Neurological Outbreak Research Articles

Equine Herpesvirus Type 1 ORF76 Encoding US9 as a Neurovirulence Factor in the Mouse Infection Model.

Equine herpesvirus type 1 (EHV-1) causes rhinopneumonitis, abortion, and neurological outbreaks (equine herpesvirus myeloencephalopathy, EHM) in horses. EHV-1 also causes lethal encephalitis in small laboratory animals such as mice and hamsters experimentally. EHV-1 ORF76 is a homolog of HSV-1 US9, which is a herpesvirus kinase. Starting with an EHV-1 bacterial artificial chromosome clone of neuropathogenic strain Ab4p (pAb4p BAC), we constructed an ORF76 deletion mutant (Ab4p∆ORF76) by replacing ORF76 with the rpsLneo gene. Deletion of ORF76 had no influence on replication, cell-to-cell spread in cultured cells, or replication in primary neuronal cells. In Western blots of EHV-1-infected cell lysates, an EHV-1 US9-specific polyclonal antibody detected multiple bands ranging from 35 to 42 kDa. In a CBA/N1 mouse infection model following intranasal inoculation, the parent and Ab4p∆ORF76 revertant caused the same histopathology in the brain and olfactory bulbs. The parent, Ab4p∆ORF76, and revertant mutant replicated similarly in the olfactory mucosa, although Ab4p∆ORF76 was not transported to the olfactory bulbs and was unable to infect the CNS. These results indicated that ORF76 (US9) plays an essential role in the anterograde spread of EHV-1.

Occurrences of avian encephalomyelitis virus in naturally infected chicks in Saudi Arabia's Eastern Province.

A neurological infectious viral disease, avian encephalomyelitis was initially discovered in 2-week-old commercial chicks in 1930 and classified as a neurotropic viral disease. A neurological outbreak caused by avian encephalomyelitis virus (AEV) in young chicks was first reported in Al-Ahsa in the Kingdom of Saudi Arabia (KSA) in 2010. The aim of this article is to examine the AEV in KSA, Al-Ahsa Province. Gizzard, proventriculus, cerebrum, cerebellum, and medulla oblongata tissue samples were collected from infected chicks for histopathology test and molecular identification. Infected chicks showed neurological signs particularly incoordination, mild head and neck tremors, stretching of legs, and lameness. The average morbidity and mortality rates were 35% and 10%, respectively. At necropsy, no obvious identifiable macroscopic lesions were found in the infected chicks. Nonsuppurative encephalomyelitis was found histopathologically in the central nervous system, mainly in the cerebral molecular layer. Microscopic lesions in the proventriculus showed masses of heavy numbers of small lymphocytes within the muscular layer. RT-PCR followed by sequence analysis revealed that The KSA strain (KJ939252) is intimately related to chicken European strains from Poland (KC912695) and the United Kingdom (AJ225173) with identity 99.6% than Chinese strains (AY225319, AY517471, and AY275539) with identity ranged between 94.6% and 95%. The phylogenetic tree analysis showed that the KSA strain is grouped in a similar clade with chicken European strains. The pattern of disease findings was typical of vertically transmitted AEV. The spread of AEV in Saudi Arabia is most likely due to the trade of birds and bird products with European countries.

Detection of Equid Alphaherpesvirus 1 from Arabian Horses with different clinical presentations between 2016-2019 in Egypt

Equid alphaherpesvirus 1 (EHV-1) is an important virus causing pathological disorders in horses. This highly contagious pathogen causes persistent outbreaks of upper respiratory tract infection, ocular affections, abortion, and neurological disorders with high mortality in Arabian horses in Egypt. The quick and accurate diagnosis is important to broaden our understanding about EHV-1 in the field, and to implicate stronger preventive, and control measures. Sixty-six Arabian horses from Cairo and Giza governorates were sampled from respiratory, abortigenic and neurological outbreaks over a period of 4 years. EHV-1 was diagnosed in these cases by immunohistochemistry using monoclonal antibody against EHV-1 glycoprotein B and molecular detection using gB, ORF33 specific real-time PCR. EHV-1 was detected in 25 cases, mostly from abortigenic outbreaks (14 abortions, 3 stillbirths, and two early neonatal deaths), in addition to 5 respiratory affections and single EHV-1 myeloencephalopathy. Molecular characterization revealed that the ORF33 sequences from this study were almost identical and closely related to the European EHV-1 strains. Furthermore, no difference in the amino acid sequences compared to previously published EHV-1 sequences from Egypt. The data in this study provides some insights about the prevalance of EHV-1 infection in Arabian horses, discusses EHV-1 diagnostic approaches, highlights the importance of accurate diagnosis and the importance of pregnant mare vaccination, and adds to the previous knowledge about EHV-1 in Egypt which may help in better controlling EHV-1 infections in the future.

