Short report: efficient oral infection of Culex pipiens quinquefasciatus by Rift Valley fever virus using a cotton stick support.

Transmission experiments are essential to assess vector competence. In an attempt to study Rift Valley fever virus (RVFV) transmission in its arthropod vector, disseminated infection rates were measured in Culex pipiens quinquefasciatus exposed to Clone 13, an avirulent variant of RVFV. We compared the classic system of glass feeders covered with different membranes (0-1%) with an alternative system in which a cotton stick is used as a support of a blood meal. The latter system showed the highest successful feeding rate (80%). Using this system, we optimized two parameters to obtain the highest numbers of engorged females and thus the highest numbers of females with disseminated infection: 1) use of freshly collected washed erythrocytes and 2) duration of the extrinsic incubation period of at least 14 days after infection.