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Research
Research EDITORIAL
Bluetongue, Schmallenberg virus… African horse sickness? Simon Carpenter Following the incursions into the UK of bluetongue virus (BTV) in 2007 and Schmallenberg virus (SBV) in 2011, an increasingly pertinent question for those tasked with predicting and responding to outbreaks of livestock arboviruses in the UK is, what is next? Culicoides, the biting midges that transmit BTV and SBV, also act as vectors for over 50 described arboviruses worldwide, although we currently know very little about the vast majority of these, even in the countries in which they were originally identified. In addition, it is likely there are a large number of previously unidentified Culicoides-borne arboviruses that have the potential to arrive in northern Europe with little warning (as in the case of SBV). While unidentified viruses pose serious challenges for the prediction of epidemiology and pathogenicity (Carpenter and others 2013), perhaps the greatest Simon Carpenter, BSc, PhD, The Pirbright Institute, Ash Road, Woking, Surrey GU24 0NF, UK e-mail: [email protected]
concern in Europe currently surrounds the potential for the emergence of a well-known Culicoides-borne arbovirus, African horse sickness virus (AHSV). AHSV is among the most lethal equine viruses, and outbreaks in endemic regions of Africa are both damaging and traumatic. While the global social and economic impact of AHSV has declined with the replacement of the horse with mechanised transport, in Britain the equine industry’s gross output is estimated to be £3.8 billion (Beta 2011) with a further £2.5 billion resulting from expenditure in the British racing industry (Deloitte 2013). In addition, the UK equine industry employs, directly and indirectly, an estimated 267,000 people, with approximately 3.5 million people riding horses at least once in 2011 (Beta 2011). In light of this, in addition to major welfare implications, the financial consequences of an AHSV outbreak could be devastating. AHSV has emerged from sub-Saharan Africa, causing outbreaks of disease in Spain during 1966 and in Spain and Portugal between 1987 and 1990. While it was assumed that Culicoides imicola, the primary
March 22, 2014 | Veterinary Record | 299
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Research vector of AHSV in sub-Saharan (a) (b) Africa, was responsible for most of the viral spread, virus was also isolated from other Culicoides species known to be present in northern Europe (see Mellor and Hamblin 2004 for a review). The presence of these Culicoides species on equine holdings in the UK and across northern Europe is already well characterised due to their role in causing seasonal dermatitis or ‘sweet-itch’ (a) Culicoides biting midge photographed while blood-feeding. (b) Horse owners are usually aware of (Mellor and McCaig 1974). From this starting point, Robin Culicoides activity as they can cause seasonal dermatitis in susceptible animals and colleagues (2014), in a paper summarised on p 301 of this issue of s3/1367616/equines-and-their-links-toThe response to a potential AHSV Veterinary Record, report a preliminary survey culicoides-biting-midges. incursion into the UK is also a major of Culicoides on equine premises in and consideration and is outlined in the African References around Newmarket using ultraviolet light horse sickness control strategy for Great BETA (2011) National Equestrian Survey 2011. British emitting diode suction traps. Their results Britain (Defra 2012). While vaccination is Equestrian Trade Association suggest that the majority of potential AHSV universally recognised as being the only Carpenter, S., Groschup, M. H., Garros, vector species of Culicoides are abundant reliable method of controlling AHSV, C., Felippe-Bauer, M. L. & Purse, B. V. (2013) Culicoides biting midges, arboviruses and public health across the area sampled and that they are movement restrictions and methods to in Europe. Antiviral Research 100, 102-113 feeding on horses. This indicates that there reduce contact between Culicoides and horses Carpenter, S. Mellor, P. S. & Torr, S. J. (2008) is the potential for transmission of AHSV are the only means of reducing transmission Control techniques for Culicoides biting midges and their application in the UK and northwestern Palaearctic. between and within livestock holdings before vaccination is implemented. Medical and Veterinary Entomology 22, 175-187 in the UK, but several other areas of These techniques have been reviewed in Defra (2012) African horse sickness control strategy uncertainty remain. These are summarised detail (Carpenter and others 2008) and for Great Britain. www.gov.uk/government/uploads/ both within the paper itself and in a recent include many options already familiar system/uploads/attachment_data/file/244348/pb13831ahs-control-strategy-20130923.pdf. Accessed March mathematical analysis of how transmission to horse owners attempting to combat 17, 2014 parameters would influence the spread of cases of sweet itch (for example, stabling Deloitte (2013) Economic Impact of British AHSV in the UK (Lo Iocono and others in screened accommodation, clearing of Racing 2013. www.britishhorseracing.com/economic_impact_2013/Economic_Impact_of_British_ 