Journal of Medical Entomology (2013) 50, 371-378

Brittany M. Nelms, Ethan Fechter-Leggett, Brian D. Carroll, Paula Macedo, Susanne Kluh and William K. Reisen (2013)
Experimental and natural vertical transmission of West Nile virus by California Culex (Diptera: Culicidae) Mosquitoes
Journal of Medical Entomology 50 (2), 371-378
Abstract: Culex (Diptera: Culicidae) mosquitoes, the primary summer vectors of West Nile virus (family Flaviviridae, genus Flavivirus, WNV), also may serve as overwintering reservoir hosts. Detection of WN viral RNA from larvae hatched from eggs deposited by infected females during late summer and fall may provide evidence for the vertical passage of WNV to overwintering cohorts. To determine whether vertical transmission to the overwintering generation occurs in populations of Culex mosquitoes throughout California, larvae from naturally infected females were tested by family for WN viral RNA by real-time quantitative reverse transcription-polymerase chain reaction during August through October 2011. Viral RNA was detected in 34 of 934 Culux tarsalis Coquillett and Cx. pipiens complex females that laid viable egg rafts. From these egg rafts, first-instar larvae from nine families tested positive, yielding an overall field vertical transmission rate of 26% (n = 34). To determine whether the WNV may be lost transtadially during development to the adult stage, first-instar larvae and adult progeny from experimentally infected Cx. pipiens complex females were assessed for the presence and quantity of WN viral RNA. Most (≈75%) WNV infections were lost from positive families during larval development to the adult stage. In field and laboratory studies, only infected mothers with mean cycle threshold scores ≤20 vertically transmitted WNV to larval progeny, adult progeny, or both. In summary, vertical transmission of WNV was detected repeatedly in naturally infected Culex mosquitoes collected throughout California during late summer and fall, with females having high titered infections capable of passing WNV onto their progeny destined for overwintering.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): William K. Reisen

Research topic(s) for pests/diseases/weeds:
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Culex tarsalis		U.S.A. (SW)
	Culex pipiens		U.S.A. (SW)