Ecological drivers of St. Louis encephalitis virus activity in mosquito communities from Argentine agroecosystems.

Saint Louis encephalitis virus (SLEV) is an endemic arbovirus in the Americas, maintained in enzootic cycles involving mosquitoes and birds. Agroecosystems influence vector ecology and SLEV dynamics. We analysed mosquito communities and SLEV activity in agroecosystems of northeastern La Pampa, Argentina, assessing environmental and biological drivers. Mosquitoes were collected at 15 sites (2017-2019) using Centers for Disease Control light traps. SLEV was detected by RT-nested PCR, and minimum infection rate was estimated. We collected a total of 3075 mosquitoes; Culex interfor Dyar (Diptera: Culicidae) s.l. and Culex mollis Dyar & Knab s.l. were the most abundant. The abundance of Cx. interfor s.l. was associated with agricultural frequency, Cx. mollis s.l. abundance and species richness, whereas Cx. mollis s.l. abundance was only associated with Cx. interfor s.l. abundance. We also extended the known distributions of Anopheles albitarsis Lynch Arribálzaga and Culex acharistus Root. SLEV was detected in 35 of 229 pools across 6 sites. Viral activity was negatively associated with Cx. mollis s.l. abundance and distance to water, highlighting key ecological factors shaping SLEV transmission.