Source: UNIVERSITY OF TENNESSEE submitted to NRP
SURVEILLANCE AND CHARACTERIZATION OF MALIGNANT CATARRHAL FEVER IN TENNESSEE
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
Reporting Frequency
Annual
Accession No.
0208342
Grant No.
(N/A)
Cumulative Award Amt.
(N/A)
Proposal No.
(N/A)
Multistate No.
(N/A)
Project Start Date
Oct 1, 2006
Project End Date
Sep 30, 2007
Grant Year
(N/A)
Program Code
[(N/A)]- (N/A)
Recipient Organization
UNIVERSITY OF TENNESSEE
2621 MORGAN CIR
KNOXVILLE,TN 37996-4540
Performing Department
PATHOLOGY
Non Technical Summary
Malignant Catarrhal Fever (MCFv) is a viral infection of ruminants that poses a potential endemic threat to the animal agriculture industry of Tennessee. This study is designed to develop preliminary surveillance to determine the prevalence of MCFv in Tennessee, exploiting established diagnostic, management, educational and production entities to gather relevant samples for diagnostic testing of the virus in domestic and wild ruminant livestock.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
3113310117025%
3113610117025%
3113820117025%
3113899117025%
Goals / Objectives
Malignant Catarrhal Fever is a viral infection of ruminants that poses a potential endemic threat to the animal agriculture industry of Tennessee. At least four ruminant species of economic consequence (cattle, sheep, goats, deer) to Tennessee are either carriers or affected by the disease. This collaborative study proposes to exploit established diagnostic, management, educational and production entities in gathering relevant samples for diagnostic testing for the virus. The results of ELISA testing, quantitative real-time PCR testing and gene sequencing are being used to delineate the distribution and prevalence of the viral strains in the diverse regions of the state. The investigators intend to employ the same networks to educate and advise producers, wildlife managers and diagnosticians regarding the incidence and risk for the disease. Two of the species populations known to harbor MCF viral strains (goats and deer) are increasing in the state of Tennessee. The state's deer herd has expanded to over 1 million animals (source TWRA). The state's goat population is second only to Texas (source: USDA Census of Agriculture). Cattle are one of the species affected by MCF and the state's cattle population exceeds two million head. There is no vaccine available for this disease, therefore control, if possible, requires an understanding of the demographics of the virus in Tennessee's ruminant domestic and wild livestock. Based on the current literature, lack of coherent surveillance on a national level, absence of surveillance on a statewide basis, species range of endemic viral strains and the potential for recrudescent sub-clinical disease, we hypothesize that there is unrecognized widespread prevalence of the Malignant Catarrhal Fever virus in Tennessee. Our objectives are to: 1) test relevant species populations (cattle, sheep, goats, deer) from across the state. 2) characterize the prevalence and strain distribution by region within the state 3) provide meaningful information regarding the disease risks to producers, managers, diagnosticians and policymakers within the state.
Project Methods
Our approach is to this problem is three-fold: 1) Identify and exploit species relevant sample sources. This aim involves the use of existing data sources and established networks of the investigators to secure permission for sample collection and retrieval with relevant distributional and exposure data. University, state, public and private sources serve as the pool from which to obtain samples of healthy and diseased livestock for testing. 2) Diagnostic preparation and testing of samples for presence of the MCF virus by real-time polymerase chain reaction and ELISA. This aim will be accomplished within the immunology service facilities of the University of Tennessee, College of Veterinary Medicine. Techniques already employed within the laboratory have been adapted to this issue. Primers have been design for real time PCR for 3 strains (OHV-1, CpHV-1 and WTD-MCF) of the malignant catarrhal fever virus. The targets of these primers have been validated by DNA sequence analysis and match published sequences for the specific strains. ELISA methodologies have been used to screen large closed herds and clinical presentation cases. The ELISA results allow assessment of herd exposure intra-herd prevalence and focused characterization of the viral strain present in the each tested herd. 3) Determination of distribution and prevalence of the MCF in the state of Tennessee for a rational response. This aim correlates the sample data gathered from specific aims 1 and 2 the incidence and the strain variation of MCF in the various geographic regions of the state. This information will be provided to relevant policy makers, wildlife managers, producer organizations and diagnosticians for their use in decision making processes regarding risk assessment and health initiatives involving the livestock industries in Tennessee.

