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Viruses2021; 13(3); doi: 10.3390/v13030398

Epidemiology and Genomic Analysis of Equine Encephalosis Virus Detected in Horses with Clinical Signs in South Africa, 2010-2017.

Abstract: Equine encephalosis virus (EEV) is a neglected virus endemic to South Africa and is considered to generally result in mild disease in equines. Specimens were analyzed from live horses that presented with undefined neurological, febrile, or respiratory signs, or sudden and unexpected death. Between 2010 and 2017, 111 of 1523 (7.3%) horse samples tested positive for EEV using a nested real-time reverse transcriptase polymerase chain reaction (rRT-PCR). Clinical signs were reported in 106 (7.2%) EEV positive and 1360 negative horses and included pyrexia (77/106, 72.6%), icterus (20/106, 18.9%) and dyspnea (12/106, 11.3%). Neurological signs were inversely associated with EEV infection (OR < 1, p < 0.05) relative to EEV negative cases despite a high percentage of animals presenting with neurological abnormalities (51/106, 48.1%). Seventeen of the EEV positive horses also had coinfections with either West Nile (5/106, 4.7%), Middelburg (4/106, 3.8%) or African Horse sickness virus (8/106, 7.6%). To investigate a possible genetic link between EEV strains causing the observed clinical signs in horses, the full genomes of six isolates were compared to the reference strains. Based on the outer capsid protein (VP2), serotype 1 and 4 were identified as the predominant serotypes with widespread reassortment between the seven different serotypes.
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Publication Date: 2021-03-02 PubMed ID: 33801457PubMed Central: PMC8001977DOI: 10.3390/v13030398Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This research focuses on the spread and genomic features of Equine Encephalosis Virus in South Africa between 2010 and 2017. The virus, typically causing mild symptoms in horses, has been found in a substantial number of symptomatic horses, leading to an analysis of the viral strains and their potential impact on the animals’ health.

Research Context and Methodology

  • The study analysed Equine Encephalosis Virus (EEV), a virus endemic to South Africa that primarily affects horses. Even though EEV generally causes mild disease, the study looked at horses presenting more severe symptoms like unexplained neurological, febrile, or respiratory signs, or sudden death.
  • From 2010 to 2017, the researchers collected and examined samples from live horses. They used a nested real-time reverse transcriptase polymerase chain reaction (rRT-PCR) to test for EEV.

Key Findings

  • Of the 1523 horse samples, 111 (7.3%) tested positive for EEV. 106 EEV-positive and 1360 EEV-negative horses displayed clinical symptoms. The prevalent symptoms among EEV-positive horses were fever (in 72.6%), icterus or jaundice (18.9%), and dyspnea or difficulty in breathing (11.3%).
  • Despite nearly half of the EEV-positive horses presenting signs of neurological disorders, an inverse association was found between neurological signs and EEV infection, meaning the instances of neurological signs were lesser in EEV-positive horses compared to EEV-negative ones.
  • A significant number of EEV-positive horses also had coinfections with other viruses like West Nile virus, Middelburg virus, and African Horse sickness virus.
  • The researchers compared the full genomes of six isolates with the reference EEV strains to try to identify a possible genetic link between the strains of EEV causing severe symptoms. The outer capsid protein (VP2) of the virus revealed serotype 1 and 4 as the predominant serotypes (distinct variations within a species), pointing to widespread genetic reassortment across the seven known serotypes of EEV.

Cite This Article

APA
Snyman J, Koekemoer O, van Schalkwyk A, Jansen van Vuren P, Snyman L, Williams J, Venter M. (2021). Epidemiology and Genomic Analysis of Equine Encephalosis Virus Detected in Horses with Clinical Signs in South Africa, 2010-2017. Viruses, 13(3). https://doi.org/10.3390/v13030398

Publication

Viruses
ISSN: 1999-4915
NlmUniqueID: 101509722
Country: Switzerland
Language: English
Volume: 13
Issue: 3

Researcher Affiliations

Snyman, Jumari
  • Centre for Viral Zoonoses, Department Medical Virology, University of Pretoria, Pretoria 0001, South Africa.
Koekemoer, Otto
  • Agricultural Research Council, Onderstepoort Veterinary Research, Onderstepoort 0110, South Africa.
van Schalkwyk, Antoinette
  • Agricultural Research Council, Onderstepoort Veterinary Research, Onderstepoort 0110, South Africa.
Jansen van Vuren, Petrus
  • Centre for Viral Zoonoses, Department Medical Virology, University of Pretoria, Pretoria 0001, South Africa.
  • National Health Laboratory Service, Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg 2131, South Africa.
Snyman, Louwtjie
  • Faculty of Veterinary Science, Department Veterinary Tropical Disease, University of Pretoria, Onderstepoort 0110, South Africa.
Williams, June
  • Department of Paraclinical Science, Section Pathology, Faculty of Veterinary Science, University of Pretoria, Onderstepoort 0110, South Africa.
Venter, Marietjie
  • Centre for Viral Zoonoses, Department Medical Virology, University of Pretoria, Pretoria 0001, South Africa.

