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. 2002 Jun;8(6):575-80.
doi: 10.3201/eid0806.010417.

Drought-induced amplification of Saint Louis encephalitis virus, Florida

Jeffrey Shaman  1 , Jonathan F Day, Marc Stieglitz
Affiliations

Drought-induced amplification of Saint Louis encephalitis virus, Florida

Jeffrey Shaman et al. Emerg Infect Dis. 2002 Jun.

Abstract

We used a dynamic hydrology model to simulate water table depth (WTD) and quantify the relationship between Saint Louis encephalitis virus (SLEV) transmission and hydrologic conditions in Indian River County, Florida, from 1986 through 1991, a period with an SLEV epidemic. Virus transmission followed periods of modeled drought (specifically low WTDs 12 to 17 weeks before virus transmission, followed by a rising of the water table 1 to 2 weeks before virus transmission). Further evidence from collections of Culex nigripalpus (the major mosquito vector of SLEV in Florida) suggests that during extended spring droughts vector mosquitoes and nestling, juvenile, and adult wild birds congregate in selected refuges, facilitating epizootic amplification of SLEV. When the drought ends and habitat availability increases, the SLEV-infected Cx. nigripalpus and wild birds disperse, initiating an SLEV transmission cycle. These findings demonstrate a mechanism by which drought facilitates the amplification of SLEV and its subsequent transmission to humans.

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Figures

Figure 1
Figure 1
Map of Indian River County, Florida, with numbered locations of the five sentinel chicken flocks. The location of the mosquito collection site is denoted by “M.”
Figure 2
Figure 2
Time series of weekly seroconversion of sentinel chickens (transmission intensity) and weekly averages of modeled mean water table depth (WTD). All five sentinel flocks had St. Louis encephalitis virus (SLEV) transmission during the study period (1986–1991).
Figure 3
Figure 3
Best fit, univariate logistic regression results. a) site 1; b) site 2; c) site 3; d) site 4; e) site 5; f) all five sites, Florida.
Figure 4
Figure 4
Best fit bivariate logistic regression model of St. Louis encephalitis virus (SLEV) incidence at all five sites combined. a) Plotted for a continuous range of modeled water table depths (WTDs) 2 weeks before transmission and fixed values of modeled WTD 17 weeks before transmission; b) plotted for a continuous range of modeled WTDs 17 weeks before transmission and fixed values of modeled WTD 2 weeks before transmission.
Figure 5
Figure 5
Total collected female Culex nigripalpus plotted as a function of modeled water table depth (WTD) (same day). Individual plots represent individual years. Mosquito collection data have been log transformed (plus one).
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References

    1. Day JF, Stark LM. Frequency of Saint Louis encephalitis virus in humans from Florida, USA: 1990–1999. J Med Entomol. 2000;37:626–33. - PubMed
    1. Day JF, Curtis GA. Annual emergence patterns of Culex nigripalpus females before, during and after a widespread St. Louis encephalitis epidemic in south Florida. J Am Mosq Control Assoc. 1993;9:249–53. - PubMed
    1. McLean RG, Bowen GS. Vertebrate hosts. In: Monath TP, editor. St. Louis encephalitis. Washington: American Public Health Association; 1980. p. 381–450.
    1. Day JF, Stark LM. Avian serology in a St. Louis encephalitis epicenter before, during, and after a widespread epidemic in south Florida, USA. J Med Entomol. 1999;36:614–24. - PubMed
    1. Monath TP. Epidemiology. In: Monath TP, editor. St. Louis encephalitis. Washington: American Public Health Association; 1980. p. 239–312.

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