Pathogenicity of a New Neurotropic Equine Herpesvirus 9(Gazelle Herpesvirus 1) in Horses.

Abstract

ABSTRACT. Pathogenicity of equine herpesvirus 9 (EHV-9), a new type of equine herpesvirus isolated from Gazella thomsoni, in horses was investigated by intranasal inoculation of EHV-9 (10 7 pfu) to two conventionally reared 8-months old half-bred weanling horses. Fever higher than 39°C was recorded. Virus was recovered from nasal swabs and peripheral blood mononuclear cells. Both horses developed neutralizing antibody to EHV-9. Perivascular infiltration of mononuclear cells and glial reaction were found in the olfactory and limbic systems. The results suggested that EHV-9 has a pathogenicity in horses.-KEY WORDS: equine, gazelle, herpesvirus.J. Vet. Med. Sci. 62(2): 215-218, 2000 describe the experimental infection of horses with EHV-9. The working seed of EHV-9 P19 [11] was prepared by propagation in fetal horse kidney (FHK) cells from the original stock of the third passage in Madin-Darby bovine kidney (MDBK) cells. The titration of viruses was conducted by plaque formation using MDBK cells and methylcellulose medium for overlay [17]. The reference viruses used were 89c25 for EHV-1 [18,19] and TH-20 for .Two half-bred weanling horses aged 8 months (H1 and H2) were used for inoculation of EHV-9. Ten ml of virus solution containing 10 7 plaque forming units (pfu) were inoculated intranasally using a nebulizer as described previously [17]. The inoculated horses were kept in a P3-level specific pathogen free facility of the Japan Racing Association, Tochigi, Japan.Rectal temperatures were recorded twice a day throughout the experiment. Fever higher than 39°C was recorded at 2, 4 and 5, and 1, 6 and 8 days post infection in H1 and H2, respectively. Other clinical symptoms were not observed. Leukocyte counts of both horses were normal during the experiment. Nasal swab and peripheral blood samples were collected daily for the first week and every other day for the second week after inoculation in order to investigate virus secretion and viremia. Viral isolation was conducted immediately after sample collection without freezing as described elsewhere [17]. A nasal swab was suspended in 2.0 ml phosphate buffered saline containing antibiotics. Approximately 10 6 mononuclear cells fractionated using Lymphoprep (Nycomed, Oslo, Norway) and 0.5 ml of nasal suspension were co-cultured with FHK cells in 25-cm 2 flasks (Nalge Nunc International Inc., Tokyo, Japan). The flasks were incubated at 37°C and observed for cytopathic effect for a week. Virus was recovered from nasal swabs from both horses on days 1 to 4, and from peripheral blood mononuclear cells in horse H1 on days 1 and 3 to 6 post infection. The recovered virus was identified as EHV-9 by A new herpesvirus was isolated from the epizootic encephalitis of Thomson's gazelles (Gazella thomsoni) kept at a zoological garden [11,25]. The outbreak occurred in a herd of ten gazelles in the fall of 1993. Seven gazelles died with or without apparent neurological symptoms. All dead gazelles had nonsuppurative encephalitis characterized by necrosis and degeneration of neuron...

Biotechnological tools for diagnosis of equine infectious diseases

“…This dilution indicates the titre of the serum tested. The sero-prevalence of EHV-1 and EHV-9 infections was reported by serum neutralization test (Borchers et al, 2005;Taniguchi et al, 2000).…”

Enfermedades Emergentes y Barrera de Especies: Riesgo del Herpesvirus Equino 9

“…La infección se caracterizó por un incremento de la temperatura, encefalitis no supurativa y neumonía acompañada de excreción de virus en cavidad nasal, además de provocar una viremia que podía ser detectada hasta el día 6 post inoculación; no se presentó mortalidad (13). Considerando la fuerte virulen-cia del EHV-9 en las gacelas versus los equinos, si un equino se encontrara infectado de manera latente, podría convertirse en una fuente de infección para otros equinos y otras especies.…”

Complete Genome Sequence of Equine Herpesvirus Type 9

“…Experimental infection in various animals, including hamster, mouse, horse, and goat, showed that EHV-9 possesses a wide host range and strong neurotropism (4,8,9,10,11,12,13). Natural EHV-9 infection has been reported to cause lethal encephalitis in a giraffe (6) and polar bear (2, 10).…”