Bunyavirus superinfection and segment reassortment in transovarially infected mosquitoes

Rapid evolution of bunyaviruses may occur by RNA segment reassortment betwe en closely related viruses. Reassortment between viruses occurs in dually i nfected mosquitoes when two different viruses are simultaneously ingested o r when the second virus is ingested within 2 days of the first virus. By 3 days after oral infection, interference to superinfection occurs, thus limi ting the potential for evolution. Aedes triseriatus mosquitoes can also be transovarially infected (TI+) with LaCrosse (LAC) virus. In these studies, the potential for oral superinfection of TI+ mosquitoes was assessed. Appro ximately 20% of mosquitoes TI+ with either a temperature-sensitive LAC viru s or wild-type (wt) LAC virus became superinfected by ingesting blood meals containing wt LAC or snowshoe hare (SSH) viruses. LAC virus TI+ mosquitoes superinfected with SSH virus were detected by blot hybridization or RT-PCR . Viruses from these mosquitoes were plaque purified and genotyped using RT -PCR. Reassortant genomes were detected in 2.3% of the viruses genotyped, a nd 4.0% of the genomes tested were diploid for one genome segment.