Experimental transmission of St. Louis encephalitis virus by Ochlerotatus j. japonicus.
Ochlerotatus japonicus japonicus a newly discovered nonindigenous mosquito species in North America, and a colonized strain of Culex pipiens were compared for their vector competence for St. Louis encephalitis virus (SLE). Infection rates in Oc. j. japonicus were 0-33% after feeding on chickens with viremias between 10(4.1) and 10(4.7) plaque-forming units (PFU)/ml of blood. In comparison, infection rates were 12-94% for Cx. pipiens that fed on the same chickens. When fed on chickens with viremias between 10(5.3) and 10(5.6) PFU/ml of blood, infection rates for Oc. j. japonicus and Cx. pipiens were similar, 96% and 100%, respectively. After 12-14 days of extrinsic incubation at 26 degrees C, all 34 infected Oc. j. japonicus had a disseminated infection. In contrast, only 23 (43%) of 54 infected Cx. pipiens had a disseminated infection after feeding on the same chickens. If they developed a disseminated infection, both species efficiently transmitted (> or = 87%) SLE. Estimated transmission rates at viral doses sufficient to infect both of the tested species were 29-84% for Oc. j. japonicus and 30-50% for Cx. pipiens. Because of its continued geographic expansion, field and laboratory evidence incriminating it as a vector of the closely related West Nile virus, and its ability to transmit SLE in the laboratory, Oc. j. japonicus should be considered as a potential enzootic or epizootic vector of SLE.
Sardelis
Michael R
MR
Division of Tropical Public Health, Department of Preventive Medicine and Biometrics, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA.
Turell
Michael J
MJ
Andre
Richard G
RG
D000818:Animals; D002645:Chickens / Q000469:parasitology / Q000821:virology; D003465:Culex / Q000821:virology; D009033:Culicidae / Q000821:virology*; D004665:Encephalitis Virus, St. Louis / Q000502:physiology*; D004674:Encephalitis, St. Louis / Q000635:transmission*; D007303:Insect Vectors / Q000821:virology*; D014766:Viremia / Q000821:virology