Active Circulation of Madariaga Virus, a Member of the Eastern Equine Encephalitis Virus Complex, in Northeast Brazil.

Laura H V G Gil,Tereza Magalhaes,Ana L S Fraiha,Raffaella B C Teixeira,Edmilson F Oliveira-Filho,Beatriz S A S Santos,Brenda M M Rocha,Roselene Ecco,Guilherme C Faria,Safira R M Drumond,Renata P A Maranhão,Erica A Costa,João L R Cunha,Zélia I P Lobato,Livia V Oliveira,Barbara C Longo,Ronaldo Furtini,Maria Isabel M C Guedes

doi:10.3390/pathogens10080983

Abstract

Madariaga virus (MADV) is a member of the eastern equine encephalitis virus (EEEV) complex that circulates in Central and South America. It is a zoonotic, mosquito-borne pathogen, belonging to the family Togaviridae. Disturbances in the natural transmission cycle of this virus result in outbreaks in equines and humans, leading to high case fatality in the former and acute febrile illness or neurological disease in the latter. Although a considerable amount of knowledge exists on the eco-epidemiology of North American EEEV strains, little is known about MADV. In Brazil, the most recent isolations of MADV occurred in 2009 in the States of Paraíba and Ceará, northeast Brazil. Because of that, health authorities have recommended vaccination of animals in these regions. However, in 2019 an equine encephalitis outbreak was reported in a municipality in Ceará. Here, we present the isolation of MADV from two horses that died in this outbreak. The full-length genome of these viruses was sequenced, and phylogenetic analyses performed. Pathological findings from postmortem examination are also discussed. We conclude that MADV is actively circulating in northeast Brazil despite vaccination programs, and call attention to this arbovirus that likely represents an emerging pathogen in Latin America.

Highlights

Eastern equine encephalitis virus (EEEV), western equine encephalitis virus (WEEV), and Venezuelan equine encephalitis virus (VEEV) are neurotropic, mosquito-borne alphaviruses of zoonotic and public health importance circulating in the Americas [1]
Diffuse hyperemia was the only central nervous system (CNS) gross lesion observed in the two horses upon necropsy
SA EEEV outbreaks have been reported in other regions of NE Brazil [19,29,35], indicating that the virus may be endemic in the NE region as it may be in other parts of the country

Summary

Introduction

Eastern equine encephalitis virus (EEEV), western equine encephalitis virus (WEEV), and Venezuelan equine encephalitis virus (VEEV) are neurotropic, mosquito-borne alphaviruses of zoonotic and public health importance circulating in the Americas [1]. They belong to the genus Alphavirus, family Togaviridae, and have a positive-sense, singlestranded, nonsegmented RNA genome of approximately 11.7 Kb [1]. The primary transmission cycle of EEEV leading to endemicity is enzootic; infections of animal species that are not the main reservoirs and of humans occur when factors disturbing the natural transmission cycles result in spillover events. NA EEEV is transmitted among passerine birds by Culiseta melanura mosquitoes [6,7]; it is unclear what vectors and reservoirs are responsible for SA EEEV maintenance and amplification in nature

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