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United States Department of Agriculture

Agricultural Research Service

Title: LEVELS OF OVINE HERPESVIRUS 2 DNA IN NASAL SECRETIONS AND BLOOD OF SHEEP: IMPLICATIONS FOR TRANSMISSION

Authors
item Li, Hong
item Hua, Y. - WASHINGTON STATE UNIV
item Snowder, Gary
item Crawford, T. - WASHINGTON STATE UNIV

Submitted to: Veterinary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 9, 2000
Publication Date: N/A

Interpretive Summary: Sheep are natural carriers of a herpesvirus that causes sheep-associated malignant catarrhal fever in several ruminants, such as cattle, bison, and deer. In this study, we use a recently-developed competitive PCR to quantitate the MCF viral genetic materials in sequential samples of nasal secretions and blood cells from both lambs and adult sheep in order to define patterns suggestive of viral shedding. The data strongly suggest that neonatal lambs are not an important source for the transmission of sheep-associated malignant catarrhal fever virus to clinically susceptible species, and that the nasal cavity is an important portal for shedding of infectious virus in sheep. Furthermore, this study failed to identify a seasonal pattern in levels of viral DNA in nasal secretions or PBL of adult sheep that would provide a basis for the traditionally held belief that clinical cases of malignant catarrhal fever are significantly associated with lambing ewes.

Technical Abstract: A recently-developed competitive PCR for ovine herpesvirus 2 (OvHV-2) was used to examine the levels of viral DNA in nasal secretions and peripheral blood leukocytes (PBL) of lambs and adult sheep. Viral DNA first appeared in the peripheral blood leucocytes (PBL) of most lambs after about 3 months of age, and the levels remained relatively constant thereafter. In most of the lambs (83%, n=12), viral DNA was undetectable by PCR in nasal secretions prior to 5 months of age. A dramatic rise of OvHV-2 DNA levels in the nasal secretions occurred starting at 5 to 6 months of age, which peaked at approximately 7 months. The highest level recorded in lamb nasal secretions was 7.5 x 108 copies/2 ?g DNA, which were 75,000 to 100,000-fold higher than the levels in PBL of the same lambs. In adult sheep (n=10), the viral DNA levels in both PBL and nasal secretions were relatively stable over the 13-month period of the study, which included a lambing season. The data strongly suggest that neonatal lambs are not an important source for the transmission of OvHV-2 to clinically susceptible species, and that the nasal cavity is an important portal for shedding of infectious OvHV-2 in sheep. Furthermore, this study failed to identify a seasonal pattern in levels of viral DNA in nasal secretions or PBL of adult sheep that would provide a basis for the traditionally held belief that clinical cases of malignant catarrhal fever are significantly associated with lambing ewes.

Last Modified: 8/31/2014
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