2013). A major advance in understanding larval development sites and application Racing2013.pdf. Accessed March 17, 2014 potential spatial spread has been achieved of insecticides or repellents). The efficacy Lo Iacono, G., Robin, C. A., Newton, J. R., in the latter study by creating a credible of such control techniques for Culicoides in Gubbins, S. & Wood, J. L. N. (2013) Where are the horses? With the sheep or cows? Uncertain host locamap of horse locations in the UK, which reducing transmission of AHSV is only tion, vector-feeding preferences and the risk of African had previously been restricted to owner poorly understood. horse sickness transmission in Great Britain. Journal of addresses. Interestingly, however, Lo Iocono The areas of interest highlighted above the Royal Society Interface 10, 20130194 and colleagues (2013) also highlight that are now being addressed through a project Mellor, P. S. & Hamblin, C. (2004) African horse sickness. Veterinary Research 35, 445-466 non-susceptible hosts (for example, cattle funded by the Horserace Betting Levy Mellor, P. S. & McCaig, J. (1974) The proband sheep) may have a significant influence Board that will examine both Culicoides host able cause of ‘sweet itch’ in England. Veterinary Record on AHSV transmission. A key question preference and the control of Culicoides on doi:10.1136/vr.95.18.411 Robin, M., Archer, D., Garros, C., Gardès, is whether the presence of these nonUK equine premises. As part of these studies, L. & Baylis, M. (2014) Threat of midgeborne equine susceptible hosts in proximity to stables equine owners are invited to contribute disease: investigation of Culicoides species on UK equine increases biting of horses by increasing information regarding their husbandry and premises. Veterinary Record doi:10.1136/vr.102151 Culicoides abundance, or reduce rates by control measures via an online questionnaire providing more attractive hosts. available at www.surveygizmo.com/ doi: 10.1136/vr.g2196
300 | Veterinary Record | March 22, 2014
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Bluetongue, Schmallenberg virus… African horse sickness? Simon Carpenter Veterinary Record 2014 174: 299-300
doi: 10.1136/vr.g2196 Updated information and services can be found at: http://veterinaryrecord.bmj.com/content/174/12/299
These include:
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Research
Research EDITORIAL
Bluetongue, Schmallenberg virus… African horse sickness? Simon Carpenter Following the incursions into the UK of bluetongue virus (BTV) in 2007 and Schmallenberg virus (SBV) in 2011, an increasingly pertinent question for those tasked with predicting and responding to outbreaks of livestock arboviruses in the UK is, what is next? Culicoides, the biting midges that transmit BTV and SBV, also act as vectors for over 50 described arboviruses worldwide, although we currently know very little about the vast majority of these, even in the countries in which they were originally identified. In addition, it is likely there are a large number of previously unidentified Culicoides-borne arboviruses that have the potential to arrive in northern Europe with little warning (as in the case of SBV). While unidentified viruses pose serious challenges for the prediction of epidemiology and pathogenicity (Carpenter and others 2013), perhaps the greatest Simon Carpenter, BSc, PhD, The Pirbright Institute, Ash Road, Woking, Surrey GU24 0NF, UK e-mail: [email protected]
concern in Europe currently surrounds the potential for the emergence of a well-known Culicoides-borne arbovirus, African horse sickness virus (AHSV). AHSV is among the most lethal equine viruses, and outbreaks in endemic regions of Africa are both damaging and traumatic. While the global social and economic impact of AHSV has declined with the replacement of the horse with mechanised transport, in Britain the equine industry’s gross output is estimated to be £3.8 billion (Beta 2011) with a further £2.5 billion resulting from expenditure in the British racing industry (Deloitte 2013). In addition, the UK equine industry employs, directly and indirectly, an estimated 267,000 people, with approximately 3.5 million people riding horses at least once in 2011 (Beta 2011). In light of this, in addition to major welfare implications, the financial consequences of an AHSV outbreak could be devastating. AHSV has emerged from sub-Saharan Africa, causing outbreaks of disease in Spain during 1966 and in Spain and Portugal between 1987 and 1990. While it was assumed that Culicoides imicola, the primary
March 22, 2014 | Veterinary Record | 299
Downloaded from http://veterinaryrecord.bmj.com/ on June 24, 2015 - Published by group.bmj.com
