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Trypanosoma cruzi is the most important parasitic infection in Latin America and is also genetically highly diverse, with at least six discrete typing units (DTUs) reported: Tc I, IIa, IIb, IIc, IId, and IIe. However, the current six-genotype classification is likely to be a poor reflection of the total genetic diversity present in this undeniably ancient parasite. To determine whether epidemiologically important information is “hidden” at the sub-DTU level, we developed a 48-marker panel of polymorphic microsatellite loci to investigate population structure among 135 samples from across the geographic distribution of TcI. This DTU is the major cause of resurgent human disease in northern South America but also occurs in silvatic triatomine vectors and mammalian reservoir hosts throughout the continent. Based on a total dataset of 12,329 alleles, we demonstrate that silvatic TcI populations are extraordinarily genetically diverse, show spatial structuring on a continental scale, and have undergone recent biogeographic expansion into the southern United States of America. Conversely, the majority of human strains sampled are restricted to two distinct groups characterised by a considerable reduction in genetic diversity with respect to isolates from silvatic sources. In Venezuela, most human isolates showed little identity with known local silvatic strains, despite frequent invasion of the domestic setting by infected adult vectors. Multilocus linkage indices indicate predominantly clonal parasite propagation among all populations. However, excess homozygosity among silvatic strains and raised heterozygosity among domestic populations suggest that some level of genetic recombination cannot be ruled out. The epidemiological significance of these findings is discussed.

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Foram estudados 233 casos de fase aguda da doença de Chagas, oriundos do Pará, Amapá e Maranhão, observados no período de 1988 a 2005, cento e sessenta deles retrospectivamente de 1988 a 2002 e setenta e três prospectivamente de 2003 a 2005. Entre os casos estudados 78,5% (183/233) faziam parte de surtos provavelmente por transmissão oral, acometendo em média 4 pessoas e 21,5% (50/233) eram casos isolados. Foram considerados casos agudos aqueles que apresentaram exames parasitológicos diretos (a fresco, gota espessa ou Quantitative Buffy Coat - QBC) e/ou IgM anti-Trypanosoma cruzi positivos. Foram feitos ainda xenodiagnósticos em 224 pacientes e hemoculturas em 213. Todos foram avaliados clinica e epidemiologicamente. As manifestações clínicas mais freqüentes foram febre (100%), cefaléia (92,3%), mialgia (84,1%), palidez (67%), dispnéia (58,4%), edema de membros inferiores (57,9%), edema de face (57,5%) dor abdominal (44,2%), miocardite (39,9%) e exantema (27%). O eletrocardiograma mostrou alterações de repolarização ventricular em 38,5% dos casos, baixa voltagem de QRS em 15,4% e desvio de SAQRS em 11,5%, extra-sístoles ventriculares em 5,8%, bradicardia em 5,8% e taquicardia em 5,8%, bloqueio de ramo direito em 4,8% e fibrilação atrial em 4,8%. A alteração mais freqüente vista no ecocardiograma foi o derrame pericárdico em 46,2% dos casos. Treze (5,6%) pacientes evoluíram para o óbito, 10 (76,9%) dos quais por comprometimento cardiovascular, dois por complicações de origem digestiva e um de causa mal definida.

An outbreak of Chagas disease occurred in Mazagão, Amapá, Brazilian Amazon in 1996. Seventeen of 26 inhabitants presented symptoms compatible with acute Chagas disease and were submitted to parasitological and serological tests. All 17 were positive in at least one parasitological test and 11 were also IgM or IgG anti-Trypanosoma cruzi positive. The nine asymptomatic patients were negative for parasites and one was positive for IgG anti-T. cruzi. Sixty-eight triatomines were captured (66 Rhodnius pictipes; two Panstrongylus geniculatus); 45 were infected with T. cruzi (43 R. pictipes; two P. geniculatus). Thirteen trypanosomatid strains were isolated: eight from humans and five from R. pictipes. Four were genotyped as T. cruzi I (two from humans; two from R. pictipes), seven as T. cruzi Z3 (six from humans; one from R. pictipes) and two as T. cruzi Z3 and T. rangeli (from R. pictipes). Treatment started for all patients leading to a decrease in parasitaemia in 16 during the follow-up period (6 months, 1, 5 and 7 years). All were serologically negative 7 years post-treatment. There was an overlap of genotypes in the same ecotope, raising the possibility of transmission through the oral route and the need for early therapeutic intervention for better patient management in the Brazilian Amazon.