A serosurvey of bluetongue and epizootic haemorrhagic disease in a convenience sample of sheep and cattle herds in Zimbabwe.

A convenience sample of sheep and cattle herds around the cities of Harare, Kwekwe and Bulawayo, located in the Highveld region of Zimbabwe, was used to estimate the seroprevalence and sero-incidence of bluetongue virus (BTV) and epizootic haemorrhagic disease virus (EHDV) antibodies. A competitive enzyme-linked immunosorbent assay was used to identify serum antibodies against BTV and EHDV across three rainy seasons. The median sero-prevalence of BTV and EHDV antibodies in cattle was 62% (interquartile range [IQR]: 30-89) and 56% (IQR: 5-77), respectively.

The sero-prevalence and sero-incidence of African horse sickness and equine encephalosis in selected horse and donkey populations in Zimbabwe.

Sentinel herds and samples submitted by private equine practitioners were used to determine the sero-prevalence and sero-incidence of African horse sickness virus (AHSV) and equine encephalosis virus (EEV) in horse and donkey populations in the Highveld region of Zimbabwe. The sero-prevalence and sero-incidence of antibodies against these viruses were determined using the competitive enzyme-linked immunosorbent assay (ELISA) for the detection of serum antibodies. In donkeys, the median sero-prevalence of AHSV antibodies, across the three rainy seasons under study, was 75% (inter quartile range [IQR] 67-83), with a seasonal median sero-incidence of 45% (IQR 40-63).

African Horse Sickness Virus: History, Transmission, and Current Status.

African horse sickness virus (AHSV) is a lethal arbovirus of equids that is transmitted between hosts primarily by biting midges of the genus Culicoides (Diptera: Ceratopogonidae). AHSV affects draft, thoroughbred, and companion horses and donkeys in Africa, Asia, and Europe. In this review, we examine the impact of AHSV critically and discuss entomological studies that have been conducted to improve understanding of its epidemiology and control.

Using shared needles for subcutaneous inoculation can transmit bluetongue virus mechanically between ruminant hosts.

Bluetongue virus (BTV) is an economically important arbovirus of ruminants that is transmitted by Culicoides spp. biting midges. BTV infection of ruminants results in a high viraemia, suggesting that repeated sharing of needles between animals could result in its iatrogenic transmission.

The occurrence of Culicoides species, the vectors of arboviruses, at selected trap sites in Zimbabwe.

A study of the distribution of Culicoides species was conducted by establishing 12 light trap sites over five rainy seasons between 1998 and 2003 covering all the geo-climatic natural regions of Zimbabwe. In total, 279 919 specimens of Culicoides were trapped over a total of 163 trapping nights. The highest median counts of Culicoides per trapping night were recorded in natural region III, which has climatic conditions conducive to the successful development of the larvae.

Environmental drivers of Culicoides phenology: how important is species-specific variation when determining disease policy?

Since 2006, arboviruses transmitted by Culicoides biting midges (Diptera: Ceratopogonidae) have caused significant disruption to ruminant production in northern Europe. The most serious incursions involved strains of bluetongue virus (BTV), which cause bluetongue (BT) disease. To control spread of BTV, movement of susceptible livestock is restricted with economic and animal welfare impacts.

Measurement of the infection and dissemination of bluetongue virus in culicoides biting midges using a semi-quantitative rt-PCR assay and isolation of infectious virus.

Background: Culicoides biting midges (Diptera: Ceratopogonidae) are the biological vectors of globally significant arboviruses of livestock including bluetongue virus (BTV), African horse sickness virus (AHSV) and the recently emerging Schmallenberg virus (SBV). From 2006-2009 outbreaks of BTV in northern Europe inflicted major disruption and economic losses to farmers and several attempts were made to implicate Palaearctic Culicoides species as vectors. Results from these studies were difficult to interpret as they used semi-quantitative RT-PCR (sqPCR) assays as the major diagnostic tool, a technique that had not been validated for use in this role.

Investigation of diel activity of Culicoides biting midges (Diptera: Ceratopogonidae) in the United Kingdom by using a vehicle-mounted trap.

