[Triatoma williami n. sp. (Hemiptera, Triatominae)].
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Insecta↗
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[Control of Triatominae with hexachlorocyclohexane in 3 departments of the South of Peru].
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Chagas Disease↗
Triatomine vectors of Trypanosoma cruzi: a molecular perspective based on nuclear ribosomal DNA markers.
Chagas disease (American trypanosomiasis) is mainly transmitted by blood-sucking bugs of the reduviid subfamily Triatominae (Hemiptera: Prosorrhyncha). Control strategies are directed mainly against these insect vectors, as no vaccine is available and, except in the very early stage of infection, there is no effective chemótherapy. Studies of deoxyribonucleic acid (DNA) will lead to major advances in our knowledge of Triatominae and their relationships to Chagas disease transmission, epidemiology and control. Analyses of complete sequences of nuclear genes coding for ribosomal ribonucleic acid (rRNA) (rRNA genes) and spacers furnish significant information at the levels of higher taxons, genera, species, subspecies, hybrids, varieties and populations of Triatominae. This paper briefly reviews the contributions of studies on the slowly-evolving 18S or small subunit (SSU) rRNA gene and the quickly-evolving second internal transcribed spacer (ITS-2). The whole 18S rRNA gene is a useful marker for supraspecific relationships in Triatominae. ITS-2 is complementary to it, enabling resolution at specific and infraspecific levels. All the evidence suggests that ITS-2 will become the DNA marker of excellence for studies of Triatominae at specific and subspecific levels, as it is in other groups of organisms. Possible applications of data obtained from the study of rRNA and ITS-2 sequences of Triatominae are discussed.
Animals↗
Comparison of techniques for detection of domestic infestations with Triatoma infestans in Brazil.
The detection of infestations of Triatominae in houses in regions endemic for Chagas's disease is a criterion frequently used in the selection of areas, or of individual houses, for treatment in insecticide campaigns as well as in the evaluation of insecticide performance. Several different methods for detecting domestic infestations with Triatominae were compared: night capture, capture of five bugs with the aid of a flushing-out agent and use of card boxes of the Gómez-Núñez type. The flushing-out and Gómez-Núñez box methods were found to be equally sensitive, although each failed to detect some infestations which the other detected. The night capture method was slightly more sensitive but was found to be impractical for insecticide trials. Improvement to the flushing-out method, notably the introduction of a systematic search technique, made it much more sensitive than the Gómez-Núñez box method for heavily infested houses and for houses three months after insecticide treatment. Although the sensitivity of the Gómez-Núñez box method increases when the boxes are left in place for a long time, this also limits the value of the information obtained regarding the evaluation of insecticides. On the basis of the results presented, the flushing-out method using a systematic search of the house was found to be the most suitable sampling technique, but it is recognized that this method still has limitations.
Animals↗
Phylogeny of triatomine vectors of Trypanosoma cruzi suggested by mitochondrial DNA sequences.
The subfamily Triatominae (Hemiptera: Reduviidae) comprises hematophagous insects, most of which are actual or potential vectors of Trypanosoma cruzi, the protozoan agent of Chagas' disease (American trypanosomiasis). DNA sequence comparisons of mitochondrial DNA (mtDNA) genes were used to infer phylogenetic relationships among 32 species of the subfamily Triatominae, 26 belonging to the genus Triatoma and six species of different genera. We analyzed mtDNA fragments of the 12S and 16S ribosomal RNA genes (totaling 848-851 bp) from each of the 32 species, as well as of the cytochrome oxidase I (COI, 1447 bp) gene from nine. The phylogenetic analyses unambiguously supported several clusters within the genus Triatoma. In the morphological classification, T. costalimai was placed tentatively within the infestans complex while T. guazu was not included in any Triatoma complex. The placement of these species in the molecular phylogeny indicated that both belong to the infestans complex. We confirmed with a strong support the inclusion of T. circummaculata, a member of a different complex based on morphology, within the infestans complex. On the other hand, the present phylogenetics analysis did not support the monophyly of the infestans complex species as it was suggested in our previous studies. While no strong inference of polyphyly of the genus Triatoma was provided by the bootstrap analyses, the other species belonging to Triatomini analyzed could not be distinguished from the species of Triatoma.
Animals↗
Epidemiology of Chagas disease in Ecuador. A brief review.
