Abstract
Evidence from field studies suggests that Culex pipiens, the primary mosquito vector of West Nile virus (WNV) in the northeastern and north central United States, feeds preferentially on American robins (Turdus migratorius). To determine the contribution of innate preferences to observed preference patterns in the field, we conducted host preference trials with a known number of adult female C. pipiens in outdoor cages comparing the relative attractiveness of American robins with two common sympatric bird species, European starling, Sternus vulgaris and house sparrow, Passer domesticus. Host seeking C. pipiens were three times more likely to enter robin-baited traps when with the alternate host was a European starling (n = 4 trials; OR = 3.06; CI [1.42–6.46]) and almost twice more likely when the alternative was a house sparrow (n = 8 trials; OR = 1.80; CI = [1.22–2.90]). There was no difference in the probability of trap entry when two robins were offered (n = 8 trials). Logistic regression analysis determined that the age, sex and weight of the birds, the date of the trial, starting-time, temperature, humidity, wind-speed and age of the mosquitoes had no effect on the probability of a choosing a robin over an alternate bird. Findings indicate that preferential feeding by C. pipiens mosquitoes on certain avian hosts is likely to be inherent, and we discuss the implications innate host preferences may have on enzootic WNV transmission.
Highlights
Heterogeneities in contact rates between arthropod vectors and hosts are important to vector-borne disease dynamics, because they can result in increased disease transmission if vector blood meals occur more commonly on pathogen-competent hosts
The objective of this study was to obtain a measure of innate hostselection in C. pipiens by comparing the relative attractiveness of American robins when paired with two other bird species common in residential areas, European starling (Sternus vulgaris) and house sparrow (Passer domesticus), in outdoor caged experiments
Host-seeking C. pipiens were significantly more attracted to robins than to either sparrows or starlings (Table 1), but no difference was detected when trials were conducted with two robins (Additional information for individual trials are provided in Supplementary Tables S1–S3)
Summary
Heterogeneities in contact rates between arthropod vectors and hosts are important to vector-borne disease dynamics, because they can result in increased disease transmission if vector blood meals occur more commonly on pathogen-competent hosts. Transmission may be reduced if blood meals are ‘diluted’ by feeding on non-competent hosts. The rate of contact is influenced by a variety of factors including innate host preferences of the vector, host availability and landscape composition and configuration. To control for environmental confounders influencing contact rates, host-choice experiments using traps baited with whole-host odors have been conducted to determine innate host preferences of a vector. A limited number of hostpreference experiments conducted with other mosquito genera provide inconclusive evidence on the presence of innate host preferences [5,8,13,14,15,16,17,18,19]
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