MeSH Terms

  • Animals
  • Genome, Viral
  • Horse Diseases / epidemiology
  • Horse Diseases / virology
  • Horses
  • Orbivirus / genetics
  • Prevalence
  • Reoviridae Infections / epidemiology
  • Reoviridae Infections / veterinary
  • Serogroup
  • South Africa / epidemiology

Conflict of Interest Statement

The authors declare no conflict of interest.

References

This article includes 46 references
  1. Erasmus B.J., Adelaar T.F., Smit J.D., Lecatsas G., Toms T.. The isolation and characterization of equine encephalosis virus. Bull. Off. Int. Epizoot. 1970;74:781–789.
  2. Mildenberg Z., Westcott D., Bellaiche M., Dastjerdi A., Steinbach F., Drew T.. Equine Encephalosis Virus in Israel. Transbound. Emerg. Dis. 2009;56:291.
    doi: 10.1111/j.1865-1682.2009.01087_1.xpubmed: 19744233google scholar: lookup
  3. Aharonson-Raz K., Steinman A., Bumbarov V., Maan S., Maan N., Nomikou K., Batten C., Potgieter C., Gottlieb Y., Mertens P.. Isolation and Phylogenetic Grouping of Equine Encephalosis Virus in Israel. Emerg. Infect. Dis. 2011;17:1883–1886.
    doi: 10.3201/eid1710.110350pmc: PMC3310674pubmed: 22000361google scholar: lookup
  4. Yadav P.D., Albariño C.D., Nyayanit D.A., Guerrero L., Jenks M.H., Sarkale P., Nichol S.T., Mourya D.T.. Equine Encephalosis Virus in India, 2008. Emerg. Infect. Dis. 2018;24:898–901.
    doi: 10.3201/eid2405.171844pmc: PMC5938759pubmed: 29664366google scholar: lookup
  5. Howell P.G., Guthrie A.J., Coetzer J.A.W.. Equine encephalosis. In: Coetzer J.A.W., Tustin R.C., editors. Infectious Diseases of Livestock. Oxford University Press; Cape Town, South Africa: 2004. pp. 1247–1251.
  6. Viljoen G.J., Huismans H.. The Characterization of Equine Encephalosis Virus and the Development of Genomic Probes. J. Gen. Virol. 1989;70:2007–2015.
    doi: 10.1099/0022-1317-70-8-2007pubmed: 2549180google scholar: lookup
  7. Thompson G.M., Jess S., Murchie A.K.. A review of African horse sickness and its implications for Ireland. Ir. Vet. J. 2012;65:9.
    doi: 10.1186/2046-0481-65-9pmc: PMC3390273pubmed: 22553991google scholar: lookup
  8. Roy P.. Orbiviruses and their replication. In: Knipe D.M., Howley P.M., editors. Fields’ Virology. 5. Lippincott Williams and Wilkins; Philadelphia, PA, USA: New York, NY, USA: 2007. pp. 1975–1997.
  9. Zientara S., Lecollinet S.. African horse sickness. Rev. Sci. Tech. 2015;34:315–327.
    doi: 10.20506/rst.34.2.2359pubmed: 26601437google scholar: lookup
  10. Saegerman C., Berkvens D., Mellor P.S.. Bluetongue Epidemiology in the European Union. Emerg. Infect. Dis. 2008;14:539–544.
    doi: 10.3201/eid1404.071441pmc: PMC2570923pubmed: 18394269google scholar: lookup
  11. Carpenter S., Mellor P.S., Fall A.G., Garros C., Venter G.J.. African Horse Sickness Virus: History, Transmission, and Current Status. Annu. Rev. Èntomol. 2017;62:343–358.
    doi: 10.1146/annurev-ento-031616-035010pubmed: 28141961google scholar: lookup
  12. Lu G., Pan J., Ou J., Shao R., Hu X., Wang C., Li S.. African horse sickness: Its emergence in Thailand and potential threat to other Asian countries. Transbound. Emerg. Dis. 2020.
    doi: 10.1111/tbed.13625pubmed: 32406171google scholar: lookup
  13. Theodoridis A., Nevill E.M., Els H.J., Boshoff S.T.. Viruses isolated from Culicoides midges in South Africa during unsuccessful attempts to isolate bovine ephemeral fever virus. Onderstepoort J. Vet. Res. 1979;46:191–198.
    pubmed: 551368
  14. Venter G.J., Groenewald D.M., Paweska J.T., Venter E.H., Howell P.G.. Vector competence of selected South African Culicoides species for the Bryanston serotype of equine encephalosis virus. Med. Vet. Entomol. 1999;13:393–400.
    doi: 10.1046/j.1365-2915.1999.00188.xpubmed: 10608228google scholar: lookup
  15. Paweska J.T., Venter G.J.. Vector competence of Culicoides species and the seroprevalence of homologous neutralizing antibody in horses for six serotypes of equine encephalosis virus (EEV) in South Africa. Med. Vet. Entomol. 2004;18:398–407.
    doi: 10.1111/j.0269-283X.2004.00524.xpubmed: 15642007google scholar: lookup
