Application of an embryonated chicken egg model to assess the vector competence of Australian <i>Culicoides</i> midges for bluetongue viruses

Saag, M. R. Van Der; Ward, Michael P.; Kirkland, Peter D.

doi:10.1111/mve.12231

Cited by 11 publications

(11 citation statements)

References 28 publications

(39 reference statements)

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“…Cq values below 25 have been shown in both colony [24] and field-collected [4, 25] specimens to indicate that viral replication has occurred in the insect so the 4 specimens with Cq values less than 25 were considered infected with BTV. These 4 specimens were all collected from Nixi and were all parous females; 2 were identified as C. tainanus , 1 was Culicoides sp.…”

Section: Resultsmentioning

confidence: 99%

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Potential vectors of bluetongue virus in high altitude areas of Yunnan Province, China

Duan

Bellis

et al. 2019

Parasites Vectors

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Background Bluetongue disease of ruminants is a typical insect-borne disease caused by bluetongue virus (BTV) of the genus Orbivirus (family Reoviridae) and transmitted by some species of Culicoides (Diptera: Ceratopogonidae). Recently, the detection of BTV in yaks in high altitude meadows of the Shangri-La district of Yunnan Province, China, prompted an investigation of the Culicoides fauna as potential vectors of BTV. Methods A total of 806 Culicoides midges were collected by light trapping at three sites at altitudes ranging from 1800 to 3300 m. The species were identified based on morphology and the DNA sequences of cytochrome c oxidase subunit 1 (cox1). PCR and quantitative PCR following reverse transcription were used to test for the presence of BTV RNA in Culicoides spp. A phylogenetic analysis was used to analyze the cox1 sequences of some specimens. Results Four species dominated these collections and cox1 barcoding revealed that at least two of these appear to belong to species new to science. Culicoides tainanus and a cryptic species morphologically similar to C. tainanus dominated low altitude valley collections while C. nielamensis was the most abundant species in the high-altitude meadow. A species related to C. obsoletus occurred at all altitudes but did not dominate any of the collections. BTV RT-qPCR analysis detected BTV RNA in two specimens of C. tainanus, in one specimen closely related to C. tainanus and in one specimen closely related to C. obsoletus by barcode sequencing. Conclusions This study suggests that BTV in high altitude areas of Yunnan is being transmitted by three species of Culicoides, two of which appear to be new to science. This research may be useful in improving understanding of the effects of global warming on arboviral disease epidemiology and further study is important in research into disease control and prevention.

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Section: Resultsmentioning

confidence: 99%

“…Fluorescence was measured at the end of each annealing step. Only reactions with Cq values of 25 or lower were regarded as indicative of replication of BTV in the midge [4, 24, 25].…”

Section: Methodsmentioning

confidence: 99%

Potential vectors of bluetongue virus in high altitude areas of Yunnan Province, China

Duan

Bellis

et al. 2019

Parasites Vectors

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“…However, we could not apply this ratio in our experiments as this would have excessively reduced the infectivity. Earlier studies have suggested minimal virus titres in the blood meals (C q values below 30 per μl blood or a minimum of 5 log 10 TCID 50 /ml) [ 49 , 79 ]. Thus, 2:1 (BTV-4 and BTV-8) or 1:1 (BTV-1) ratios were used in our experiments to fulfil these requirements.…”

Section: Discussionmentioning

confidence: 99%

Vector competence of pre-alpine Culicoides (Diptera: Ceratopogonidae) for bluetongue virus serotypes 1, 4 and 8

