SPATIAL-DISTRIBUTION OF TRIATOMA GUASAYANA (HEMIPTERA, REDUVIIDAE) INHARDWOOD FOREST BIOTOPES IN SANTIAGO DEL ESTERO, ARGENTINA

In the study area Triatoma guasayana Wygodzinsky & Abalos is the only wild triatomine found sympatric with Triatoma infestans (Klug) in peri domestic premises. The Trypanosoma cruzi Chagas wild cycle is centered around the same biotopes occupied by T. guasayana, which are also vis ited mainly by opossums with annual prevalences of 29-50%. Twelve hect ares were sampled for 4 consecutive years during all seasons. During t hat time, 420 T. guasayana individuals were collected in 11.3% of 1,18 8 biotopes of 4 types, which included quimiles (the cactus Opuntia qui milo), chaguares (several species of bromeliads), trees, and logs. Qui miles had the highest percentage of positive biotopes (31.5%) followed by chaguares (22.3%), whereas 5% of the logs were found infested. Dur ing all seasons, 9.6-15.2% of biotopes were found infested. Distance t o 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 nu mber of triatomines was higher in chaguares during all seasons. Triato mine abundance by biotope and season strata showed a clumped distribut ion, except for the quimiles biotope during the summer. When pooling b y seasons, the mean number of triatomines in chaguares and quimiles bi otope was higher than in logs and trees, with all biotopes showing a s trong 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. guasaya na in the hardwood forest biotopes may explain the maintenance of the wild cycle of T. cruzi, despite the low numbers and the low prevalence s of the insect vector.