Analysis of the Pathogenetic Basis for Shedding and Transmission of Ovine Gamma Herpesvirus 2

Abstract

Ovine herpesvirus 2 (OvHV-2), a member of the viral subfamily Gammaherpesvirinae, shares numerous similarities with human herpesvirus 8 (HHV-8). Both viruses are apathogenic in their healthy original host, may cause lymphoprolipherative diseases, cannot routinely be propagated in cell culture, and may be sexually transmitted. However, the pathways of sexual transmission of these viruses, as well as the underlying pathogenetic dynamics, are not well understood. Organs from naturally OvHV-2-infected, as well as OvHV-2-free, sheep were quantitatively analyzed for OvHV-2 by the DNA amplification techniques. The dynamics of OvHV-2 multiplication and excretion were monitored after experimental infections and, most importantly, subsequent to vasectomy. The OvHV-2 DNA load in various tissues and internal organs was not merely reflecting the viral DNA load in the bloodstream, which suggested compartmentalization of OvHV-2. Moreover, OvHV-2 DNA was detected at several portals for virus shedding, i.e., the respiratory, alimentary, and urogenital tracts. Transient OvHV-2 excretion was detected in ejaculates of experimentally infected rams. Upon vasectomy, OvHV-2 DNA reappeared in the ejaculatory plasma, but the titers did not decline after reaching a peak. Spiking and fractionation experiments revealed an inhibitory activity, associated with the spermatozoa, which was able to suppress detection of viral DNA but which was no longer present in samples from vasectomized animals. Therefore, epidemiological studies on viruses that may be transmitted by the ejaculatory pathway and for whose tracing nucleic acid amplification methods are used, i.e., OvHV-2, HHV-8, and the human immunodeficiency virus, should include vasectomized males.The hallmarks of gamma herpesviruses, i.e., ovine herpesvirus 2 (OvHV-2; the causative agent of malignant catarrhal fever) and the tumorigenic human herpesvirus 8 (HHV-8), include restricted host range and causing host-specific, proliferative, immunopathological diseases (13,15,19). HHV-8 and OvHV-2 share at least three important features:(i) Normally, they are not associated with disease in the healthy original host. However, in the immunologically ill adapted host, they are causative agents of lymphoproliferative diseases. (ii) Natural isolates cannot routinely be propagated in cell culture (7,18). Therefore, efficient tracing of these viruses relies on DNA amplification techniques. (iii) Several lines of evidence suggest that they may be sexually transmitted (2, 3, 14, 16). However, the reported prevalences of HHV-8 in prostate and semen range from zero to Ͼ90% (reviewed in reference 9). To date, hardly any information concerning the pathogenesis and shedding of OvHV-2 has been presented.Good animal models for studying HHV-8 infections are not available (4). However, specific-OvHV-2-free sheep may be employed to gain significant information on infection, pathogenesis, and transmission of gammaherpesviruses.To gain insight into the pathogenetic basis for gammaherpesvirus excretion, organs from natu...

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Experimental Transmission of Ovine Herpesvirus-2 in Sheep

“…Though we did not attempt other transmission routes in this study, there have been several reports that no OvHV-2 DNA was detected in the urinary bladder [2], urine or faeces [7,8]. Consequently, it is suggested that nasal secretions play an active role in transmission of the virus among sheep.…”

Sheep associated malignant catarrhal fever: an emerging disease of bovids in India

“…OvHV-2 collected from ovine nasal secretions can infect naive sheep, cattle or bison [79,80]. OvHV-2 viral DNA also has been detected in samples from the alimentary, respiratory and uro-genital tracts of sheep [35] indicating that some infection of offspring may occur during or shortly after lambing or calving. However, other studies have documented spread of OvHV-2 from sheep to bison over distances of up to 5 km [49].…”

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