Development and evaluation of gold nanoprobe based lateral flow device for rapid and sensitive serodetection of Bluetongue in sheep

Bluetongue (BT) disease is a viral, insect borne, noncontagious illness of small ruminants caused by Orbivirus, impacting huge economic loss worldwide. The existing BT diagnostic techniques are costly, time-consuming and require both specialized equipment and also skilled personnel. So there is need to develop a rapid, sensitive, on site detection assay for diagnosis of BT. This study utilized secondary antibody derivatized Gold nanoprobes for rapid and sensitive detection of BT over lateral flow device (LFD). The detection limit for this assay was found 1.875 µg of BT IgG/ml and a comparison between LFD and indirect ELISA was performed and the sensitivity and specificity was found at 96% and 99.23%, respectively, with observed kappa value of 0.952. This developed LFD may therefore offer a quick, affordable and accurate diagnosis of BT disease at the field level.

Economic Impact of a Bluetongue Serotype 8 Epidemic in Germany

Background and Objectives: Germany was affected by Bluetongue virus serotype 8 (BTV-8) from 2006 to 2009 and recorded new cases since December 2018. We assessed the economic impact of the epidemic from the first cases in 2006 until 2018. Direct costs include production losses, animal deaths, and veterinary treatment. Indirect costs include surveillance, additional measures for animal export, disease control (preventive vaccination and treatment with insecticides), vector monitoring, and administration. Methodology: To estimate the financial impact of BTV-8 on different species and production types at the animal level, we performed a gross margin analysis (GMA) for dairy and beef cattle, and sheep. To estimate the impact on the national level, we used a modified framework described by Rushton et al. (1) and applied a methodology described by Bennett (2). Both the GMA and the economic model on national level were implemented in Excel and the Excel Add-in @Risk. The tools, which are widely applicable, also for other diseases, are made available here. Results: The financial impact of a BTV-8 infection at the animal level was estimated at 119-136 Euros in dairy cattle, at 27 Euros in beef cattle, and at 74 Euros in sheep. At the national level, the impact of the BTV-8 epidemic ranged between 157 and 203 million Euros (mean 180 million Euros). This figure consisted of 132 (73%) and 48 (27%) million Euros for indirect and direct costs. Indirect costs included 89 million Euros (67%) for vaccination, 18 million Euros (14%) for insecticide treatment, 15 million Euros (11%) for diagnostic testing of animals dispatched for trade, 8 million Euros (6%) for monitoring and surveillance, and 3 million Euros (2%) for administration. The highest costs were induced by a compulsory vaccination campaign in 2008 (51 million Euros; 28% of the total costs) and the disease impact on cattle in 2007 (30 million Euros; 17%). Discussion: We compare the outcome of our study with economic analyses of Bluetongue disease in other countries, and discuss the suitability of GMA and the developed tools for a wider application in veterinary economics.

Simultaneous detection of five notifiable viral diseases of cattle by single-tube multiplex real-time RT-PCR

Multiplexed real-time PCR (qPCR) assays enable the detection of several target genes in a single reaction, which is applicable for simultaneous testing for the most important viral diseases in samples obtained from ruminants with unspecific clinical symptoms. Here, reverse transcription qPCR (RT-qPCR) systems for the detection of bovine viral diarrhoea virus (BVDV) and bluetongue virus (BTV) were combined with an internal control system based on the beta-actin gene. Additionally, a background screening for three further major pathogens of cloven-hoofed animals reportable to the World Organisation for Animal Health, namely foot-and-mouth disease virus, epizootic haemorrhagic disease virus, and Rift Valley fever virus, was integrated using the identical fluorophore for the respective RT-qPCR assays. Every pathogen-specific assay had an analytical sensitivity of at least 100 genome copies per reaction within the multiplex approach, and a series of reference samples and clinical specimens obtained from cattle, but also from small ruminants, were detected reliably. The qPCR systems integrated in the background screening were even not influenced by the simultaneous amplification of very high BVDV and BTV genome copy numbers. The newly developed multiplex qPCR allows the specific and sensitive detection of five of the most important diseases of ruminants and could be used in the context of monitoring programs or for differential diagnostics.

