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Venezuelan equine encephalitis

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Venezuelan equine encephalitis
Other names: Venezuelan equine encephalitis virus infection[1]
  • Top:Geographical distribution of the VEEV in the Americas[2]
  • Bottom: Transmission cycles of Venezuelan equine encephalitis virus[3]
SpecialtyInfectious disease
SymptomsFever, chills, headache[4]
CausesVEEV[4]
Diagnostic methodELISA[4]
Differential diagnosisLyme disease,Malaria,Western equine encephalitis,Bacterial meningitis[4]
TreatmentCare is primarily supportive[4]

Venezuelan Equine Encephalitis (VEE) in humans is a mosquito-borne viral infection that typically presents as a brief, severe flu-like illness marked by high fever, intense headache, and muscle pain. While most healthy adults recover completely within a few days, a small percentage of cases, especially in children and the elderly, can progress to a severe neurological disease, or encephalitis, causing seizures, confusion, and sometimes death.[4]

VEE can affect all equine species. After infection, equines may suddenly die or show progressive central nervous system disorders. Humans also can contract this disease. Healthy adults who become infected by the virus may experience flu-like symptoms, such as high fevers and headaches. People with weakened immune systems and the young and the elderly can become severely ill or die from this disease.The virus that causes VEE is transmitted primarily by mosquitoes that bite an infected animal and then bite and feed on another animal or human. The speed with which the disease spreads depends on the subtype of the VEE virus and the density of mosquito populations. Enzootic subtypes of VEE are diseases endemic to certain areas. Generally these serotypes do not spread to other localities. Enzootic subtypes are associated with the rodent-mosquito transmission cycle. These forms of the virus can cause human illness but generally do not affect equine health.[4][2][5]

Epizootic subtypes, on the other hand, can spread rapidly through large populations. These forms of the virus are highly pathogenic to equines and can also affect human health. Equines, rather than rodents, are the primary animal species that carry and spread the disease. Infected equines develop an enormous quantity of virus in their circulatory system. When a blood-feeding insect feeds on such animals, it picks up this virus and transmits it to other animals or humans. [4][5]

Signs and symptoms

In terms of the presentation of VEE we find the following:[4]

Complications

As to complications in an individual with VEE we find the following :[4]

  • Stillbirth
  • Offspring may have neurological sequelae

Virology

Venezuelan equine encephalitis virus
Virus classification e
(unranked): Virus
Realm: Riboviria
Kingdom: Orthornavirae
Phylum: Kitrinoviricota
Class: Alsuviricetes
Order: Martellivirales
Family: Togaviridae
Genus: Alphavirus
Species:
Alphavirus venezuelan

The virion is spherical and approximately 70 nm in diameter. It has a lipid membrane with glycoprotein surface proteins spread around the outside. Surrounding the nuclear material is a nucleocapsid that has an icosahedral symmetry of T = 4, and is approximately 40 nm in diameter.Serology testing performed on this virus has shown the presence of six different subtypes . These have been given names, including Mucambo, Tonate, and Pixuna subtypes. There are seven different variants in subtype I, and three of these variants, A, B, and C are the epizootic strains.[6][7][2]

The Mucambo virus (subtype III) appears to have evolved ~1807 AD (95% credible interval: 1559–1944).[8]

Mechanism

In terms of the mechanism of Venezuelan Equine Encephalitis we find it begins with a mosquito bite, where it first infects dendritic cells and macrophages in skin. The virus uses these immune cells to travel to regional lymph nodes, where it replicates, leading to high-titer viremia and systemic spread to other lymphoid tissues, often causing lymphocyte depletion. In some cases the high viral load facilitates neuroinvasion, either by crossing the blood-brain barrier or via peripheral nerves . VEEV replicates in neurons and other cells, causing severe meningoencephalitis, neuronal damage, and inflammation which can cause long-term neurological sequelae[9][10][4]

Diagnosis

In terms of diagnosis we find that virus detection can be conducted in serum or cerebrospinal fluid using serological analysis. VEEV-specific blocking ELISA has high efficacy in identifying the serotype [4]

Differential diagnosis

Red blood cells infected with malaria

As to the DDx of VEE in an infected individual we find the following:[4]

Prevention

There is an inactivated vaccine containing the C-84 strain for VEE virus that is used to immunize horses. Another vaccine, containing the TC-83 strain, is used on humans in military and laboratory positions who risk contracting the virus. The human vaccine can result in side effects and does not fully immunize the patient. The TC-83 strain was generated by passing the virus 83 times through a guinea pig heart cell culture; C-84 is a derivative of TC-83.[4][11]

Treatment

In terms of management presently there is no specific treatment available for Venezuelan equine encephalitis. Management of these conditions relies completely on supportive or palliative care[4]

Epidemiology

VEE in Columbia , April to October 1995[12]

