Vectorial capacity of Triatoma guasayana (Wygodzinsky & Abalos) (Hemiptera: Reduviidae) compared with two other species of epidemic importance

Abstract

-Triatoma guasayana (Wygodzinsky & Abalos) is a peridomestic triatomine with epidemiological importance in Bolivia, that may play an important role in the transmission of Trypanosoma cruzi (Chagas). In this study, two parameters of vectorial capacity were evaluated: the interval of feeding-defecation time and metacyclogenesis, in adult males and females and nymphal instars II to V of T. guasayana with comparisons with Triatoma infestans (Klug) and T. sordida (Stal). The results showed a close relationship between ingestion of blood and beginning of defecation. Values were negative in T. infestans, and T. sordida for instars II, III, IV, and V and also males and females but were positive in female T. sordida. Triatoma guasayana showed only negative values for instar II. Adults and nymphs began defecation as soon as they had finished feeding and required an average of 29.8 min. The analysis of metacyclogenesis showed that T. guasayana was superior to T. infestans and T. sordida. However, the vectorial effectiveness of T. guasayana was significantly affected regarding the percentage of metacyclic trypomastigotes during instars III to V and showed a progressive increase. Females had higher proportions despite their ingestion being half that of T. infestans. The different instars of T. guasayana had a higher parasitic load than those of T. sordida and, although ingestion was 1/3 of that of female T. infestans, there was a progressive increase in metacyclic trypomastigotes in the different nymphal stages of T. guasayana that decreased in adults.

Feeding and Defecation Behavior of Triatoma rubida (Uhler, 1894) (Hemiptera: Reduviidae) under Laboratory Conditions, and Its Potential Role as a Vector of Chagas Disease in Arizona, USA

“…For instance, fifth-instar T. sordida and T. guasayana need to eat an average minimum of 60-100 and 115 mg of blood, respectively, for defecation to occur during feeding or soon thereafter. 23,33 In our experiments, although 52% of fifth-instar T. rubida ingested more than 100 mg of blood, we found that only 18% of those insects defecated while feeding. We also found that most female T. rubida ate 114 ± 9 mg (mean ± SE; median = 117 mg) of blood, which is more than the amount reportedly required for defecation to occur during feeding in female T. sordida and T. guasayana .…”

“…Similarly, it was also reported that adult males of Panstrongylus megistus and Triatoma barberi , and nymphs of Triatoma guasayana and Triatoma vitticeps , do not defecate while feeding. 17,23,32 Although we found that most juvenile insects and none of the adult males defecated while feeding, transmission of the parasite to humans can occur if the engorged insects remain in close contact with the host after feeding, possibly defecating and urinating to eliminate the extra weight gained during a blood meal. 18 Indeed, it has been proposed that triatomines that defecate within 10 minutes after the end of feeding are potentially effective vectors of T. cruzi .…”

“…We also found that most female T. rubida ate 114 ± 9 mg (mean ± SE; median = 117 mg) of blood, which is more than the amount reportedly required for defecation to occur during feeding in female T. sordida and T. guasayana . 23,33 Our experimental design, in which insects were allowed to feed ad libitum during the experimental period, did not allow us to establish this minimum value because all but one of the females tested defecated while feeding ( Figure 4A ). We found, however, that the amount of blood ingested by females correlated negatively with the time to the first defecation, as described in other triatomine species.…”

“…21 Other important factors that determine transmission of T. cruzi to humans include the frequency of contacts between infected triatomines and humans, the rate of infection of triatomines with T. cruzi , and the frequency of infective parasites in feces. 22,23 In the United States, and particularly in Arizona, Chagas disease could become a health problem because human populations are rapidly expanding into habitats where infected triatomines and wild mammalian reservoirs are plentiful. 4,6,24 Arizona is noteworthy as the state with the highest number of triatomine-human contacts reported in the United States (sources: American Association of Poison Control Centers, Arizona Poison and Drug Information Center, and University of Arizona Health Sciences Center).…”

Comportamiento alimenticio de Rhodnius robustus Larrousse, 1927 (Hemiptera, Reduviidae) en condiciones de laboratorio

“…Sin embargo, debido a que algunos triatominos silvestres pueden llegar al peridomicilio o hacer intrusiones dentro del domicilio, es necesario tener en cuenta las características de su biología que favorezcan su competencia vectorial. Esta última se entiende como la habilidad de un vector (artrópodo o molusco) para transmitir un agente patógeno mediante diversos factores determinantes biológicos, como: supervivencia; características anatómicas, especialmente del aparato bucal y sistema digestivo; características fisiológicas, como la cantidad de sangre ingerida y el tiempo de emisión de la primera deyección en el caso de insectos que ya se encuentran infectados; además de características genéticas de los vectores, como la propensión a la infección por las distintas unidades discretas de tipificación (Discrete Unit of Typification, DTU) de T. cruzi (2,3) Los vectores de T. cruzi pueden dividirse en vectores primarios, o principales, y secundarios. Las especies consideradas vectores primarios son aquellas que pueden colonizar las viviendas en altas densidades, tienen acentuada antropofilia y altas tasas de infección con T. cruzi.…”