Spatial Distribution of Triatoma guasayana (Hemiptera: Reduviidae) in Hardwood Forest Biotopes in Santiago del Estero, Argentina

Abstract

In the study area Triatoma guasayana Wygodzinsky & Abalos is the only wild triatomine found sympatric with Triatoma infestans (Klug) in peridomestic premises. The Trypanosoma cruzi Chagas wild cycle is centered around the same biotopes occupied by T. guasayana, which are also visited mainly by opossums with annual prevalences of 29-50%. Twelve hectares were sampled for 4 consecutive years during all seasons. During that time, 420 T. Guasayana individuals were collected in 11.3% of 1,188 biotopes of 4 types, which included quimiles (the cactus Opuntia quimilo), chaguares (several species of bromeliads), trees, and logs. Quimiles had the highest percentage of positive biotopes (31.5%) followed by chaguares (22.3%), whereas 5% of the logs were found infested. During all seasons, 9.6-15.2% of biotopes were found infested. Distance to artificial biotopes was not statistically significant when comparing the frequency of triatomine numbers per biotope in all biotope-season combinations. With the exception of quimiles in the fall, the mean number of triatomines was higher in chaguares during all seasons. Triatomine abundance by biotope and season strata showed a clumped distribution, except for the quimiles biotope during the summer. When pooling by seasons, the mean number of triatomines in chaguares and quimiles biotope was higher than in logs and trees, with all biotopes showing a strong clumped distribution. When pooling by biotopes, the mean number of T. guasayana was relatively similar for all seasons, with a strong clumped distribution. The strong contagious distribution of T. guasayana in the hardwood forest biotopes may explain the maintenance of the wild cycle of T. cruzi, despite the low number and the low prevalences of the insect vector.

Characterization of Triatoma guasayana biotopes in a hardwood forest of Santiago del Estero, Argentina

“…Our results confirm previous observations in the same locality indicating that T. guasayana more frequently colonizes quimiles and chaguares than logs (Wisnivesky-Colli et al 1997). However, in the present study the mean number of triatomines recorded per biotope and the infestation rate were higher than those recorded previously.…”

“…Because T. guasayana selects biotopes regardless of their location in open (peridomestic) or forested (wild) areas (Wisnivesky-Colli et al 1997), the general environmental condition (macrohabitat) may not be a determinant factor. On the contrary, biotope structure seems to be a key factor for T. guasayana colonization.…”

“…Mean annual rainfall is 740 mm and relative humidity ranges between 55 and 68% (Anonymous 1982). The environmental features of the area have been described in a previous work performed between 1989and 1992(Wisnivesky-Colli et al 1997. In 1993, an intense deforestation resulted in scattered patches of forest.…”

“…Those biotopes, considered as wild parasite transmission foci, showed very low T. guasayana densities (Wisnivesky-Colli et al 1997), probably due to the methods used to capture triatomines. Conventional sampling methods (man/hour method, inspection using dislodging substances) do not ensure an accurate estimation of the population inhabiting a biotope.…”

Triatomines intrahaemocoelic inoculation protocol: a useful tool to check infectivity in insects

“…Such is the case of Triatoma guasayana and Triatoma patagonica [5,6]. Regarding triatomines in Colombia, 26 species have been reported, 15 out of them considered of epidemiological importance such as Triatoma dimidiata, Triatoma maculata and Rhodnius prolixus [7][8][9].…”