Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


The pathogenesis of equine herpesvirus type 1 (EHV-1) and type 2 (EHV-2) respiratory infection was studied in cell and organ cultures by infectivity assays following experimental infections (growth kinetics), and by light, scanning and transmission electron microscopy. The cell cultures included fetal donkey and pony alveolar macrophages (FDAM/FPAM), fetal equine kidney (FEK), rabbit kidney (LLC-RK(,1)), and african green monkey kidney (VERO) cells. Organ cultures were derived from respiratory tissues (nasal, tracheal and pharyngeal mucosae) of seronegative donkey (F1D1) and pony (F1M1) fetuses, and of a seropositive adult pony (A1). In the cell cultures, EHV-1 multiplied and produced cytopathic effects (CPE) as early as 6 hours post inoculation (HPI) in LLC-RK(,1) cells characterized mainly by cell rounding and lysis. EHV-2 multiplied more slowly and produced CPE as early as 48 HPI in LLC-RK(,1), FDAM, and FEK cells. The CPE caused by EHV-2 in the various cultures consisted principally of rounding of cells and syncytia formation. In EHV-2 infected FPAM, the appearance of CPE was preceded by changes in organization of microfilaments and microtubules. In the organ cultures morphogenesis of EHV-2 was observed in the nucleus of infected F1M1 nasal epithelial cells. All the cultures supported the growth of EHV-1 and EHV-2 except F1M1 pharyngeal and A1 nasal cultures which were non permissive for EHV-2. EHV-1 and EHV-2 were recovered from infected F1D1 cultures for 10 and 30 days, respectively. Cytopathic alterations produced by EHV-1 and EHV-2 were observed in the epithelial layer of organ cultures and were characterized by cessation of ciliary activity, rounding and shedding of ciliated and non ciliated cells. Epithelial damage was most extensive in EHV-1 infected cultures.