Chagas disease is a complex public health problem that has been underestimated in Ecuador. Here we review the relevant published information, and present unpublished and new data that help to understand the current Chagas disease epidemiological situation and its evolution in the country. Three main characteristics have been identified: (i) persistence of Trypanosoma cruzi transmission in already known foci; (ii) a marked endemicity in some urban areas of Guayaquil; and (iii) the transformation of new Amazon foci into truly endemic areas. The situation in other suspect areas remains uncertain. Five Triatominae species have been implicated in the transmission of T. cruzi to people in Ecuador (Triatoma dimidiata, Rhodnius ecuadoriensis, R. pictipes, R. robustus and Panstrongylus geniculatus), but some others may also play a role in some areas (P. rufotuberculatus, P. howardi, T. carrioni and P. chinai). Other Triatominae reported seem to have little or no epidemiological relevance (T. venosa, T. dispar, Eratyrus mucronatus, E. cuspidatus, P. lignarius and Cavernicola pilosa). High frequency of acute cases and severe chronic disease has been observed. Although cardiomyopathy is more frequent, serious digestive disease is also present. It is estimated that around 120,000-200,000 people may be infected. 2.2 to 3.8 million people are estimated to live under transmission risk conditions.
Animals↗
Adult and nymphs of Microtriatoma trinidadensis (Lent, 1951) (Hemiptera: Reduviidae) caught from peridomestic environment in Bolivia.
This is the first report of adult and nymphs (20 nymphs of all stages and 4 adults) of Microtriatoma trinidadensis (Lent 1951) (Hemiptera: Reduviidae: Triatominae) collected in peridomestic environment, in the department of La Paz, Bolivia. These specimens were associated to Rhodnius stali Lent, Jurberg & Galvão 1993. The exceptional finding of M. trinidadensis in peridomestic environment, illustrates the general tendency of triatominae to adapt to human dwellings and dependences.
Animals↗
Active transmission of human chagas disease in Colima Mexico.
Despite efforts to eradicate American trypanosomiasis (AT) and Chagas disease from the Americas, there are still areas of active transmission that can eventually become a source of reinfection in previously controlled regions. Mexico could be one of those areas, where there are no formal preventive control programs despite the presence of communities infested by Triatominae bugs infected with Trypanosoma cruzi. This study explored the prevalence of T. cruzi infection in 405 habitants of 17 communities in the state of Colima, on the Pacific Mexican coast, through a seroepidemiological probabilistic survey. The results revealed a point seroprevalence of 2.4% positive for anti-T. cruzi. In addition, 2 clinical cases of chronic and 2 of acute Chagas disease were detected in the explored communities. These findings confirm the risk of active transmission of AT in Western Mexico, especially in rural and suburban communities infested with intra-domestic triatominae, where control programs should be implemented.
Adolescent↗
Isobutyric acid from the Brindley's glands of Triatoma lecticularia.
The contents of the Brindley's gland of Triatoma lecticularia (Stål) (Heteroptera: Reduviidae: Triatominae) have been identified by gas chromatography-mass spectrometry as isobutyric acid. This compound is found in similar secretions from certain other members of the Triatominae, and is suggested to play a role as a defensive pheromone and for intraspecies communication.
Animals↗
[The use of insecticide fumigant canister to protect an insectarium and its residual effect against triatomine bugs, in laboratory conditions].
An insecticide fumigant canister based on synthetic pyrethroids and dichlorvos was employed against cockroaches and ants which were invading an insectarium used for rearing triatominae. After removal of the Triatominae, the canister was activated and found to kill all the invading insects within 48 hours. Possible residual action against triatomines was then monitored by a 24-hour exposure of eggs, nymphs and adults of Triatoma infestans, Panstrongylus megistus and Rhodnius neglectus in the treated insectarium. No ovicidal action was observed but some mortality of adults and nymphs of the three species was observed up to 72 hours after the fumigation.
Animals↗
Repeated plasticization and recovery of cuticular stiffness in the blood-sucking bug Triatoma infestans in the feeding context.
Triatominae bugs experience changes in the mechanical properties of their cuticle prior to feeding. This process-plasticization-allows a rapid stretching of the unsclerotized abdominal cuticle of triatominae larvae and it is evoked by sensory inputs related to feeding. We tested: (a) whether the cuticle recovers its original mechanical properties after plasticization, (b) whether repeated stimulation would be able to evoke recurrent plasticization along the same larval instar, (c) the temporal course of recovering cuticular stiffness. We injected Ringer solution into the body cavity of the bugs at constant pressure, using the injection rate (ml/min) as a measure of the cuticle extensibility. To trigger plasticization, individuals were allowed to feed on blood from an artificial feeder at 32+/-2 degrees C. After plasticization occurred, the abdominal cuticle gradually recovered its original mechanical properties. Bugs were capable of plasticizing for a second time when repeatedly stimulated. The effects of plasticization vanished between 1 and 2 h after stimulation. Although one full meal could suffice to accomplish moult in other Triatomine species, Triatoma infestans is able to feed repeatedly during a single larval instar. Accordingly to this, their cuticle recovers stiffness in some hours and becomes able to respond repeatedly to sensory inputs associated with feeding.
