25 Infectious diseases caused by mosquito-borne viruses constitute health and economic 26 problems worldwide. St. Louis encephalitis virus (SLEV) is endemic and autochthonous in 27 the American continent. Culex pipiensquinquefasciatus is the primary urban vector of 28 SLEV; however, Culex interforandCulex saltanensishave also been found naturally infected 29 with the virus, suggesting their potential role as vectors. 30 OBJETIVE The aim of this study was to determine the vector competence of Cx. interfor 31 and Cx. saltanensisfor SLEVfrom central Argentinain comparison to a Cx. 32 p.quinquefasciatus. 33 METHODSAdult female mosquitoes of the three Culex species were orally infected by 34 feeding on viremic chicks that had been inoculated with SLEV CbaAr-4005, it is the same 35 strain detected in the US and Argentina, and responsible for human disease.Then, 36 abdomens, legs and saliva blood-fed mosquitoes were analyzed by viral plaque assay and 37 the presence of cytopathic effect on the cell culture monolayer. 38 RESULTS Mosquitoes were permissive to orallyacquire infections, to virus 39 dissemination,and transmission of SLEV in the saliva. Culex saltanensis and Cx. interfor 40 are potential vectors of SLEV. 41 CONCLUSIONS Our results demonstrate that in Argentina both Culex saltanensis and 42 Culex interfor are susceptible to SLEV and competent for its transmission.Moreoverthey 43 are abundant during SLEV epidemicperiod in urban area, positive for this virus in nature, 44 and found to feed on natural hosts.45