Temporal Connections between Culex tarsalis Abundance and Transmission of Western Equine Encephalomyelitis Virus in California

Abstract

Definition of targets for vector control requires an understanding of the relationship between vector abundance and the intensity of arbovirus transmission. Using an extensive surveillance dataset with observations from sentinel chicken flocks and mosquito traps paired in time and space, hierarchical autoregressive logistic regression models were developed to predict the probability of seroconversion in chickens for western equine encephalomyelitis virus (WEEV) based on the relative abundance of the principal vector, Culex tarsalis. After adjustments for confounders, the abundance of Cx. tarsalis 29–42 d before the date of chicken sampling was credibly associated with the risk of WEEV transmission in both the Central and Coachella Valleys, and a doubling of relative Cx. tarsalis abundance was associated with a 58% increase in the odds of seroconversion. The critical time windows identified in our study highlight the need for surveillance of vector populations and forecasting models to guide proactive vector control measures before the detection of transmission to sentinel chickens.

Seasonal Abundance of <I>Culex tarsalis</I> and <I>Culex pipiens</I> Complex Mosquitoes (Diptera: Culicidae) in California

“…Therefore, it is likely that the abundance of infective females (and therefore the risk of virus transmission) would peak later than the overall female abundance observed in this study. This has been observed for WNV in the Colorado River HR (Reisen et al 2008), Tulare Lake HR (Reisen et al 2009), South Coast HR (Kwan et al 2010), and northern Colorado (Bolling et al 2009), and for other arboviruses in central and southern California (Barker et al 2010; Reisen et al 1990, 1992a, 1992b). Although these selected areas have been investigated, a broader comparative study of the period since the arrival of WNV is needed to determine how abundance patterns affect WNV dynamics.…”

Sentinel Chicken Seroconversions Track Tangential Transmission of West Nile Virus to Humans in the Greater Los Angeles Area of California

“…tarsalis to sentinel chickens in California, where maximum temperatures were predictive 1-3 weeks before seroconversion. 38 Increases in the minimum temperature increased the accumulation of suitable degree-days for viral amplification 39 which, in turn, accelerated local transmission. This point was emphasized by the sites at Griffith Park, Whittier Narrows, and Sepulveda Basin achieving the minimum EIP earliest and also experiencing the greatest WNV activity, whereas Machado Lake rarely achieved the minimum EIP and had the least WNV activity.…”

Seasonal Abundance ofCulex tarsalisandCulex pipiensComplex Mosquitoes (Diptera: Culicidae) in California

“…Therefore, it is likely that the abundance of infective females (and therefore the risk of virus transmission) would peak later than the overall female abundance observed in this study. This has been observed for WNV in the Colorado River HR (Reisen et al 2008), Tulare Lake HR (Reisen et al 2009), South Coast HR (Kwan et al 2010), and northern Colorado (Bolling et al 2009), and for other arboviruses in central and southern California (Barker et al 2010;Reisen et al , 1992aReisen et al , 1992b. Although these selected areas have been investigated, a broader comparative study of the period since the arrival of WNV is needed to determine how abundance patterns affect WNV dynamics.…”