Biologia do Triatoma vitticeps (Stal, 1859) em condições de laboratório (Hemiptera: Reduviidae: Triatominae): II. Resistência ao jejum

Em prosseguimento ao estudo da biologia do Triatoma vitticeps (Gonçalves et al., 1988), foram feitas observações sobre a sua resistência ao jejum. Dos 286 ovos obtidos, apenas 201 eclodiram e atingiram o estádio pretendido para as observações. Os demais não eclodiram, não completaram a muda ou morreram sem motivo aparente. As ninfas foram acondicionadas, individualmente em frascos de Borrel, devidamente registrados. Para a alimentação foram utilizados camundongos e a medida que as ninfas atingiam o estágio pretendido a alimentação era suspensa até ocorrer a morte. A avaliação da resistência ao jejum foi feita da seguinte forma: o intervalo de dias entre o último repasto e a morte e entre a muda e a morte. Verificou-se que a resistência está diretamente relacionada com a fase de desenvolvimento. Para os parâmetros último repasto/morte e muda/morte, ambos os sexos foram menos resistentes do que as ninfas de 3º e 2º estádios, respectivamente. O experimento teve duração de 15 meses e neste período as temperaturas máxima e mínima e a umidade relativa do ar variaram em média de 25 ± 2ºC e 81 ± 3% UR, respectivamente. O material foi proveniente da criação de triatomíneos mantida no Departamento de Entomologia do Instituto Oswaldo Cruz.

Influência da temperatura na biologia de triatomíneos: IX. Rhodnius nasutus Stal, 1859 (Hemiptera, Reduviidae)

Estudou-se a influência da temperatura na biologia de Rhodnius nasutus Stal, 1859 (Hemiptera, Reduviidae), tendo em vista a sua criação em grande escala, em laboratório, para serem utilizados no xenodiagnóstico e fornecer informações que subsidien as ações de controle. Os experimentos realizaram-se em duas câmaras climatizadas, a 25 ± 0,5ºC e 3º ± 1ºC, com umidade relativa de 70 ± 5% e fotoperíodo de 12 horas. Apresentam-se os dados relativos ao ciclo evolutivo, pré-postura, fecundidade, fertilidade, sobrevivência ao jejum e quantidade de sangue ingerido. A duração média do ciclo evolutivo foi de 145,7 dias a 25ºC e de 114,2 dias, a 30ºC. A quantidade de sangue ingerido para completar o ciclo evolutivo foi de 304,3mg e 350,3 mg, a 25º e 30ºC, respectivamente. A sobrevivência ao jejum absoluto foi significativamente maior a 25º do que a 30ºC, ao nível de 1%.

Estudos sobre a resistência ao jejum e aspectos nutricionais de Triatoma lecticularia (Stal, 1859) (Hemiptera, Reduviidae, Triatominae)

Foi feito um estudo sobre a resistência ao jejum em todas as fases evolutivas e pesagens em diferentes situações nutricionais de Triatoma lecticularia (alimentado; não alimentado; na morte após o jejum) com temperatura e umidade registradas. Observou-se que os períodos de resistência das fases ninfais apresentaram médias (dias) crescentes: 1º: 45,84; 2º: 61; 3º: 88,74; 4º: 123,47; 5º 162,30. Na fase adulta as médias foram aproximadas à do 3º estádio (para os machos 88,94 e para as fêmeas 83,66). O procedimento de pesagens permitiu registrar a quantidade de sangue ingerido, a perda de peso durante o jejum e o respectivo percentual em relação ao peso inicial. Esta espécie tem assinalada sua distribuição geográfica na região Neártica, onde tem sido encontrda infectada com Trypanosoma cruzi associada a Neotoma micropus Baird e Spermophilus variagatus (Erxeleben).

