Changes in nuclear phenotype frequencies following sequential cold shocks in Triatoma infestans (Hemiptera, Reduviidae)

The nuclear phenotypes of Malpighian tubule cells in fifth instar nymphs of Triatoma infestans, one of the most important vectors of Chagas disease, were studied following sequential shocks at 0ºC, separated by intervals of 8 h and 24 h at 30ºC, under conditions of moderate fasting and full nourishment. The insects pertained to colonies reared in the laboratory and originated from domestic specimens collected in the Brazilian states of Säo Paulo (north) and Minas Gerais (south). Since nuclear phenotypes in this species are affected by single cold shocks, it was expected that these phenotypes could also be changed by sequential shocks. Nuclear phenotypes indicative of mechanisms of cell survival (nuclear fusion and heterochromatin decondensation) and cell death (apoptosis and necrosis) were observed concomitantly in all the conditions tested. Nuclear fusion and heterochromatin decondensation were not found relevant for the presumed acquisition of the cold-hardening response in T. infestans. The decreased frequency of apoptosis and necrosis following sequential cold shocks including under fasting conditions, indicated that tolerance to sequential cold shocks occurred in T. infestans of the mentioned origin

Effect of sequential cold shocks on survival and molting rate in Triatoma infestans Klug

The survival and molting incidence in Triatoma infestans, a vector of Chagas disease, were investigated following sequential shocks at 0ºC in fifth instar nymphs under moderate fasting and full nutritional conditions. The shocks were separated by intervals of 8 h and 24 h at 30ºC. The results indicated that in terms of insect survival, T. infestans is tolerant to a single cold shock at 0ºC even for 12 h, or to sequential cold shocks, regardless of the nutritional state of the specimens. In terms of molting rate, fasting enhanced the tolerance to sequential cold shocks, but did not exceed the tolerance acquired by fully-nourished specimens, except when cold shocks were separated by an 8 h interval at 30ºC. The protective action elicited by fasting was assumed to be additive to that induced by a single mild cold shock or sequential cold shocks. The cold-tolerance response of T. infestans may have favoured its survival in areas of South America with low temperatures, even considering that this species is predominantly associated with human habitats

Changes in nuclear phenotypes following cold shock in Panstrongylus megistus (Burmeister)

The nuclear phenotypes of Malpighian tubule epithelial cells of 5th instar male nymphs of the blood-sucking insect Panstrongylus megistus were studied immediately after a short (1 h) cold shock at 0o.C, and 10 and 30 days later. The objective was to compare the responses to a cold shock with those known to occur after hyperthermia in order to provide insight into the cellular effect of cold in this species. Nuclei which usually exhibited a conspicuous Y chromosome chromocenter were the most frequent phenotype in control and treated specimens. Phenotypes in which the heterochromatin was unravelled, or in which there was nuclear fusion or cell death were more abundant in the shocked specimens. Most of the changes detected have also been found in heat-shocked nymphs, except for nuclear fusion which generates giant nuclei and which appeared to be less effective or necessary than that elicited after heat shock. Since other studies showed that a short cold shock does not affect the survival of more than 14 percent of 5th instar nymphs of P. megistus with domestic habit and can induce tolerance to a prolonged cold shock, heat shock proteins proteins are probably the best candidates for effective protection of the cells and the insects from drastic damage caused by low temperature shocks

Chagas disease in an area of recent occupation in Cochabamba, Bolivia

A descriptive, entomological and seroepidemiological study on Chagas disease was conducted in a place of recent occupation on the outskirts of Cochabamba, Bolivia: Avaroa/Primer de Mayo (population: 3.000), where the socio-economic level is low no control measures have been made available. Methods - The immunofluorescent antibody test (IFAT) was used for IgG and IgM anti-Trypanosoma cruzi antibodies in filter paper bloodspot eluates from 128 subject age, gender, birthplace, occupation, duration of residence and building materials used in their houses were recorded. Vectors were captured both in domestic and peridomestic environments. Results - Seropositive, 12,5 per cent (16/128): females, 15.1 per cent (11/73); males, 9.1 per cent (5/55). Average time of residence: 6.1 years for the whole population sample and 7.4 years for the seropositive subjects. Most houses had abobe walls (76.7 per cent, n = 30), galvanized iron rooves (86.7 per cent) and earthen floors (53.4 per cent) 80 per cent of the walls had crevices. One hundred forty seven specimens of Triatoma infestans were captured, of which 104 (70.7 per cent) were domestic, and 1 peridomestic Triatoma sordida. Precipitin host identification: birds, 67.5 per cent; humans, 27.8 per cent; rodents, 11.9 per cent; dogs, 8.7 per cent; cats, 1.6 per cent. House infestation and density indices were 53.3 and 493.0 respectively. We found 21 (14.3 per cent) specimens of T. infestans infected with trypanosomes, 18 (85.7 per cent) of which domestic environments. Discussion - The elements for the vector transmission of Chagas disease are present in Avaroa/Primer de Mayo and the ancient custom of keeping guinea pigs indoors adds to the risk of human infection. In neighboring Cochabamba, due to sub-standard quality control, contaminated blood transfusions are not infrequent, which further aggravates the spread of Chagas disease. Prompt action to check the transmission of this infection, involving additionally the congenital and transfusional modes of acquisition, is required.