In the Americas, there have been 21 reported outbreaks of Venezuelan equine encephalitis virus.[13] Outbreaks occurred in Central American and South American countries. This virus was isolated in 1938, and outbreaks have been reported in many different countries since then. Mexico, Colombia, Venezuela, and the United States are just some of the countries that have reported outbreaks.[14] Outbreaks of VEE generally occur after periods of heavy precipitation that cause mosquito populations to thrive.Between December 1992 and January 1993, the Venezuelan state of Trujillo experienced an outbreak of this virus. Overall, 28 cases of the disease were reported along with 12 deaths. June 1993 saw a bigger outbreak in the Venezuelan state of Zulia, as 55 humans died as well as 66 equine deaths.[13][15][2][16]

A much larger outbreak in Venezuela and Colombia occurred in 1995. On May 23, 1995, equine encephalitis-like cases were reported in the northwest portion of the country. Eventually, the outbreak spread more towards the north as well as to the south. The outbreak caused about 11,390 febrile cases in humans as well as 16 deaths. About 500 equine cases were reported with 475 deaths.[17][6][15]

An outbreak of this disease occurred in Colombia in September 1995. This outbreak resulted in 14,156 human cases that were attributable to Venezuelan equine encephalitis virus with 26 human deaths.[18] A possible explanation for the serious outbreaks was the particularly heavy rain that had fallen. This could have caused increased numbers of mosquitoes that could serve as vectors for the disease. [18][15]

History

Fred Soper, PhD

As to history the Venezuelan equine encephalitis virus was first isolated and described in 1938 by Fred L. Soper, William C. Reeves, during an outbreak in Venezuela. The virus was identified as the cause of a severe epizootic disease affecting horses, with occasional spillover into humans[19][20]

Society and culture

In April 2009, the U.S. Army Medical Research Institute of Infectious Diseases at Fort Detrick reported that samples of Venezuelan equine encephalitis virus were discovered missing during an inventory of a group of samples left by a departed researcher. The report stated the samples were likely among those destroyed when a freezer malfunctioned.[21] During the Cold War, both the United States biological weapons program and the Soviet biological weapons program researched and weaponized VEE.[22]

Research

A 2024 study demonstrated the efficacy of a potent neutralizing antibody targeting the E2 glycoprotein of VEEV.The antibody showed strong therapeutic potential in treating established encephalitic alphavirus infections, emphasizing the role Fc effector functions[23]

