Biology subjects

O'Meara, D.

Publications and source records attributed to O'Meara, D..

4 recordsLinked to original sources

bioRxiv2026

Molecular identification of vertebrate blood meals in Culicoides biting midges reveals host-vector associations relevant to arbovirus transmission in Ireland

Understanding the vertebrate hosts exploited by Culicoides biting midges is fundamental to assessing the transmission risk of livestock arboviruses. Blood meal analysis provides direct evidence of host-vector interactions under natural conditions; however, molecular data on Culicoides host feeding are lacking in Ireland. This study aimed to identify the vertebrate blood meal hosts of Culicoides species of veterinary importance and establish host-vector associations relevant to arbovirus transmission. A total of 115 morphologically blood-fed Culicoides females collected from 13 sites across Ireland were analysed using a sequential molecular workflow. Species-specific real-time PCR assays were used to screen for vertebrate hosts, with positive detections confirmed by mitochondrial DNA sequencing. Blood-fed Culicoides were subsequently identified to species level using DNA barcoding, enabling direct linkage between vector species and their vertebrate hosts. Vertebrate DNA was detected in 50 specimens, with cattle and horses accounting for the majority of identified blood meals. Culicoides obsoletus accounted for most cattle (n = 12) and horse (n = 11) blood meals. Culicoides scoticus fed on cattle (n = 6), horses (n = 4) and sheep (n = 1), while C. dewulfi and C. chiopterus fed predominantly on cattle, with occasional horse blood meals. Four cattle blood meals were identified from C. punctatus. No cervid-derived blood meals were detected. This study provides the first molecular characterisation of Culicoides blood meal hosts in Ireland, confirming host-vector associations between major vector species and livestock hosts of veterinary importance. Although the number of successfully characterised blood meals was modest, reflecting the inherent difficulty of recovering recently blood-fed Culicoides from field collections, the findings establish an important baseline for Ireland. The sequential molecular workflow provides a practical framework for future blood meal investigations and will support improved understanding of host-vector interactions relevant to arbovirus surveillance and risk assessment.

molecular biology↗

bioRxiv2025

Design and optimisation of rapid real-time PCR assays for the detection of key Culicoides species

In extensive surveillance programmes of Culicoides biting midges (Diptera: Ceratopogonidae), morphological identification can be time-consuming and difficult, while DNA barcoding, although highly accurate, may not be cost-effective or suitable for rapid analysis, as it requires individual specimen processing. To address these limitations, we developed a rapid screening method using real-time PCR assays with either SYBR Green or hydrolysis probe-based detection chemistries. Species-specific primers and, where necessary, hydrolysis probes were designed based on the updated sequences of the ITS2 region of seven Culicoides species. The specificity and efficiency of these assays were validated both in silico and through real-time PCR testing on target and non-target Culicoides species, tested individually and as mixed-species samples. The new real-time PCR assays detect vector species including C. obsoletus, C. scoticus, C. chiopterus, C. dewulfi, C. pulicaris, C. punctatus, and C. impunctatus in pools of individual specimens, with single-specimen sensitivity. The molecular techniques developed in this study provide a valuable tool for accurate and high-throughput Culicoides surveillance, which can be used for year-round monitoring of adult midges in traps and larvae in environmental samples, potentially revealing novel insights into the spatial and temporal turnover of Culicoides species. These methods can be applied to large-scale vector screening programmes involving pooled samples, addressing the limitations of previously described methods used in midge surveillance.

molecular biology↗

bioRxiv2025

Molecular characterisation of common Culicoides Biting Midges (Diptera: Ceratopogonidae) in Ireland

BackgroundBiting midges in the genus Culicoides (Diptera: Ceratopogonidae) act as vectors for several arboviruses, including Bluetongue virus (BTV) and Schmallenberg virus (SBV), which affect livestock health and productivity. In Ireland, limited genetic data are available regarding the diversity of Culicoides species. This study represents the first attempt to characterise Culicoides in this region using molecular techniques. MethodsAdult Culicoides samples were captured using Onderstepoort Veterinary Institute (OVI) traps across six locations in Ireland. Subsequent molecular analyses involved polymerase chain reaction (PCR) and sequencing of the cytochrome oxidase subunit 1 (CO1) and the internal transcriber spacer (ITS) barcoding regions to obtain species identities. Additionally, using both markers, we inferred the population genetic structure and potential colonisation pathways of Culicoides obsoletus sensu stricto (s. str.), the major vector species in Ireland. ResultsDNA barcoding facilitated identification of 177 specimens. Eight common Culicoides species were identified through DNA barcoding of CO1 and ITS gene regions. The presence of putative vectors of Bluetongue virus (BTV) and Schmallenberg virus (SBV) were also confirmed, including species in the subgenus Avaritia (C. obsoletus s. str., C. scoticus, C. chiopterus, and C. dewulfi) and subgenus Culicoides s. str. (C. pulicaris and C. punctatus). Phylogenetic analysis confirmed the relationship between these vector species and facilitated the placement of Culicoides sp. which could not be identified to species level through DNA barcoding. Haplotype network analysis of C. obsoletus showed that some haplotypes of these species are shared between Continental Europe, the UK, and Ireland, suggesting a possible incursion pathway for this vector. ConclusionDNA barcoding employing a combination of two barcodes, CO1 and ITS, proved effective in identifying Culicoides, especially species within the obsoletus complex, which are difficult to morphologically distinguish. Our findings also suggest that investigation of the population genetic structure of Culicoides spp. could be used to model the potential introduction routes of midge-borne pathogens into the country.

molecular biology↗

bioRxiv2022

Resource competition drives an invasion-replacement event among shrew species on an island

O_LIInvasive mammals are responsible for the majority of native species extinctions on islands. While most of these extinction events will be due to novel interactions between species (e.g. exotic predators and naive prey), it is more unusual to find incidences where a newly invasive species causes the decline/extinction of a native species on an island when they normally coexist elsewhere in their overlapping mainland ranges. C_LIO_LIWe investigated if resource competition between two insectivorous small mammals was playing a significant role in the rapid replacement of the native pygmy shrew (Sorex minutus) in the presence of the recently invading greater white-toothed shrew (Crocidura russula) on the island of Ireland. C_LIO_LIWe used DNA metabarcoding of gut contents from >300 individuals of both species to determine each species diet and measured the size of individuals (weight and length) during different stages of the invasion in Ireland (before, during and after the species come into contact with one another) and on a French island where both species have long coexisted (acting as a natural control site). Dietary composition, niche width and overlap and size were compared in these different stages. C_LIO_LIThe size of the invasive C. russula and composition of its diet changes between when it first invades an area and after it becomes established. Individuals are larger and they consume larger invertebrates at the invasion front, before switching towards the smaller prey taxa that are more essential for the survival of the native species after establishment. As a result, the level of interspecific dietary overlap increases from between 11-14% when they first come into contact with each other to between 39-46% after the invasion. C_LIO_LIHere we show that an invasive species can quickly alter its dietary niche in a new environment, leading to negative impacts that were not previously predicted based on the coexistence of these species in other parts of their mainland ranges. As well as causing the replacement of a native small mammal, the invasive shrew may be rapidly exhausting local resources of larger invertebrate species. These subsequent changes in terrestrial invertebrate communities could have severe impacts further downstream on ecosystem functioning and services. C_LI

ecology↗