Vanda Cunha

Trapping Triatominae in Silvatic Habitats

Large-scale trials of a trapping system designed to collect silvatic Triatominae are reported. Live-baited adhesive traps were tested in various ecosystems and different triatomine habitats (arboreal and terrestrial). The trials were always successful, with a rate of positive habitats generally over 20% and reaching 48.4% for palm trees of the Amazon basin. Eleven species of Triatominae belonging to the three genera of public health importance (Triatoma, Rhodnius and Panstrongylus) were captured. This trapping system provides an effective way to detect the presence of triatomines in terrestrial and arboreal silvatic habitats and represents a promising tool for ecological studies. Various lines of research are contemplated to improve the performance of this trapping system.

Biologia do triatoma vitticeps (Stal, 1859) em condiçoes de laboratórios (Hemiptera: Reduvidae: Triatominae) I. Ciclo evolutivo

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 virgen 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 X (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 occured 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°C - 28 ± 2°C and 80 ± 2%, respectively. The material belongs to the triatomine colony held at the Oswaldo Cruz Institute, Department of Entomology.

Alguns aspectos da biologia de Triatoma pseudomaculata Correa & Espinola, 1964, em condicoes de laboratorio (Hemiptera: Reduviidae: Triatominae)

: Observations were made on the evolutive cycle of Triatoma pseudomaculata, held under laboratory conditions, fed weekly on bird (pigeon). Of 60 eggs obtained, only 34 nymphs reached the adult stage in a period of X(S) = 398 +/- 76 days. The following parameters were observed: the time immature stages took to develop from egg to adult emergence; the occurrence of the first meal; the time-lapse between the presenting of the blood-meal and the beginning of feeding; time of feeding; amount of blood ingested; variation of weight 24 hr after the blood-meal and until the next blood-meal; and the defecation pattern. The experiment was carried out for 20 months, held in BOD incubator with the average of temperature and humidity of 28 +/- 1 degrees C and 80 +/- 5% RU, respectively.

Biologia do Triatoma nitida Usinger, 1939 em laboratório (Hemiptera: Reduviidae)

Triatoma nitida is a wild species occurring in Mexico and Central America. In order to establish the length of its life cycle and transmission potential, the following parameters were observed: the incubation period, the interval between hatching, or moulting, and the first feeding; the number of blood meals and the time of development. The time-lapse before the bite, the length of feeding and the interval between the end of the blood meal and defecation, as well as the site of defecation were also analyzed. Average length of the egg incubation period was 18.2 days. Time interval between the food source offering and the bite was less than 4 min in 60//of the analyzed cases, except in the fifth instar, where only 38//of the insects began feeding in less than 5 min. The blood-sucking period was long and rising until the fifth instar, decreasing in adults, and ranging from 1 min to 2 and a half hours. Only 26//of the blood meals were followed by defecations within 20 min. The average length of the life cycle was 897.5 days.

Foco de doença de Chagas em Arcádia, estado do Rio de Janeiro, Brasil

Following the report of triatomine nymphs in a house in Arcadia, Miguel Pereira, state of Rio de Janeiro, Brazil, the infested dwelling was checked. Several eggs and 46 specimens of Triatoma vitticeps (Stal, 1859) were collected. Among them, adults and nymphal instars accounted for 43.5% and 56.5%, respectively. Analysis of blood meals showed the ecletism of this species; 24 (52.2%) were single feeds, 18 insects (39.1%) fed on two hosts and 4 (8.7%) on three hosts. Trypanosoma cruzi infection rate of examined specimens was 13%. Finally one of the residents of the house was positive for anti-T. cruzi antibodies using indirect immunofluorescence.

Triatoma pintodiasi sp. nov. do subcomplexo T. rubrovaria (Hemiptera, Reduviidae, Triatominae)

Uma nova especie criptica de Triatoma e descrita dentro do subcomplexo T. rubrovaria. As diferencas entre T. pintodiasi sp. nov. e T. circummaculata incluem, entre outras, o padrao cromatico e diferencas morfologicas nas estruturas falicas, como nos parâmeros, suporte do falosoma, processo do endosoma e vesica. Analises bioquimicas realizadas na hemolinfa e a comparacao morfometrica da cabeca tambem registraram diferencas entre as duas especies e outras do subcomplexo T. rubrovaria.

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

Following the study on the biology of Triatoma vitticeps (Goncalves 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 mult/death. The starvation was directly related with the developmental stage. In relation to the parameters las 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 ± 2oC and 81 ± 3% UR, respectively. The material spent belongs to the triatomine colony of the Oswaldo Cruz Institut Department of Entomology.

Ciclo Biológico em Laboratório de Rhodnius brethesi Matta, 1919 (Hemiptera, Reduviidae, Triatominae), Potencial Vetor Silvestre da Doença de Chagas na Amazônia

R. brethesi is a sylvatic species from the Amazon region; it has been incriminated as responsible for the transmission of Chagas disease in collectors of piacaba in this region. The aim of present study was to investigate the efficiency of these insects as potential vectors of Trypanosoma cruzi. Aspects related with feeding and defecation patterns, life time, and mortality had been observed in each instar of R. brethesi. We use 5th instar nymphs to get adults virgins, after the moulting 3 groups with 6 females and 2 males each were created to obtain eggs. After hatching, 1st instar nymphs had been weighed and kept in bottles until the next moult. Insects were fed once a week in mice. Results showed that the average period of incubation was 17 days, the number of blood meal was increasing from the 1st to the 5th instar nymph with 7 (average) to become adult, a significative numbers of the defecations occurring immediately after the bloodmeals. The total percentual of mortality was 16%. This results suggests that this species presents a good exploitation of blood meals and a brief nymphal development in laboratory conditions reflecting its behavior in sylvatic environments.

Comparative biology of the two sister species of Triatominae (Hemiptera: Reduviidae).

INTRODUCTION Triatoma pseudomaculata and T. wygodzinskyi (Hemiptera: Reduviidae: Triatominae) are two Brazilian vectors of Chagas disease. The first is an arboricolous species in sylvatic environment and considered a vector of T. cruzi in peridomestic structures; the second, a rupicolous species in the wild environment of no epidemiological importance. In order to test the assumption that sister species share biological traits, comparative studies of their development cycle and blood ingestion were conducted. METHODS Eggs laid by five field females of each species were randomly selected. The nymphs were observed daily and fed on mice weekly. The time required to pass through the different stages to adulthood was recorded in days. The triatomines were weighed individually before and after feeding. The mortality rate according to each nymphal stage was calculated. RESULTS AND CONCLUSIONS Analysis of the results shows that they display only minor biological differences even though they exhibit a distinct ecology. This suggests that the biological traits are important criteria to determine the relationship between species.

Influência da temperatura no ciclo de vida de Triatoma melanosoma Martínez, Olmedo & Carcavallo, 1987 (Hemiptera, Reduviidae)

Authors studied the temperature influence in the life cycle of Triatoma melanosoma Martinez, Olmedo & Carcavallo, 1987. Two study groups were used, one was maintained at temperatures of 28 ± 1oC and 80 ± 5% RH, with a photophase of 12 hr, the other was kept at environmental temperature, daily recorded, and a RH varying from 70 to 90%. After hatching, insects were fed once a week on pigeons. Results were analyzed with the Mann-Whitney test, showing that a mean increase of 2oC was suficient for a significant acceleration of the embryonic development. Comparing nymphal stages of both groups, no significant differences were found, except in the second instar nymphs.