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

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.