A newly emergent genotype of West Nile virus is transmitted earlier and more efficiently by Culex mosquitoes.
Studies examining the evolution of West Nile virus since its introduction into North America have identified the emergence of a new dominant genotype (WN02) that has displaced the introduced genotype (NY99). The mechanistic basis for this displacement, however, remains obscure. Although we found no detectable difference in vitro between the genotypes in either replication or fitness, there were significant differences in vivo in Culex mosquitoes. After peroral infection, the extrinsic incubation period (EIP) of the WN02 genotype was up to 4 days shorter than the EIP of the NY99 genotype; however, after intrathoracic inoculation, there was no difference in EIP between the genotypes, suggesting that differences in genotype interaction with the mosquito midgut are likely to play a role in this phenotype. These results suggest a model for the displacement of the NY99 genotype, where earlier transmission of WN02 viruses leads to higher WN02 infection rates in avian reservoir hosts.
Moudy
Robin M
RM
Arbovirus Laboratories, Wadsworth Center, New York State Department of Health, 5668 State Farm Road, Slingerlands, NY 12159, USA. rmoudy@wadsworth.org
Meola
Mark A
MA
Morin
Laura-Lee L
LL
Ebel
Gregory D
GD
Kramer
Laura D
LD
D000818:Animals; D003465:Culex / Q000821:virology*; D005260:Female; D005838:Genotype; D007303:Insect Vectors / Q000821:virology*; D014779:Virus Replication / Q000235:genetics / Q000502:physiology; D014901:West Nile Fever / Q000635:transmission* / Q000821:virology*; D014902:West Nile virus / Q000235:genetics / Q000254:growth & development / Q000502:physiology*