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PubMedDate not supplied

[The prevalence, infection indices and feeding habits of the Triatominae captured in an area of epidemiological surveillance].

Prevalence of triatomines and their infection by Trypanosoma cruzi, were studied during 1974-1981, in the Administrative Region of Campinas, São Paulo, Brazil. This investigation was continued (1982-1986), blood meal tests with bird, marsupial, rodent and human antisera having been added. Panstrongylus megistus, predominant in the region, whose winged instars are often found infected by T. cruzi in inhabited houses, displayed and alimentary eclecticism. From a sample of 7,785, 14.78 percent reacted positively with human antisera. A similar, but less marked behaviour was observed in Rhodnius neglectus. Triatoma sordida, the second most important species in the Region, was neither demonstrated to be feeding on humans nor to be infected by T. cruzi. Changes in their natural habitat probably caused sharp rises in T. arthurneivai populations in the human dwellings. The capture of three specimens of Microtriatoma borbai marks the first occurrence of this species in the State São Paulo. "Focus investigation" in areas in the surveillance phase can detect triatomines in the process of domiciliation.

Animals↗
PubMedDate not supplied

[Importance of the method for obtaining feces from triatominae in the assessment of triatomine susceptibility to Trypanosoma cruzi].

Two patients on the acute phase of Chagas' disease were submitted to xenodiagnosis examination with different species of triatomine bugs, in order to study bug susceptibility to Trypanosoma cruzi. Species used were Dipetalogaster maximus, Rhodnius neglectus, R. prolixus, R. robustus, Triatoma infestans and T. rubrovaria. Both the number of infected bugs, and the number of excreted trypanosomes by bug, were used as parameters for evaluation of species susceptibility. Xenodiagnosis reading was performed by two methods, the classic abdominal compression and the spontaneous dejection method; this was more efficient than the former in relation to the number of parasites per wet smear (by Wilcoxon test). When susceptibility was evaluated by the number of infected bugs, in one of the patients all D. maximus and R. neglectus became infected (100%), 95% of R. robustus, 90% of R. prolixus and T. rubrovaria, and 85% of T. infestans. When evaluation was performed through the number of excreted parasites in this patient with reading by abdominal compression, the higher susceptibility was with R. neglectus, followed by R. prolixus, D. maximus and R. robustus, T. infestans and T. rubrovaria; reading by spontaneous dejection yielded better results for D. maximus and R. prolixus followed by T. rubrovaria, R. robustus, T. infestans and R. neglectus. For the other patient susceptibility evaluated by the number of excreted parasites was similar by both reading methods and did show the same susceptibility pattern (R. neglectus and then T. rubrovaria and T. infestans), but the number of excreted trypanosomes was much higher by the spontaneous dejection method.

Adolescent↗
PubMedDate not supplied

[Morphogenetic effects of precocene II on nymphs of Rhodnius prolixus (Stal, 1859) (Hemiptera-Triatominae)].

The morphogenetic effects of Precocene II in nymphs of 1st-, 2nd-, 3rd-, and 4th-instar of Rhodnius prolixus were studied. A high number of insects underwent precocious metamorphosis by topical treatment (10-30 micrograms/insect) or adding the drug to the blood meal (25 micrograms/ml of blood). Adultoids of 4th- and 5th-instar, obtained by both treatments of 3rd- and 4th-instar, respectively, had mainly fully adult abdominal cuticle, ocelli, three segmented tarsi, rudimentary wings containing adult articulation with the thorax and deformed genitalia while adultiforms of 2nd- and 3rd-instar had very slight imaginal morphological characteristics. Topical treatment induced a high mortality in nymphs of 1st-instar and Precocene II given orally produced a high number of adultoids in this instar. The mode of application and the action of Precocene II on different nymphal instars were interpreted.

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PubMedDate not supplied

Efficacy of ivermectin against the bloodsucking insect, Rhodnius prolixus (Hemiptera, Triatominae).

Ivermectin (0.2 mg/kg body weight) caused a high mortality in nymphs and adults of Rhodnius prolixus following a single meal in mice sub-cutaneously injected with the drug. This effect was more evident in nymphs of 1st-and 2nd-instar than in older nymphs and adults. Third-instar nymphs presented a high mortality when fed on mice treated with ivermectin 24 and 48 hours previously, while mortality was significantly reduced in nymphs fed on mice treated 72 hours before. Surviving 3rd-instar nymphs did not molt. When adult females were fed once on mice treated for 24 hours with ivermectin there was a considerable reduction in egg production. This inhibition was not reversed by a second feeding on normal mice. We concluded that sub-lethal doses of ivermectin caused toxic effects interfering in the neuro-endocrine control of development and reproduction of this bloodsucking insect.

Animals↗
PubMedDate not supplied

[Biology of Triatoma vitticeps (Stal, 1859) under laboratory conditions (Hemiptera: Reduviidae: Triatominae). I. Evolutive cycle].

