Population dynamics and feeding behavior of Triatoma brasiliensis and Triatoma pseudomaculata, main vectors of Chagas disease in Northeastern Brazil

Abstract

Biological parameters of Triatoma brasiliensis and T. pseudomaculata that could influence the epidemiological importance of these insects as vectors ofTriatoma brasiliensis Neiva, 1911 and T. pseudomaculata Corrêa & Espínola, 1964 are the most important vectors of Trypanosoma cruzicausative agent of Chagas disease -in the arid caatinga region of Northeastern Brazil. Both species occupy a range of domestic, peridomestic, and sylvatic ecotopes, with T. brasiliensis often associated with small rodents amongst rocky outcrops, and T. pseudomaculata more usually associated with birdnests and hollow trees (Forattini et al. 1981). Application of residual insecticides can eliminate domestic colonies of both species, but houses can then be reinvaded from the silvatic and peridomestic habitats. Our aim in this study, was to compare the two species in terms of various factors that could influence their epidemiological importance as domestic vectors of T. cruzi. MATERIALS AND METHODSSpecimens of T. brasiliensis were collected from peridomestic habitats in the municipality of Simplício Mendes, State of Piauí, and specimens of T. pseudomaculata were similarly collected in the municipality of Crateús, State of Ceará, Brazil. Eggs from the collected adults (40 from T. brasiliensis, 33 from T. pseudomaculata) were placed individually in small pots and observed daily until eclosion. The resulting nymphs were offered a daily feed on an anaesthetized mouse. Those that started feeding were allowed to engorge; those that did not start to feed within 30 min were left until the following day. Once bugs had taken a first blood meal, they were then offered a weekly feed. This regime (maintained at 24 ± 2ºC; 56 ± 6% rh) allowed us to establish the incubation period, the interval between hatching or moulting and the first feeding, the number of blood meals required by each instar, the development time, the net reproductive rate (Ro) and the instantaneous daily reproductive rate (r). In the case of 4th and 5th instar nymphs and adults, we also noted the time-lapse before starting feeding, the duration of feeding and timing of defecation.To determine bloodmeal intake, we used 30 bugs of each instar, weighed before and immediately after feeding. The blood meal intake ratios were calculated in relation to the body weight of each insect using the formula (R = (Wf -Wi)/Wi), where Wf is the weight after feeding (mg) and Wi is the weight before feeding. Blood ingestion velocity was calculated by the formula (V = Wb/T), where Wb is the ingested blood weight (mg) and T is the interval time (minutes) between the beginning and the end of the feeding process.

Triatoma rubrovaria (Blanchard, 1843) (Hemiptera-Reduviidae-Triatominae) III: patterns of feeding, defecation and resistance to starvation

“…Table II shows the defecation patterns for males and females reported by several authors for various species during the blood meal or in less than 1 min after the feeding. Accordingly, it was found that the females of T. rubrovaria demonstrate defecation rates similar to those obtained for T. infestans (Dias 1956, Zeledon et al 1977 and for T. brasiliensis, and T. pseudomaculata (Soares et al 2000). It is important to emphasize that according to the Brazilian Health Foundation (Funasa), in RS, the records of domiciliary positivity for T. rubrovaria refer to capture and notification of adult specimens (Almeida et al 2000).…”

“…This correlation was not observed for other triatomine species, such as Triatoma dimidiata (Latreille, 1811), T. infestans, and R. prolixus (Zeledon et al 1977). Soares et al (2000) carried out studies on biological parameters of T. brasiliensis Neiva, 1911 andT. pseudomaculata Corrêa &Espínola, 1964 associated to their epidemiological importance as vectors of T. cruzi.…”

“…The assessment of the vectorial capacity of the triatomines through biological studies is essential to define monitoring actions and serves as a basis for control measures (Perlowagora-Szumlewics 1969, Costa 1999, Soares et al 2000. In order to clarify bionomic aspects that could influence the vectorial capacity of T. rubrovaria, the patterns of feeding, defecation and resistance to starvation were evaluated.…”

Comparación de los patrones de alimentación y defecación de Rhodnius colombiensis y Rhodnius prolixus (Hemiptera, Reduviidae, Triatominae) en condiciones de laboratorio

“…Por otro lado, Rocha da Silva D. et al mostraron que los adultos de R. pictipes presentan mayor timidez y que, por lo tanto, en ellos transcurre mayor tiempo entre el ofrecimiento de la comida y la picada (6). Igualmente se observó en los adultos de T. brasilensis un mayor tiempo entre el ofrecimiento de la comida y la picada que en los demás estados ninfales; en T. pseudomaculata las N4 fueron más tímidas para la toma del alimento que los demás estadios ninfales (7). Una posible causa de esta variabilidad en el comportamiento de los triatominos con relación al tiempo transcurrido entre el ofrecimiento de la comida y la picada podría ser la fuente de alimento, como fue sugerido por Martínez-Ibarra et al, quienes observaron que cuando Meccus picturatus es alimentado sobre gallinas, los adultos son más tímidos para iniciar la picada que los restantes estadios ninfales, pero cuando esta misma especie es alimentada sobre conejos, las N4 son las más tímidas (8).…”

Toxicological profile of deltamethrin in Triatoma brasiliensis (Hemiptera: Reduviidae) in State of Ceará, Northeastern Brazil

“…The species of greatest epidemiological relevance in this region is Triatoma brasiliensis. Studies conducted in Bahia (2) , Piauí (3) and Ceará (4) have indicated that T. brasiliensis is the most common species in domestic environments, occasionally forming colonies of more than 100 specimens (5) and having high levels of natural infection via Trypanosoma cruzi; thus, this species is one of the most effi cient transmitters of CD to humans. Domestic infestation occurs more commonly during the dry season, and triatomines are usually attracted to light (6) .…”