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Transbound Emerg Dis. 2019 Jul;66(4):1737-1751. doi: 10.1111/tbed.13210. Epub 2019 May 8.

First description of Theiler's disease-associated virus infection and epidemiological investigation of equine pegivirus and equine hepacivirus coinfection in Brazil.

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Laboratório de Desenvolvimento Tecnológico em Virologia, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil.
Laboratório de Virologia Molecular, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil.
Laboratório de Flavivírus, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil.
Instituto de Veterinária, Universidade Federal Rural do Rio de Janeiro, Rio de Janeiro, Brazil.
Coordenação de Produção Integrada ao Ensino, Pesquisa e Extensão, Reitoria, Universidade Federal Rural do Rio de Janeiro, Rio de Janeiro, Brazil.
Laboratório de Pesquisa Clínica e Diagnóstico Molecular Professor Marcílio Dias do Nascimento, Departamento de Patologia e Clínica Veterinária, Faculdade de Veterinária, Universidade Federal Fluminense, Niterói, Brazil.
Laboratório de Hantaviroses e Rickettsioses, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil.
Laboratório de Retroviroses, Escola de Veterinária, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
Programa de Computação Científica, Fiocruz, Rio de Janeiro, Brazil.


Recent advances in the study of equine pegivirus (EPgV), Theiler's disease-associated virus (TDAV) and equine hepacivirus (EqHV) highlight their importance to veterinary and human health. To gain some insight into virus distribution, possible risk factors, presence of liver damage and genetic variability of these viruses in Brazil, we performed a cross-sectional study of EPgV and TDAV infections using a simultaneous detection assay, and assessed EqHV coinfection in different horse cohorts. Of the 500 serum samples screened, TDAV, EPgV and EPgV-EqHV were present in 1.6%, 14.2% and 18.3%, respectively. EPgV-positive horses were present in four Brazilian states: Espírito Santo, Mato Grosso do Sul, Minas Gerais and Rio de Janeiro. Serum biochemical alterations were present in 40.4% of EPgV-infected horses, two of them presenting current liver injury. Chance of infection was 2.7 times higher in horses ≤5 years old (p = 0.0008) and 4.9 times higher in horses raised under intensive production systems (p = 0.0009). EPgV-EqHV coinfection was 75% less likely in horses older than 5 years comparatively to those with ≤5 years old (p = 0.047). TDAV-positive animals were detected in different horse categories without biochemical alteration. Nucleotide sequences were highly conserved among isolates from this study and previous field and commercial product isolates (≥88% identity). Tree topology revealed the formation of two clades (pp = 1) for both EPgV and TDAV NS3 partial sequences. In conclusion, the widespread presence of EPgV-RNA suggests an enzootic infection with subclinical viremia in Brazil. Horse management can influence virus spread. This first report of TDAV-infected horses outside the USA reveals the existence of subclinical viremic horses in distant geographical regions. EPgV and TDAV have similar circulating isolates worldwide. These findings contribute to global efforts to understand the epidemiology and pathogenesis of these equine viruses.


Brazil; Theiler's disease-associated virus; equine hepacivirus; equine pegivirus; genetic variability; horse; liver enzymes; risk factors

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