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Venezuelan equine encephalitis

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Datasheet

Venezuelan equine encephalitis

Summary

  • Last modified
  • 03 September 2020
  • Datasheet Type(s)
  • Animal Disease
  • Preferred Scientific Name
  • Venezuelan equine encephalitis
  • Overview
  • Venezuelan equine encephalitis virus (VEEV) is a mosquito-borne alphavirus capable of causing large outbreaks of encephalitis in humans and equids. VEEV has caused periodic outbreaks of febrile and neurological disease, primarily in Latin America...

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    Compendia
    CAB International
    Wallingford
    Oxfordshire
    OX10 8DE
    UK
    compend@cabi.org
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Identity

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Preferred Scientific Name

  • Venezuelan equine encephalitis

International Common Names

  • English: Venezuelan equine encephalomyelitis

Overview

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Venezuelan equine encephalitis virus (VEEV) is a mosquito-borne alphavirus capable of causing large outbreaks of encephalitis in humans and equids. VEEV has caused periodic outbreaks of febrile and neurological disease, primarily in Latin America since the 1930s. Many outbreaks have involved tens to hundreds of thousands of equine and human cases, have spread over large geographical regions, and have lasted up to several years (Weaver et al., 2004). VEEV is also a highly developed biological weapon amenable to use in warfare or terrorism (Hawley and Eitzen, 2001; Reichert et al., 2009).

Venezuelan equine encephalitis (or encephalomyelitis) is on the list of diseases notifiable to the World Organisation for Animal Health (OIE).

Host Animals

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Animal nameContextLife stageSystem
EquusDomesticated host; Wild host
Equus asinus (donkeys)
Equus caballus (horses)Domesticated host
Homo sapiens
mules

Hosts/Species Affected

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VEEV causes disease in horses, donkeys, mules and man.

Distribution

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VEE complex viruses are endemic to South and Central America, Mexico, and Florida (Weaver et al., 2004). Epizootics in North America have been limited (OIE, 2020). For the most recent, detailed information on the occurrence of this disease worldwide, see the OIE World Animal Health Information Database (WAHID) interface.

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Last updated: 10 Jan 2020
Continent/Country/Region Distribution Last Reported Origin First Reported Invasive Reference Notes

Africa

AlgeriaAbsent, No presence record(s)
BeninAbsent, No presence record(s)
BotswanaAbsent, No presence record(s)
BurundiAbsent, No presence record(s)
Cabo VerdeAbsent, No presence record(s)
CameroonAbsent, No presence record(s)
Central African RepublicAbsent, No presence record(s)
Congo, Democratic Republic of theAbsent, No presence record(s)
Côte d'IvoireAbsent, No presence record(s)
EgyptAbsent, No presence record(s)
EswatiniAbsent, No presence record(s)
KenyaAbsent, No presence record(s)
LesothoAbsent, No presence record(s)
LibyaAbsent, No presence record(s)
MadagascarAbsent, No presence record(s)
MauritiusAbsent, No presence record(s)
MoroccoAbsent, No presence record(s)
MozambiqueAbsent, No presence record(s)
NamibiaAbsent, No presence record(s)
NigeriaAbsent, No presence record(s)
RéunionAbsent, No presence record(s)
São Tomé and PríncipeAbsent, No presence record(s)
SeychellesAbsent, No presence record(s)
SomaliaAbsent, No presence record(s)
South AfricaAbsent, No presence record(s)
SudanAbsent, No presence record(s)
TunisiaAbsent, No presence record(s)
ZambiaAbsent, No presence record(s)
ZimbabweAbsent, No presence record(s)

