An Ocular Infection Model Using Suckling Hamsters Inoculated With Equine Herpesvirus 9 (EHV-9)

Abstract

By using a new member of the neurotropic equine herpesviruses, EHV-9, which induced encephalitis in various species via various routes, an ocular infection model was developed in suckling hamsters. The suckling hamsters were inoculated with EHV-9 via the conjunctival route and were sacrificed after 6,12,24,36, 48, 72, 96, 120, and 144 hours (h) post inoculation (PI). Three horizontal sections of the brains, including the eyes and cranial cavity, were examined histologically to assess the viral kinetics and time-course neuropathological alterations using a panoramic view. At 6 to 24 h PI, there were various degrees of necrosis in the conjunctival epithelial cells, as well as frequent mononuclear cell infiltrations in the lamina propria and the tarsus of the eyelid, and frequent myositis of the eyelid muscles. At 96 h PI, encephalitis was observed in the brainstem at the level of the pons and cerebellum. EHV-9 antigen immunoreactivity was detected in the macrophages circulating in the eyelid and around the fine nerve endings supplying the eyelid, the nerves of the extraocular muscles, and the lacrimal glands from 6 h to 144 h PI. At 96 h PI, the viral antigen immunoreactivity was detected in the brainstem at the level of the pons and cerebellum. These results suggest that EHV-9 invaded the brain via the trigeminal nerve in addition to the abducent, oculomotor, and facial nerves. This conjunctival EHV-9 suckling hamster model may be useful in assessing the neuronal spread of neuropathogenic viruses via the eyes to the brain. Keywords EHV-9, eye, suckling hamsters, neuropathogenesis EHV-9, the newest member of the equine herpesvirus family, is a highly neurotropic herpesvirus first isolated in an outbreak of encephalitis in a herd of Thomson's gazelles (Gazella thomsoni) kept at a zoological garden. 13,36 Although the natural host of EHV-9 and the complete host range are still unknown, a member of the equidae is suspected to be a natural host of EHV-9, as domestic horses (Equus caballus) inoculated intranasally with EHV-9 exhibited only mild encephalitis and there were no resulting deaths. 34 In addition, a high seroprevalence for EHV-9 without any signs was detected among Burchell's zebras (Equus burchelli) in Serengeti National Park in Tanzania. 2 Recently, it has been reported that the host range of EHV-9 has expanded to include Grevy's zebras (Equus grevysi) and polar bears (Ursus maritimus), 7,31 as well as a giraffe (Giraffa camelopardalis reticulata).18 EHV-9 is most closely related to the recently re-emergent neurotropic pathogen, EHV-1; however, cleavage by restriction enzymes showed that the DNA fingerprint of EHV-9 is different from that of EHV-1 and other equine herpesviruses. 13Emerging EHV-9 infections are of special interest because there is a wide range of susceptible hosts, which includes mice and rats, 13 hamsters, 12 goats, 35 pigs, 26 dogs and cats, 37,38 and common marmosets. 21 Recently, EHV-9 was used to induce encephalitis in hamsters by different routes of inoculation, including th...

Effect of a single point mutation on equine herpes virus 9 (EHV-9) neuropathogenicity after intranasal inoculation in a hamster model

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Cranial nerve III and/or VI function abnormalities associated with active herpesvirus infection: Clinical experience and literature review

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<b>Susceptibilidade de hamsters frente à infecção pelo herpesvirus equino tipo 1 causando encefalite e doença respiratória</b>

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