Observations were made on the evolutive cycle of Triatoma vitticeps, held under laboratory conditions and fed weekly in mice. Of the 435 eggs obtained, from 4 virgin couples, 149 were purposed for the biological cycle study and 286 to evaluate their resistance to starvation, which shall be a second part of this work. Only 50 specimens reached the adult stage in a period of means (S) = 270 +/- 45 days. At the incubation time, the first and second instars were of less than a month for each, while the third, fourth and fifth instars requires approximately one, two and three months, respectively. The search for the first meal occurred clearly on the 3rd, 6th and 10th day. During all the stages, more than 50% of the specimens had only one blood-meal, except the fifth one, when two blood-meals were required. In relation to the time-lapse between the presenting of the blood-meal and the beginning of feeding, as well as the length of the blood-meal, it was observed that these increased gradually according to the stage. From the 423 blood-meals performed, 390 were not followed by defecation in the settled period of 10 min. Under this point of view, T. vitticeps seems to be a poor transmissor of T. cruzi. The experiment was carried out for 13 months and by this time the averages of minimum and maximum temperatures and the humidity were 25 +/- 2 degrees C - 28 +/- 2 degrees C and 80 +/- 2%, respectively. The material belongs to the triatomine colony held at the Oswaldo Cruz Institute, Department of Entomology.

Animals↗
PubMedDate not supplied

[Biology of Triatoma vitticeps (Stal, 1859) under laboratory conditions (Hemiptera: Reduviidae: Triatominae). II. Resistance to fasting].

Following the study on the biology of Triatoma vitticeps (Gonçalves et al., 1988) observations have been made on its resistance to starvation. Of the 286 eggs obtained only 201 hatched and reached the intended stage for observation. The others did not eclode, neither reached the ecdisis nor died, without explanation. The nymphs were kept, separately, in Borrel flasks and properly listed. The blood-meal was performed in mice, although the insects were kept without feeding as soon as moulted. The starvation was evaluated in two ways: the time-lapse in days between the last meal/death and between moult/death. The starvation was directly related with the developmental stage. In relation to the parameters last meal/death and moult/death, both sexes were less resistant than 3rd and 2nd stage, respectively. The experiment have been carried out for 15 months and by this time the average minimum and maximum temperatures and the humidity were 25 +/- 2 degrees C - 28 +/- 2 degrees C and 81 +/- 3% UR, respectively. The material spent belongs to the triatomine colony of the Oswaldo Cruz Institute Department of Entomology.

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PubMedDate not supplied

[Bionomic studies of Cavernicola lenti Barrett & Arias, 1985 (Hemiptera, Reduviidae, Triatominae)].

In the biological study, the development of the biological cycle of the insect under different feeding conditions was evaluated. The insects were fed on either mouse blood (c) or pigeon blood (p) using two types of rearing techniques (individual or group) at 28 degrees C and 90% relative humidity (which is equivalent to their natural environment). A fifth cycle studied, was fed on mouse blood reared on group, and maintained at laboratory environmental temperature. In the five cycles analyzed, it was found that groups on mouse blood at near natural conditions developed more rapidly (between 60 and 73 days) and had a lower rate of mortality (16.66%). The daily handling and changes in environment, of the individually reared insects, for observation of biological characteristics (no. and duration of bloodmeal, defecation and first fed of each stage) had a negative influence. None of the individuals fed on mouse or pigeon blood reached adult hood. It was found that the longevity and the fertility rate were significantly superior on couples maintained individually on mouse blood. These males had an average lifespan of 110.26 days and the females had an average lifespan of 104.46 days. The average number of eggs laid by each female was 21.26. Four couples kept in groups (five couples in each group) under the same condition, the longevity for males was 51.86 days and for females was 81.06 days. An average of 10.5 eggs were laid by each female. However, the percentage of fertile eggs was higher in couples kept in groups (72.15%) than in the individual couples (57.68%).

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PubMed1992

[Bionomic studies of Dipetalogaster maximus (Uhler, 1894) (Hemiptera, Reduviidae, Triatominae). III. Population dynamics].

A population dynamics study of D. maximus was carried out under laboratory conditions (28 degrees C e 65% +/- 5% U.R.), and the methodology was the same that has been used for rearing these insects. In order to evaluate the population growth rate of this species, during a 24 months period, five colonies started with a couple recently emerged were observed. Each couple (a male and a female) was maintained in a glass container measuring 20 cm of diameter and 20 cm in height with filter paper on the bottom. The insects were monthly feeding with normal mice blood, and at this day the number of eggs, nymphal stages and adults was registered. All graphical representations of the populations growth showed the same shape. It was found that the average of nymphal stage represented 64.3% of the holè population whereas the oviposition curve showed to be inverse to this one (28.57%) a small percentage of adults was found: males 3.85% and females 3.12%. In this study observations on the biological cycle, longevity and fertility rates were also carried out.

Animals↗
PubMedDate not supplied

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.

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