Why German farmers have their animals vaccinated against Bluetongue virus serotype 8: results of a questionnaire survey

In response to the Bluetongue disease epidemic in 2006-2007, Germany started in 2008 a country-wide mandatory vaccination campaign. By 2009 the number of new outbreaks had decreased so that vaccination became voluntary in 2010. We conducted a questionnaire survey in cattle and sheep farms in three German federal states, namely North-Rhine Westphalia, Rhineland Palatinate and Saxony-Anhalt to estimate the vaccination uptake in 2010, the intention to vaccinate in 2011 and the main determinants of refusal or acceptance to do so. The results showed that 42.8% (40.6-45.1) of the cattle farmers and 33.8% (31.8-35.8) of the sheep farmers had their animals vaccinated in 2010, whereas 40.7% (38.5-43.0) of cattle and 37.93% (35.8-40.1) sheep farmers expressed their intention to vaccinate in 2011. The main reasons mentioned for having animals vaccinated against BTV-8 were ability to export animals, prevention of production losses, subsidized vaccination, and recommendation by the veterinarian. Motives for refusing vaccination were presumed low risk of infection, costs, absence of clinical BT symptoms, presumed negative cost-benefit ratio, and negative experience with previous vaccination events (side effects). We assume that in order to increase farmers' motivation to have their animals immunized against BTV-8, (1) the vaccination needs to be subsidized, (2) combined vaccines with several different BT serotypes or even other diseases should be available and (3) farmers need to be better informed about the safety and benefit of vaccination.

Larval development sites of the main Culicoides species (Diptera: Ceratopogonidae) in northern Europe and distribution of coprophilic species larvae in Belgian pastures

Some Culicoides species of biting midges (Diptera: Ceratopogonidae) are biological virus vectors worldwide and have indeed been associated with outbreaks of important epizoonoses in recent years, such as bluetongue and Schmallenberg disease in northern Europe. These diseases, which affect domestic and wild ruminants, have caused considerable economic losses. Knowledge of substrates suitable for Culicoides larval development is important, particularly for the main vector temperate species. This study, realized during two years, aimed to highlight the larval development sites of these biting midge species in the immediate surroundings of ten Belgian cattle farms. Moreover, spatial distribution of the coprophilic Culicoides larvae (C. chiopterus and C. dewulfi) within pastures was studied with increasing distance from farms along linear transects (farm-pasture-woodland). A total of 4347 adult specimens belonging to 13 Culicoides species were obtained by incubation of 2131 soil samples belonging to 102 different substrates; 18 of these substrates were suitable for larval development. The Obsoletus complex (formed by two species) was observed in a wide range of substrates, including silage residues, components of a chicken coop, dung adhering to walls inside stables, leftover feed along the feed bunk, a compost pile of sugar beet residues, soil of a livestock trampling area, and decaying wood, while the following served as substrates for the other specimens: C. chiopterus, mainly cow dung; C. dewulfi, cow dung and molehill soil; C. circumscriptus, algae; C. festivipennis, algae and soil in stagnant water; C. nubeculosus, algae and silt specifically from the edge of a pond; C. punctatus, mainly wet soil between silage reserves; C. salinarius, algae; and C. stigma, algae and wet soil between silage reserves. We also recorded significantly higher densities of coprophilic larvae within pastures in cow dung located near forests, which is likely due to the localization of potential hosts; the presence of these larvae within cow dung is, however, uninfluenced by relative distance from farms. A better knowledge of the microhabitats of Culicoides biting midges and their spatial distribution may allow the development of targeted species-specific vector control strategies, and may help to prevent the creation of new larval development sites.

Pulmonary artery haemorrhage in newborn calves following bluetongue virus serotype 8 experimental infections of pregnant heifers

The emergence of bluetongue disease (BT) among livestock in Europe in 2006 raised many questions including the occurrence and epidemiological significance of foetal infections in cattle. To clarify these aspects, vaccinated and unvaccinated pregnant heifers were sequentially infected twice in an isolation facility (biosafety level 3) with a northern European outbreak strain of Bluetongue virus serotype 8 (BTV-8). The study was terminated 2 months after calving with necropsy of the dams and their offspring. The cattle were monitored throughout the study by clinical scoring and for the presence of circulating neutralising antibodies, and after calving for the presence of infectious virus and viral RNA in blood and milk. Four calves, one born from a vaccinated dam and three from non-vaccinated ones, that were infected at 120 days of gestation had obvious haemorrhage of the pulmonary artery at necropsy. Although haemorrhage of the pulmonary artery is highly characteristic of BT, viral RNA was not detected in any of these calves. Furthermore, although none of the calves born from heifers infected prior to mid-gestation had teratogenic BTV typical brain lesions, some had lesions at birth suggestive of in utero BTV infection. Despite the lack of viral RNA detection, the presence of haemorrhage of the pulmonary artery deserves to be reported as a new observation in the context of the multiple investigations having as main subject the BTV placental crossing in cattle.