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Viral Encephalitis

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Front. Microbiol. | doi: 10.3389/fmicb.2019.01240

The first case of bovine astrovirus-associated encephalitis in the Southern hemisphere (Uruguay), uncovers evidence of viral introduction to the Americas from Europe

 Federico Giannitti1*, Rubén D. Caffarena1,  Patricia Pesavento2, Francisco A. Uzal2, Leticia Maya3,  Martin Fraga1, Rodney Colina3 and  Matías Castells3
  • 1Instituto Nacional de Investigación Agropecuaria (INIA), Uruguay
  • 2Department of Pathology, Microbiology & Immunology, School of Veterinary Medicine, University of California, Davis, United States
  • 3Laboratory of Molecular Virology, Regional University Center Litoral Norte Salto, University of the Republic, Uruguay

Astrovirus species members of the Mamastrovirus genus (family Astroviridae) have been increasingly recognized as neuroinvasive pathogens in various mammals, including humans, mink, cattle, sheep, and pigs. While cases of astrovirus-associated encephalitis have been reported in North America, Europe and Asia, their presence has never been documented in the Southern hemisphere. This paper describes a case of astrovirus-associated encephalitis in cattle in Uruguay that broadens the geographic distribution and genetic diversity of neuroinvasive astroviruses and provides phylogeographic evidence of viral introduction to the Americas from Europe. A 22-month-old Holstein steer from a farm in Colonia department, Uruguay developed progressive neurological signs over a 3-day period before dying. Histopathological examination of the brain and proximal cervical spinal cord revealed disseminated, moderate to severe lymphocytic, histiocytic and plasmacytic poliomeningoencephalomyelitis with neuronal necrosis. A Mamastrovirus strain in the CH13/NeuroS1 clade we called bovine astrovirus (BoAstV)-Neuro-Uy was identified by reverse transcriptase PCR followed by nearly complete genome sequencing. Additionally, BoAstV was detected intralesionally in the brain by chromogenic RNA in situ hybridization within neuronal perikarya, axons and dendrites. Phylogenetic analysis of BoAstV-Neuro-Uy revealed a close relationship to neurotropic BoAstVs within the Virginia/Human-Mink-Ovine clade, which contains a growing cadre of neuroinvasive astroviruses. Analyzing the complete coding region of neuroinvasive BoAstVs sequences available in GenBank, we estimated an evolutionary rate of 4.27x10-4 (95% HPD 2.19–6.46x10-4) nucleotide substitutions/site/year. Phylogeographic analysis suggests that the common viral ancestor circulated in Europe between 1794-1940, and was introduced in Uruguay between 1849-1967, to later spread to North America and Japan.

Keywords: bovine astrovirus, Cattle, Encephalitis, infectious diseases, Mamastrovirus-13, Phylogeography, South America, Uruguay

Received: 22 Mar 2019; Accepted: 17 May 2019.

Edited by:

Mei-Ling LI, Rutgers University, The State University of New Jersey, United States

Reviewed by:

Marta Canuti, Memorial University of Newfoundland, Canada
Torsten Seuberlich, University of Bern, Switzerland  

Copyright: © 2019 Giannitti, Caffarena, Pesavento, Uzal, Maya, Fraga, Colina and Castells. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Federico Giannitti, Instituto Nacional de Investigación Agropecuaria (INIA), Montevideo, 11100, Uruguay, fgiannitti@inia.org.uy