Estudo comparado do ciclo evolutivo de triatomíneos a duas temperaturas

We studied the life cicle of several triatominae species: Dipetalogaster maximus (Uhler, 1894); Panstrongylus herreri Wygodzinsky, 1948; Panstrongylus megistus (Burmeister, 1835); Rhodnius ecuadoriensis Lent & Leon, 1958; Rhodnius nasutus Stal, 1859; Rhodnius neglectus Lent, 1954; Rhodnius pictipes Stal, 1872; Rhodnius prolixus Stal, 1859; Rhodnius robustus Larrousse, 1927; Triatoma brasiliensis Neiva, 1911; Triatoma infestans (Klug, 1834); Triatoma maculata (Erichson, 1848); Triatoma matogrossensis Leite & Barbosa, 1953; Triatoma platensis Neiva, 1913; Triatoma protracta (Uhler, 1894); Triatoma sordida (Stal, 1859); Triatoma tibiamaculata (Pinto, 1926) e Triatoma vitticeps (Stal, 1859) (Hemiptera, Reduviidae). The main purpose of the study was to obtain information to improve control measures specially in those peridomiciliar species. The experiments were performed in two climatized chambers, both with an humidity of 70 ± 5% and photoperiod of 12 hours. One was maintained at 25 ± 0,5ºC and the other at 30 ± 1ºC.

Aspects of classification of Hemiptera hemocytes from six triatomine species

The objective of this work was to characterize, and compare different morphological types of hemocytes of Rhodnius prolixus, Rhodnius, Rhodnius neglectus, Triatoma infestans, Panstrongylus megistus, and Dipetalogaster maximus. This information provides the basis for studying the cellular immune systems of these insects. Seven morphological hemocyte types wereidentified by phase-contrast microscopy: prohemocytes, plasmatocytes, granular cells, cytocytes, oenocytoids, adipohemocytes and giant cells. All seven types of hemocytes are not present in every species. For example, adipohemocytes and oenocytoids were not observed in P. megistus and P. infestans, and giant cells were rarely found in any of the species studied. The hemocytes of rhodnius and Dipetalogaster are more similar to each other than those from Triatoma and Panstrongylus which in turn closely resemble each other. Emphasis is placed on methodological problems arising in this work wicah are discussed in detail.

The importance of the opossum (Didelphis albiventris) as a reservoir for Trypanosoma cruzi in Bambuí, Minas Gerais state

In a survey realized on the sylvatic and peridomestic environment at Bambuí county, Minas Gerais State, 44 (37.9%) out of 116 opossums (Didelphis albiventris) captured were found to be naturally infected with Trypanosoma cruzi. One handred and forty three parasite samples were obtanied from 43 infected opossums using simultaneously hemoculture, xenodiagnosis (Triatoma infestans, Panstrongylus megistus and Rhodnius neglectus) and examination of anal glands contents. The parasite samples were characterized according to six isoenzyme patterns. All samples, independently of the method of isolation, presented an isoenzyme pattern similar to the standard T. cruzi Z1, showing that either xenodiagnosis or hemoculture can used without selecting parasite subpopulation from naturally infected opossums. Preveous isoenzyme patterns reported for human T.cruzi isolates from same region were completely different. This isoenzyme dissimilarity between sylvatic and domiciliar environments suggests the existence of two independent T. cruzi transmission cycles in Bambuí. The epidemiological implicatinos of these results are discussed.

A cost-benefit analisys of chagas disease control

Chagas disease transmission can be effetively interrupted by insecticidal control of its triatomine bug vectors. We present here a simple model comparing the costs and benefits of such a programme, designed to eliminate domestic populations of Triatoma infestans throughout its known area of distribution over the seven southernmost countries of Latin America. The model has been simplified to require only four financial estimates relating to the unit cost of housing spraying and benefits due to avoidance of premature death in the acute phase of the disease, avoidance of supportive treatment and care in the chronic phase of the disease, and avoidance of corrective digestive and cardiac surgery. Exceptfor these direct medical costs, al other potential benefits have been ignored. Nevertheless, the model shows that the direct financial benefits of such a programme would far outweigh the costs, and the project would support a remarkably high internal rate of return under the least optimistic estimates.

