First detection of the equine herpesvirus 1 neuropathogenic variant in Brazil

Abstract

SummaryThis report describes the first detection of an equine herpesvirus 1 (EHV-1) neuropathogenic variant (G 2254 /D 752 ) in Brazil from a case of fatal equine herpesvirus myeloencephalopathy (EHM) in a mare. The results of nucleotide sequencing of the EHV-1 ORF30 gene showed that two other Brazilian EHV-1 isolates from EHM cases are representatives of the non-neuropathogenic variant (A 2254 /N 752 ), suggesting that other unidentified factors are probably also involved in the neuropathogenicity of EHV-1 in horses. These findings will contribute to the epidemiological knowledge of EHV-1 infection in Brazil. KeywordsBrazil -DNA polymerase gene -Equine herpesvirus 1 -Neurological diseaseNeuropathogenic.Equine herpesvirus type 1 (EHV-1) is an important and ubiquitous pathogen, which causes extensive economic losses in the horse industry. The virus induces respiratory disease in young horses, abortion in pregnant mares, perinatal foal mortality, and neurological disease. Infection may involve a single animal or an entire herd (8, 11).In recent years, the occurrence of equine herpesvirus myeloencephalopathy (EHM) among horse populations in North America and Europe has increased both in frequency and severity, leading the United States Department of Agriculture to designate EHM as an emerging infectious disease (2). Nugent et al. (9) showed that a single nucleotide polymorphism within the gene encoding the catalytic subunit of EHV-1 DNA polymerase (ORF30) is associated with clinical cases of EHM. The substitution of adenine (A) for guanine (G) at position 2,254 (A 2254 to G 2254 ) causes a replacement of asparagine (N) by aspartic acid (D) at amino acid position 752 (N 752 to D 752 ). During the leukocyte-associated viraemia that follows EHV-1 infections in horses, the neuropathogenic variant (G 2254 /D 752 ) replicates at higher levels and for a longer duration than the nonneuropathogenic variant (A 2254 /N 752 ) (1). However, the mechanism by which this leukocyte-associated viraemia leads to EHM, and when, is not yet understood. Although the first isolation of EHV-1 (from an equine aborted fetus) was recorded in Brazil in 1966, the first EHM case report occurred only in 2005. This fatal EHM case was of a single mare, housed in an equestrian facility (7).Recent studies using real-time polymerase chain reaction (PCR) showed that 7% (4/54) of the EHV-1 strains isolated in Argentina from abortion outbreaks were associated with the neuropathogenic variant (G 2254 /D 752 ), and only two of those four cases were associated with simultaneous neurological disease (15). The ORF30 genotyping of Brazilian EHV-1 isolates derived from abortions or neurological cases has not been reported. This paper is a report of three EHM cases, including the first reported neuropathogenic (G 2254 /D 752 ) EHV-1 isolate from Brazil.Brain tissues were fixed in 10% formalin, processed routinely, embedded in paraffin, sectioned at 5 µm thickness, and stained with haematoxylin and eosin (HE).Virus isolation was attempted with clinical samples (...

A review of traditional and contemporary assays for direct and indirect detection of Equid herpesvirus 1 in clinical samples

“…29,40,57 However, there is growing evidence that this is not the only nucleotide substitution responsible for the neuropathogenic phenotype of EHV-1. 8,37,43,55 The neurologic form of EHV-1 infection appears to be becoming more prevalent with an increasing number of outbreaks characterized by a high case-fatality rate among affected horses in many countries. 8,27,33,37,43,55 Accurate and timely detection of EHV-1 infection in horses is important for equine practitioners, horse owners, breeders, and trainers.…”

Phylogenomic assessment of 23 equid alphaherpesvirus 1 isolates obtained from USA-based equids

“…Since being described almost 20 years ago [ 20 ], the ORF 30 A2254G substitution has been investigated in the context of equine herpes myeloencephalopathy (EHM) [ 2 , 9 , 13 – 15 , 17 , 41 , 42 ]. Although the substitution has been shown to be significantly associated with neurological disease [ 20 ], notably the substitution is not present in all isolates recovered from hosts with EHM [ 17 ].…”

Occurrence of Antibodies against Herpesvirus and Arteritis Virus in Equines from the State of Rio Grande do Norte, Brazil

“…O Herpesvirus Equino (HVE) e o Vírus da Arterite Viral Equina (VAVE), possuem elevada capacidade de disseminação, permanecendo latentes no organismo, até que o animal apresente imunossupressão [12,19], levando a surtos de abortos, morte neonatal, quadros neurológicos e respiratórios [13,17,27,34,37]. Os levantamentos sorológicos de HVE, no Nordeste, foram realizados em Mossoró, Rio Grande do Norte, com equinos de vaquejada [14] e região metropolitana de Fortaleza, Ceará [2] com ocorrências de 19,3% (22/114) e 41,2% (28/68) de positivos respectivamente, enquanto outros estudos nacionais variaram de 0 a 87% [1,2,[7][8][9][10]14,15,20,[23][24][25]27,30,32,38]. O vírus já foi isolado no Brasil, em casos de doença neurológica [6], abortamentos e mortalidade perinatal [34].…”