Survival and molting incidence after heat and cold shocks in Panstrongylus megistus burmeister

Survival and molting incidence were studied after heat (40ºC) and cold (0ºC) shocks in specimens of Panstrongylus megistus with the aim of establishing its response to temperature stress under laboratory rearing conditions and to understand occasional changes in the biological characteristics of specimens captured in nature. The response to the thermal shocks was found to vary as a function of the temperature an duration of the shock, developmental phase and sex of the specimens, and in certain cases, the insect habit and nourishment conditions. P. megistus specimens were found to be less resistant to the heat shock assay than Triatoma infestans, another reduviid species. The short cold shock affected survival of P. megistus more than did the heat shock, survival of fully-nourished specimens being preferencial. The response of adults to the short cold shock was affected by sex, males being generally less resistant. The insect sylvatic habit was found to seldom affected the thermal shock response established for specimens with domestic habit. A decrease in molting frequency and sometimes a slowdown of the molting rate were found after the short heat and cold shocks, possibly promoted by changes in hormonal balance, and differing from patterns reported for T. infestans. The results indicate that no generalization should be made for different reduviid species in terms of the effects of temperature shocks.

Triatoma brasiliensis (Neiva, 1911) (Hemiptera, Reduviidae): observaçoes sobre seu comportamento em relaçäo à fonte alimentar em galinheiro experimental / Triatoma brasiliensis (Neiva, 1911) (hemiptera. Reduviidae): observations on dynamics of feeding behavior in an artificial ecotope

Estuda o comportamento de triatomíneos no interior de ecótopos artificiais. Construiu-se um galinheiro experimental com paredes internas formadas por blocos de barros desmontáveis, abringando aves como fonte alimentar. O galinheiro foi subdividido em quatro áreas, duas destas separadas por telas e tijolos furados, sendo a menor o local de soltura dos triatomíneos e a maior o galinheiro propriamente dito. Dessa maneira buscou-se a coleta de informaçoes a respeito do deslocamento sobrevida e locais de abrigo de ninfas do 4§ estágio de Triatoma brasiliensis, na certeza de que os mesmos iriam se acomodar nas proximidades da fonte alimentar. As paredes do galinheiro foram desmontadas e pesquisadas mensalmente durante 6 meses e as ninfas encontradas, marcadas com diferentes cores de acordo com o mes da leitura e a posiçäo das mesmas nas áreas. Os resultados alcançados mostraram que 88,5 por cento das ninfas estavam engorgitadas e foram encontradas próximas ao local de repouso (poleiro) de fonte alimentar. Após a primeira alimentaçäo, näo abandonavam as proximidades da fonte. Os resultados alcançados apresentaram interesse epidemiológico e também interesse na área de controle dos vetores da doença de Chagas, tendo em vista as possíveis implicaçoes quanto aos procedimentos na aplicaçäo do inseticida.

Sobrevivência e ocorrência de muda em Triatoma infestans Klug (Hemiptera, Reduviidae) após choque de temperatura / Survival and occurrence of molting in Triatoma infestans Klug (Hemiptera, Reduviidae) after temperature shock

A sobrevivência e a ocorrência de mudas em espécies de Triatoma infestans foram estudadas num período de 30 dias após choques de temperatura. Foi demonstrado que choques hipertérmico e hipotérmico interferem nesses processos, na dependência da temperatura do choque, tempo de sua duraçäo, fase de desenvolvimento e sexo dos espécimes. Dentre as situaçöes experimentais utilizadas, o choque a 0§C por 12 h pareceu produzir a açäo mais deletéria, porém choques a 40§C e 0§

Primeiro caso autóctone de tripanossomíase americana do Estado do Acre (Brasil) e sua correlaçäo com as cepas isoladas do caso humano e de triatomíneos silvestres da área / The first autochthonous case of American trypanosomiasis in the State of Acre, Brazil, and its correlation with the strains identified in the human case and the sylvatic triatomines in the area

Säo apresentados os resultados obtidos na investigaçäo entomo-epidemiológica realizada no estudo do primeiro caso humano autóctone de tripanossomíase americana no Estado do Acre (Brasil). A investigaçäo demonstrou ausência de domiciliaçäo triatomínea, ficando descartada totalmente a possibilidade de transmissäo congênita ou transfusional. Näo foi possível verificar se a transmissäo foi metaxênica através da invasäo domiciliar de barbeiro silvestre, ou se por via digestiva através de alimentos contaminados. Foram isoladas duas cepas de Trypanosoma cruzi, uma do caso humano chamada Acre-Humana (AH) e outra de Rhodnius robustus coletados em palmeiras uricuri (Attalea sp) nas proximidades da casa, chamada Acre-Silvestre (AS). Ficou comprovada a existência de correlaçäo entre os caracteres morfobiológicos e patogênicos das duas amostras estudadas: mostraram-se patogênicas para camundongos, infectando 100% dos animais, quer com formas metacíclicas de triatomíneos, quer com formas sanguícolas de doadores em fase aguda. A infecçäo dos camundongos nas duas amostras é grave com curto período pré-patente, parasitemia elevada e taxa de letalidade alta. Em ambas as cepas, em fase aguda, säo abundantes ninhos de amastigotas, principalmente no coraçäo e fígado. As amostras AH e AS conferem aos animais que sobrevivem boa resitência contra infecçöes pela amostra Y. Cultivaram-se facilmente em meios líquidos e semi-sólidos e infectaram experimentalmente seis espécies de triatomíneos. Os resultados comprovam mais uma vez a presença de focos naturais desta parasitose na regiäo.