Culicoides

A prospective study was undertaken during 2013 and 2014, to determine the prevalence of African horse sickness virus (AHSV) in Culicoides midges and the incidence of infection caused by the virus in 28 resident horses on two equine establishments on the East Rand, Gauteng Province, South Africa. Field caught Culicoides midges together with whole blood samples from participating horses were collected every two weeks at each establishment. Culicoides midges and blood samples were tested for the presence of AHSV RNA by real-time quantitative reverse transcription polymerase chain reaction. Nine immunised horses became infected with AHSV during the study period, although infections were subclinical. African horse sickness virus was also identified from a field-collected midge pool. The observations recapitulate previously published data in another setting, where further investigation is warranted to determine what role subclinical infection plays in the diseases epidemiology.

African horse sickness virus (AHSV) is a virus species in the genus Orbivirus of the family Reoviridae. There are nine serotypes of AHSV showing different levels of cross neutralization. AHSV is transmitted by species of Culicoides biting midges and causes African horse sickness (AHS) in equids, with a mortality rate of up to 95% in naive horses. AHS has become a serious threat for countries outside Africa, since endemic Culicoides species in moderate climates appear to be competent vectors for the related bluetongue virus (BTV). To control AHS, live-attenuated vaccines (LAVs) are used in Africa. We used reverse genetics to generate "synthetic" reassortants of AHSV for all nine serotypes by exchange of genome segment 2 (Seg-2). This segment encodes VP2, which is the serotype-determining protein and the dominant target for neutralizing antibodies. Single Seg-2 AHSV reassortants showed similar cytopathogenic effects in mammalian cells but displayed different growth kinetics....

Background: Culicoides biting midges are hematophagous insects of veterinary importance able to transmit viruses such as bluetongue virus and Schmallenberg virus to livestock. The aim of this work was to describe the average temporal abundance of biting midges at a continental scale, by comparing the seasonal variation at six different latitude ranges from southern Spain to northern Sweden. Materials and methods: We gathered Culicoides obsoletus group trap data collected by national surveillance programs in nine European countries (Spain, France Germany, Switzerland, Austria, Denmark, Sweden, Norway, Poland) from 2007-2013. In total, 904 farms were sampled for Culicoides midges using UV light traps. We divided Europe into 6 latitudinal bands of 5° width and calculated the average weekly midge abundance as well as the average annual cumulative sum of biting midges for each of these bands. We plotted the results to visualize the spatial and temporal patterns at a continental scale. Re...

Background Culicoides biting midges transmit viruses resulting in disease in ruminants and equids such as bluetongue, Schmallenberg disease and African horse sickness. In the past decades, these diseases have led to important economic losses for farmers in Europe. Vector abundance is a key factor in determining the risk of vector-borne disease spread and it is, therefore, important to predict the abundance of Culicoides species involved in the transmission of these pathogens. The objectives of this study were to model and map the monthly abundances of Culicoides in Europe. Methods We obtained entomological data from 904 farms in nine European countries (Spain, France, Germany, Switzerland, Austria, Poland, Denmark, Sweden and Norway) from 2007 to 2013. Using environmental and climatic predictors from satellite imagery and the machine learning technique Random Forests, we predicted the monthly average abundance at a 1 km2 resolution. We used independent test sets for validation and t...

The stable fly Stomoxys calcitrans (Diptera: Muscidae) is considered as the main mechanical vector of the lumpy skin disease virus (LSDV). In addition, the mosquito species Aedes aegypti (Diptera: Culicidae) was shown to transmit the virus from donor to receptor animals. Retention of the virus for several days was shown for two additional tropical mosquito species and the biting midge Culicoides nubeculosus (Diptera: Ceratopogonidae). In the present study, viral retention for 10‐ or 7‐days post feeding on virus‐spiked blood through a membrane was shown for field‐collected Aedes japonicus and laboratory‐reared Culex pipiens, two widely distributed mosquito species in temperate regions. Viral DNA could be detected from honey‐coated Flinders Technology Associates (FTA) cards and shedded faeces for 1 or 4 days after an infectious blood meal was given to Ae. aegypti. Virus increase over time and virus dissemination was observed in laboratory‐reared C. nubeculosus, but the virus could be ...

An updated catalogue of Culicoides of Mexico is presented. It includes 86 species with their regional distribution and corresponding record references, known immature stages and associated pathogens. In addition, a taxonomic key for subgenera and species groups for Mexico is presented and an index of species by state is included.

Bluetongue is a non-contagious acute viral disease affecting ruminants. It is a disease of great clinical importance for the physical deterioration and the long convalescence that it causes and, from the economic point of view, for the colossal production losses and prevention and control expenses. It is highly feared in spite of being innocuous for man and of only medium mortality. Bluetongue virus spreads from animal to animal by biting insects of the genus Culicoides and this is the reason for the disease being more prevalent in the geographic areas where climate conditions are favorable for the insect development. The disease was described in detail in early 1900, and at present, is one of the main concerns in animal health, being studied in order to clarify its epidemiology and pathogenesis and to control its spreading. In this review, an attempt has been made to summarize some aspects of the disease related to its history, economic importance and etiological agent, the viral g...