  16. Nomikou K., Hughes J., Wash R., Kellam P., Breard E., Zientara S., Palmarini M., Biek R., Mertens P.P.C.. Widespread Reassortment Shapes the Evolution and Epidemiology of Bluetongue Virus following European Invasion. PLoS Pathog. 2015;11:e1005056.
    doi: 10.1371/journal.ppat.1005056pmc: PMC4529188pubmed: 26252219google scholar: lookup
  17. Weyer C.T., Grewar J.D., Burger P., Rossouw E., Lourens C.W., Joone C., Le Grange M., Coetzee P., Venter E.H., Martin D.P.. African Horse Sickness Caused by Genome Reassortment and Reversion to Virulence of Live, Attenuated Vaccine Viruses, South Africa, 2004–2014. Emerg. Infect. Dis. 2016;22:2087–2096.
    doi: 10.3201/eid2212.160718pmc: PMC5189153pubmed: 27442883google scholar: lookup
  18. Bremer C.W., Huismans H., Van Dijk A.A.. Characterization and cloning of the African horse sickness virus genome. J. Gen. Virol. 1990;71:793–799.
    doi: 10.1099/0022-1317-71-4-793pubmed: 2324709google scholar: lookup
  19. Belhouchet M., Jaafar F.M., Firth A.E., Grimes J.M., Mertens P.P.C., Attoui H.. Detection of a Fourth Orbivirus Non-Structural Protein. PLoS ONE. 2011;6:e25697.
    doi: 10.1371/journal.pone.0025697pmc: PMC3192121pubmed: 22022432google scholar: lookup
  20. Verwoerd D.W., Els H.J., De Villiers E.-M., Huismans H.. Structure of the Bluetongue Virus Capsid. J. Virol. 1972;10:783–794.
    doi: 10.1128/JVI.10.4.783-794.1972pmc: PMC356534pubmed: 4117349google scholar: lookup
  21. Roy P.. Bluetongue virus: Dissection of the polymerase complex. Pt 8. J. Gen. Virol. 2008;89:1789–1804.
    doi: 10.1099/vir.0.2008/002089-0pmc: PMC2735681pubmed: 18632949google scholar: lookup
  22. Dhama K., Pawaiya R.V.S., Karthik K., Chakraborty S., Tiwari R., Verma A.. Equine encephalosis virus (EEV): A Review. Asian J. Anim. Vet. Adv. 2014;9:123–133.
    doi: 10.3923/ajava.2014.123.133google scholar: lookup
  23. Nason E.L., Rothagel R., Mukherjee S.K., Kar A.K., Forzan M., Prasad B.V.V., Roy P.. Interactions between the Inner and Outer Capsids of Bluetongue Virus. J. Virol. 2004;78:8059–8067.
    doi: 10.1128/JVI.78.15.8059-8067.2004pmc: PMC446137pubmed: 15254177google scholar: lookup
  24. Hyatt A.D., Zhao Y., Roy P.. Release of Bluetongue Virus-like Particles from Insect Cells is Mediated by BTV Nonstructural Protein NS3/NS3A. Virology. 1993;193:592–603.
    doi: 10.1006/viro.1993.1167pubmed: 8384747google scholar: lookup
  25. Howell P.G., Groenewald D., Visage C.W., Bosman A.M., Coetzer J.A.W., Guthrie A.J.. The classification of seven sero-types of equine encephalosis virus and the prevalence of homologous antibody in horses in South Africa. Onderstepoort J. Vet. Res. 2002;69:179–193.
    pubmed: 12092781
  26. Barnard B.J.H., Paweska J.T.. Prevalence of antibodies against some equine viruses in zebra (Zebra burchellt) in the Kruger National Park, 1991–1992. Onderstepoort J. Vet. Res. 1993;60:175–179.
    pubmed: 7970572
  27. Nevill E.M., Erasmus B.J., Venter G.J.. A six-year survey of viruses associated with Culicoides biting midges throughout South Africa (Diptera: Ceratopogonidae). In: Walton T.E., Osburn B.I., editors. Bluetongue, African Horse Sickness and Related Orbiviruses, Proceedings of the Second International Symposium, Miami, FL, USA, 15–19 March 1992. CRC Press; Boca Raton, FL, USA: 1992. pp. 314–319.
  28. Howell P.G., Nurton J.P., Nel D., Lourens C.W., Guthrie A.J.. Prevalence of serotype specific antibody to equine encephalosis virus in Thoroughbred yearlings in South Africa (1999–2004). Onderstepoort J. Vet. Res. 2008;75:153–161.
    doi: 10.4102/ojvr.v75i2.14pubmed: 18788209google scholar: lookup
  29. Paweska J.. A Fatal Case of Equine Encephalosis in the Port Elizabeth District, South Africa. AnimalNet 1999.
  30. Grewar J.D., Thompson P.N., Lourens C.W., Guthrie A.J.. Equine encephalosis in Thoroughbred foals on a South African stud farm. Onderstepoort J. Vet. Res. 2015;82:966.
    doi: 10.4102/ojvr.v82i1.966pmc: PMC6238798pubmed: 26842364google scholar: lookup
  31. Wescott D.G., Mildenberg Z., Bellaiche M., McGowan S.L., Grierson S.S., Choudhury B., Steinbach F.. Evidence for the circulation of equine encephalosis virus in Israel since 2001. PLoS ONE. 2013;8:e70532.
    doi: 10.1371/journal.pone.0070532pmc: PMC3741287pubmed: 23950952google scholar: lookup