Fonte alimentar e potencial vetorial de Triatoma vitticeps (Stal, 1859) com relação à doença de Chagas humana no estado do Espírito Santo, Brasil (Hemiptera, Reduviidae)

In paralel with several other epidemiologic and entomologic data of 19 Municipalities of Espírito Santo State, Brazil, the feeding pattern of 222 Triatoma vitticeps is studied through precipitin tests. Very high levels of natural infection with Trypanosoma cruzi are observed in adult insects, in contrast with the abscence or minimum degrees of infection among nymphs and human individuals. The precipitin tests showed the contact of the insects with multiple blood sources, chiefly human and birds, followed by rodents and marsupials. The data suggest that T. vitticeps in spite of being highly antropophilic, become infected by T. cruzi in sylvatic ambient and occasionally invade houses. The species doesn't seem to be - at least until now - a good vector in the domestic cycle of Chagas' disease. Several factors seem to be involved in this conclusion, mainly the low density of the insect in the houses, its hardness to coloniza them, its slowness concerning to suction and defecation and possibly its low susceptibility to different T. cruzi strains.

Trypanosoma rangeli (Tejera, 1920) isolated from a sylvatic rodent (Echimys dasythrix) in Santa Catarina island, Santa Catarina state: first report of this trypanosome in southern Brazil

A trypanosome strain isolated from a sylvatic rodent (Echimys dasythrix) from Santa Catarina Island (Santa Catarina State, Brazil) was characterized by the following methods: experimental transmission and development in invertebrate hosts, morphometry, cross protection, complement sensitivity, lectin agglutination and isoenzyme profiles. Comparasions were made with standard Trypanosoma cruzi and T. rangeli strains. All methods except isoenzyne analysis led to the identification of the isolate as T. rangeli. The isoenzyme differences found could be explained on the basis of polymorphism. Therefore this is the first report of T. rangeli in southern Brazil, increasing the geographical distribution of this parasite.

Trypanosoma rangeli (Tejera, 1920): observations upon pleomorphism

Metatrypomastigotes of Trypanosoma rangeli Tejera, 1920, harvested from LIT medium, were inoculated i.p. or s.c. into 6, 16, and 26g NMRI mice, these representing increasing degrees of immunological maturity. In all cases, similar pleomorphic patterns were observed. Four morphobiometrically differentiable types of trypanosome were encountered in an overlapping temporal sequence. These observations, taken in comparison with those on pleomorphism in this and other species of Trypanosoma by other workers, are consistent with the hypothesis that the pleomorphic types represent the natural development of the parasite, rather than the result of the immune response of the mammal host. Small, slender trypanosomes prevalent at the onset of the parasitemia either reinvade the tissue cells for relatively limited subsequent generations of tissue reproduction, or else differentiate toward the forms that are only capable of colonizing the insect vector.

An Investigation on the Ecology of Triatoma vitticeps (Stal, 1859) and its Possible Role in the Transmission of Trypanosoma cruzi, in the Locality of Triunfo, Santa Maria Madalena Municipal District, State of Rio de Janeiro, Brazil

From January 1989 to April 1995, 465 specimens of Triatoma vitticeps were collected in the locality of Triunfo, 2nd District of Santa Maria Madalena municipal district, State of Rio de Janeiro. The bugs were found indoors by local residents with predominance of adults. The flight activity was high in hot months when the incidence in the domicile also increased. Two hundred and two bugs (111 alive and 91 dead) were examined for Trypanosoma cruzi infection. This was detected in 31 of the dead bugs (34%) and 88 (79%) of the live bugs examined. With a view to investigate the possible vertebrate hosts of the T. cruzi isolates, the blood of 122 mammals was examined through Giemsa-stained smears, hemocultures and xenodiagnosis. T. cruzi was detected in three specimens of Didelphis marsupialis and T. (M.) theileri was detected in one specimen of Bos taurus. The parasites were isolated from triatomine feces, xenoculture and hemoculture. No evidence of human infection was detected in 58 inhabitants examined, as evaluated by indirect imunofluorescence technique using T. cruzi epimastigotes as antigens. These results show that T. vitticeps is still a sylvatic species although nymphs have been found inside the domicile. Thus, an epidemiological vigilance is necessary to know the behaviour of this species following the continuous modifications promoted by the presence of man.