Evaluation of the xenodiagnosis of chronic Chagas patients infected ten years or over in an area where transmission has been interrupted - Iguatama and Pains, west Minas Gerais State, Brazil

To evaluate the results of xenodiagnosis in chronic Chagas patients infected for ten years or over in an area where transmission has been stemmed as well as the performance of these tests applied one or more times to determine the presence of the paraiste in serum-positive patients for Trypanosoma cruzi infection, 570 xenodiagnosis were performed in 246 patients by exoposing each pacient to 40 Triatoma infestans nymphs of 3 rd/4th stage once, twice or three times, at 30 days intervals. The 570 xenodiagnosis showed overall positive results in 50.7% with a peak 78% in patients under 20 years of age, and 60.5% in those over 60. Of the l58 patients who underwent three xenodiagnosis, 51 (32.3%) had three positive tests, 48 (30.3%) had all negative results, and the remainder had alternating positve and negative findings. There was no difference in number of positive results between the 1st, 2nd and 2rd tests; however, the 1st and 2nd trials added up to 53.2% and the sum total of all three trials was 57.7%.

Sexual distinction between 5th instar nymphs of six species of Triatominae (Hemiptera, Reduviidae)

The aim of this paper is to present the analysis of sexual morphological differences observed in 5th instar nymphs of the following species: Panstrongylus megistus; Rhodnius neglectus; Triatoma brasiliensis; T. infestans; T. matogrosensis and T. tibiamaculata. Male and female nymphs were examined and photographed with a Scanning Electron Microscope. The 9th segment dimensions of dorsal and ventral faces were determined through a Profile Projector. Results and statistical analysis showed significant differences: the 9th sternite is significantly broader in male than female nymphs, while in five species; tergites in female nymphs are broad and in male are narrow.

Cytogenetics as a tool for Triatomine species distinction (Hemiptera-Reduviidae)

Several cytogenetic traits were tested a species diagnostic characters on five triatomine species: Rhodnius pictipes, R. nasutus, R. robustus, Triatoma matogrossensis and T. pseudomaculata. Four of them are described for the first time. The detailed analysis of the meiotic process and the application of C-banding allowed us to identify seven cytogenetic characters wich result useful to characterize and differentiate triatomine species.

Aggregation pheromone in five species of Triatominae (Hemiptera: Reduviidae)

An aggregation pheromone found in the faeces of 5th instar nymphs and adults of Triatoma mazzottii Usinger, Triatoma longipennis Usinger, Triatoma pallidipennis (Stal), Triatoma barberi Usinger and Rhodnius prolixus (Stal) was studied under laboratory conditions. Bioassays were performed using a 30 cm-diameter arena and wind tunnel. T. longipennis nymphs showed a stronger response than the other triatomine nymphs tested. There were no significant differences in faecal attractiveness to nymphs, but the faeces of T. longipennis and T. pallidipennis were most active. The responses of all species to male and female faeces of T. mazzottii was significantly different, but there was no significant difference in the responses of the development stages to male and female faeces of T. mazzottii. However, male faeces were more active than female faeces. The feeding status of nymphs did not affect the response.

Revalidação do gênero Mepraia, Mazza, Gajardo & Jorg, 1940 (Hemiptera, Reduviidae, Triatominae)

The authors revalidate the genus Mepraia, described in 1940 by Mazza, Gajardo & Jörg. The genus is monotypic and represented by the species M. spinolai (Porter, 1934). Based on the characteres described below the authors considered the separation of the genus Triatoma Laporte, 1832 and the return of the genus Mepraia. Strongly alar polymorphism, the abdomen of female with connexivum like in genus Dipetalogaster Usinger 1939, seven testicular follicles, like in Triatoma, however with a different relation of lenghts; external male genitalia showing a big and foliar process of the conjunctiva, vesica with an arch-shape, struts and endosoma process absent.

In vivo differentiation of Trypanosoma cruzi - 1. Experimental evidence of the influence of vector species on metacyclogenesis

Vector species has not hitherto been studied as influencing metacyclogenesis of Trypanosoma cruzi, while the role of the parasite strain has been frequently stressed as of dominant importance in this process. In order to fill this gap in our knowledge, metacyclogenesis was monitored in nine triatomine species. The first part of this paper presents photographs of the main and intermediate parasite stages in each vector species studied. In the second part of the study the proportional distribution of all these forms, as seen in Giemsa stained smears is summarized, thus providing an opportunity to analyze both: the length of time between the ingestion of the blood trypomastigotes and the appearance of metacyclic forms and the rates of developmental stages leading to these latter. The most remarkable observation was that metacyclogenesis rates in vivo appear to be vector dependent, reaching 50 in Rhodnius neglectus, 37 in its congener R. prolixus and being dramatically lower in the majority of Triatoma species (5 in T. sordida, 3 in T. brasiliensis and 0 in T. pseudomaculata) at the 120th day of infection. These observations suggest that through screening of different vector species it is possible to find some that are capable of minimizing or maximizing metacyclic production.