Asia

ArmeniaAbsent, No presence record(s)
AzerbaijanAbsent, No presence record(s)
BahrainAbsent, No presence record(s)
BangladeshAbsent, No presence record(s)
BhutanAbsent, No presence record(s)
BruneiAbsent, No presence record(s)
ChinaAbsent, No presence record(s)
GeorgiaAbsent, No presence record(s)
IndiaAbsent, No presence record(s)
IndonesiaAbsent, No presence record(s)
IranAbsent, No presence record(s)
IraqAbsent, No presence record(s)
IsraelAbsent, No presence record(s)
JapanAbsent, No presence record(s)
JordanAbsent, No presence record(s)
KazakhstanAbsent, No presence record(s)
KuwaitAbsent, No presence record(s)
KyrgyzstanAbsent, No presence record(s)
LaosAbsent, No presence record(s)
LebanonAbsent, No presence record(s)
MalaysiaAbsent, No presence record(s)
-Peninsular MalaysiaAbsent, No presence record(s)
-SabahAbsent, No presence record(s)
MongoliaAbsent, No presence record(s)
MyanmarAbsent, No presence record(s)
North KoreaAbsent, No presence record(s)
OmanAbsent, No presence record(s)
PakistanAbsent, No presence record(s)
PhilippinesAbsent, No presence record(s)
QatarAbsent, No presence record(s)
Saudi ArabiaAbsent, No presence record(s)
SingaporeAbsent, No presence record(s)
South KoreaAbsent, No presence record(s)
Sri LankaAbsent, No presence record(s)
TaiwanAbsent, No presence record(s)
TajikistanAbsent, No presence record(s)
TurkmenistanAbsent, No presence record(s)
United Arab EmiratesAbsent, No presence record(s)
UzbekistanAbsent, No presence record(s)
VietnamAbsent, No presence record(s)

Europe

AndorraAbsent, No presence record(s)
AustriaAbsent, No presence record(s)
BelarusAbsent, No presence record(s)
BelgiumAbsent, No presence record(s)
Bosnia and HerzegovinaAbsent, No presence record(s)
BulgariaAbsent, No presence record(s)
CroatiaAbsent, No presence record(s)
CyprusAbsent, No presence record(s)
CzechiaAbsent, No presence record(s)
DenmarkAbsent, No presence record(s)
EstoniaAbsent, No presence record(s)
FinlandAbsent, No presence record(s)
FranceAbsent, No presence record(s)
GermanyAbsent, No presence record(s)
GreeceAbsent, No presence record(s)
HungaryAbsent, No presence record(s)
IcelandAbsent, No presence record(s)
IrelandAbsent, No presence record(s)
Isle of ManAbsent, No presence record(s)
ItalyAbsent, No presence record(s)
JerseyAbsent, No presence record(s)
LatviaAbsent, No presence record(s)
LiechtensteinAbsent, No presence record(s)
LithuaniaAbsent, No presence record(s)
LuxembourgAbsent, No presence record(s)
MaltaAbsent, No presence record(s)
MoldovaAbsent, No presence record(s)
MontenegroAbsent, No presence record(s)
NetherlandsAbsent, No presence record(s)
North MacedoniaAbsent, No presence record(s)
NorwayAbsent, No presence record(s)
PolandAbsent, No presence record(s)
PortugalAbsent, No presence record(s)
RomaniaAbsent, No presence record(s)
RussiaAbsent, No presence record(s)
Serbia and MontenegroAbsent, No presence record(s)
SlovakiaAbsent, No presence record(s)
SloveniaAbsent, No presence record(s)
SpainAbsent, No presence record(s)
SwedenAbsent, No presence record(s)
SwitzerlandAbsent, No presence record(s)
UkraineAbsent, No presence record(s)
United KingdomAbsent, No presence record(s)
-Northern IrelandAbsent, No presence record(s)

