BACKGROUND : Culicoides spp. biting midges transmit bluetongue virus (BTV), the aetiological agent of bluetongue
(BT), an economically important disease of ruminants. In southern India, hyperendemic outbreaks of BT exert high
cost to subsistence farmers in the region, impacting on sheep production. Effective Culicoides spp. monitoring
methods coupled with accurate species identification can accelerate responses for minimising BT outbreaks.
Here, we assessed the utility of sampling methods and DNA barcoding for detection and identification of
Culicoides spp. in southern India, in order to provide an informed basis for future monitoring of their populations
in the region.
METHODS : Culicoides spp. collected from Tamil Nadu and Karnataka were used to construct a framework for future
morphological identification in surveillance, based on sequence comparison of the DNA barcode region of the
mitochondrial cytochrome c oxidase I (COI) gene and achieving quality standards defined by the Barcode of Life
initiative. Pairwise catches of Culicoides spp. were compared in diversity and abundance between green (570 nm)
and ultraviolet (UV) (390 nm) light emitting diode (LED) suction traps at a single site in Chennai, Tamil Nadu over
20 nights of sampling in November 2013.
RESULTS : DNA barcode sequences of Culicoides spp. were mostly congruent both with existing DNA barcode data
from other countries and with morphological identification of major vector species. However, sequence differences
symptomatic of cryptic species diversity were present in some groups which require further investigation. While
the diversity of species collected by the UV LED Center for Disease Control (CDC) trap did not significantly vary
from that collected by the green LED CDC trap, the UV CDC significantly outperformed the green LED CDC trap
with regard to the number of Culicoides individuals collected.
CONCLUSIONS : Morphological identification of the majority of potential vector species of Culicoides spp. samples
within southern India appears relatively robust; however, potential cryptic species diversity was present in some
groups requiring further investigation. The UV LED CDC trap is recommended for surveillance of Culicoides in
Additional file 1: Table S1. GenBank sequences used in genetic
analyses of Culicoides from southern India. Table S2. Barcode Index
Numbers (BINs) assigned within the Barcode of Life Database (BOLD)
for specimens collected within this study.
Additional file 2: Table S3. Uncorrected percentage sequence
distances, mean with range shown in parentheses. Intraspecific distances
are shown in bold along the diagonal, interspecific distances are shown
in the lower triangle (NA indicates comparison not possible due to
singleton specimen present; number of specimens per species (n) shown
in brackets with the number of specimens originating from this study;
followed by the number originating from GenBank in parentheses).