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United States Department of Agriculture

Agricultural Research Service

Title: Shedding of Ovine Herpesvirus 2 in Domestic Sheep: Frequency, Intensity and Duration

Authors
item Li, Hong
item Taus, Naomi
item Lewis, G - WSU
item Traul, Donald
item Kim, O - WSU
item Crawford, T - WSU

Submitted to: Herpesvirus International Workshop
Publication Type: Abstract Only
Publication Acceptance Date: April 6, 2004
Publication Date: July 26, 2004
Citation: Li, H., Taus, N.S., Lewis, G.S., Traul, D., Kim, O., Crawford, T.B. 2004. Shedding of ovine herpesvirus 2 in domestic sheep: frequency, intensity and duration [abstract]. Herpesvirus International Workshop. p. 12.

Interpretive Summary: Ovine herpesvirus 2 (OvHV-2), a member of a subgroup of ruminant rhadinoviruses, is the major causative agent of malignant catarrhal fever (MCF) in ruminant species worldwide. Using real-time PCR, we examined 5416 nasal secretion samples collected serially, on a daily basis from both 6 to 9 month-old adolescent sheep (n =56, 3062 samples) and from adult sheep (n = 33, 2354 samples), which included ewes during the lambing period. The sample set was assembled from 5 different serial studies conducted from 2001 through 2004. The goal of the study was to define the frequency, intensity and duration of OvHV-2 shedding for adolescent and adult sheep. At least one short-lived peak of viral DNA, ranging from 100 thousand to over 100 million copies/2 ug total sample DNA, was detected in nasal secretions from 60.7% of adolescent sheep, but only in 18% of adult sheep. The shedding frequency differed significantly between adolescent sheep and adult sheep (p < 0.000001). On a given day, adolescent sheep were 7.43 (95% CI: 3.31 - 17.17, p < 0.000001) times more likely to shed virus in nasal secretions than the adult sheep in this study. The mean viral DNA level in total nasal secretion samples from adolescent sheep (262,189 +/- SEM 113,817) was 61 times greater than that from adult sheep (4,278 +/- SEM 2,721) (p < 0.05). The duration of viral shedding episodes in the majority of individual sheep was 24 to 36 hours, suggesting that this was the product of a single cycle of viral replication. No corresponding fluctuations in DNA levels were found in either peripheral blood leukocytes or plasma. The data described herein show that nasal shedding is the major mode of OvHV-2 transmission among domestic sheep, and that adolescents represent the highest risk group for transmission.

Technical Abstract: Ovine herpesvirus 2 (OvHV-2), a member of a subgroup of ruminant rhadinoviruses, is the major causative agent of malignant catarrhal fever (MCF) in ruminant species worldwide. Using real-time PCR, we examined 5416 nasal secretion samples collected serially, on a daily basis from both 6 to 9 month-old adolescent sheep (n =56, 3062 samples) and from adult sheep (n = 33, 2354 samples), which included ewes during the lambing period. The sample set was assembled from 5 different serial studies conducted from 2001 through 2004. The goal of the study was to define the frequency, intensity and duration of OvHV-2 shedding for adolescent and adult sheep. At least one short-lived peak of viral DNA, ranging from 100 thousand to over 100 million copies/2 ug total sample DNA, was detected in nasal secretions from 60.7% of adolescent sheep, but only in 18% of adult sheep. The shedding frequency differed significantly between adolescent sheep and adult sheep (p < 0.000001). On a given day, adolescent sheep were 7.43 (95% CI: 3.31 - 17.17, p < 0.000001) times more likely to shed virus in nasal secretions than the adult sheep in this study. The mean viral DNA level in total nasal secretion samples from adolescent sheep (262,189 +/- SEM 113,817) was 61 times greater than that from adult sheep (4,278 +/- SEM 2,721) (p < 0.05). The duration of viral shedding episodes in the majority of individual sheep was 24 to 36 hours, suggesting that this was the product of a single cycle of viral replication. No corresponding fluctuations in DNA levels were found in either peripheral blood leukocytes or plasma. The data described herein show that nasal shedding is the major mode of OvHV-2 transmission among domestic sheep, and that adolescents represent the highest risk group for transmission.

Last Modified: 4/19/2014