  32. Van Niekerk M., Freeman M., Paweska J.T., Howell P.G., Guthrie A.J., Potgieter A.C., Van Staden V., Huismans H.. Variation in the NS3 gene and protein in South African isolates of bluetongue and equine encephalosis viruses. J. Gen. Virol. 2003;84:581–590.
    doi: 10.1099/vir.0.18749-0pubmed: 12604809google scholar: lookup
  33. Potgieter A.C., Page N.A., Liebenberg J., Wright I.M., Landt O., van Dijk A.A.. Improved strategies for sequence-independent amplification and sequencing of viral double-stranded RNA genomes. J. Gen. Virol. 2009;90:1423–1432.
    doi: 10.1099/vir.0.009381-0pubmed: 19264638google scholar: lookup
  34. Sakamoto K., Mizukoshi N., Apiwatnakorn B., Iwata A., Tsuchiya T., Ueda S., Imagawa H., Sugiura T., Kamada M., Fukusho A.. The complete sequences of African horse sickness virus serotype 4 (vaccine strain) RNA segment 2 and 6 which encode outer capsid protein. J. Vet. Med. Sci. 1994;56:321–327.
    doi: 10.1292/jvms.56.321pubmed: 8075221google scholar: lookup
  35. Vreede F.T., Cloete M., Napier G.B., van Dijk A.A., Viljoen G.J.. Sequence-independent amplification and cloning of large dsRNA virus genome segments by poly(dA)-oligonucleotide ligation. J. Virol. Methods. 1998;72:243–247.
    doi: 10.1016/S0166-0934(98)00031-7pubmed: 9694332google scholar: lookup
  36. Van Vuren P.J., Wiley M., Palacios G., Storm N., McCulloch S.D., Markotter W., Birkhead M., Kemp A., Paweska J.T.. Isolation of a Novel Fusogenic Orthoreovirus from Eucampsipoda africana Bat Flies in South Africa. Viruses. 2016;8:65.
    doi: 10.3390/v8030065pmc: PMC4810255pubmed: 27011199google scholar: lookup
  37. Djikeng A., Halpin R., Kuzmickas R., DePasse J., Feldblyum J., Sengamalay N., Afonso C., Zhang X., Anderson N.G., Ghedin E.. Viral genome sequencing by random priming methods. BMC Genom. 2008;9:5.
    doi: 10.1186/1471-2164-9-5pmc: PMC2254600pubmed: 18179705google scholar: lookup
  38. Stamatakis A.. RAxML version 8: A tool for phylogenetic analysis and post-analysis of large phylogenies. Bioinformatics. 2014;30:1312–1313.
    doi: 10.1093/bioinformatics/btu033pmc: PMC3998144pubmed: 24451623google scholar: lookup
  39. Bremer C.W., Viljoen G.J.. Detection of African horse sickness virus and discrimination between two equine orbivirus serogroups by reverse transcription polymerase chain reaction. Onderstepoort J. Vet. Res. 1998;65:1–8.
    pubmed: 9629584
  40. Williams R., Du Plessis D.H., Van Wyngaardt W.. Group-reactive ELISAs for detecting antibodies to African horse sickness and equine encephalosis viruses in horse, donkey, and zebra sera. J. Vet. Diagn. Investig. 1993;5:3–7.
    doi: 10.1177/104063879300500102pubmed: 8385502google scholar: lookup
  41. Menzies F.D., McCullough S.J., McKeown I.M., Forster J.L., Jess S., Batten C., Murchie A.K., Gloster J., Fallows J.G., Pelgrim W.. Evidence for transplacental and contact transmission of bluetongue virus in cattle. Vet. Rec. 2008;163:203–209.
    doi: 10.1136/vr.163.7.203pubmed: 18708653google scholar: lookup
  42. Darpel K.E., Batten C.A., Veronesi E., Williamson S., Anderson P., Dennison M., Clifford S., Smith C., Philips L., Bidewell C.. Transplacental Transmission of Bluetongue Virus 8 in Cattle, UK. Emerg. Infect. Dis. 2009;15:2025–2028.
    doi: 10.3201/eid1512.090788pmc: PMC3044536pubmed: 19961692google scholar: lookup
  43. Wilson A., Mellor P.S., Szmaragd C., Mertens P.P.C.. Adaptive strategies of African horse sickness virus to facilitate vector transmission. Vet. Res. 2008;40:16.
    doi: 10.1051/vetres:2008054pmc: PMC2695022pubmed: 19094921google scholar: lookup
  44. MacLachlan N.J., Guthrie A.J.. Re-emergence of bluetongue, African horse sickness, and other Orbivirus diseases. Vet. Res. 2010;41:35.
    doi: 10.1051/vetres/2010007pmc: PMC2826768pubmed: 20167199google scholar: lookup
  45. Laegrid W.W.. Virus infections of equines. In: Studdert M.J., editor. Equine Encephalosis. Elsevier; New York, NY, USA: 1996. pp. 1–125.
  46. Barnard B.J.. Antibodies against some viruses of domestic animals in southern African wild animals. Onderstepoort J. Vet. Res. 1997;64:95–110.
    pubmed: 9352558

