Against the flow: flooding and its impact on phlebotomine bionomics in the Chaco region, Argentina

Tegumentary leishmaniasis in Argentina presents multiple hotspots and sporadic outbreaks, especially in the Humid Chaco. This study examined ecological and behavioral adaptations of phlebotomine sandflies in flood-affected areas, focusing on breeding sites, vertical stratification, and seasonal abundance, with emphasis on the dominant vector Nyssomyia neivai. The influence of flooding, climate variables, and environmental change on disease risk and control strategies was assessed. Sampling was conducted (2011–2014) in Puerto Antequeras, Chaco, across domicile, peridomicile, and extradomicile ecotopes. From September 2011 to December 2012, eight mini-CDC light traps were installed monthly at ground level (1.5 m) and in canopies (10 m), also soil samples were collected. From January 2013 to December 2014, ground-level mini-CDC and emergence traps were used. Meteorological data informed negative binomial models relating sandfly abundance to climatic and ecological variables. A total of 28462 phlebotomines were captured in the first period and 32009 in the second, with Ny. neivai dominant, particularly in the extradomicile. Abundance was greater at ground level, but canopy fauna was more diverse. Peaks occurred in summer and spring, and abundance increased post-flooding. Minimum temperature positively affected abundance, whereas river height and precipitation were negative predictors. In the first period, soil samples produced only one Ny. neivai male; emergence traps produced 15 individuals emerged from five traps, mainly in the extradomicile, peaking in autumn. Emergence increases with minimum temperature and decreases with precipitation. Flooding may shift breeding sites, and climate change could increase urban transmission risk. Control should integrate vector surveillance with habitat management.