chickens obtained after euthanasia of the animals. After the peptic digestion the homogenate tissues was intraperitoneally inoculated in groups of three Swiss mice each which were daily observed in order to detect signs of acute toxoplasmosis. The asymptomatic mice were euthanized after 60 days followed by serologic analysis through indirect immunofluorescence. Fragments of brain from these animals were observed under optic microscopy in order to visualize tissue cysts. Part of the homogenate was submitted to DNA extraction and polymerase chain reaction (PCR) in which 75% (18/24) cats and 64% (32/50) backyard chickens were positive. The correlation between IHA and PCR from both animals was considered weak. It was not possible to obtain isolate strains from cats. From the chickens it was possible to obtain 15 isolates strains from which 8 presented tachyzoites (acute toxoplasmosis) and 7 presented brain tissues (chronic toxoplasmosis). After the DNA extraction from the isolates the RFLP-PCR was performed using the following primers SAG1, 5’-3’ SAG2, altSAG, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, Apico and CS3. It was possible to define the genotype from 9 isolates. According to ToxoDB seven isolates corresponded to genotype #65 and two isolates have not been described previously. The genetic analysis showed high diversity and variability. The virulence essays showed that the mortality rate in mice in seven isolates that presented tachyzoites, from the same genotype, detected high virulence in 4 isolates and intermediary virulence in 3. The morphometry analysis of the tachyzoites of these isolates showed statistical difference in at least one of the analyzed variables such as length or nuclei-apical complex distance. These phenotypic differences in isolates from the same genotype show the need to the continuity of the genetic characterization of the parasite using other primers which could be related to the isolated phenotype. The study demonstrated the importance of knowledge about the molecular epidemiology of T. gondii in the metropolitan region of Goiânia, which presents high rates of seroprevalence in hosts.
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REZENDE, H. H. A. Epidemiologia molecular de isolados de toxoplasma Gondii na região metropolitana de Goiânia, Goiás, Brasil. 2018. 150 f. Tese (Doutorado em Medicina Tropical e Saúde Publica) - Universidade Federal de Goiás, Goiânia, 2018.