Resistance to starvation of Rhodnius neivai Lent, 1953 (Hemiptera: Reduviidae: Triatominae) under experimental conditions.
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The period of resistance to starvation and the loss of weight until death of Rhodnius neivai in all stages of development were studied. Work was based on experiments conducted under controlled laboratory conditions. One hundred specimens of each nymphal instar were observed: 50 were fed on chicken and 50 on rabbit. Adult females and males were kept together and fed on each host. All bugs were weighed weekly until death. Laid eggs were collected weekly and observed during five weeks to obtain hatchability. Resistance to starvation was similar with both hosts and increased with the evolutionary stage, excepting the 5th nymphal instar and adults. With both hosts, loss of weight was abrupt in the first week and steady in the following weeks. In adults, on the first weeks after eating, there was little or no mortality, after which mortality increased rapidly with the starving time. Reproductive output was higher in the bugs fed on rabbit. R. neivai is among the least resistant triatomine species. (+info)
Biogeography of Triatominae (Hemiptera: Reduviidae) in Ecuador: implications for the design of control strategies.
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Chagas disease control strategies strongly depend on the triatomine vector species involved in Trypanosoma cruzi transmission within each area. Here we report the results of the identification of specimens belonging to various species of Triatominae captured in Ecuador (15 species from 17 provinces) and deposited in the entomological collections of the Catholic University of Ecuador (Quito), Instituto Oswaldo Cruz (Brazil), the Natural History Museum London (UK), the London School of Hygiene and Tropical Medicine (UK), the National Institute of Hygiene (Quito), and the Vozandes Hospital (Quito). A critical review of published information and new field records are presented. We analysed these data in relation to the life zones where triatomines occur (11 life zones, excluding those over 2,200 m altitude), and provide biogeographical maps for each species. These records are discussed in terms of epidemiological significance and design of control strategies. Findings relevant to the control of the main vector species are emphasised. Different lines of evidence suggest that Triatoma dimidiata is not native to Ecuador-Peru, and that synanthropic populations of Rhodnius ecuadoriensis in southern Ecuador-northern Peru might be isolated from their sylvatic conspecifics. Local eradication of T. dimidiata and these R. ecuadoriensis populations might therefore be attainable. However, the presence of a wide variety of native species indicates the necessity for a strong longitudinal surveillance system. (+info)
Adult and nymphs of Microtriatoma trinidadensis (Lent, 1951) (Hemiptera: Reduviidae) caught from peridomestic environment in Bolivia.
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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 & Galvao 1993. The exceptional finding of M. trinidadensis in peridomestic environment, illustrates the general tendency of triatominae to adapt to human dwellings and dependences. (+info)
Rhodnius robustus in Bolivia identified by its wings.
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Wings of a Rhodnius specimen from Alto Beni (Bolivia) was examined for identification and compared with R. stali, R. robustus, (certified Bolivian species), R. pictipes and R. prolixus (suspected Bolivian species). A projection of the unidentified wings as supplementary data into a discriminant analysis of shape revealed clear cut differences with R. stali and R. pictipes, less differences with R. prolixus, and none with R. robustus. Combining global size and shape of the wings, the unknown specimen was identified as R. robustus. Thus, this study confirmed the presence of R. robustus in Bolivia. It also highlighted the possibility of morphometrics to taxonomically interpret one individual, or even one piece of an individual, when related species data are available for comparison. (+info)
Differentiation and genetic analysis of Rhodnius prolixus and Rhodnius colombiensis by rDNA and RAPD amplification.
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Domiciliated Rhodnius prolixus and sylvatic R. colombiensis were analyzed in order to confirm their genetic divergence and verify the risk that the latter represents in the domiciliation process, and to provide tools for identifying the sources of possible reinfestation by triatomines in human dwellings allowing control programs to be undertaken. Comparison of random amplified polymorphic DNA amplification patterns and cluster analysis suggests reproductive discontinuity between the two species. The calculated statistical F value of 0.24 and effective migration rate of 0.6 individuals per generation are insufficient to maintain genetic homogeneity between them and confirm the absence of present genetic flow. R. colombiensis presents higher intrapopulation variability. Polymerase chain reaction of ribosomal DNA supports these findings. The low genetic flow between the two species implies that R. colombiensis do not represent an epidemiological risk for the domiciliary transmission of Trypanosoma cruzi in the Tolima Department. The lower variability of the domiciliated R. prolixus could result in greater susceptibility to the use of pesticides in control programs. (+info)
Effect of diet viscosity on the operation of the pharyngeal pump in the blood-feeding bug Rhodnius prolixus.
