Abstract
Vectorial capacity is an equation that integrates major aspects of vector biology to predict the number of new mosquito-borne disease infections. Developed for studying transmission of malaria, vectorial capacity is rarely applied to zoonotic vector-borne diseases and is not often adjusted to account for seasonal changes in vector ecology. We used field data from Florida, USA to expand the understanding of how vectorial capacity of Culiseta melanura (Coquillett), the primary enzootic vector of eastern equine encephalitis virus (EEEV), changes seasonally and its effect on EEEV risk. We determined parity via dissection and identified bloodmeals by PCR for field-collected Cs. melanura females from central Florida. We used density of the vector, proportion of avian hosts fed upon, parity state of the vector, and mean temperature of the study area to quantify vectorial capacity as a function of season. The calculated values of vectorial capacity shifted significantly with season, with highest values observed in the summer with an additional peak in December. Linear regression revealed a strong positive correlation between vectorial capacity values and Florida EEEV equine cases in 2018, as well as cases reported during the last decade. The relationship between virus infections in equids and vectorial capacity lends support to the large effect that enzootic transmission has on epizootic outbreaks of zoonotic vector-borne pathogens.
Highlights
The ecology of zoonotic vector-borne pathogens is inherently complex, given the diversity of vectors and/or multiple hosts that are involved in their transmission (Kuno et al, 2017)
Culiseta melanura density in Central Florida was highest in the late spring and summer (June–August) which contrasts with results from Edman et al (1972) and Blosser et al (2017)
Infections in equids and vectorial capacity of the vector was observed, supporting the hypothesis that enzootic transmission by Cs. melanura has a large effect on epizootic outbreaks
Summary
The ecology of zoonotic vector-borne pathogens is inherently complex, given the diversity of vectors and/or multiple hosts that are involved in their transmission (Kuno et al, 2017). Many bird species that are commonly bitten by Cs. melanura serve as amplifying hosts for the virus throughout its range (Figure 1). Transmission of EEEV in the United States is seasonal, and epizootic activity primarily occurs in the summer months and declines in autumn (Tenbroeck et al, 1935; Bigler et al, 1976; Scott and Weaver, 1989). Cases in equids can occur during winter in the southern United States because of its warmer climate (Bigler et al, 1976; Bingham et al, 2015; Burkett-Cadena et al, 2015). The summer peak in transmission coincides with increased mosquito abundance and EEEV antibody seroprevalence in young birds (Tenbroeck et al, 1935; Elias et al, 2017)
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