African horse sickness ahs is a serious arthropodborne viral disease of equids, with a. Spatial distribution modelling of culicoides diptera. Culicoides imicola is a midge species serving as vector for a number of viral diseases of livestock, including bluetongue, and african horse sickness. African horse sickness ahs is an equine disease endemic to senegal. The disease is caused by infection with african horse sickness virus. There are nine recognized serotypes of the culicoidestransmitted orbivirus responsible for african horse sickness. However, the two diseases with the greatest veterinary impact among these are. Culicoides species as potential vectors of african horse. African horse sickness caused by genome reassortment and. Evaluating african horse sickness virus in horses and. African horse sickness ahs is a peracute, acute, subacute or mild infectious but noncontagious disease of equids caused by african horse sickness virus ahsv. African horse sickness ahs is well known as one of the worst diseases affecting horses out there. Serotype 9 is widespread in the endemic region, while serotypes 1 to 8 occur in limited areas.
The vectors involved in the transmission of this arbovirus have never been studied specifically in senegal. Updating the global occurrence of culicoides imicola, a. African horse sickness caused by genome reassortment. Just like both ebola in people and african swine fever virus in pigs, it causes severe haemorrhage and oedema in all organ systems. Ahs is transmitted by certain species of midges, most commonly culicoides imicola which is usually restricted to the southern parts of europe, but otherwise found throughout africa. Since 1997, south africa has maintained an ahs controlled area. Detection of african horse sickness virus in culicoides. Sop manual 12 african horse sickness etiology and ecology 1. 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. Pdf african horse sickness virus ahsv is a lethal arbovirus of equids. African horse sickness an overview sciencedirect topics. While unidentified viruses pose serious challenges for the prediction of epidemiology and pathogenicity carpenter and others 20, perhaps the greatest concern in europe currently surrounds the potential for the emergence of a wellknown culicoidesborne arbovirus, african horse sickness virus ahsv. Infectious disease is transmitted by culicoides spp.
This vectorborne, viral disease affects all members of the equidae family. African horse sickness ahs, a noncontagious infectious disease caused by a rna virus in the orbivirus genus within the reoviridae family affecting all equids, is endemic in subsaharan africa. With the related bluetongue virus, which utilises the same vector species of culicoides this has, since 1998, precipitated the worst outbreaks of bluetongue disease. African horse sickness ahs is a highly infectious and deadly disease caused by african horse sickness virus.
This disease can be caused by any of the nine serotypes of this virus. African horse sickness ahs is caused by a virus of the family reoviridae of the. Etiology african horse sickness s epidemiology african. Culicoides species abundance and potential overwintering of african horse sickness virus in the onderstepoort area, gauteng, south africa. The african horse sickness epizootic in senegal in 2007 caused considerable mortality in the equine population and hence major economic losses. This study focused on detection of ahsv in culicoides imicola diptera. Miller, arnon gal, in pathologic basis of veterinary disease sixth edition, 2017. African horse sickness is a devastating disease that causes great suffering and many fatalities amongst horses in subsaharan africa. African horse sickness virus is a doublestranded rna virus which causes a noncontagious, infectious arthropodborne disease of equines and occasionally dogs. Culicoides is a genus of biting midges in the family ceratopogonidae.
It can be acute, subacute, or subclinical and is characterized by clinical signs and lesions associated with respiratory and circulatory impairment. Like leptoconops, the genus has a long fossil record, with earliest known fossils being from the burmese amber, around 99 million. A proven vector of the disease is culicoides imicola mellor and boorman, 1995. The spatial and seasonal distribution of african horse. Several studies were initiated in the niayes area in order to better characterize culicoides.
The only proven field vector is the biting midge culicoides imicola, although c. It is endemic in subsaharan africa and thought to be the most lethal viral disease of horses. For example, medications and therapy to alleviate colic may be offered. In senegal, the last epidemic of african horse sickness ahs occurred in 2007. The virus is transmitted to horses by biting midges in the genus culicoides. The stabling of horses at night reportedly offers protection from african horse sickness and the most significant vector of the disease, culicoides imicola kieffer, has been shown to be exophilic.
This first study of the spatial and temporal dynamics of the culicoides diptera. In addition to the african horse sickness virus ahsv, culicoides may also transmit bluetongue virus btv, epizootic haemorrhagic disease virus ehdv, equine encephalitis virus eev, akabane virus, bovine ephemeral fever virus and viruses in the palyam group. Africa african horse sickness arbovirus culicoides equids midges orbivirus. African horse sickness is an insectborne culicoides spp.