North America

BarbadosAbsent, No presence record(s)
BelizeAbsent, No presence record(s)
BermudaAbsent, No presence record(s)
British Virgin IslandsAbsent, No presence record(s)
CanadaAbsent, No presence record(s)
Cayman IslandsAbsent, No presence record(s)
CubaAbsent, No presence record(s)
CuraçaoAbsent, No presence record(s)
DominicaAbsent, No presence record(s)
Dominican RepublicAbsent, No presence record(s)
El SalvadorAbsent, No presence record(s)
GreenlandAbsent, No presence record(s)
GuatemalaPresent, Localized
HaitiAbsent, No presence record(s)
HondurasAbsent, No presence record(s)
JamaicaAbsent, No presence record(s)
MartiniqueAbsent, No presence record(s)
MexicoAbsent, No presence record(s)
PanamaAbsent, No presence record(s)
Saint Kitts and NevisAbsent, No presence record(s)
Saint Vincent and the GrenadinesAbsent, No presence record(s)
United StatesAbsent, No presence record(s)

Oceania

AustraliaAbsent, No presence record(s)
French PolynesiaAbsent, No presence record(s)
New CaledoniaAbsent, No presence record(s)
New ZealandAbsent, No presence record(s)
SamoaAbsent, No presence record(s)
VanuatuAbsent, No presence record(s)

South America

ArgentinaAbsent, No presence record(s)
BoliviaAbsent, No presence record(s)
BrazilAbsent, No presence record(s)
ChileAbsent, No presence record(s)
ColombiaPresent
EcuadorAbsent, No presence record(s)
Falkland IslandsAbsent, No presence record(s)
French GuianaAbsent, No presence record(s)
GuyanaAbsent, No presence record(s)
ParaguayAbsent, No presence record(s)
PeruAbsent, No presence record(s)
UruguayAbsent, No presence record(s)
VenezuelaAbsent, No presence record(s)

Pathology

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Gross lesions of the central nervous system in horses associated with VEE are generally nonspecific, varying from no lesions to extensive necrosis with haemorrhages. Histopathologically, the predominant lesions are related to a diffuse necrotising meningoencephalitis; varying from some perivascular mixed cellular reaction to marked vascular necrosis with associated haemorrhages, gliosis, and clear neuronal necrosis (OIE, 2020).

Diagnosis

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A confirmatory diagnosis of VEE is based on the isolation and identification of the virus or on the demonstration of seroconversion. For detailed information regarding laboratory diagnostic methodologies, refer to the OIE Manual of Diagnostic Tests and Vaccines for Terrestrial Animals.

Disease Course

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In horses, infections with epidemic VEE viruses may be asymptomatic, mild, severe or fatal. In symptomatic horses, a febrile prodrome with depression, tachycardia, and inappetence is sometimes followed by neurological signs indicative of encephalitis. Some animals also have diarrhoea and colic. Death can occur within hours after the onset of neurological signs; after a protracted illness accompanied by dehydration and extreme weight loss; or in animals without signs of encephalitis. Sudden death has also been reported (Spickler, 2017). Enzootic VEE viruses tend not to (but can sometimes) cause overt signs of disease in equids, but they can cause clinical disease in humans (OIE, 2020).

Epidemiology

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Haematophagous insects play a central role in the transmission of VEE viruses. Epizootic strains have been isolated from the genera: Aedes, Anopheles, Culex, Deinocerites, Mansonia and Psorophora. Mechanical transmission of epizootic VEE has been demonstrated for blackflies (Simulium spp.). Enzootic VEE variants and subtypes cycle in tropical ecosystems among rodents, and possibly birds, by the feeding of mosquitoes. In the epizootic/epidemic cycle, horses are the main amplifying host (high, prolonged viraemia) and infect a wide range of mosquitoes. Non-vector spread of disease via direct contact or aerosols has been suggested (OIE, 2020).

Zoonoses and Food Safety

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In humans, VEE is usually an acute, often mild, systemic illness. The symptoms caused by endemic and epidemic strains are similar. The initial signs may include fever, chills, generalized malaise, headache, photophobia and myalgia. Coughing, sore throat, nausea, vomiting, diarrhoea and a rash may also be seen. Mild to severe neurological signs can be seen in a small percentage of affected children, and to a lesser extent in adults over the age of 50 years, but in few healthy adults (e.g., less than 1% of symptomatic young adults). VEE usually resolves within 1 to 2 weeks, with acute symptoms subsiding after 4 to 6 days, and deaths are rare. In pregnant women, VEE can affect the fetus (Spickler, 2017).

