2. Persistence of Equine Herpesviruses in Experimentally Infected Horses and the Experimental Induction of Abortion |
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| Authors: | A J Turner MVScM J Studdert MVSc PhD J E Peterson BVSc |
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| Institution: | School of Veterinary Science, University of Melbourne, Parkville, Victoria, 3052.;Division of Animal Health, Animal Health Research laboratory, CSIRO, Parkville, Victoria, 3052. |
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| Abstract: | An 8-month-old filly (No. 2) developed an acute vulvo-vaginitis and respiratory disease following inoculation of equine herpesvirus (EH virus) type 1 (EH 39 virus; equine rhinopneumonitis virus) into the vestibule of the vagina. The same virus produced acute respiratory disease but not balanoposthitis following intranasal, intravenous and intrapreputial inoculation of a 12-month-old colt (No. 3). A second 8-month-old filly (No. 1) developed a mild respiratory disease but not vulvo-vaginitis following intravestibular inoculation of EH 39 virus. EH viruses that were slowly cytopathic for equine foetal kidney cell cultures and serologically unrelated to the inoculated EH 39 virus were isolated from the buffy coat cells at 3 days and from the nasal cavity at 6 days after inoculation of horse No. 1. EH virus that was slowly cytopathic and serologically unrelated to EH 39 virus was isolated at 16 days from the vagina of the filly (No. 2) that developed acute vulvovaginitis and was frequently isolated from the nasal cavities of 2 of the 3 horses for 83 days and from the nasal cavity of the third horse for 57 days under conditions that precluded reinfection from other equidae except from each other. EH viruses were recovered from the 3 horses for a further 58 days under conditions where contact with other equidae may, although was not known to, have occurred between 83 and 141 days postinoculation. It was concluded that these viruses represented a single virus type that was present in the nasal cavity (designated EH 1–6 virus) perhaps also the blood stream of filly No. 1 at the time the 3 horses were purchased and that this virus was subsequently transmitted to the vagina of 1 and the nasal cavities of the other 2 horses. Accordingly a carrier state for EH 39 virus was not shown to occur. These findings are discussed in relation to the natural history of EH virus infections. Attempts to reactivate the EH viruses to cause clinical respiratory disease, by a series of injections of adrenalin and cortisone, were inconclusive. The 3 horses showed no clinical evidence of respiratory disease when they were reinfected intranasally with EH 39 virus 360 days (1 horse) and 412 days (2 horses) after the initial infection with this virus. Abortion was produced when EH 39 virus was inoculated directly into the allantoic or amniotic cavity of a pregnant mare although naturally occurring EH virus abortion remains unrecognised in Australia. |
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