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1. The rate of pumping and total number of pump strokes was recorded whilst Rhodnius prolixus fed on measured amounts of artificial diets. 2. Increasing the viscosity of the diet caused a decline in both the frequency with which the pharyngeal pump operates and the average stroke volume of the pump. 3. In 5th-instar Rhodnius, the stroke volume tends toward a maximum value of about 60 nl at viscosities lower than about 3 cP. 4. Feeding rates (volume per unit time) agree with Poiseuille's law at high viscosities, but are less than predicted at low viscosities. 5. The maximum power output of the pump occurs at a viscosity between 1 and 3 cP, which is probably the range of the effective viscosity of blood in tubes with the dimensions of Rhodnius stylets. 6. These results are inconsistent with a hypothesis of a central nervous system 'oscillator' controlling the pump muscle, independent of feedback, but are consistent with a model involving peripheral feedback from stretch receptors, with an appropriate delay. (+info)
On the pro-oxidant effects of haemozoin.
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Haemozoin (Hz) is a haem aggregate produced in some blood-feeding organisms. There is a general belief that Hz formation would be a protective mechanism against haem toxicity. Here we show that when aggregated into Hz, haem is less deleterious than its free form. When haem was added to phosphatidylcholine (PC) liposomes, there was an intense stimulation of oxygen consumption, which did not occur when Hz was incubated with the same preparation. Evaluation of oxygen radical attack to lipids, by measurement of thiobarbituric acid reactive substances (TBARS), showed significantly lower levels of lipid peroxidation in samples containing PC liposomes incubated with Hz than with haem. However, TBARS production induced by Hz was much higher when using 2-deoxyribose (2-DR) as substrate, than with PC liposomes. Spin-trapping analysis by electron paramagnetic resonance (EPR) of Hz and tert-butylhydroperoxide (tert-BuOOH) showed that production of methoxyl and tert-butoxyl radicals was only slightly reduced compared to what was observed with haem. Interestingly, when large Hz crystals were used in 2-DR TBARS assays and tert-BuOOH EPR experiments, the pro-oxidant effects of Hz were strongly reduced. Moreover, increasing concentrations of Hz did not induce erythrocyte lysis, as occurred with haem. Thus, the reduced capacity of Hz to impose radical damage seems to result from steric hindrance of substrates to access the aggregated haem, that becomes less available to participate in redox reactions. (+info)
Is Rhodnius robustus (Hemiptera: Reduviidae) responsible for Chagas disease transmission in Western Venezuela?
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We present evidence for the putative role of Rhodnius robustus as extradomestic vector of Chagas disease in Western Venezuela. First, we assessed the validity of this triatomine species by genetic characterization in relation with some other species of the prolixus group. Random amplified polymorphic DNA data showed a clear separation between this species and R. prolixus and indicated a probable genetic heterogeneity within R. robustus. Faeces and gut contents were microscopically examined in 54 of 137 R. robustus collected in palm trees. According to this morphological examination, 18% were positive for Trypanosoma cruzi, 11% harboured T. rangeli and 11% showed mixed infection. Five of the seven samples examined gave a polymerase chain reaction major band of 270 bp specific of T. cruzi. The hybridization probes showed that R. robustus may transmit clones 20 and 39 (or genetically related ones) in Venezuela. Such a transmission might occur when, in absence of domestic R. prolixus and attracted by artificial light, R. robustus enters houses and feeds on humans, or when people are bitten outdoors. The lack of bugs inside houses could mean that the insects leave houses after feeding, or die without reproducing there. (+info)