Truck trap collections of Culicoides biting midges (Diptera: Ceratopogonidae) were made during 2 yr of sampling from 2008 to 2009 at a farm site in southern England. Samples were collected from 810 sample runs carried out over 52 d and contained 7,095 Culicoides of which more than half (50.3%) were identified as Culicoides obsoletus Meigen by using a multiplex polymerase chain reaction assay.

Involvement of the skin during bluetongue virus infection and replication in the ruminant host.

Bluetongue virus (BTV) is a double stranded (ds) RNA virus (genus Orbivirus; family Reoviridae), which is considered capable of infecting all species of domestic and wild ruminants, although clinical signs are seen mostly in sheep. BTV is arthropod-borne ("arbovirus") and able to productively infect and replicate in many different cell types of both insects and mammalian hosts. Although the organ and cellular tropism of BTV in ruminants has been the subject of several studies, many aspects of its pathogenesis are still poorly understood, partly because of inherent problems in distinguishing between "virus replication" and "virus presence".

Saliva proteins of vector Culicoides modify structure and infectivity of bluetongue virus particles.

Bluetongue virus (BTV) and epizootic haemorrhagic disease virus (EHDV) are related orbiviruses, transmitted between their ruminant hosts primarily by certain haematophagous midge vectors (Culicoides spp.). The larger of the BTV outer-capsid proteins, 'VP2', can be cleaved by proteases (including trypsin or chymotrypsin), forming infectious subviral particles (ISVP) which have enhanced infectivity for adult Culicoides, or KC cells (a cell-line derived from C.

Selective cloning, characterization, and production of the Culicoides nubeculosus salivary gland allergen repertoire associated with equine insect bite hypersensitivity.

Salivary gland proteins of Culicoides spp. have been suggested to be among the main allergens inducing IgE-mediated insect bite hypersensitivity (IBH), an allergic dermatitis of the horse. The aim of our study was to identify, produce and characterize IgE-binding salivary gland proteins of Culicoides nubeculosus relevant for IBH by phage surface display technology.

Distribution of Culicoides in Greece.

Culicoides biting midges (Diptera: Ceratopogonidae) were trapped between 1999 and 2004 at 122 locations in mainland Greece and on most of the larger Aegean and Ionian islands, using OVI light traps, in order to determine the distribution and seasonal activity of bluetongue virus vectors and other Culicoides species. Thirty-nine Culicoides species were identified, six of which (C. furcillatus, C.

The spread of bluetongue virus serotype 8 in Great Britain and its control by vaccination.

Background: Bluetongue (BT) is a viral disease of ruminants transmitted by Culicoides biting midges and has the ability to spread rapidly over large distances. In the summer of 2006, BTV serotype 8 (BTV-8) emerged for the first time in northern Europe, resulting in over 2000 infected farms by the end of the year. The virus subsequently overwintered and has since spread across much of Europe, causing tens of thousands of livestock deaths.

Transplacental transmission of bluetongue virus 8 in cattle, UK.

To determine whether transplacental transmission could explain overwintering of bluetongue virus in the United Kingdom, we studied calves born to dams naturally infected during pregnancy in 2007-08. Approximately 33% were infected transplacentally; some had compromised health. In all infected calves, viral load decreased after birth; no evidence of persistent infection was found.

Viraemia and clinical disease in Dorset Poll sheep following vaccination with live attenuated bluetongue virus vaccines serotypes 16 and 4.

The spread of bluetongue virus (BTV) is most successfully controlled by vaccination of susceptible ruminant populations. Currently two different types of BTV vaccines are used for this purpose; inactivated, mostly monovalent vaccine formulations and modified live virus vaccines (MLVs). Clinical signs and viraemia in Dorset Poll sheep vaccinated with BTV-4 and BTV-16 MLVs or inoculated with homogenates of midges (C.

A modeling framework to describe the transmission of bluetongue virus within and between farms in Great Britain.

Background: Recently much attention has been given to developing national-scale micro-simulation models for livestock diseases that can be used to predict spread and assess the impact of control measures. The focus of these models has been on directly transmitted infections with little attention given to vector-borne diseases such as bluetongue, a viral disease of ruminants transmitted by Culicoides biting midges. Yet BT has emerged over the past decade as one of the most important diseases of livestock.

Bluetongue in Europe: past, present and future.