Dalí et le dynamisme des formes. L'élaboration de l'activité « paranoïaque-critique » dans le contexte socioculturel des années 1920-1930

RESUME Dalí et le dynamisme des formes. L'élaboration de l'activité « paranoïaque-critique » dans le contexte socioculturel des années 1920-1930 Rendre à nouveau lisibles des textes dont on ne sait plus reconnaître les enjeux historiques et cognitifs, tel est le principal défi que cet ouvrage consacré aux écrits surréalistes de Dalí se propose de relever. La thèse fait ressortir l'image sans doute un peu déroutante d'un créateur stratège qui, assimilant de manière originale les savoirs les plus variés et dialoguant avec les intellectuels de son temps, propose au tournant des années 1930 une théorie du surréalisme novatrice, capable de redynamiser un groupe en pleine crise. L'étude, combinant des perspectives sociologiques et linguistiques, explore tout d'abord les écrits à caractère manifestaire et dessine les traits conceptuels et stylistiques qui font la singularité du projet de Dalí dans le cadre du mouvement surréaliste. S'inspirant des images-devinettes, de la production des fous, de l'interprétation des figures aux formes indéterminées, le Catalan conçoit une méthode créative et cognitive qui se fonde sur une pensée subconsciente active, schématisant et fertilisant automatiquement toute donnée perçue. Dans le domaine de la peinture, ce sont les formes des objets qui sont surdéterminées par les désirs subconscients du créateur et du spectateur et qui acquièrent ainsi des significations inattendues. Dans le domaine de l'écriture, ce sont les formes sonores et graphiques des mots ou encore l'ossature discursive qui, investies par les fantasmes de l'écrivain et du lecteur, génèrent une multitude d'images. A l'aune des modes de connaissance propres à l'époque, l'étude porte ensuite sur deux modèles de pensée - le paradigme photographique et l'imaginaire lié à la notion d'espace-temps développée par Einstein dans le cadre de la théorie de la relativité générale - qui sont en vogue pendant les années 1930 et que le peintre se réapproprie pour signifier la dimension « révélatrice » et « objective » de ses oeuvres. Premièrement, pour penser la méthode « paranoïaque-critique », le Catalan reprend et détourne les phases de production du cliché : loin de reproduire fidèlement le visible, le dispositif photographique dalinien permet de révéler les pensées subconscientes. Deuxièmement, dès 1933-1934, Dalí reformule le modèle de l'espace-temps de la relativité générale d'Einstein pour penser la façon dont une entité invisible (le fantasme) s'objective et se matérialise dans la réalité extérieure. L'étude du dynamisme psychique conféré par Dalí aux formes des objets, aux formes verbales et picturales permet finalement de mettre en lumière le foisonnement mais aussi l'extrême cohérence de l'univers surréaliste du Catalan, et de souligner la valeur de l'approche « paranoïaque-critique » de la réalité tant sur le plan de l'histoire culturelle que sur le plan de la connaissance.

Triatoma sordida Stål 1859 (Hemiptera, Reduviidae: Triatominae) in palms of northeastern Argentina

Several palms species provide an important habitat for triatomines and associate vertebrates in tropical America. The objective of this work is to identify the triatomine species living in the palms of rural areas in the Province of Corrientes, and to estimate the potential epidemiological risk they represent for the residents of nearby houses. The survey was carried out in a palm community in Colonia Laurel, Department San Roque, Province of Corrientes, Argentina. Samplings were performed in October, November and December 1998; January, February and March 1999; May and June 1999. Thirty palms: 27 (90%) Butia yatay (Mart.) Becc. and 3 Acrocomia aculeata (Jacq.) Lodd ex Mart. were dissected. Triatoma sordida Stål 1859 was found in 96.2% of B. yatay and in all the A. aculeata palms. A total of 272 live T. sordida was collected; 36 of them (13.2%) were found in bird nests in the frond and the remainder in other locations of the tree. The mean number of triatomines per palm was 9.6 (range 1-60, mode 2). T. sordida was collected during all the sampling months and all stages were present at all seasons. The highest population density was reached in spring and the lowest in autumn. Trypanosoma cruzi was detected in 38.5% in feces of 174 examined insects and identified as such, both by microscopical examination and PCR. This is the first finding of T. sordida populations in B. yatay, an endemic palm of South America distributed in southern Brazil, Uruguay and northeastern Argentina. The high infection prevalence found in this work suggests that T. sordida plays an essential role in the maintenance of the wild T. cruzi transmission cycle in northeastern Argentina.