Abstract
BackgroundIn the Brazilian Amazon, clinical and epidemiological frameworks of Chagas disease are very dissimilar in relation to the endemic classical areas of transmission, possibly due to genetic and biological characteristics of the circulating Trypanosoma cruzi stocks. Twenty six T. cruzi stocks from Western Amazon Region attributed to the TcI and TcIV DTUs were comparatively studied in Swiss mice to test the hypothesis that T. cruzi clonal structure has a major impact on its biological and medical properties.Methodology/Principal FindingsSeventeen parameters were assayed in mice infected with 14 T. cruzi strains belonging to DTU TcI and 11 strains typed as TcIV. In comparison with TcI, TcIV stocks promoted a significantly shorter pre-patent period (p<0.001), a longer patent period (p<0.001), higher values of mean daily parasitemia (p = 0.009) and maximum of parasitemia (p = 0.015), earlier days of maximum parasitemia (p<0.001) and mortality (p = 0.018), higher mortality rates in the acute phase (p = 0.047), higher infectivity rates (p = 0.002), higher positivity in the fresh blood examination (p<0.001), higher positivity in the ELISA at the early chronic phase (p = 0.022), and a higher positivity in the ELISA at the late chronic phase (p = 0.003). On the other hand TcI showed higher values of mortality rates in the early chronic phase (p = 0.014), higher frequency of mice with inflammatory process in any organ (p = 0.005), higher frequency of mice with tissue parasitism in any organ (p = 0.027) and a higher susceptibility to benznidazole (p = 0.002) than TcIV. Survival analysis showing the time elapsed from the day of inoculation to the beginning of the patent period was significantly shorter for TcIV strains and the death episodes triggered following the infection with TcI occurred significantly later in relation to TcIV. The notable exceptions come from positivity in the hemocultures and PCR, for which the results were similar.Conclusion/Significance T. cruzi stocks belonging to TcI and TcIV DTUs from Brazilian Amazon are divergent in terms of biological and medical properties in mice.
Highlights
Chagas disease is an important health problem, affecting 8–9 million individuals, with approximately 50,000 new cases annually, in Central and Latin America [1]
Conclusion/Significance: T. cruzi stocks belonging to TcI and TcIV Discrete typing unit (DTU) from Brazilian Amazon are divergent in terms of biological and medical properties in mice
We carried out the biological characterization in mice of T. cruzi isolates belonging to TcI and TcIV DTUs from the State of Amazonas, Western Brazilian Amazon
Summary
Chagas disease is an important health problem, affecting 8–9 million individuals, with approximately 50,000 new cases annually, in Central and Latin America [1]. The illness is caused by Trypanosoma cruzi and has a variable clinical course that may include symptomless infection, overwhelming acute disease or a severe chronic condition. The latter may be hallmarked by cardiovascular and/or gastrointestinal involvement. Poverty, poor housing and sub-standard living conditions and deforestation promote an incipient adaptation of triatomine vectors to both humans and domestic animals, with increased efficiencies of the wild, domestic, and peridomestic cycles of T. cruzi transmission in the areas where Chagas disease emerges [2,3]. In the Brazilian Amazon, clinical and epidemiological frameworks of Chagas disease are very dissimilar in relation to the endemic classical areas of transmission, possibly due to genetic and biological characteristics of the circulating Trypanosoma cruzi stocks. Twenty six T. cruzi stocks from Western Amazon Region attributed to the TcI and TcIV DTUs were comparatively studied in Swiss mice to test the hypothesis that T. cruzi clonal structure has a major impact on its biological and medical properties
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