Urban Persistence of Triatoma infestans: Post-Spraying Reinfestation Dynamics and Evaluation of Alternative Surveillance Tools.

Abstract

Objectives: Chagas disease has shifted from a predominantly rural infection to an increasingly urban health concern. In the Southern Cone, Triatoma infestans remains the main vector of Trypanosoma cruzi and is frequently detected in Argentine cities, with urban areas of San Juan representing the principal hotspot of active vector-borne transmission. We evaluated post-spraying house-level T. infestans infestation persistence and compared detection by active manual searches (AS) with chemically baited adhesive sensors (CS).

Methods: The study was conducted in the metropolitan area of San Juan, Argentina, where 432 houses were inspected at baseline. Houses with detected triatomines and adjacent houses were sprayed with beta-cypermethrin. Follow-up surveys were performed at 1, 3, 6, and 12 months. During the first three surveys, previously infested houses were randomly assigned to either AS or CS detection methods; at 12 months, all houses were reassessed using AS.

Results: At baseline, 369 T. infestans (adults and nymphs) were detected in 20 houses. After spraying, infestation and abundance declined sharply and remained low over 12 months. Infested houses decreased from 20 to 5, and total abundance from 369 to 6 individuals. Most post-spraying detections were sporadic and low-density. Manual searches were the only method that consistently detected triatomine infestation. Although most highly infested houses showed marked reductions, one exhibited a later increase, and occasional shifts between outdoor and indoor infestation.

Conclusions: These findings indicate that residual spraying can reduce T. infestans infestation in urban settings for at least 1 year, and that active manual searches show a strong operational performance for detecting low-density residual infestations during urban surveillance compared to chemically baited sensors.