Hepacivirus Infection in Domestic Horses, Brazil, 2011–2013

To the Editor: An estimated ≈150 million persons (3% of the world population) are chronically infected with hepatitis C virus (HCV). This virus is the prototype of the genus Hepacivi-rus and a major cause of liver cirrhosis and hepatocellular carcinoma around the world. Every year, 3–4 million persons become infected with HCV, and ≈350,000 die of this infection (1). Development of an HCV vaccine has been hampered by the difficulty of in vitro cultivation of the agent and by lack of animal models for studies of viral functions and host immune reactions (1,2). The only effective experimental model that can be infected with HCV and in which the course of infection is similar to that in humans is the chimpanzee. Since the discovery of HCV-like virus in dogs with respiratory disease and nonspecific gastrointestinal disorder in the United States in 2011, tentatively named canine hepacivirus (2), new hepaciviruses have been detected in insectivorous bats (3), Old World monkeys (4), wild rodents (5,6), and domestic horses (6–8). These animals could potentially serve as HCV models , but the accuracy of HCV tissue tro-pism, pathology, and immunology in natural hosts needs to be demonstrated. No official nomenclature for these recently described hepaciviruses has been defined by the International Committee of Viral Taxonomy. In this article, we refer to the viruses detected in horses as conventional nonprimate hepaciviruses (NPHVs). The aim of this study was to verify NPHV infection in horses from 8 locations in the eastern Brazilian Amazon.Techapp1.pdf). Samples came from 265 horses (Equus caballus), 30 mules (Equus mulus), and 5 donkeys (Equus asinus). All procedures for obtaining and using the samples were approved by the Ethics Committee on the Use of Animals in Research from the Evandro Cha-gas Institute (protocol code 0023/2012 CEUA/IEC/CENP/SVS/MS). Viral RNA was extracted from serum samples by using the TRIzol LS Reagent (Invitrogen, Carlsbad, CA, USA), and a target sequence in the nonstructural 3 protein (NS3) region of the NPHV genome was amplified from the cDNA by using a previously reported nested PCR protocol (8). Second-round product reactions of ≈380 bp were considered positive. We used the BigDye Terminator version 3.1 Cycle Sequencing Kit and an ABI 3500 Genetic Analyzer (both from Applied Biosystems, Foster City, CA, USA) for sequencing. To obtain consensus sequences, we used BioEdit software, version 7.0.5.3 To phylogenetically analyze the virus sequences based on an NS3 partial nucleotide sequence of 294 bp, we …