Chagas' disease in the Brazilian Amazon: II. A serological survey

Abstract

A serological survey, involving indirect immunofluorescence testing of blood sera samples, was carried out on the residents of one in every five dwellings in the town of Barcelos (in the northern part of the State of Amazonas, on the right bank of the Rio Negro, 490 Km from Manaus by river) and on the rural populations of the villages of Piloto and Marará (also on the right bank of the Rio Negro, 30 minutes by boat from Barcelos). A total of 710 sera samples were tested, 628 from the resident population in the town of Barcelos, 35 from Piloto and 47 from Marará. The tests were carried out using human anti-gammaglobulin type IgG (Biolab) and antigen from formolized culture of T.cruzi Y strain. The sera were serially diluted from 1:40 to 1:320 in PBS 7.2. Of the 710 samples examined 89(12.5%) were positive for anti-T.cruzi antibodies: 2 of these (2.2%) at a dilution of 1:320; 12(13.4%) at 1:160; 38 (42.6%) at 1:80; and the remainder at 1:40, giving a median serological dilution of 1:80. The following questions are discussed: the high serological prevalence for Chagas'infection found in our survey; the possibility of serological cross-reactions; the need for confirmatory tests for the positives reactions; and the strong correlation between our results and preliminary epidemiological data (such as the level of human contact with wild triatominae, know locally as "Piacava's lice". We draw attention to the isolation by xenodiagnosis of one strain of T.cruzi from a patient with positive serology for Chagas' infection.

Chagas disease: What is known and what should be improved: a systemic review

“…Over the last 20 years (1991-2011), we have developed seroepidemiological surveys and clinical, radiological and electrocardiographic studies among populations that were seropositive for Chagas infection, in the middle and upper regions of the Negro River, in the State of Amazonas [72][73][74][76][77][78] . Several typical and fatal chronic cases of Chagas disease were described 94,95 , involving more than 7,000 screening serological reactions and more than 300 confirmatory serological reactions.…”

Morphobiological aspects of Rhodnius brethesi Matta, 1919 (Hemiptera:Reduviidae) from the Upper and Middle Negro River, Amazon region of Brazil: I - scanning electron microscopy

“…Key words: Rhodnius brethesi -external morphology -taxonomy -scanning electron microscopy -Amazon region -Brazil Over recent years, attention has been drawn to Chagas disease infection in the Amazon region of Brazil because of increased numbers of reports of acute cases and the presence of individuals who are serologically positive for this infection (Coura et al 1995, 2002a, Fraiha Neto et al 1995, Valente et al 1999, Dias et al 2002. So far, it is unclear whether these growing numbers of human cases are due to increased transmission or whether they are the result from an active search for positive cases.…”

“…The buccula and the stridulatory sulcus presented notable differences in specimens of different genera and also of different species. These data make it possible to suggest that the details presented in these structures can be included as diagnostic characteristics to be used in new dichotomous keys, thereby contributing towards studies of taxonomy and systematics and furnishing backing for comparative analysis of specimens collected from different localities.Key words: Rhodnius brethesi -external morphology -taxonomy -scanning electron microscopy -Amazon region -Brazil Over recent years, attention has been drawn to Chagas disease infection in the Amazon region of Brazil because of increased numbers of reports of acute cases and the presence of individuals who are serologically positive for this infection (Coura et al 1995, 2002a, Fraiha Neto et al 1995, Valente et al 1999, Dias et al 2002. So far, it is unclear whether these growing numbers of human cases are due to increased transmission or whether they are the result from an active search for positive cases.…”

“…Initial investigations by Coura et al (1994Coura et al ( , 1995 indicated that the presence of human infection in areas of the Negro River were associated with extractive activities relating to the collection of fiber from the native palm tree Leopoldinia piassaba Wallace, 1853 transmission cycle was pinpointed as the contact between the fiber gatherer and the species of triatomines present in the extraction areas (Coura et al 2002a). The data obtained though that investigation showed that two vector species were present in the extraction areas: Rhodnius brethesi Matta, 1919, andPanstrongylus geniculatus (Latreille, 1811).…”

Avaliação em laboratório da atividade de voo de Rhodnius brethesi Matta, 1919, potencial vetor silvestre do Trypanosoma cruzi na Amazônia Brasileira. (Hemiptera:Reduviidae:Triatominae)

“…Transmission of Trypanosoma cruzi to families working on the extraction of piassaba fibers has been recorded in the Municipality of Barcelos, north of the Negro 5,6,7,8 River, in the natural ecotope of R. brethesi .Infection of humans, reservoirs and vectors with T. cruzi and autochthonous cases of Chagas disease have been reported in most countries in the Amazon Basin. Interest in Chagas disease has increased over the past two decades in this area.…”