Abstract
BackgroundBiting midges of the genus Culicoides (Diptera: Ceratopogonidae) exert a significant impact on animal agriculture worldwide because they transmit bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) to ruminants. Without effective vaccines, BTV/EHDV vector management strategies are needed, particularly in commercial white-tailed deer (WTD) facilities. However, detailed information on the ecology of midge immatures in/around cervid operations is currently lacking. Towards filling this knowledge gap, we conducted two-choice oviposition experiments with field-collected Culicoides stellifer Coquillett (a suspected vector of BTV/EHDV in the USA) under laboratory conditions to examine which natural source from the larval habitat is relatively more attractive for midge oviposition.MethodsField-collected C. stellifer females (CDC-UV light traps) were given a blood meal from live chicken and examined for their oviposition preferences for individual (or mixed) potential larval habitat oviposition stimuli in two-choice bioassays. Substrates included mud from C. stellifer habitat, mud from allopatric site, vegetation (Sphagnum spp. mosses), field water, WTD manure and de-ionized water (control).ResultsThe majority of midges (91%) oviposited in only one dish, with few females (9%) ovipositing in both the dishes. Gravid females demonstrated an overall oviposition preference for substrates with mud and vegetation from the larval habitat, depositing a significantly higher proportion of eggs on mud (52.3%) and vegetation (81.8%) than on controls (≤ 18.2%) (P ≤ 0.0320). Moreover, greater number of eggs per female were deposited on mud (29.5–40.7 depending on trial) and vegetation (38.2) than on controls (≤ 5.8). WTD manure, field water and mud from allopatric site were not found to be more attractive than controls for oviposition. Combining individual substrates (mud + WTD manure; mud + moss + WTD manure + field water) did not elicit greater oviposition responses than mud or moss alone.ConclusionsManagement strategies to discourage C. stellifer oviposition in/around commercial cervid facilities should likely focus on mud and/or vegetation, rather than WTD manure. However, further studies are needed to examine whether the spatial distributions of C. stellifer and Sphagnum spp. moss are correlated, and to determine whether targeting vegetation in/around cervid facilities can contribute to reductions in local midge densities.
Highlights
Biting midges of the genus Culicoides (Diptera: Ceratopogonidae) exert a significant impact on animal agriculture worldwide because they transmit bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) to ruminants
The odds of a female choosing the mud substrate for oviposition was 4.4 times higher than Deionized water (DI) controls, with no significant difference between the two trials conducted (Wald χ21, 10 = 0.02, P = 0.8890) (Fig. 2a, b, Table 1)
Our findings demonstrate that white-tailed deer (WTD) manure does not play a significant role in the oviposition of C. stellifer and suggest that the field sites receiving manure influx from WTD in commercial cervid farms may not be relatively more attractive for C. stellifer oviposition over muds without WTD manure
Summary
Biting midges of the genus Culicoides (Diptera: Ceratopogonidae) exert a significant impact on animal agriculture worldwide because they transmit bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) to ruminants. Among the several pathogen classes that Culicoides species transmit, two arboviruses affecting ruminants, bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) (Genus Orbivirus, Family Reoviridae), cause significant morbidity, mortality, and economic losses in animal agriculture worldwide [3]. These viruses affect a variety of domestic and wild ruminants, BTV affects primarily sheep and cattle, while EHDV affects mainly white-tailed deer (WTD) (Odocoileus virginianus Zimmermann) and cattle [4]. The distribution of C. insignis in the USA is primarily limited to Florida and neighboring states; recent reports suggest a northward range expansion of this species as well [10]
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