Citations

This article has been cited 5 times.
  1. Piketh G, Viljoen A, Eberhardt C. Clinical signs, clinical pathology and outcomes in horses infected naturally with equine encephalosis virus. Equine Vet J 2026 Mar;58(2):434-443.
    doi: 10.1111/evj.70117pubmed: 41235818google scholar: lookup
  2. Gallichotte EN, Fitzmeyer EA, Williams L, Spangler MC, Bosco-Lauth AM, Ebel GD. WNV and SLEV coinfection in avian and mosquito hosts: impact on viremia, antibody responses, and vector competence. J Virol 2024 Oct 22;98(10):e0104124.
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  3. Fehér OE, Fehérvári P, Tolnai CH, Forgách P, Malik P, Jerzsele Á, Wagenhoffer Z, Szenci O, Korbacska-Kutasi O. Epidemiology and Clinical Manifestation of West Nile Virus Infections of Equines in Hungary, 2007-2020. Viruses 2022 Nov 18;14(11).
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  4. Tirosh-Levy S, Steinman A. Equine Encephalosis Virus. Animals (Basel) 2022 Jan 29;12(3).
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  5. Snyman J, Venter GJ, Venter M. An Investigation of Culicoides (Diptera: Ceratopogonidae) as Potential Vectors of Medically and Veterinary Important Arboviruses in South Africa. Viruses 2021 Oct 1;13(10).
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