The equids most severely affected by the virus are horses, ponies, and european donkeys. Geographic distribution african horse sickness is endemic in subsaharan africa. Fever will be addressed with medication to reduce it, and if there is a need for oxygen supplementation, this will be provided. The african horse sickness virus ahsv is transmitted to the. In certain highlying regions of south africa, however, c. Introduction african horse sickness ahs, an arthropodborne viral disease affecting all equines, is considered to be the most lethal viral disease of horses. The western part of the country the niayes area concentrates modern farms with exotic horses of high value and was highly affected during the 2007 outbreak that has started in the area. The african horse sickness wales regulations 20 provide the legal powers to allow the control of african horse sickness ahs. There are over species in the genus, which is divided into many subgenera. With mortality reaching up to 95% in susceptible horses and the apparent reoccurrence of cases in regions deemed non. Affected horses essentially suffocate as their lungs fill with fluid. The principal vectors for transmission of ahsv are culicoides biting midges. Bluetongue, schmallenberg virus african horse sickness. It is caused by a virus of the genus orbivirus belonging to the family reoviridae.
Classification of the causative agent resistance to. African horse sickness virus, culicoides vectors, horses, south africa, subclinical. The occurrence is seasonal because the insect vectors thrive in hot, wet conditions. There was a recent epizootic of ahs in iberia 1987. Use of realtime quantitative reverse transcription. African horse sickness and the overwintering of culicoides spp. Summary a prospective study was undertaken during 20 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 vaccinated resident horses on two equine.
African horse sickness ahs is an infectious, noncontagious arthropodborne disease of equids, caused by the african horse sickness virus ahsv, an orbivirus of the reoviridae family. African horse sickness ahs and bluetongue bt are the two most important animal diseases caused by culicoidestransmitted viruses and are of major international significance. African horse sickness, equine movements, import risk assessment, risk of introduction, culicoides, quantitative risk, midge background african horse sickness ahs is a highly fatal viral vectorborne disease that is transmitted among equine hosts by culicoides midges diptera. African horse sickness ahs is an arboviral disease of equids transmitted by culicoides biting midges.
The multiplication of african horsesickness virus in two. The document is structured with the following broad sections that follow events as they might. Several species are known to be vectors of various diseases and parasites which can affect animals. This is the most lethal of equine diseases, with mortality in excess of 90%. Reoviridae, of which there are nine serotypes, all transmitted by. Pdf culicoides species abundance and potential over. It is the only equine disease for which the world organization for animal health has introduced specific guidelines for member countries seeking official recognition of diseasefree status. African horse sickness aetiology epidemiology diagnosis prevention and control references aetiology classification of the causative agent african horse sickness ahs is caused by a virus of the family reoviridae of the genus orbivirus. Ahsv is transmitted by the midges culicoides imicola. Stabling and the protection of horses from culicoides. Ahsv affects draft, thoroughbred, and companion horses and donkeys in africa, asia, and europe. Although ahs currently occurs only in subsaharan africa, various species of culicoides midges occur throughout the entire inhabited world. Pdf orbivirus detection from culicoides collected on.
Nine distinct, internationally recognised serotypes of the virus have so far been identified. Modeling the global distribution of culicoides imicola. The african horse sickness scotland order 2012 and. In mules, the mortality rate is approximately 50%, and in european and asian donkeys, 5% to 10%. Ahs is caused by african horse sickness virus ahsv, which. Animals that recover from african horse sickness develop good immunity to the infecting serotype and partial immunity to other serotypes. African horse sickness and the overwintering of culicoides.
African horse sickness ahs is an insectborne, viral disease of equids that is endemic to subsaharan africa. African horse sickness ahs is one of a number of diseases known to be potentially damaging to the livestock economy. Unfortunately, there is no cure for african horse sickness, however supportive care may be offered. Culicoides imicola is the main vector transmitting viruses causing animal diseases such as bluetongue, african horse sickness, and schmallenberg. African horse sickness ahs is a vectorborne viral disease, affecting all species of equidae. African horse sickness ahs is an infectious, noncontagious, vectorborne viral. A spatiotemporal model to assess the introduction risk of. Ahs is not directly contagious, but is known to be spread by insect. African horse sickness is an economically highly important noncontagious but infectious orbivirus disease that is transmitted by various species of culicoides midges.
African horse sickness ahs virus causes a noncontagious. Ahs is usually confined to africa south of the sahara but periodically makes excursions into southern europe and across asia as far as pakistan and india mellor and. A possible role for domestic dogs in the spread of african. African horse sickness ahs is a hemorrhagic viral fever of horses. The presence at different latitudes and the seasonal distribution of two known or potential vectors of african horse sickness ahs virus culicoides imicola and c. Type 9 african horsesickness virus multiplied to a high titre in bothculicoides nubeculosus andc.
The first research on subsaharan culicoides dates to 1908 when two species were described from namibia. Ceratopogonidae midges, the vectors of african horse sickness virus a hostvector contact study in the niayes area of senegal. African horse sickness veterinary research, a journal on animal. The possibility that outbreaks of bluetongue bt and african horse sickness ahs might occur via longdistance wind dispersion ldwd of their insect vector culicoides spp. The disease has significant economic consequences for the equine industry both in southern africa and. African horse sickness ahs, a disease of equids caused by the ahs virus, is of major concern in south africa. It is caused by nine different serotypes of the orbivirus african horse sickness virus ahsv and it is spread by culicoid midges.
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