Abdomen↗
Morphometrics of domestic Panstrongylus rufotuberculatus in Bolivia.
The trend to domesticity in Triatominae may represent a transitionary phase, towards increasing vectorial importance in the transmission of Chagas disease to humans, and requires sustained entomological surveillance. Although generally considered a sylvatic species, Panstrongylus rufotuberculatus has been recently captured inside human dwellings in the provinces of Nor Yungas and Muñecas in the Department of La Paz, Bolivia, providing evidence of this species' ability to colonise domestic habitats. The results of previous research on domestic and sylvatic specimens of other species of Triatominae indicate that morphometrics could be used to monitor this adaptive process. The most likely cause of differences seen in the size and shape of bugs from domestic colonies of P. rufotuberculatus from two neighbouring villages in Bolivia is probably genetic drift rather than environmental influences. Comparison with allopatric sylvatic specimens, including the holotype of P. rufatuberculatus, showed a general reduction in size from sylvatic to domestic specimens.
Animals↗
Ticks, ivermectin, and experimental Chagas disease.
Following an infestation of dogticks in kennels housing dogs used for long-term studies of the pathogenesis of Chagas disease, we examined the effect of ivermectin treatment on the dogs, ticks, trypanosome parasites, and also on triatomine vectors of Chagas disease. Ivermectin treatment was highly effective in eliminating the ticks, but showed no apparent effect on the dogs nor on their trypanosome infection. Triatominae fed on the dogs soon after ivermectin treatment showed high mortality, but this effect quickly declined for bugs fed at successive intervals after treatment. In conclusion, although ivermectin treatment may have a transient effect on peridomestic populations of Triatominae, it is not the treatment of choice for this situation. The study also showed that although the dogticks could become infected with Trypanosoma cruzi, this only occurred when feeding on dogs in the acute phase of infection, and there was no evidence of subsequent parasite development in the ticks.
Acute Disease↗
[Triatoma infestation in the San Luis del Palmar Department of Corrientes Province, Argentina].
The purpose of this study was to determine domestic and peridomestic infestation of Triatominae, Trypanosoma cruzi infection rates, and the prevalence of human seroreactivity in rural areas of the Department of San Luis del Palmar, Corrientes, Argentina (Fig. 1). The study took place from April 1986 to May 1989. The Department of San Luis del Palmar covers an area of 2551 km2 and is part of the Neotropical biogeographic region, Chacoan Dominion and Province. The climate is of the subhumid type. The mean annual temperature is 21.6 degrees C. Some localities were chosen because of the presence of triatominae. Households were carefully examined and classified according to their building materials. A 0.2% solution of tetrametrine was sprayed in all possible hiding places to dislodge bugs, which were collected by capture/hour/man methods. A survey to determine the socioeconomical, sanitary, and cultural conditions of house-dwellers was carried out. The same method was used to examine peridomiciles and total demolition was carried out in the positive ones. Fecal examination was carried out to verify the presence of T. cruzi in collected insects and observed at 400X. Human blood was obtained through venipuncture. The serum was kept in a freezer until examined. Serologic studies included indirect hemagglutination test (IHAT) and indirect immunofluorescence antibody test (IFAT). Positive titer for IHAT and IFAT was 1/64. Seroreactives were those that had two positive assays. The whole data obtained was analyzed by chi 2 tests. From one hundred households studied, 80% belonged to huts and 20% to houses. Mud walls were predominant in huts while brick walls were predominant in houses.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
Effect of fasting on the composition of the fat body lipid of Dipetalogaster maximus, Triatoma infestans and Panstrongylus megistus (Hemiptera: Reduviidae).