Most people are infected by exposure to VEEV-infected arthropods, but cases have been documented after laboratory accidents or exposure to aerosolized debris from the cages of infected laboratory rodents (Spickler, 2017). Horse-to-human and human-to-human transmission has not been recorded (OIE, 2020). VEEV is highly infectious in aerosol form and is a known biowarfare agent. Several candidate vaccines against VEEV are at various stages of development (Sharma and Knollmann-Ritschel, 2019).

Disease Treatment

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There is no effective treatment for VEE. Supportive care may include administration of fluids to horse unable to drink and therapy with antiinflammatory agents and anticonvulsants (OIE, 2020).

Prevention and Control

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Epizootics of VEE are most effectively controlled by quarantine and movement controls of all Equidae and vaccination of animals. Vector control measures include elimination of mosquito breeding locations (i.e. pooled or stagnant water), stabling equids in screened housing and use of repellents and fans (OIE, 2020).

Vaccination

Approved vaccines for equids include attenuated and inactivated vaccines (made with strain TC-83). For details, see the OIE Manual of Diagnostic Tests and Vaccines for Terrestrial Animals.

References

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Hawley RJ, Eitzen EM Jr, 2001. Biological weapons - a primer for microbiologists. Annual Review of Microbiology, 55:235-253

OIE Handistatus, 2002. World Animal Health Publication and Handistatus II (dataset for 2001). Paris, France: Office International des Epizooties

OIE Handistatus, 2003. World Animal Health Publication and Handistatus II (dataset for 2002). Paris, France: Office International des Epizooties

OIE Handistatus, 2004. World Animal Health Publication and Handistatus II (data set for 2003). Paris, France: Office International des Epizooties

OIE Handistatus, 2005. World Animal Health Publication and Handistatus II (data set for 2004). Paris, France: Office International des Epizooties

OIE, 2009. World Animal Health Information Database - Version: 1.4. World Animal Health Information Database. Paris, France: World Organisation for Animal Health. http://www.oie.int

OIE, 2020. Venezuelan equine encephalitis (updated January 2020). In: OIE Technical disease cards Paris, France: World Organisation for Animal Health.https://www.oie.int/fileadmin/Home/eng/Animal_Health_in_the_World/docs/pdf/Disease_cards/VEE.pdf

Reichert E, Clase A, Bacetty A, Larsen J, 2009. Alphavirus antiviral drug development: scientific gap analysis and prospective research areas. Biosecurity and Bioterrorism: Biodefense Strategy, Practice and Science, 7(4):413-427. http://www.liebertonline.com/bsp

Sharma, A., Knollmann-Ritschel, B., 2019. Current understanding of the molecular basis of Venezuelan equine encephalitis virus pathogenesis and vaccine development. Viruses, 11(2), 164. doi: 10.3390/v11020164

Spickler, A. R., 2017. Eastern, Western and Venezuelan equine encephalomyelitis (updated January 2015). Iowa, USA: Center for Food Security and Public Health (CFSPH), Iowa State University.http://www.cfsph.iastate.edu/DiseaseInfo/factsheets.php

Weaver SC, Ferro C, Barrera R, Boshell J, Navarro JC, 2004. Venezuelan equine encephalitis. Annual Review of Entomology, 49:141-174

Distribution References

OIE Handistatus, 2005. World Animal Health Publication and Handistatus II (dataset for 2004)., Paris, France: Office International des Epizooties.

OIE, 2009. World Animal Health Information Database - Version: 1.4., Paris, France: World Organisation for Animal Health. https://www.oie.int/

Distribution Maps

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