Evaluation of ovine herpesvirus type 2 infections, as detected by competitive inhibition ELISA and polymerase chain reaction assay, in dairy cattle without clinical signs of malignant catarrhal fever.
OBJECTIVE
To monitor ovine herpesvirus type 2 (OvHV-2) infection status and the association between OvHV-2 infection and development of clinical signs of malignant catarrhal fever (MCF) in cattle.


METHODS
Longitudinal study.


METHODS
30 mature adult cows and 18 cattle submitted for necropsy.


METHODS
Blood and milk samples were collected at monthly intervals from 30 adult cows for 20 consecutive months. Nasal and ocular swab specimens were also collected during months 9 through 20. Polymerase chain reaction (PCR) assay for detection of OvHV-2 was performed on blood, milk, nasal swab, and ocular swab specimens. Competitive inhibition ELISA (CI-ELISA) for detection of antibodies against MCF viruses was performed on serum samples obtained prior to study initiation and monthly during the last 12 months. Tissues obtained from herdmates without clinical signs of MCF that were submitted for necropsy were analyzed for OvHV-2 DNA via PCR assay for possible sites of latency.


RESULTS
Initially, 8 of 30 cows had positive CI-ELISA results. Seroconversion was detected in 4 cows. Ovine herpesvirus type 2 DNA was intermittently detected in blood, milk, nasal secretions, or ocular secretions from 17 of 30 cows. Twenty-one cows had positive CI-ELISA or PCR assay results. No cattle in the study developed clinical signs of MCF. Results of PCR assays performed on tissue samples from 2 of 18 animals submitted for necropsy were positive for OvHV-2. CONCLUSIONS AND CLINICAL RELEVANCE; OvHV-2 infection can occur in cattle without concurrent development of clinical MCF. Ovine herpesvirus type 2 DNA was detected intermittently, suggesting fluctuating viral DNA loads or reinfection in subclinical cattle. A definitive site of latency was not identified from tissues obtained during necropsy.
Powers
Jenny G
JG
Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523-1620, USA.
VanMetre
David C
DC
Collins
James K
JK
Dinsmore
R Page
RP
Carman
Jane
J
Patterson
Gage
G
Brahmbhatt
Dipa
D
Callan
Robert J
RJ
D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D002353:Carrier State / Q000175:diagnosis / Q000662:veterinary* / Q000821:virology; D002417:Cattle; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000662:veterinary; D005260:Female; D006564:Herpesviridae / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D008137:Longitudinal Studies; D008304:Malignant Catarrh / Q000150:complications / Q000175:diagnosis*; D008892:Milk / Q000821:virology; D016133:Polymerase Chain Reaction / Q000379:methods / Q000662:veterinary; D012680:Sensitivity and Specificity
D000914:Antibodies, Viral