Research vector of AHSV in sub-Saharan (a) (b) Africa, was responsible for most of the viral spread, virus was also isolated from other Culicoides species known to be present in northern Europe (see Mellor and Hamblin 2004 for a review). The presence of these Culicoides species on equine holdings in the UK and across northern Europe is already well characterised due to their role in causing seasonal dermatitis or ‘sweet-itch’ (a) Culicoides biting midge photographed while blood-feeding. (b) Horse owners are usually aware of (Mellor and McCaig 1974). From this starting point, Robin Culicoides activity as they can cause seasonal dermatitis in susceptible animals and colleagues (2014), in a paper summarised on p 301 of this issue of s3/1367616/equines-and-their-links-toThe response to a potential AHSV Veterinary Record, report a preliminary survey culicoides-biting-midges. incursion into the UK is also a major of Culicoides on equine premises in and consideration and is outlined in the African References around Newmarket using ultraviolet light horse sickness control strategy for Great BETA (2011) National Equestrian Survey 2011. British emitting diode suction traps. Their results Britain (Defra 2012). While vaccination is Equestrian Trade Association suggest that the majority of potential AHSV universally recognised as being the only Carpenter, S., Groschup, M. H., Garros, vector species of Culicoides are abundant reliable method of controlling AHSV, C., Felippe-Bauer, M. L. & Purse, B. V. (2013) Culicoides biting midges, arboviruses and public health across the area sampled and that they are movement restrictions and methods to in Europe. Antiviral Research 100, 102-113 feeding on horses. This indicates that there reduce contact between Culicoides and horses Carpenter, S. Mellor, P. S. & Torr, S. J. (2008) is the potential for transmission of AHSV are the only means of reducing transmission Control techniques for Culicoides biting midges and their application in the UK and northwestern Palaearctic. between and within livestock holdings before vaccination is implemented. Medical and Veterinary Entomology 22, 175-187 in the UK, but several other areas of These techniques have been reviewed in Defra (2012) African horse sickness control strategy uncertainty remain. These are summarised detail (Carpenter and others 2008) and for Great Britain. www.gov.uk/government/uploads/ both within the paper itself and in a recent include many options already familiar system/uploads/attachment_data/file/244348/pb13831ahs-control-strategy-20130923.pdf. Accessed March mathematical analysis of how transmission to horse owners attempting to combat 17, 2014 parameters would influence the spread of cases of sweet itch (for example, stabling Deloitte (2013) Economic Impact of British AHSV in the UK (Lo Iocono and others in screened accommodation, clearing of Racing 2013. www.britishhorseracing.com/economic_impact_2013/Economic_Impact_of_British_ 2013). A major advance in understanding larval development sites and application Racing2013.pdf. Accessed March 17, 2014 potential spatial spread has been achieved of insecticides or repellents). The efficacy Lo Iacono, G., Robin, C. A., Newton, J. R., in the latter study by creating a credible of such control techniques for Culicoides in Gubbins, S. & Wood, J. L. N. (2013) Where are the horses? With the sheep or cows? Uncertain host locamap of horse locations in the UK, which reducing transmission of AHSV is only tion, vector-feeding preferences and the risk of African had previously been restricted to owner poorly understood. horse sickness transmission in Great Britain. Journal of addresses. Interestingly, however, Lo Iocono The areas of interest highlighted above the Royal Society Interface 10, 20130194 and colleagues (2013) also highlight that are now being addressed through a project Mellor, P. S. & Hamblin, C. (2004) African horse sickness. Veterinary Research 35, 445-466 non-susceptible hosts (for example, cattle funded by the Horserace Betting Levy Mellor, P. S. & McCaig, J. (1974) The proband sheep) may have a significant influence Board that will examine both Culicoides host able cause of ‘sweet itch’ in England. Veterinary Record on AHSV transmission. A key question preference and the control of Culicoides on doi:10.1136/vr.95.18.411 Robin, M., Archer, D., Garros, C., Gardès, is whether the presence of these nonUK equine premises. As part of these studies, L. & Baylis, M. (2014) Threat of midgeborne equine susceptible hosts in proximity to stables equine owners are invited to contribute disease: investigation of Culicoides species on UK equine increases biting of horses by increasing information regarding their husbandry and premises. Veterinary Record doi:10.1136/vr.102151 Culicoides abundance, or reduce rates by control measures via an online questionnaire providing more attractive hosts. available at www.surveygizmo.com/ doi: 10.1136/vr.g2196
300 | Veterinary Record | March 22, 2014
Downloaded from http://veterinaryrecord.bmj.com/ on June 24, 2015 - Published by group.bmj.com
Bluetongue, Schmallenberg virus… African horse sickness? Simon Carpenter Veterinary Record 2014 174: 299-300
doi: 10.1136/vr.g2196 Updated information and services can be found at: http://veterinaryrecord.bmj.com/content/174/12/299
These include:
References Email alerting service
This article cites 6 articles, 0 of which you can access for free at: http://veterinaryrecord.bmj.com/content/174/12/299#BIBL Receive free email alerts when new articles cite this article. Sign up in the box at the top right corner of the online article.
Notes
To request permissions go to: http://group.bmj.com/group/rights-licensing/permissions To order reprints go to: http://journals.bmj.com/cgi/reprintform To subscribe to BMJ go to: http://group.bmj.com/subscribe/