The cave-like sense organ in the antennae of Triatominae bugs

In the second segment of the antennae of haematophagous reduviids an unusual cave-like organ is found the function os which was investigated in Triatoma infestans. the morphology of the organ makes it difficult to ascribe it to a mechno- or chemoreceptive function, but shows some characteristics shared with thermoreceptors of other animals. The electrical activity of sense cells was recorded in the presence of stimuli that evoke behavioural responses in this species, i.e. warm, CO2, lactic and butyric acids at different concentrations. The three compounds tested failed to evoke a response at all concentrations assayed. Only thermal stimulation evinced a clear modification in the electrical activity of the sense cells.Both the morphological and electrophysiological findings support a thermoreceptive finding, habitat selection and circadian synchronization.

The use and mis-use of some ecological terms and concepts in epidemiology

The article discusses the current use and mis-use of ecological terms and concepts in epidemiological literature, and in special, in works dealing with zoonotic diseases. A selection of examples was taken from papers recently published on the transmission of Chagas' disease by Triatoma sordida. Proper definitions are listed, with the intent of helping non-ecologists to use those terms and concepts correctly.

Chagas Disease Vector Control in Tupiza, Southern Bolivia

Heavy domestic and peridomestic infestations of Triatoma infestans were controlled in two villages in southern Bolivia by the application of deltamethrin SC25 (2.5% suspension concentrate) at a target dose of 25 mg a.i./m². Actual applied dose was monitored by HPLC analysis of filter papers placed at various heights on the house walls, and was shown to range from 0 to 59.6 about a mean of 28.5 mg a.i./m². Wall bioassays showed high mortality of T. infestans during the first month after the application of deltamethrin. Mortality declined to zero as summer temperatures increased, but reappeared with the onset of the following winter. In contrast, knockdown was apparent throughout the trial, showing no discernible temperature dependence. House infestation rates, measured by manual sampling and use of paper sheets to collect bug faeces, declined from 79% at the beginning of the trial to zero at the 6 month evaluation. All but one of the houses were still free of T. infestans at the final evaluation 12 months after spraying, although a small number of bugs were found at this time in 5 of 355 peridomestic dependencies. Comparative cost studies endorse the recommendation of large-scale application of deltamethrin, or pyrethroid of similar cost-effectiveness, as a means to eliminate domestic T. infestans populations in order to interrupt transmission of Chagas disease

Hermanlentia n. gen. da tribo Triatomini, com um rol de espécies de Triatominae (Hemiptera, Reduviidae)

Hermanlentia n. gen. of Tribe Triatomini, with a List of Species of Triatominae (Hemiptera, Reduviidae) - Hermanlentia n. gen. was established in the tribe Triatomini, based on differences of external morphology, phallic structures and chromatic characters of Triatoma matsunoi Fernandez-Loayza 1989, in relation to other species of Triatoma. The head is long with disproportionally small eyes 1:0,16; the relation of the head and the pronotum is 1: 0,4; and the coloration of the hemelytron is whitish. Characters of the male genitalia that distinguish the new genus are the articulatory apparatus with twice the size of the aedeagus, phallosoma with fingerlike apex, 1 + 1 dorsal conjuntive processes with the inner edge toothed, and absence of endosoma process and vesica

Biomorphological Alterations Induced by an Anti-juvenile Hormonal Compound, 2-(2-EthoxyEthoxy)Ethyl Furfuryl Ether, on Three Species of Triatominae Larvae (Hemiptera, Reduviidae)

Applied topically to larvae of Rhodnius prolixus Stal, Triatoma infestans (Klug) and Panstrongylus herreri Wygodzinsky, vectors of Trypanosoma cruzi, the causative agent of Chagas'disease, a synthetic, furan-containing anti-juvenile hormonal compound, 2-(2-ethoxyethoxy)ethyl furfuryl ether induced a variety of biomorphological alterations, including precocious metamorphosis into small adultoids with adult abdominal cuticle, ocelli, as well as rudimentary adultoid wings. Some adultoids died during ecdysis and were confined within the old cuticle. The extension of these biomorphological responses is discussed in terms of the complexity of the action of anti-juvenile hormonal compounds during the development of triatomines