Twenty-eight Chagas disease patients (CD), 22 with the indeterminate clinical form (IND) and six with the cardiac or digestive form (CARD/DIG), were treated with benznidazole and underwent clinical and laboratorial analysis before (IND and CARD/DIG) and nine years after [patients after treatment (CDt), patients with the indeterminate clinical form at treatment onset (INDt) and with the cardiac or digestive form at treatment onset (CARD/DIGt)] treatment. The data demonstrate that 82.1% of CDt patients (23/28) remained clinically stable and 95.4% of the INDt (21/22) and 33.3% of the CARD/DIGt (2/6) patients showed unaltered physical and laboratorial examinations. The clinical evolution rate was 2%/year and was especially low in INDt patients (0.5%/year) relative to CARD/DIGt patients (7.4%/year). Positive haemoculture in treated patients was observed in 7.1% of the cases. None of the INDt (0/21) and 33.3% of the CARD/DIGt (2/6) patients displayed positive cultures. The PCR presented a positive rate significantly higher (85.2%, 23/27) than haemoculture and two samples from the same patient revealed the same result 57.7% of the patients. Conventional serology-ELISA on 16 paired samples remained positive in all individuals. Semi-quantitative ELISA highlighted significant decreases in reactivity, particularly in INDt relative to IND. Non-conventional serology-FC-ALTA-IgG, after treatment, showed positive results in all sera and 22 paired samples examined at seven and nine years after treatment, demonstrated significantly lower reactivity, particularly in INDt patients. This study was retrospective in nature, had a low number of samples and lacked an intrinsic control group, but the data corroborate other results found in the literature. The data also demonstrate that, even though a cure has not been detected in the none-treated patients, the benefits for clinical evolution were selectively observed in the group of INDt patients and did not occur for CARD/DIGt patients.

The goals of the present study were to evaluate the kinetics of blood parasitism by examination of fresh blood, blood culture (BC) and PCR assays and their correlation with heart parasitism during two years of infection in Beagle dogs inoculated with the Be-78, Y and ABC Trypanosoma cruzi strains. Our results showed that the parasite or its kDNA is easily detected during the acute phase in all infected animals. On the other hand, a reduced number of positive tests were verified during the chronic phase of the infection. The frequency of positive tests was correlated with T. cruzi strain. The percentage of positive BC and blood PCR performed in samples from animals inoculated with Be-78 and ABC strains were similar and significantly larger in relation to animals infected with the Y strain.Comparison of the positivity of PCR tests performed using blood and heart tissue samples obtained two years after infection showed two different patterns associated with the inoculated T. cruzi strain: (1) high PCR positivity for both blood and tissue was observed in animals infected with Be-78 or ABC strains; (2) lower and higher PCR positivity for the blood and tissue, respectively, was detected in animals infected with Y strains. These data suggest that the sensitivity of BC and blood PCR was T. cruzi strain dependent and, in contrast, the heart tissue PCR revealed higher sensitivity regardless of the parasite stock.

Trypanosoma cruzi is a hemoflagelate parasite associated with heart dysfunctions causing serious problems in Central and South America. Beagle dogs develop the symptoms of Chagas disease in humans, and could be an important experimental model for better understanding the immunopathogenic mechanisms involved in the chagasic infection. In the present study we investigated the relation among biological factors inherent to the parasite (trypomastigote polymorphism and in vitro infectivity) and immunoglobulin production, inflammation, and fibrosis in the heart of Beagle dogs infected with either T. cruzi Y or Berenice-78 strains. In vitro infectivity of Vero cells as well as the extension of cardiac lesions in infected Beagle was higher for Y strain when compared to Berenice-78 strain. These data suggested that in vitro infectivity assays may correlate with pathogenicity in vivo. In fact, animals infected with Y strain, which shows prevalence of slender forms and high infectivity in vitro, presented cardiomegaly, inflammation, and fibrosis in heart area. Concerning the immunoglobulin production, no statistically significant difference was observed for IgA, IgM or IgG levels among T. cruzi infected animals. However, IgA together IgM levels have shown to be a good marker for the acute phase of Chagas disease.