See also

References

  1. ↑ "Venezuelan equine encephalitis virus infection (Concept Id: C0014078) - MedGen - NCBI". www.ncbi.nlm.nih.gov. Archived from the original on 2 February 2025. Retrieved 9 October 2025.
  2. ↑ 2.0 2.1 2.2 2.3 Guzmán-Terán, Camilo; Calderón-Rangel, Alfonso; Rodriguez-Morales, Alfonso; Mattar, Salim (19 May 2020). "Venezuelan equine encephalitis virus: the problem is not over for tropical America". Annals of Clinical Microbiology and Antimicrobials. 19 (1): 19. doi:10.1186/s12941-020-00360-4. ISSN 1476-0711. PMC 7236962. PMID 32429942.
  3. ↑ Go, Yun Young; Balasuriya, Udeni B. R.; Lee, Chong-kyo (1 January 2014). "Zoonotic encephalitides caused by arboviruses: transmission and epidemiology of alphaviruses and flaviviruses". Clinical and Experimental Vaccine Research. 3 (1): 58–77. doi:10.7774/cevr.2014.3.1.58. ISSN 2287-3651. PMID 24427764.
  4. ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 4.12 4.13 4.14 Crosby, Brianna; Crespo, Maria E. (2025). "Venezuelan Equine Encephalitis". StatPearls. StatPearls Publishing. PMID 32644758. Archived from the original on 3 September 2025. Retrieved 9 October 2025.
  5. ↑ 5.0 5.1 "VENEZUELAN EQUINE ENCEPHALITIS" (PDF). woah. Archived (PDF) from the original on 22 February 2025. Retrieved 28 October 2025.
  6. ↑ 6.0 6.1 Vlak, Just M. (July 2007). "Gernot H. Bergold (1911–2003)". Journal of Invertebrate Pathology. 95 (3): 231–232. Bibcode:2007JInvP..95..231V. doi:10.1016/j.jip.2007.03.015.
  7. ↑ "VENEZUELAN EQUINE ENCEPHALOMYELITIS STANDARD OPERATING PROCEDURES" (PDF). USDA. Retrieved 23 October 2025.
  8. ↑ Auguste, Albert J.; Volk, Sara M.; Arrigo, Nicole C.; Martinez, Raymond; Ramkissoon, Vernie; Adams, A. Paige; Thompson, Nadin N.; Adesiyun, Abiodun A.; Chadee, Dave D.; Foster, Jerome E.; Travassos Da Rosa, Amelia P.A.; Tesh, Robert B.; Weaver, Scott C.; Carrington, Christine V.F. (September 2009). "Isolation and phylogenetic analysis of Mucambo virus (Venezuelan equine encephalitis complex subtype IIIA) in Trinidad". Virology. 392 (1): 123–130. doi:10.1016/j.virol.2009.06.038. PMC 2804100. PMID 19631956.
  9. ↑ Gardner, Christina L.; Burke, Crystal W.; Tesfay, Mulu Z.; Glass, Pamela J.; Klimstra, William B.; Ryman, Kate D. (November 2008). "Eastern and Venezuelan equine encephalitis viruses differ in their ability to infect dendritic cells and macrophages: impact of altered cell tropism on pathogenesis". Journal of Virology. 82 (21): 10634–10646. doi:10.1128/JVI.01323-08. ISSN 1098-5514. PMC 2573165. PMID 18768986.
  10. ↑ Sharma, Anuj; Knollmann-Ritschel, Barbara (18 February 2019). "Current Understanding of the Molecular Basis of Venezuelan Equine Encephalitis Virus Pathogenesis and Vaccine Development". Viruses. 11 (2): 164. doi:10.3390/v11020164. ISSN 1999-4915. PMC 6410161. PMID 30781656.
  11. ↑ Paessler, Slobodan; Weaver, Scott C. (5 November 2009). "Vaccines for Venezuelan equine encephalitis". Vaccine. 27 Suppl 4: D80–85. doi:10.1016/j.vaccine.2009.07.095. ISSN 1873-2518. PMC 2764542. PMID 19837294.
  12. ↑ "Venezuelan Equine Encephalitis -- Colombia, 1995". www.cdc.gov. Archived from the original on 7 September 2025. Retrieved 21 October 2025.
  13. ↑ 13.0 13.1 Weaver, Scott C.; Ferro, Cristina; Barrera, Roberto; Boshell, Jorge; Navarro, Juan-Carlos (7 January 2004). "Venezuelan equine encephalitis". Annual Review of Entomology. 49 (1): 141–174. doi:10.1146/annurev.ento.49.061802.123422. PMID 14651460.
  14. ↑ Osorio, Jorge E.; Yuill, Thomas M. (2017). "Venzuelan Equine Encephalitis". In Beran, George W. (ed.). Handbook of zoonoses. Vol. Section B Viral Zoonoses. CRC Press. ISBN 9781351441797.
  15. ↑ 15.0 15.1 15.2 Aguilar, Patricia V.; Estrada-Franco, Jose G.; Navarro-Lopez, Roberto; Ferro, Cristina; Haddow, Andrew D.; Weaver, Scott C. (2011). "Endemic Venezuelan equine encephalitis in the Americas: hidden under the dengue umbrella". Future Virology. 6 (3): 721–740. doi:10.2217/FVL.11.5. ISSN 1746-0794. PMC 3134406. PMID 21765860.
  16. ↑ Weaver, Scott C.; Salas, Rosalba; Rico-Hesse, Rebeca; Ludwig, George V.; Oberste, M. Steven; Boshell, Jorge; Tesh, Robert B. (17 August 1996). "Re-emergence of epidemic Venezuelan equine encephalomyelitis in South America". The Lancet. 348 (9025): 436–440. doi:10.1016/S0140-6736(96)02275-1. ISSN 0140-6736. PMID 8709783. Retrieved 28 October 2025.
  17. ↑ Acha, Pedro N.; Szyfres, Boris (2001). Zoonoses and Communicable Diseases Common to Man and Animals: Chlamydioses, rickettsioses, and viroses. Pan American Health Org. ISBN 978-92-75-11580-0.
  18. ↑ 18.0 18.1 Beaman, Joseph R.; Turell, Michael J. (1 January 1991). "Transmission of Venezuelan Equine Encephalomyelitis Virus by Strains of Aedes albopictus (Diptera: Culicidae) Collected in North and South America". Journal of Medical Entomology. 28 (1): 161–164. doi:10.1093/jmedent/28.1.161. PMID 2033608.
  19. ↑ "09.20.2004 - William C. Reeves, professor emeritus and giant in arbovirology, dies at 87". newsarchive.berkeley.edu. Archived from the original on 24 January 2025. Retrieved 17 October 2025.
  20. ↑ Soper, F. L., & Reeves, W. C. (1938). Venezuelan equine encephalitis epidemic: Report on virus isolation and outbreak investigation. U.S. Public Health Service.https://stacks.cdc.gov/view/cdc/62709 Archived 2025-05-14 at the Wayback Machine
  21. ↑ Shaughnessy, Larry (22 April 2009). "Army: 3 vials of virus samples missing from Maryland facility". CNN.
  22. ↑ Croddy, Eric (2002). "The Post-World War II Era and the Korean War". Chemical and Biological Warfare: A Comprehensive Survey for the Concerned Citizen. Springer Science & Business Media. pp. 30–31. ISBN 978-0-387-95076-1.
  23. ↑ Schwedler, Jennifer L.; Stefan, Maxwell A.; Thatcher, Christine E.; McIlroy, Peter R.; Sinha, Anupama; Phillips, Ashlee M.; Sumner, Christopher A.; Courtney, Colleen M.; Kim, Christina Y.; Weilhammer, Dina R.; Harmon, Brooke (31 December 2024). "Therapeutic efficacy of a potent anti-Venezuelan equine encephalitis virus antibody is contingent on Fc effector function". mAbs. 16 (1) 2297451. doi:10.1080/19420862.2023.2297451. PMC 10766394. PMID 38170638.

Further reading

External links

Classification
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