et al. 2018

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BackgroundBluetongue disease, caused by bluetongue virus serotype 8 (BTV-8), appeared for the first time in the northern part of Europe in 2006, and subsequently rapidly spread causing severe economic losses to the farming industry. The implicated vectors of BTV in Europe are Culicoides species within the subgenus Avaritia (C. chiopterus, C. dewulfi, C. obsoletus and C. scoticus). Epidemiological data from Switzerland have shown that BTV, whose spread was eliminated at an early stage by vaccination campaigns, had not been circulating among livestock at higher altitudes where other species dominate the Culicoides fauna. In this study, we investigated the extent that Culicoides spp. prevailing at higher altitudes (mainly C. grisescens) can act as vectors for BTV.MethodsCulicoides were collected at farms in the pre-alpine region (two sites at 1550 m above sea level, masl, referred to as pre-alpine I; one site at 2030 masl, pre-alpine II) and, for comparative purposes, from the Swiss Plateau (one site, 650 masl). They were fed on bovine blood/BTV suspensions (BTV-1, 4 or 8) and incubated for eight days under a fluctuating temperature regime (13–25 °C, mean 19 °C), reflecting a mid-summer warm spell in the pre-alpine region. Susceptibility to BTV transmission was assessed from head homogenates by RT-qPCR and virus isolation.ResultsOverall, 9196 female Culicoides were exposed to the three BTV strains through an artificial membrane, with feeding rates of 14–27%. Survival rates of blood-engorged Culicoides females at eight days post-infection depended on both virus serotype and altitude of origin. Virus dissemination (Cq ≤ the cut-off value as determined by serial virus dilutions) was confirmed only for BTV-1 in C. scoticus (dissemination efficiency 22.5%; 9/40) and C. obsoletus (5.6%; 1/18) from the Swiss Plateau area. There was no strong evidence of susceptibility to infection for Culicoides from the pre-alpine area when fed with all BTV strains (BTV-1, 4 and 8).ConclusionsThis study confirms the susceptibility of C. scoticus and C. obsoletus to BTV-1 infection, including under cooler temperatures. Culicoides grisescens, which is highly abundant at higher altitudes, cannot be considered a potential vector under these temperature conditions.Electronic supplementary materialThe online version of this article (10.1186/s13071-018-3050-y) contains supplementary material, which is available to authorized users.

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“…Small invertebrates and small vertebrates were preserved in absolute ethanol. Pooled tissues or whole bodies from ethanol fixed animals were prepared for nucleic acid extraction by first digesting in proteinase K solution as described previously [ 17 ]. Full details of the species, the samples collected and the numbers examined are listed in Table 2 .…”

Section: Methodsmentioning

confidence: 99%

Identification of a novel nidovirus as a potential cause of large scale mortalities in the endangered Bellinger River snapping turtle (Myuchelys georgesi)

et al. 2018

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In mid-February 2015, a large number of deaths were observed in the sole extant population of an endangered species of freshwater snapping turtle, Myuchelys georgesi, in a coastal river in New South Wales, Australia. Mortalities continued for approximately 7 weeks and affected mostly adult animals. More than 400 dead or dying animals were observed and population surveys conducted after the outbreak had ceased indicated that only a very small proportion of the population had survived, severely threatening the viability of the wild population. At necropsy, animals were in poor body condition, had bilateral swollen eyelids and some animals had tan foci on the skin of the ventral thighs. Histological examination revealed peri-orbital, splenic and nephric inflammation and necrosis. A virus was isolated in cell culture from a range of tissues. Nucleic acid sequencing of the virus isolate has identified the entire genome and indicates that this is a novel nidovirus that has a low level of nucleotide similarity to recognised nidoviruses. Its closest relatives are nidoviruses that have recently been described in pythons and lizards, usually in association with respiratory disease. In contrast, in the affected turtles, the most significant pathological changes were in the kidneys. Real time PCR assays developed to detect this virus demonstrated very high virus loads in affected tissues. In situ hybridisation studies confirmed the presence of viral nucleic acid in tissues in association with pathological changes. Collectively these data suggest that this virus is the likely cause of the mortalities that now threaten the survival of this species. Bellinger River Virus is the name proposed for this new virus.

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Application of an embryonated chicken egg model to assess the vector competence of Australian Culicoides midges for bluetongue viruses

Cited by 11 publications

References 28 publications

Potential vectors of bluetongue virus in high altitude areas of Yunnan Province, China

Potential vectors of bluetongue virus in high altitude areas of Yunnan Province, China

Vector competence of pre-alpine Culicoides (Diptera: Ceratopogonidae) for bluetongue virus serotypes 1, 4 and 8

Identification of a novel nidovirus as a potential cause of large scale mortalities in the endangered Bellinger River snapping turtle (Myuchelys georgesi)

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