The acute Chagas disease (ACD) is endemic in the Brazilian Amazon, and its main
transmission route is oral, throughout family and multi-family outbreaks. This route is independent from
the colonization of triatomine bugs in dwellings and its occurrence is regular, with mean rates of 100 cases per year and a lethality rate of 5%. The disease has a well-defined spatio-temporal distribution, which makes it a relevant public health concern in the states of Pará, Amapá and Amazonas. The existence of wild mammals and triatomine bugs naturally infected with Trypanosoma cruzi inhabiting different terrestrial and arboreal ecotopes maintains an intense enzootic cycle all over the Amazon region. Molecular profiles of T. Cruzi lineages in the region are associated with mammal reservoirs (including humans), triatomine bugs, ecotopes and clinical manifestations. We analyzed four ACD outbreaks in the municipalities of Barcarena, Belém and Cachoeira do Arari on Pará State, and Santana on Amapá State, based on epidemiologic features (laboratory, parasitological and serological diagnoses, clinical manifestations and the reservoirs and wild triatomines related to the outbreaks). We also investigated the domestic and wild transmission cycles of T. cruzi in São Luis on Maranhão State, without the occurrence of ACD cases. This study comprised molecular genotyping of T. cruzi on the mini-exon gene of the isolates associated with both transmission cycles (humans, mammals and wild
triatomine vectors). Parasitological diagnosis was confirmed in 63 patients with the following sensitivity
rates: 41.3% (26/63) for the thick blood film method; 58.7% (37/63) for QBC; 79.4% (50/63) for
xenodiagnosis; and 61.9% (39/63) for blood culture. The serological diagnosis of 2648 individuals by
indirect hemagglutination assay (IHA) was of 3.05% (81/2648), whereas the results of the indirect
immunofluorescence test (IIF) were 2.49% (66/2648) for IgG and 2.37% (63/2648) for IgM. All tests
carried out in São Luís were negative. A total of 24 mammals, 13 Didelphis marsupialis, 1 Marmosa
cinerea, 5 Philander opossum, 3 Metachirus nudicaudatus, 1 Oryzomys macconnelli, 1 Oecomys bicolor and 433 R. rattus were captured. The infection rate for T. cruzi was of 7.14% (29/404). A total of 3279
triatomine bugs were captured: T. rubrofasciata (n=3008) and infection rate (IR) of 30.46%, (39/128)
and R. robustus (n=137) IR of 76% (79/104), R. pictipes (n=94), IR of 56.9% (49/86%) E. mucronatus
(n=6) and P. geniculatus (n=12) IR of 50% and the other non-infected species R. neglectus (n=5) and P.
lignarius (n=6). Palm trees were the main ecotopes for the wild triatomine bugs. S. martiana was infested with 47.41% (101/213) of the triatomines; Maximiliana regia, 35,21% (75/213); Orbgnya speciosa, 5.16% (11/213); Eleas melanoccoca), 1.87% (4/213); and Oenocarpus bacaba, 10.32% (22/213). Genotyping was carried out using 46 isolates of trypanosomes obtained from humans, 31 from wild mammals and 74 from samples of triatomine bugs. All isolates were characterized as belonging to the Tcl lineage. All human cases in Pará were characterized as positive by parasitological testing. Not all the cases in Santana were tested positive because of the delay on diagnosis, but they were defined as positive. Xenodiagnosis, blood culture and QBC® were more sensitive than the thick blood film. Serological examinations by IHA and IIF (IgG and IgM) presented an optimal sensitivity to detect acute
cases in different moments of infection. Mammals (D. marsupialis) and wild triatomine bugs (R. pictipes
and P. geniculatus) infected with high infection rates of T. cruzi in the patients’ peridomicile area account for the importance of these reservoirs in the transmission cycle of the ACD, and are associated with its transmission. Even though several genotypes of T. cruzi circulate in the Amazon Region, only the Tcl lineage was identified in the patients, mammals and triatomines investigated in this study. In São Luís, in spite of these having no record of human cases of ACD, it has a domestic cycle associated with the black rat and the triatomine bugs of the species T. rubrofasciata, as well as a sylvatic cycle associated with didelphids. The Tcl cycles circulate in both cycles. Studies with isolates of local T. cruzi using markers with a higher definition might help clarify the transmission cycles, transmission routes and the reservoirs involved in cases of ACD in the Amazon Region.
|