Progress 10/01/06 to 09/30/07

Outputs
This report represents progress after an initial year of funding. We have employed real-time polymerase chain reaction (PCR) to examine convenience ante-mortem and/or post-mortem collected samples of a mixed population of relevant species (sheep, goats, cattle, white-tail deer and elk). PCR identified positive cattle, sheep, goats and deer viral strain sequencing has been done by the UT DNA sequencing and gene analysis core facility. The results matched published sequences available for OvHV-2, CpHV-2 and MCFV-WTD but, with some evidence of sequence divergence. A total of 183 real time-PCR (OHV-2, CpHV-2 & MCFV-WTD) positive samples have been identified from approximately 1500 samples collected. The samples are archived and represent a significant resource for further evaluation. The herd/flock of origin of the majority OHV-2 positive samples is known and can be revisited for secondary collection. In situations where heparinized blood was available the samples were screened for antibodies to MCF using a commercial competitive inhibition ELISA kit. Results are consistent with published percentages of exposure to OHV-2. Follow up PCR on select samples is also consistent with reported rates of viremia. CI-ELISA tested serum samples obtained from cattle presented either for illness or death had a ten-fold increase in sero-prevalence (26 percent) compared to the sero-prevalence of well herds (2.5 percent). In blood or lymph node samples from dead or down cattle tested by real-time PCR (508) the percentage of OHV-2 positive samples (22 percent) approximated the sero-prevalence of the population. This data adds additional support to the potential importance of recrudescence, and previous reports of chronic/latent infections and raises the concern that MCF may play an unrecognized importance in morbidity and mortality in cattle. Sequence analysis of at least one OHV-2 sample, obtained from a sheep flock associated with clinical MCF in closely housed bison, is in variance with the published Genbank sequences. This variance suggests genetic drift within the OHV-2 strain. From the perspective of host interaction and disease development such drift could have far reaching implications for diagnosis, prophylaxis and epidemiologic situations. Using known samples of MCFV-WTD strain, we have developed a real-time PCR test for investigating the presence of the White-tailed deer MCF virus strain. Results of testing on lymph node samples shows evidence of a widespread MCFV-WTD (32 percent) in wild white tail deer in the eastern and middle areas of Tennessee. The real-time PCR findings have been confirmed by traditional gel PCR and sequencing of the amplified DNA polymerase gene fragment. Extension of this real-time PCR testing to limited numbers of blood samples from ELISA positive cattle as well as fresh and fixed lymphoid tissues from dead and clinically normal cattle has revealed the presence of MCFV-WTD in cattle in East Tennessee from counties in which the strain was detected in fixed tissues from wild deer. This finding raises potentially serious disease issues at the wildlife/livestock interface.

Impacts
Malignant Catarrhal Fever (MCF) is an endemic disease of ruminants that sporadically results in substantial economic loss. Clinical diagnosis of MCF, frequently involves differential etiologies including differentiation from the foreign animal disease variant (AlHV-1) as well as other foreign animal diseases. Identification of MCF viral strain is critical for animal health personnel and producers to rationally manage and protect livestock. Our findings to date suggests that MCF plays a greater role than previously recognized in the morbidity and mortality of cattle and that additional sources (such a white tail deer) of the disease may be involved. This study may lead to changes in livestock and wildlife management as well as revise our current understanding of the ecology of this virus. The development of new test methodologies offers more specific strain identification in support of both endemic and foreign animal disease diagnostics and surveillance.

Publications

  • Cissell RL, Wahab SA, Donnell RL, Kania SA. Detection of antibodies to ovine herpes virus-2 interleukin-10 homologue in sheep-associated malignant catarrhal fever. 8th International Veterinary Immunology Symposium (8IVIS) Ouro Preto, Brazil. August 16-19, 2007