EHV‐1 neurological outbreak during a show‐jumping competition: a clinical and epidemiological study

EHV‐1 neurological outbreak during a show‐jumping competition: a clinical and epidemiological study

Genetic diversity of equine herpesvirus 1 isolated from neurological, abortigenic and respiratory disease outbreaks.

SummaryEquine herpesvirus 1 (EHV‐1) causes respiratory disease, abortion, neonatal death and neurological disease in equines and is endemic in most countries. The viral factors that influence EHV‐1 disease severity are poorly understood, and this has hampered vaccine development. However, the N752D substitution in the viral DNA polymerase catalytic subunit has been shown statistically to be associated with neurological disease. This has given rise to the term “neuropathic strain,” even though strains lacking the polymorphism have been recovered from cases of neurological disease. To broaden understanding of EHV‐1 diversity in the field, 78 EHV‐1 strains isolated over a period of 35 years were sequenced. The great majority of isolates originated from the United Kingdom and included in the collection were low passage isolates from respiratory, abortigenic and neurological outbreaks. Phylogenetic analysis of regions spanning 80% of the genome showed that up to 13 viral clades have been circulating in the United Kingdom and that most of these are continuing to circulate. Abortion isolates grouped into nine clades, and neurological isolates grouped into five. Most neurological isolates had the N752D substitution, whereas most abortion isolates did not, although three of the neurological isolates from linked outbreaks had a different polymorphism. Finally, bioinformatic analysis suggested that recombination has occurred between EHV‐1 clades, between EHV‐1 and equine herpesvirus 4, and between EHV‐1 and equine herpesvirus 8.

An insight into a combination of ELISA strategies to diagnose small ruminant lentivirus infections

A single broadly reactive standard ELISA is commonly applied to control small ruminant lentivirus (SRLV) spread, but type specific ELISA strategies are gaining interest in areas with highly prevalent and heterogeneous SRLV infections. Short (15-residue) synthetic peptides (n=60) were designed in this study using deduced amino acid sequence profiles of SRLV circulating in sheep from North Central Spain and SRLV described previously. The corresponding ELISAs and two standard ELISAs were employed to analyze sera from sheep flocks either controlled or infected with different SRLV genotypes. Two outbreaks, showing SRLV-induced arthritis (genotype B2) and encephalitis (genotype A), were represented among the infected flocks. The ELISA results revealed that none of the assays detected all the infected animals in the global population analyzed, the assay performance varying according to the genetic type of the strain circulating in the area and the test antigen.Five of the six highly reactive (57–62%) single peptide ELISAs were further assessed, revealing that the ELISA based on peptide 98M (type A ENV-SU5, consensus from the neurological outbreak) detected positives in the majority of the type-A specific sera tested (Se: 86%; Sp: 98%) and not in the arthritic type B outbreak. ENV-TM ELISAs based on peptides 126M1 (Se: 82%; Sp: 95%) and 126M2 0,65 0.77 (Se: 68%; Sp: 88%) detected preferentially caprine arthritis encephalitis (CAEV, type B) and visna/maedi (VMV, type A) virus infections respectively, which may help to perform a preliminary CAEV vs. VMV-like typing of the flock. The use of particular peptide ELISAs and standard tests individually or combined may be useful in the different areas under study, to determine disease progression, diagnose/type infection and prevent its spread.

Visna/Maedi virus genetic characterization and serological diagnosis of infection in sheep from a neurological outbreak

An extensive outbreak characterized by the appearance of neurological symptoms in small ruminant lentivirus (SRLV) infected sheep has been identified in Spain, but the genetic characteristics of the strain involved and differential diagnostic tools for this outbreak remain unexplored. In this work, 23 Visna-affected naturally infected animals from the outbreak, 11 arthritic animals (both groups presenting anti-Visna/Maedi virus serum antibodies), and 100 seronegative animals were used. Eight of the Visna-affected animals were further studied post-mortem by immunohistochemistry. All had lesions in spinal cord, being the most affected part of the central nervous system in six of them. A representative strain of the outbreak was isolated. Together with other proviral sequences from the outbreak the virus was assigned to genotype A2/A3. In vitro culture of the isolate revealed that viral production was slow/low in fibroblast-like cells but it was high in blood monocyte-derived macrophages. The long terminal repeat (LTR) of the viral genome of this isolate lacked an U3-duplication, but its promoter activity in fibroblast-like cells was normal compared to other strains. Thus, viral production could not be inferred from the LTR promoter activity in this isolate. Analysis of the viral immunodominant epitopes among SRLV sequences of the outbreak and other known sequences allowed the design of a synthetic SU peptide ELISA that detected the Visna affected animals, representing a tool of epidemiological interest to control viral spread of this highly pathogenic strain.