The recent arrival in Northern and Western (NW) Europe of bluetongue virus (BTV), which causes the ruminant disease 'bluetongue', has raised the profile of this vector-borne ruminant disease and sparked discussions on the reasons for its sudden emergence so far north. This expansion has not happened in isolation and the disease has been expanding into Southern and Eastern Europe for the last decade. This shifting disease distribution is being facilitated by a number of different introduction mechanisms including the movement of infected livestock, the passive movement of infected Culicoides on the wind and, in NW Europe, an unknown route of introduction.

Culicoides and the emergence of bluetongue virus in northern Europe.

In June 2006, bluetongue virus, an arboviral pathogen of ruminants, appeared in northern Europe for the first time, successfully overwintered and subsequently caused substantial losses to the farming sector in 2007 and 2008. This emergence served as a test of how the probability of arboviral incursion into new regions is assessed and has highlighted the reliance of decision making on paradigms that are not always underpinned by basic biological data. In this review, we highlight those areas of the epidemiology of bluetongue that are poorly understood, reflect upon why certain vital areas of research have received little attention and, finally, examine strategies that could aid future risk assessment and intervention.

Adaptive strategies of African horse sickness virus to facilitate vector transmission.

African horse sickness virus (AHSV) is an orbivirus that is usually transmitted between its equid hosts by adult Culicoides midges. In this article, we review the ways in which AHSV may have adapted to this mode of transmission. The AHSV particle can be modified by the pH or proteolytic enzymes of its immediate environment, altering its ability to infect different cell types.

Where does bluetongue virus sleep in the winter?

Bluetongue recently spread to northern Europe for the first time. Outbreaks in temperate regions are often interrupted by cold weather, but may reappear months later. Where, then, might bluetongue virus sleep in the winter?

Bluetongue in Europe and the Mediterranean Basin: history of occurrence prior to 2006.

Bluetongue virus (BTV) exists around the world in a broad band covering much of the Americas, Africa, southern Asia and northern Australia. Historically, it also occasionally occurred in the southern fringes of Europe. It is considered to be one of the most important diseases of domestic livestock.

Sequence analysis of bluetongue virus serotype 8 from the Netherlands 2006 and comparison to other European strains.

During 2006 the first outbreak of bluetongue ever recorded in northern Europe started in Belgium and the Netherlands, spreading to Luxemburg, Germany and north-east France. The virus overwintered (2006-2007) reappearing during May-June 2007 with greatly increased severity in affected areas, spreading further into Germany and France, reaching Denmark, Switzerland, the Czech Republic and the UK. Infected animals were also imported into Poland, Italy, Spain and the UK.

Bluetongue virus: virology, pathogenesis and immunity.

Bluetongue (BT) virus, an orbivirus of the Reoviridae family encompassing 24 known serotypes, is transmitted to ruminants via certain species of biting midges (Culicoides spp.) and causes thrombo-hemorrhagic fevers mainly in sheep. During the 20th century, BTV was endemic in sub-tropical regions but in the last ten years, new strains of BTV (serotypes 1, 2, 4, 8, 9, 16) have appeared in Europe leading to a devastating disease in naive sheep and bovine herds (serotype 8).

Bluetongue epidemiology in the European Union.

Bluetongue (BT) is a reportable disease of considerable socioeconomic concern and of major importance in the international trade of animals and animal products. Before 1998, BT was considered an exotic disease in Europe. From 1998 through 2005, at least 6 BT virus strains belonging to 5 serotypes (BTV-1, BTV-2, BTV-4, BTV-9, and BTV-16) were continuously present in the Mediterranean Basin.

Quantifying bluetongue virus in adult Culicoides biting midges (Diptera: Ceratopogonidae).

A TissueLyser system (QIAGEN) was used to rapidly and accurately estimate bluetongue virus "loads" in individual adult Culicoides sonorensis Wirth & Jones (Diptera: Ceratopogonidae). The optimized homogenization program that was developed, involved shaking insects for 1 min at 25 Hz with 2- or 3-mm stainless steel ball bearings. This program was used to measure the quantities of bluetongue virus present in insects that had either been inoculated or had ingested a viremic bloodmeal through an artificial membrane.