Feeding and Defecation Patterns of Nymphs of Triatoma rubrofasciata (De Geer, 1773) (Hemiptera: Reduviidae), and its Potential Role as Vector for Trypanosoma cruzi

Abstract

Although Triatoma rubrofasciata is occasionally found naturally infected by Trypanosoma cruzi (AR da Silva 1983 Trans R Soc Trop Med Hyg 77: 568-569, RP Brazil et al. 1985 it is not considered an important vector of Chagas disease. It is normally the vector of Trypanosoma conorhini which infects Rattus rattus since this insect is in close association with the rat. It is found mostly in port cities (H Lent & P Wygodzinsky 1979 Bull Am Mus Nat Hist 163: 125-520) and the knowledge on its biology is still scarce.Aiming at understanding the role of this species in the transmission of Chagas disease, the feeding and defecation patterns of nymphs of each instar were observed.The eggs and nymphs were separated from a colony maintained in the Laboratory of Biology and Control of Vector Insects, Oswaldo Cruz Institute. As soon as the hatchings occurred, or 5 to 10 days after molting, the nymphs were separated and fed individually on Swiss mouse. The mouse was immobilized in a nylon mosquito net "sandwich", put in a wide glass container, and the nymphs were allowed to search for the food source for a maximum period of 2 hr. The following parameters were observed for all instar nymphs: time spent to begin feeding, duration of feeding, number of interruptions during feeding and number of times that the nymphs eliminated a dark excreta and a clear excreta during and soon after feeding. The data were statistically analyzed by the KruskalWallis one-way test and the Chi-square test (S Siegel 1956 Nonparametric Statistics for the Behavioral Sciences, New York, 350 pp).In all instars more than 70% of the nymphs spent less than 10 min to begin feeding after being placed in the glass container, although some of them, from 1st to 4th, have spent more than 20 min. Among these, the major percentage occurred in the 2nd instar (20%) and the lesser in the 1st (7%). All 5th instar nymphs began feeding before 20 min after being placed in the container. With exception of the 3rd instar, approximately 60% of the nymphs from 1st, 2nd, and 4th instars and 90% from the 5th instar spent more than 15 min feeding. More than 50% of the nymphs from the 1st to the 4th instar and 35% from 5th instar did not interrupt feeding.Comparing the results for all instars shown in Table I, the statistical analysis was significantly different for the duration of feeding (H=20.5, P<0.05). The time spent to begin feeding and the number of interruptions during feeding did not show any statistical difference (H=2.1, P>0.05 and H=1.3, P>0.05, respectively). However, some discrepancies occurred. In the 2nd instar, one nymph spent 54 min to begin feeding and only 17 min to feed and in the 3rd instar, a nymph spent 39 min to begin and only 11 min to feed. Table II shows the percentages of nymphs that eliminated the dark and clear excreta during or soon after feeding. The percentages of defecation during feeding were very low (maximum of 5% in the 5th instar) and defecation soon after feeding on or near the host were lower than 10% in all instars. However, approximate...

Assessment of the anti‐feeding and insecticidal effects of the combination of dinotefuran, permethrin and pyriproxyfen (Vectra®3D) against Triatoma infestans on rats

“…This strong feeding rate showed that the population of T. infestans used in the experiment was robust and the challenge was reliable. This is consistent with previous observations in experiments conducted in Triatoma rubrofasciata fed on Swiss mice (Braga & Lima, ) and T. infestans fed on Sprague–Dawley rats, in which more than 86% of bugs were seen to bite the host (Canals et al ., ). The single topical treatment of DPP had an immediate effect after administration, as demonstrated by the high anti‐feeding efficacy (> 80%) that started at day 1 and lasted until day 21 after treatment.…”

Excretion/defecation patterns in Triatoma infestans populations that are, respectively, susceptible and resistant to deltamethrin

“…Efficient vectors defecate during and shortly after feeding. Several authors have studied defecation patterns during and after feeding in different triatomine species (Wood, ; Zeledón et al ., ; Trumper & Gorla, ; Crocco & Catalá, ; Braga & Lima, ; Nattero et al ., ; Almeida et al ., ; Rodríguez et al ., , ; Reisenman et al ., ) and, according to their respective patterns, assessed the competence of these species as T. cruzi vectors.…”

Fine structure of the male accessory glands of Triatoma rubrofasciata (De Geer, 1773) (Hemiptera, Triatominae)

“…It is commonly the vector of Trypanosoma conorhini, which infects Rattus rattus, and this insect is in close association with the rat. Natural infection of T. rubrofasciata with T. cruzi has been reported in Brazil (Dias and Neves, 1943;Lucena, 1940) although, the biting and defecation habits of this bug make it a relatively inefficient vector (Braga and Lima, 1999).…”