Modifications in content and lipid composition induced by fasting were examined in fat bodies from adults of Triatominae, Dipetalogaster maximus, Triatoma infestans and Panstrongylus megistus. With fasting, total lipid stores dropped approximately 50% for T. infestans and more than 70% for P. megistus. Total lipids analyzed by thin layer chromatography and fractionated by column chromatography on Unisil showed triacylglycerols as the main component in the three species, although P. megistus showed high levels of diacylglycerols (31-46%). Cholesterol amounted to 8-15%. In diacylglycerol fractions, C16:0, C18:1 and C18:0 fatty acids were detected; their ratio varied with species but it was not dependent on nutritional status. In triacylglycerol fractions C18:1 fatty acid was the major component at different times (48-68%); the ratio of monounsaturated to saturated in this fraction was 1.3, 2.6 and 1.2 for D. maximus, T. infestans and P. megistus respectively. The remarkable drop in lipid stores without noticeable changes in their relative composition would suggest that all types of lipid are used at similar rates. The higher content of diacylglycerols in P. megistus may be associated with the better flight performance of this species.
Animals↗
Blood-sucking bugs as a gentle method for blood-collection in water budget studies using doubly labelled water.
During doubly-labelled water (DLW) experiments, blood collection by venous puncture may traumatize animals and consequently affect the animals' behaviour and energy budget. Recent studies have shown that blood-sucking bugs (Triatominae; Heteroptera) can be used instead of conventional needles to obtain blood from animals. In this paper, we validate the bug method in captive nectar-feeding bats, Glossophaga soricina, for water budget analysis by comparing the daily water flux estimated with the DLW method with values measured by an energy balance method. As the mean daily water flux of the DLW method was not significantly deviating from the expected value, blood-sucking bugs may substitute more invasive methods of blood collection in DLW experiments. Based on the DLW estimates, daily energy and water intake rates were calculated and compared to values measured with the energy balance method. The DLW method and the energy balance method yielded on average similar results regarding the daily energy intake (DLW method: 48.8+/-14.2 kJ d(-1) versus energy balance method: 48.1+/-9.9 kJ d(-1)) and daily water intake (DLW method: 13.7+/-2.4 mL d(-1) versus energy balance method: 14.7+/-3.0 mL d(-1)). Based on the calculated water and sugar intake per day, we estimated the sugar concentration of ingested nectar to equal on average 16.2+/-2.4% (mass/mass), which fell close to the measured sugar concentration of 17% (mass/mass) bats fed on during the experiment. We conclude that it is possible to extrapolate mean daily energy and water intake for animal groups, populations and species based on DLW estimates, but due to the large variance of results (low accuracy), it seems inadequate to calculate values for single individuals.
Animals↗
Cuticular hydrocarbons of triatomines.
Triatomine insects (Hemiptera) are the vectors of Chagas disease. Their cuticular surface is covered by a thin layer of lipids, mainly hydrocarbons, wax esters, fatty alcohols, and free or esterified fatty acids. These lipids play a major role in preventing a lethal desiccation, altering the absorption of chemicals and microorganism penetration, they also participate in chemical communication events. Lipid components are biosynthetically related, the synthesis of long chain and very long chain fatty acids was first shown in the integument of Triatoma infestans through the concerted action of fatty acid synthases (FAS's) and fatty acyl-CoA elongases. A final decarboxylation step produces the corresponding hydrocarbon. Capillary gas chromatography coupled to mass spectrometry analyses showed that cuticular hydrocarbons of Triatominae comprise saturated straight and methyl-branched chains, from 18 to more than 43 carbon atoms. Odd-chain hydrocarbons, mostly from 27 to 33 carbons, are the major straight chains. Different isomers of mono, di, tri, and tetramethylcomponents, mostly from 29 to 39 atoms in the carbon skeleton, account for the major methyl-branched hydrocarbons. The presence, absence, and relative quantities of these hydrocarbons represent characters for their chemical phenotype, and are useful for differentiating genera, species and populations. In this review, we will discuss the metabolic pathways involved in hydrocarbon formation, and their structure, together with their role in insect survival. We will also review the utility of cuticular hydrocarbon fingerprints in chemotaxonomy.
Animals↗
Field tests of carbon dioxide and conspecifics as baits for Mepraia spinolai, wild vector of Chagas disease.
In spite of extensive evidence showing an association between host stimuli and insect finding behaviour, the importance of carbon dioxide in attracting Triatominae is not entirely understood. We assessed the potential of conspecific individuals and CO2 in attracting free-ranging individuals of Mepraia spinolai in a Chilean semiarid locality. While the presence of conspecific individuals had no effect on the triatomine behaviour, solid CO2-baited traps were more effective in attracting M. spinolai than control (empty) traps. We conclude that CO2 trapping is an effective field technique for M. spinolai detection and potential control.
Animals↗