Differential parasitological, molecular, and serological detection of Trypanosoma cruzi I, II, and IV in blood of experimentally infected mice.

Trypanosoma cruzi is the etiological agent of American trypanosomiasis (Chagas' disease), which affects 6-7 million people worldwide, mainly in Latin America. It presents great genetic and biological variability that plays an important role in the clinical and epidemiological features of the disease. Our working hypothesis is that the genetic diversity of T. cruzi has an important impact on detection of the parasite using diagnostic techniques. The present study evaluated the diagnostic performance of parasitological, molecular, and serological techniques for detecting 27 strains of T. cruzi that belonged to discrete typing units (DTUs) TcI (11 strains), TcII (four strains), and TcIV (12 strains) that were obtained from different hosts in the states of Amazonas and Paraná, Brazil. Blood samples were taken from experimentally infected mice and analyzed by fresh blood examination, hemoculture in Liver Infusion Tryptose (LIT) medium, polymerase chain reaction (PCR), and enzyme-linked immunosorbent assay (ELISA). Polymerase chain reaction presented the best detection of TcI, with 80.4% positivity. For all of the detection methods, the animals that were inoculated with TcII presented the highest positivity rates (94.1-100%). ELISA that was performed 7 months after inoculation presented a higher detection ability (95.4%) for TcIV. Intra-DTU comparisons showed that the reproducibility of the majority of the results that were obtained with the different methods was weak for TcI and good for TcII and TcIV. Our data indicate that the detection capability of different techniques varies with the DTUs of the parasites in mammalian blood. The implications of these findings with regard to the diagnosis of human T. cruzi infection are discussed.

Weak relation between genetic and biological diversity of natural populations of Trypanosoma cruzi - DOI: 10.4025/actascibiolsci.v28i2.1044 / Fraca relação entre diversidade genética e biológica de populações naturais de Trypanosoma cruzi - DOI: 10.4025/actascibiolsci.v28i2.1044

This paper studies the relation between genetic and biological diversity of natural populations of Trypanosoma cruzi (in Parana State, Brazil) isolated from humans (H), classified as T. cruzi II, and from sylvatic reservoirs (G) and triatomines (T), classified as T. cruzi I. Twenty-five biological parameters were evaluated concerning the kinetic of growth and of metacyclogenesis in mediums LIT and M16, to the infectivity to BALB/c mice, and to the susceptibility to benznidazole. The data support the conclusion of a weak relation between genetic distance and biological diversity using strains. The statistical comparison of the means of each parameter, with regard to the different hosts, showed that group T. cruzi II (H) was significantly different from group T. cruzi I (G and/or T) in 13 of the 25 parameters studied: group H differed from G and T in three parameters, and from G or T in 10 parameters. The major differences found in those parameters were related to the kinetic of growth and of metacyclogenesis. One biological implication from these differences is that the lowest growth of parasite observed in group T. cruzi II (H) makes parasitological diagnoses more difficult and provides lower pathogenicity for mice.

Este trabalho estudou a relação entre diversidade genética e biológica de populações naturais de Trypanosoma cruzi do Estado do Parana, isoladas de humanos (H), classificadas como T. cruzi II, e de reservatórios silvestres (G), e triatomíneos (T) classificadas como T. cruzi I. Foram avaliados 25 parâmetros biológicos relacionados à cinética de crescimento e de metaciclogênese em meios LIT e M16, à infectividade em camundongos BALB/c e à suscetibilidade ao benznidazol. Os achados falam a favor de uma fraca relação entre distância genética e diferenças biológicas utilizando cepas. A comparação estatística entre as médias de cada parâmetro, considerando os diferentes hospedeiros, mostrou que o grupo T. cruzi II (H) foi significativamente diferente do grupo T. cruzi I (G e/ou T) em 13 dos 25 parâmetros estudados, onde o grupo H diferiu de G e T em 3 parâmetros e de G ou T em 10 parâmetros. As maiores diferenças ocorreram nos parâmetros relacionados à cinética de metaciclogênese e de crescimento. Entre as implicações biológicas destas diferenças, o crescimento mais lento de parasitas do grupo T. cruzi II (H) prejudica o diagnóstico parasitológico e proporciona menor patogenicidade para camundongos.