Bluetongue has been listed as a notifiable disease by the World Organization for Animal Health (OIE). Over the past two decades, the bluetongue virus has caused severe outbreaks in domestic and wild ruminants in several countries outside the range of 40°N and 35°S due to the migration of Culicoides spp. at increasing latitudes where ruminants are susceptible. Climate change, driven by global warming, could contribute to the spread of the virus beyond those limits , mainly through the creation of more suitable conditions for the propagation and reproduction of vectors. This review provides a summary of some previously compiled data of the different BTV serotypes that are present in the Americas and the Caribbean region, specified by serological techniques or viral isolation, as well as vector species involved in disease transmission.

We report here the first nearly complete genome sequence related to curionopolis virus (CURV), that of strain AR440009, isolated from a pool of Culicoides sp. midges in Serra Norte, Pará State, northern Brazil. All genes showed similarities to those belonging to members of the family Rhabdoviridae .

Bluetongue is a major infectious disease of ruminants caused by bluetongue virus (BTV), an arbovirus transmitted by Culicoides. Here, we assessed virus and host factors influencing the clinical outcome of BTV infection using a single experimental framework. We investigated how mammalian host species, breed, age, BTV serotypes, and strains within a serotype affect the clinical course of bluetongue. Results obtained indicate that in small ruminants, there is a marked difference in the susceptibility to clinical disease induced by BTV at the host species level but less so at the breed level. No major differences in virulence were found between divergent serotypes (BTV-8 and BTV-2). However, we observed striking differences in virulence between closely related strains of the same serotype collected toward the beginning and the end of the European BTV-8 outbreak. As observed previously, differences in disease severity were also observed when animals were infected with either blood from a...

Culicoides insignis Lutz is incriminated as a vector of bluetongue virus (BTV) to ruminants in America. In South America, almost all countries have serological evidence of BTV infections, but only four outbreaks of the disease have been reported. Although clinical diseases have never been cited in Argentina, viral activity has been detected in cattle. In this study, we developed a potential distribution map of Culicoides insignis populations in northwestern Argentina using Maximum Entropy Modeling (Maxent). For the analyses, information regarding both data of specimen collections between 2003 and 2013, and climatic and environmental variables was used. Variables selection was based on the ecological relevance in relation to Culicoides spp. biology and distribution in the area. The best Maxent model according to the Jackknife test included 53 C. insignis presence records and precipitation of the warmest quarter, altitude, and precipitation of the wettest month. Accuracy was evaluated...

The vector/host ratio and host preference are important parameters for the modelling of vector-borne livestock diseases. It can be anticipated that Culicoides abundance is not homogeneously distributed in the landscape. We investigated the influence of host species (dairy cow, sheep, and a light-trap (LT) as a surrogate host) and distance of measurement to hosts on Culicoides abundance using a randomized block-design with 12 measuring days and seven 3-min aerial sweep-netting sessions per whole hour at three distances to the host (0, 10, and 25 m), from five hours before to and including one hour after sunset. Dairy cows were found to be a far stronger attractor of Culicoides midges than sheep, while both hosts were far stronger attractors of midges than the LT. Culicoides abundance declined significantly with increasing distance from the livestock hosts; this phenomenon was much stronger for dairy cows than for ewes. In contrast, Culicoides abundance increased with increasing dista...

Bluetongue was introduced into northern Europe in 2006, and members of the Obsoletus group of Culicoides biting midges were implicated as vectors of the disease. Identification of two of the four members of this group is considered difficult, if not impossible, when undertaken morphologically. Previous studies have attempted to determine morphological techniques to differentiate these species, yet have nor investigated the effect of seasonally, or geographical location on midge morphology. Here, midges were collected from two sampling locations the UK, France and Spain. Morphometric measurements were compared between the start, middle and end of the vector. While both geographical and seasonal variation in midge morphology was identified, identification techniques, based on the morphology of the abdomen, were also determined. (Resume d'auteur)

BackgroundReunion Island regularly faces outbreaks of epizootic haemorrhagic disease (EHD) and bluetongue (BT), two viral diseases transmitted by haematophagous midges of the genusCulicoides(Diptera: Ceratopogonidae) to ruminants. To date, five species ofCulicoidesare recorded in Reunion Island in which the first two are proven vector species:Culicoides bolitinos,C. imicola,C. enderleini,C. grahamiiandC. kibatiensis. Meteorological and environmental factors can severely constrainCulicoidespopulations and activities and thereby affect dispersion and intensity of transmission ofCulicoides-borne viruses. The aim of this study was to describe and predict the temporal dynamics of allCulicoidesspecies present in Reunion Island.MethodsBetween 2016 and 2018, 55 biweeklyCulicoidescatches using Onderstepoort Veterinary Institute traps were set up in 11 sites. A hurdle model (i.e. a presence/absence model combined with an abundance model) was developed for each species in order to determine me...