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Veterinary sciences2026; 13(1); 71; doi: 10.3390/vetsci13010071

Isolation of Madariaga Virus (MADV) in a Horse Coinfected with Equine Infectious Anemia in Venezuela: A Review of MADV Circulation in the Country.

Abstract: Madariaga virus (MADV), formerly known as the South American variant of Eastern Equine Encephalitis virus (EEEV), is an alphavirus that belongs to the family and has been periodically infecting equids in Venezuela since its first identification in 1975. This study reports the isolation and molecular characterization of MADV isolated from a horse in December 2024 in the context of MADV cases reported in Venezuela. Methods: Antibodies to the rabies virus were detected by indirect immunofluorescence, and to the Equine Infectious Anemia virus (EIAV) by passive immunodiffusion. MADV RNA was detected by qRT-PCR. The sequence of the complete viral genome was obtained by next-generation sequencing. Results: The sequence of this virus was highly similar to that of the only human case of MADV reported in the country in 2016, as well as to a sequence of a virus isolated from a horse in Colombia in 2002. The horse was found to be co-infected with EIAV. Conclusions: The continuous circulation of MADV in Venezuela warrants reinforcing the preventive measures against these alphaviruses, which ignore borders, and may cause important animal and human health concerns.
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Publication Date: 2026-01-10 PubMed ID: 41600727PubMed Central: PMC12846461DOI: 10.3390/vetsci13010071Google Scholar: Lookup
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Summary

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Isolation of Madariaga virus (MADV) from a horse coinfected with Equine Infectious Anemia virus (EIAV) in Venezuela highlights the ongoing circulation of MADV in the country and underlines the importance of preventive measures against alphavirus infections affecting both animals and humans.

Introduction and Background

  • Madariaga virus (MADV) is an alphavirus previously known as the South American variant of Eastern Equine Encephalitis virus (EEEV).
  • MADV has been periodically infecting equids (horses and related animals) in Venezuela since it was first identified in 1975.
  • The virus poses health risks to animals and humans, with documented cases of infection and encephalitis.
  • This study focuses on the isolation and molecular characterization of MADV in a horse from Venezuela in December 2024.

Methods

  • Detection of antibodies to rabies virus was performed using indirect immunofluorescence.
  • Antibodies to Equine Infectious Anemia virus (EIAV) were detected via passive immunodiffusion.
  • Presence of MADV RNA was confirmed and quantified by quantitative reverse transcription PCR (qRT-PCR).
  • The complete viral genome sequence was obtained using next-generation sequencing (NGS) techniques, allowing detailed molecular characterization.

Results

  • MADV was successfully isolated from the horse, confirming active infection.
  • Genetic sequencing revealed the virus’s genome was highly similar to the MADV strain isolated from the only reported human case in Venezuela in 2016.
  • The viral genome also showed close similarity to a MADV strain isolated from a horse in Colombia in 2002, indicating regional genetic relatedness.
  • The horse was concurrently infected with Equine Infectious Anemia virus (EIAV), demonstrating a coinfection scenario.

Conclusions and Implications

  • The study confirms the continuous circulation of MADV in Venezuela, emphasizing it as an ongoing veterinary and public health concern.
  • Co-infection with EIAV in the horse indicates that animals can simultaneously harbor multiple infectious agents, potentially complicating disease dynamics and clinical outcomes.
  • MADV and related alphaviruses can cross national borders, necessitating regional collaboration for surveillance and control.
  • Preventive measures should be reinforced to protect animal health and reduce the risk of human infection, including enhanced monitoring, vaccination strategies, and vector control programs.

Overall Significance

  • This research provides new molecular evidence of MADV persistence in Venezuelan equids more than four decades after its initial detection.
  • The genetic relationship between Venezuelan and Colombian MADV strains suggests ongoing regional circulation and potential spread.
  • Understanding coinfections such as with EIAV may help in framing better diagnostic and treatment protocols for equine diseases.
  • The study contributes valuable data to the epidemiology of alphaviruses in South America, supporting better preparedness and response to emerging zoonotic threats.

Cite This Article

APA
Garzaro D, Rodríguez N, Medina G, Alcazar W, Gualdron M, Siem JA, Sulbaran Y, Barrios M, Liprandi F, Jaspe RC, Pujol FH. (2026). Isolation of Madariaga Virus (MADV) in a Horse Coinfected with Equine Infectious Anemia in Venezuela: A Review of MADV Circulation in the Country. Vet Sci, 13(1), 71. https://doi.org/10.3390/vetsci13010071

Publication

Veterinary sciences
ISSN: 2306-7381
NlmUniqueID: 101680127
Country: Switzerland
Language: English
Volume: 13
Issue: 1
PII: 71

Researcher Affiliations

Garzaro, Domingo
  • Laboratorio de Virología Molecular, Centro de Microbiología y Biología Celular, Instituto Venezolano de Investigaciones Científicas, Caracas 1020, Venezuela.
Rodríguez, Nardraka
  • Instituto Nacional de Salud Animal Integrada, Maracay 2101, Venezuela.
Medina, Gladys
  • Edificio de Sanidad Animal, Laboratorio de Arbovirus-CENIAP/INIA, Maracay 2101, Venezuela.
Alcazar, Wilmer
  • Instituto Nacional de Salud Animal Integrada, Maracay 2101, Venezuela.
Gualdron, Marisol
  • Instituto Nacional de Salud Animal Integrada, Maracay 2101, Venezuela.
Siem, José Alejandro
  • Instituto Nacional de Salud Animal Integrada, Maracay 2101, Venezuela.
Sulbaran, Yoneira
  • Laboratorio de Virología Molecular, Centro de Microbiología y Biología Celular, Instituto Venezolano de Investigaciones Científicas, Caracas 1020, Venezuela.
Barrios, Miguel
  • Laboratorio de Virología Molecular, Centro de Microbiología y Biología Celular, Instituto Venezolano de Investigaciones Científicas, Caracas 1020, Venezuela.
Liprandi, Ferdinando
  • Laboratorio de Biología de Virus, Centro de Microbiología y Biología Celular, Instituto Venezolano de Investigaciones Científicas, Caracas 1020, Venezuela.
Jaspe, Rossana C
  • Laboratorio de Virología Molecular, Centro de Microbiología y Biología Celular, Instituto Venezolano de Investigaciones Científicas, Caracas 1020, Venezuela.
Pujol, Flor H
  • Laboratorio de Virología Molecular, Centro de Microbiología y Biología Celular, Instituto Venezolano de Investigaciones Científicas, Caracas 1020, Venezuela.

Grant Funding

  • N/A / MinCyt

Conflict of Interest Statement

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

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