Genomic stability of La Crosse virus during vertical and horizontal transmission.

We have used ribonuclease T1 oligonucleotide fingerprint analysis to study genomic stability of La Crosse virus (Bunyaviridae) during vertical and horizontal transmission in the laboratory. No RNA genomic changes were detected in vertebrate cell culture-propagated virus isolated (following ingestion and replication) from the natural host, Aedes triseriatus. Genomic changes were not detected during transovarial passage of the virus through two generations of mosquitoes, nor were changes detected in the genomes of virus isolated from suckling mice that had been fed upon by second generation transovarially-infected mosquitoes. These results demonstrate that despite the well-documented phenomena of rapid nucleotide change in RNA virus genomes under various conditions, the La Crosse virus genome can remain stable during transovarial transmission in the insect host and during transfer between the insect and vertebrate hosts. The evolutionary implications of these results are discussed.